Coastal ecosystem responses to late stage Deccan Trap ... · Coastal ecosystem responses to late stage Deccan Trap volcanism: the post K–T boundary (Danian) palynofacies of Mumbai

www.elsevier.com/locate/palaeo

Palaeogeography, Palaeoclimatology, Pa

Coastal ecosystem responses to late stage Deccan Trap volcanism:

the post K–T boundary (Danian) palynofacies of Mumbai

(Bombay), west India

J.A. Crippsa,*, M. Widdowsonb, R.A. Spicerb, D.W. Jolleyc

aSchool of Earth Sciences and Geography, Kingston University, Kingston-upon-Thames, KT1 2EE, United KingdombDepartment of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, United Kingdom

cCentre for Palynology, University of Sheffield, Sheffield, S3 7HF, United Kingdom

Received 24 March 2004; received in revised form 23 August 2004; accepted 12 November 2004

Abstract

The Deccan Trap continental flood basalt eruptions of India occurred c. 67–63 Ma, thus spanning the Cretaceous–Tertiary

boundary (65 Ma). Deccan eruptions were coeval with an interval of profound global environmental and climatic changes and

widespread extinctions, and this timing has sparked controversy regarding the relative influence of Deccan volcanism upon end-

Cretaceous catastrophic events. If Deccan Trap activity was capable of affecting global ecosystems, evidence should be present

in proximal Indian sedimentary facies and their palaeontological contents. The impact of late stage Deccan volcanism upon

biota inhabiting Mumbai (Bombay) Island’s post K–T boundary lagoonal systems is documented here. Sediments (or

bintertrappeansQ) which accumulated within these lagoons are preserved between Trap lavas that characterise the closing stages

of this flood basalt episode.

Mumbai Island Formation intertrappean faunal and floral communities are conspicuously distinct from those common to

many pre K–T boundary, late Maastrichtian intertrappeans across the Deccan province. The latter sedimentary intercalations

mostly developed in cognate semiarid, palustrine ecosystems; by contrast, those around Mumbai evolved in sheltered,

peripheral marine settings, within subsiding continental margin basins unique to this late Deccan stage, and under an

increasingly humid Danian climate. Geochemical analyses reveal that Mumbai sedimentation and diagenesis were intimately

related to local explosive volcanic and regional intrusive activity at c. 65–63 Ma. Although tectonic and igneous events

imprinted their signatures throughout these sedimentary formations, organisms usually sensitive to environmental perturbations,

including frogs and turtles, thrived. Critically, palynofacies data demonstrate that, whilst plant material deposition was

responsive to environmental shifts, there were no palpable declines in floral productivity following Mumbai pyroclastic

discharges. Therefore, it is implausible that this late stage explosive volcanism influenced major ecosystem collapses globally.

D 2004 Elsevier B.V. All rights reserved.

Keywords: K–T boundary; Deccan Traps (India); Flood basalt; Mass extinction; Palaeoecology; Palynofacies

* Corresponding author. Fax: +44 20 8547 7497.

0031-0182/$ - s

doi:10.1016/j.pa

E-mail addr

laeoecology 216 (2005) 303–332

ee front matter D 2004 Elsevier B.V. All rights reserved.

laeo.2004.11.007

ess: [email protected] (J.A. Cripps).

J.A. Cripps et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 216 (2005) 303–332304

1. Introduction

Continental flood basalt provinces are laterally

extensive lava accumulations of substantial thickness

and low topographic relief (Rampino and Stothers,

1988). India’s dominantly tholeiitic Deccan Trap

flood basalt province presently extends across approx-

imately one sixth of the subcontinent, encompassing

up to 106 km2 of its western portion (Deshmukh,

1982; Fig. 1). The basalts include Traps downfaulted

into the Arabian Sea west of Mumbai (Bombay) and

forming part of the Seychelles microcontinent (Tan-

don, 2002; Devey and Stephens, 1991), and possibly

originally occupied a volume of up to 106 km3 prior to

their erosion (Courtillot et al., 1986).

The duration of the whole Deccan volcanic episode

remains a polemic issue, and advocates exist for both

a brief (b1 m.yrs., e.g., Duncan and Pyle, 1988;

Hofmann et al., 2000) and extended (e.g., Widdowson

et al., 2000; Sheth et al., 2001a) period of activity.

This theme is particularly pertinent when assessing

the effects of flood basalt volcanism upon local,

regional and even global ecosystems. A rapid

Fig. 1. Present-day Deccan Trap outcrop extent. Major

emplacement of an entire flood basalt province would

theoretically prove more detrimental than a series of

events separated by protracted dormant intermissions.

Proof of quiescent phases exists in the form of

sedimentary sequences that accrued between the

Traps. Subsequent extrusives often preserved these

bintertrappeansQ, and evidence can be sought within

them regarding the influence of volcanism upon

sedimentary systems, microclimates and biota.

Because substances released during mafic erup-

tions are less likely to reach potentially damaging

stratospheric levels than those expelled by felsic

volcanism, the effects of late stage, increasingly

felsic, explosive Mumbai volcanism are of interest.

Controversially, a study of massive, well-constrained

pyroclastic events (Erwin and Vogel, 1992) found

that these did not reduce the ecological diversities of

land and marine ecosystems on regional or global

scales, and hence were unlikely to be responsible for

mass extinctions. A bolide impacting Mexico’s

Chicxulub platform (Hildebrand et al., 1991) is

broadly accepted to have exacerbated, if not singu-

larly forced, end Maastrichtian extinctions across the

tectonic structures redrawn from Biswas (1991).

J.A. Cripps et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 216 (2005) 303–332 305

planet (e.g., Pope et al., 1994; Sweet et al., 1999;

Vajda et al., 2001).

The literature review we offer draws together c.

100 years of disparate observations, with the benefit

of a much improved chronostratigraphic framework,

and represents the most comprehensive overview yet

produced on Mumbai sequences. Data presented here

are placed within this context, to illustrate the

ecology of a Deccan volcanic region towards the

close of this flood basalt episode. This is one of the

Fig. 2. Mumbai District, including localities visited, a

first attempts to evaluate ecosystems within a flood

basalt succession using an integrated palaeobotanical,

geochemical, geochronological and sedimentological

approach.

A similar study was conducted for central India’s

Jabalpur region, near the Narmada–Tapti rift zone,

and the Nagpur area to the south, by Tandon (2002;

Fig. 1). Tandon’s article described the environmental

changes leading up to the onset of local Trap

emplacement that are recorded in central Indian

dapted from Subbarao and Sukheswala (1979).

Table 1

Intertrappean sample lithologies chosen for palynomorph analyses

and additional techniques

Section Sample Description

Bandra tunnel B 2800 2800 m From entrance:

coaly layer


dark, flat-laminated shale


compact, flat-laminated shale


dark shale with pyrite cubes

Jogeshwari Bom 1/98 Fairly coarse, carbonate-rich

Jogeshwari Bom 2/98 Dark, carbon-rich, laminated

Jogeshwari Bom 3/98 Coarse, pale and dark laminations

Jogeshwari Bom 4/98 Thick, carbon-rich,

burrows, pyrite

Jogeshwari Bom 5/98 Rippled silt

Jogeshwari Bom 6/98 Predominantly coarse

Jogeshwari Bom 7/98 Tuff

Jogeshwari Bom 8/98 Fissile, laminated

Jogeshwari Bom 9/98 Tuff/calcareous mix

Jogeshwari Bom 10/98 Dark, carbon-rich

Jogeshwari Bom 11/98 Coarse, plainly bedded

Jogeshwari Bom 12/98 Dark shale and pale,

coarser sediment interlaminated

Jogeshwari Bom 13/98 Dark shale

Jogeshwari Bom 15/98 From bdoggerQ layerwith calcite veins

Jogeshwari Bom 16/98 Ash containing small white flecks

Jogeshwari Bom 17/98 Light olive-grey silt

Jogeshwari Bom 18 /98 Trap basalt (top of section)

Jogeshwari Bom 19/98 Rippled, dark grey silt

Jogeshwari Bom 20/98 Finely laminated very

dark grey silt

Jogeshwari Bom 22/98 Float crustacean claw

Jogeshwari Bom 23/98 Fragments from coarse bed,

possible tuff

Jogeshwari Bom 1/99 Phlogopite-rich, ?rhyolitic tuff

Jogeshwari Bom 2/99 Slatey layers, flat-bedded,

v.dark, ?organic-rich

Jogeshwari Bom 3/99 Volcanic bombs

Worli tunnel Wo 2001 2001 m west from shaft,

organic-rich shale


organic-rich shale

Worli tunnel Wo 2210a 2210 m west from shaft,

organic-rich shale

Worli tunnel Wo 2210b 2210 m west from shaft,

organic-rich shale


organic-rich shale


organic-rich shale


organic-rich shale

Table 1 (continued)

Section Sample Description


organic-rich shale


organic-rich shale


organic-rich shale


organic-rich shale


Lameta Formation sediments. Here, topographic

adjustments caused fluvial currents to redirect, and

periodically submerged terrain to became increasingly

subaerial. Although this dynamic landscape was

influenced by regional volcanic activity, it was

exploited by sauropod dinosaurs prior to the first

local lava incursion (Tandon, 2002).

The Mumbai peninsula is investigated by the

present authors. Originally a series of islands (e.g.,

Bombay Island, Salsette Island), the landmass projects

southwards into the Arabian Sea at c. 198 north (Fig.

2). Three intertrappean sections on the western side of

the peninsula were investigated: an outcrop at Amboli

quarry in Jogeshwari, and two tunnel cuttings exca-

vated seawards from the coast, just south of Worli and

near Bandra (Fig. 2). Both tunnels extend westward

into the Arabian Sea, and samples were extracted

along them between 2001 and 3408 m in the Worli

tunnel, and 1890 and 3740 m in the Bandra tunnel

(Table 1). Since completing fieldwork, the Amboli

section has been demolished for housing construction.

This work provides a graphic log and field summary

of the lost section. A brief description of Amboli,

Worli and Bandra lithologies is given in Table 1.

2. Geological setting

2.1. Stratigraphy and field relationships

The Mumbai and Salsette Islands landmass com-

prises a linear depression bounded by easterly and

westerly ridges (Sukheswala, 1956). Muddy sedi-

ments deposited in the central lowland dip 12–158west, and lavas up to 258 west (Sheth et al., 2001a). A

separate classification to the Deccan chemostratigra-

phy, established in the Western Ghats and now

Table 3

Stratigraphical position of present samples within the Salsette

Subgroup, after Sethna (1999)

Subgroup Formation Geology Samples

Salsette

Subgroup

Manori Formation Trachyte and

basalt intrusions

–

Mahd–Utan

Formation

Rhyolite lava flows –

Mumbai Island

Formation

Hyaloclastites,

spilites, basalts

and shales

Bom, Wo, B


covering much of the main Deccan province (MDP),

exists for the distinct geochemistries of Mumbai

intrusives and extrusives (Sethna, 1999; Table 2).

The Amboli (Bom), Worli (Wo) and Bandra (B)

intertrappean shale sections detailed here occur within

the Mumbai Island Formation, the lowermost of the

Salsette Subgroup (Table 3). Sethna (1999) placed this

above the highest of the MDP, the Wai Subgroup.

According to him, Worli intertrappeans occur strati-

graphically above the Malabar Hill flow (Fig. 3).

Sethna (1999) estimated this shale’s thickness at c.

150 m, interrupted only by a 10-m tuffaceous breccia

(hyaloclastite) horizon, and a 5-m basaltic layer. The

nearby Bandra tunnel also runs through this sedi-

mentary unit, and the onshore Amboli section

possibly represents a lateral equivalent.

Pandey and Agrawal (2000) detected several

sedimentary basins offshore of Mumbai and in

adjacent western Indian offshore areas, retaining

India’s largest hydrocarbon reserves (Gombos et al.,

1995). Stratified intertrappeans in quarries around

Jogeshwari (Fig. 2) have been intruded by a columnar

jointed tholeiitic lopolith (Subbarao and Sukheswala,

1979) and are conformably overlain by a basaltic lava

flow. The position of Jogeshwari exposures within the

regional stratigraphy, and possible provincial north–

south correlations, are given in Fig. 4.

Table 2

Deccan chemostratigraphy from Mitchell and Widdowson (1991)

Subgroup Formation

Salsette (4) Manori (4)

Madh–Utan

Mumbai Island (4)

Wai (3) Desur

Panhala

Mahabaleshwar (1)

Ambenali (1)

Poladpur (1)

Lonavala (3) Bushe (2)

Khandala (3)

Kalsubai (3) Bhimashankar (3)

Thakurvadi (3)

Neral (3)

Igatpuri (3)

Jawhar (3)

Data compiled from: (1) Cox and Hawkesworth (1984), (2) Cox and

Hawkesworth (1985), (3) Beane et al. (1986) and (4) Sethna (1999).

Initial Salsette Subgroup eruptions were coeval with Mahabalesh-

war-Desur Formations of the Wai Subgroup.

Magnetostratigraphical correlations between Mum-

bai flows and the MDP volcanic pile have been

attempted. Vandamme et al. (1991) and Vandamme

and Courtillot (1992) detected a reversed-normal

boundary obscured by a secondary palaeomagnetic

component in some localities. These authors estab-

lished that the changeover occurred at much lower

altitudes than the typical 600-m elevation observed

elsewhere in the Deccan (e.g., Western Ghats), and

interpreted the Mumbai boundary to possibly repre-

sent a later, younger magnetic reversal.

2.2. Age

An early Tertiary age was first assigned to

uppermost Mumbai intertrappeans by Blanford

(1867), and an inferred close affinity of Mumbai

intertrappean biota with modern forms led Sukhes-

wala (1956) to support this. However, Singh and

Sahni (1996) found that several Mumbai taxa addi-

tionally occurred in intertrappeans as divergent as

Kutch (Gujarat), Jabalpur (Madhya Pradesh), Nagpur

(Maharashtra), Gurmatkal and Marepalli (Andhra

Pradesh; Fig. 1), indicating correlations between all

these sections. Mumbai ostracod assemblages were

observed to have affinities with late Cretaceous and

Palaeocene forms. The authors ultimately ascribed a

Maastrichtian date, attributing contrasts between

Mumbai and other Deccan facies to environment

rather than age differences.

Highly accurate radiometric dates of Mumbai

extrusives recently obtained (e.g., Table 4) are closely

comparable with those received for late stage MDP

feeder dykes (Widdowson et al., 2000). Sheth et al.

(2001a) argued that Mumbai volcanism continued for

Fig. 3. Schematic section across Mumbai Island identifying the major lava flows, separated by intertrappeans (marked as bIQ), encountered in

boreholes and detected outcropping at Sewri and Malabar Hill, from Sethna (1999).


z1 m.yrs. Hence, it strongly appears that Salsette

Subgroup igneous activity was coeval with terminal

Wai Subgroup eruptions along the Western Ghats,

although the flow-types are not geochemically related.

By this closing stage, the most intense and volumi-

nous MDP lava formations had already erupted (Table

2). Locally restricted Mumbai Island magmatism

directly proceeded the major K–T boundary global

Fig. 4. Possible correlation of Mu

extinctions, and represents the final throes of the

Deccan flood basalt episode.

2.3. Tectonic setting

Sukheswala (1956) determined that a narrow basin

and common volcanic centres occurred along subsur-

face fracture zones, trending north–south across the

mbai province stratigraphy.

Table 4

Published ages of a variety of Deccan igneous rocks occurring around the Mumbai and Salsette Islands, in reverse chronological order (dates

acquired from Amboli samples by M. Widdowson); wr=whole rock, pl=plagioclase

Rock Method Date (Ma) Confidence Comments Reference

Basalt (tholeiite) 40Ar/39Ar (wr) 64.55F0.59 2 r Sample Bom18/98 Widdowson et al. (2000)

Rhyolitic tuff 40Ar/39Ar (wr) 64.64F0.39 2 r Sample Bom1/99

Trachyte 40Ar/39Ar (wr) 60.4F0.3 2 r Unaltered sample Sheth et al. (2001b)

Trachyte 40Ar/39Ar (wr) 61.8F0.3 2 r Unaltered sample

Basalt (tholeiite) 40Ar/39Ar (wr) 60.5F1.2 2 r Unaltered sample Sheth et al. (2001a)

Intermediate rock 40Ar/39Ar (wr) 62.4F1.0 Unspecified From Salsette Island Kaneoka et al. (1997)

Not specified K–Ar (pl) 60.2F2.5 1 r Unaltered sample Vandamme et al. (1991)

Not specified K–Ar (pl) 62.8F3.0 1 r Unaltered sample

Trachyte Rb–Sr (wr) ~60 – No clear isochron Lightfoot et al. (1987)

Rhyolite Rb–Sr (wr) 61.5F1.9 Unspecified High initial 87Sr/86Sr

Basalt (tholeiite) K–Ar (pl) 88.8F4.0 1 r Argon excess Balasubrahmanyan and Snelling (1981)

Olivine nephelinite 40Ar/39Ar (wr) 72.0F6.9 – No plateau ages Kaneoka (1980)

Basalt (tholeiite) 40Ar/39Ar (wr) 74.1F3.3 – No plateau ages

Mugearite K–Ar (wr) 38.7F0.9a 1 r Altered sample Kaneoka and Haramura (1973)

a Age corrected with new decay constants by Vandamme et al. (1991).


Mumbai and Salsette Islands. A regional, oval-

shaped, 12 km height by 35 km base diameter

positive gravity anomaly, with its focus along the

west coast of Salsette Island, coincides with an area of

high heat flow (Negi et al., 1992, 1993; Fig. 1).

Hooper (1999) and Sen (2001) inferred that mildly

alkaline and tholeiitic dykes bearing mantle xenoliths,

again trending roughly north–south, created this

gravity high, and Sethna (2003) associated the

Mumbai anomaly with intermediate and felsic igneous

rocks underplated by gabbroic intrusive complexes.

Vertical movements played a key role in shaping

Mumbai Trap palaeoenvironments. Blanford (1872)

proposed a mechanism which instigated alternating

rising and sinking events across Mumbai Island, and

structures across the district have recently been

attributed to tectonic deformation (Widdowson,

1997; Sheth and Ray, 2002). North–south trending

fractures through, and the block tilting of, offshore

Mumbai basement rock have been related to the

western margin of India rifting from Madagascar, then

the Seychelles bank, respectively, before or during the

Deccan volcanic episode (e.g., Devey and Lightfoot,

1986; Singh and Sahni, 1996).

Inferring a different sequential order from flow-

mapping, Hooper (1990) concluded that the litho-

spheric thinning, shearing and rotation which pro-

duced the present regional westward dips only ensued

after Reunion mantle plume emplacement, litho-

spheric doming and MDP eruptions. This crustal

extension arguably promoted the mantle upwarping

that resulted in the Mumbai gravity anomaly (Dessai

and Bertrand, 1995). Lightfoot et al. (1987) consid-

ered this to have triggered partial melting of lower

crust gabbroic complexes and an associated produc-

tion of trachytic magmas, whilst contamination from

assimilated crust was debated to have generated the

more acidic suites present.

Negi et al. (1992) interpreted the Salsette Island

gravity anomaly as a magma conduit, discrete from

the main Deccan plume, which breached the con-

tinental margin fracture zone offshore of Mumbai.

This fracture, and the Seychelles block detachment,

were stated to be related to a bolide collision.

Chatterjee and Rudra (1996) submitted the Mumbai

High (Fig. 1) oilfield and Deccan intrusives as

evidence of an impact (the bShiva craterQ), embroiling

a putative offshore Mumbai meteorite strike with K–T

boundary extinctions. Shale organic maturation was

allegedly instigated by impact-induced lithospheric

heating, and the offshore region, uplifted by earlier

Deccan magma accumulation, sank in response

(Pandey and Agrawal, 2000).

Mumbai regional tectonic characteristics are more

widely implied to be entirely products of terrestrial

processes (e.g., Sethna, 2003; Table 5). Gombos et al.

(1995) suggested that India’s west coast hydrocarbon

reserves resulted from a Mesozoic collapse of

Proterozoic mobile belts into passive margin basins,

during and following the rifting that produced the

Table 5

Chronology of tectonic events influencing Mumbai Island For-

mation pyroclastic and sedimentary facies

Stage Events

Stage 1 Lithospheric doming above Reunion plume,

flood basalt activity across main Deccan province

Stage 2 Rifting begins along previously existing

N–S crustal fractures, crustal blocks tilted westward

Stage 3 Development of shallow gulf as rifting and

subsidence propagate, water invades depressions

Stage 4 Magma upwells beneath thinned crust

and intrudes into tensive crustal fractures

Stage 5 Mumbai Island Formation explosive

volcanism; shale and ash deposition

into basin systems

Stage 6 Intertrappeans buried as subsidence

continues and thermally metamorphosed by intrusions

Stage 7 Tertiary erosion onshore and deposition

offshore isostatically enhances westward dips


Mumbai High fault block. Sedimentation into Mum-

bai High rifts was dominated by organic-rich shales,

with continued subsidence promoting their thermal

heating and maturation (Gombos et al., 1995).

Widdowson (1997) attributed the current western

Indian margin geomorphology to simultaneous

onshore erosion and offshore deposition operating

throughout the Tertiary.

2.4. Facies

The crustal subsidence that accompanied Mumbai

Island Formation activity represents the waning phase

of Deccan activity (Singh and Sahni, 1996). Con-

sequentially, Mumbai intertrappeans are generally

much thicker than MDP sequences. An exceptionally

thick shale overlying the Malabar Hill flow reflects a

prolonged volcanic hiatus (Sethna, 1999; Fig. 3), and

The Worli and Bandra tunnels cut into extensive,

carbonaceous shales (Sethna, 1999). Sukheswala

(1956) described the western ridge at Malabar and

Worli as composed of a repetitive series of green and

black ashes, and similar facies occur further north,

around Jogeshwari (Sukheswala and Awate, 1957;

Fig. 2). Volcanic and pyroclastic units were substan-

tially reworked during repose phases, becoming

increasingly clay and organic-rich, as reflected in a

transition from greenish ashes and rhyolites to dark,

fossiliferous shales in the Malabar and Worli hills of

the western ridge (Sukheswala, 1956).

Structures including ripple marks prompted Sukhes-

wala (1956) to advocate shallow lakes as likely

depositional environments for the lowermost sedi-

ments. Oblong concretions of V10 cm diameter in a

prominent ash bed exposed along Mumbai Island’s

western ridge were interpreted by this author to

represent ash bombs which coalesced during pyroclas-

tic eruptions, and a recurring subaqueous influence was

deduced from the widespread occurrence of laminated

beds. Deshmukh (1984) recognised that breccias had

evolved from explosive volcanic activity, such vola-

tility being enhanced by the invasion of water follow-

ing subsidence.

Sethna (1999) described most Mumbai district

flow facies as at least partially subaqueous. Extrusive

breccias in the Amboli section, Jogeshwari, are

composed of basaltic and altered vesicular glass clasts

in a fine- to medium-grained clay, carbonate and

quartz-rich matrix. Their petrography indicated a

spilitic origin to Tolia and Sethna (1990), the

hyaloclastites having consolidated during phreato-

magmatic basalt effusions. These authors did not

detect volcanic bombs, finding infrequent subcircular

objects possessing chilled margins to be pillow

structures. The angular shapes of most volcanic

fragments suggested to Singh (2000) that these

underwent minimal aqueous transportation; conse-

quentially, the eruptive centres themselves are likely

to have occupied low-grounds.

Sharma and Pandit (1998) assigned ignimbrite

facies to cycles of felsic tuffs overlying intermediate

to mafic pyroclastic flows in the Sasunavghar–

Juchundra area, c. 5 km north of Salsette Island.

The greater pyroclastic content of such sequences

around Mumbai than other Deccan fringe regions was

regarded by Singh and Sahni (1996) to reflect a closer

proximity to their volcanic source, their evolved

chemistries pointing to the termination of Deccan

events.

Igneous, tectonic and hydrological activity greatly

influenced Mumbai shale as well as ash facies.

Amboli intertrappeans display a hardened, baked

margin where they contact the tholeiitic lopolith,

and elsewhere exhibit plastic deformation (Tolia and

Sethna, 1990). Singh (2000) attributed shale baking to

heat conducted from overlying lavas. Mumbai shales

are indicative of sedimentation under waters with low

oxygen concentrations (Singh and Sahni, 1996), as


reflected in pyrite precipitation along many carbona-

ceous laminations (Singh, 2000). However, occasional

subaerial exposure led to desiccation and swamp

formation under semiarid climes, as evidenced by

calcite-filled rain prints and mud cracks (Singh,

2000).

2.5. Geochemistry

Sukheswala (1956) identified pyroxenes and feld-

spars flanking calcite crystals in a Worli ash, and thus

inferred a mafic chemistry. Partially decomposed

feldspars, pyroxenes and biotite also occur in Jogesh-

wari tuffs, with calcite and quartz forming the major

minerals here. Amboli hyaloclastites contain higher

H2O and Na2O proportions than the local tholeiites,

these enrichments in hydrous and alkali phases having

been influenced by magma contacting water during its

crystallisation according to Tolia and Sethna (1990).

These authors recognised Amboli plagioclase to be a

sodium-rich variety, and found that much of the

calcite and quartz occurred as secondary minerals

filling veins alongside zeolites. Metasomatism related

to tectonism and intrusions is likely to have instigated

zeolite precipitation across the Mumbai district

(Sabale and Vishwakarma, 1996).

Evidence of pyroclastic activity associated with

terminal Deccan tensional regimes is preserved in the

clay fractions of Mumbai shales. An X-ray diffraction

(XRD) study of Amboli, Worli and Malabar inter-

trappean mineralogies (Singh, 2000) revealed match-

ing mineral suites that indicated a mafic ash

provenance for the shales’ clastic components. Pyrox-

enes degraded, glass devitrified and smectitic clays

evolved during reworking, the smectites producing

few reflection angle peaks due to their weak crystal

structure development (Singh, 2000). Smectites and

chlorite constitute the most important Mumbai clays,

and combine to form a mixed-layer superlattice.

2.6. Palaeontology

Owen (1847) assigned frog remains within shales

underlying the Malabar Hill Trap at Worli Hill the

species Rana pusilla, although the fossil evidence for

Maastrichtian Indian ranids has since been queried

(Bossuyt and Milinkovitch, 2001). Turtles and mol-

luscs from this section were detailed by Blanford

(1867), and additional species of frogs, the most

abundant faunal element, by Chiplonkar (1940).

Sukheswala (1956) extracted two Carteremys leithii

freshwater Pelomedusidae turtle specimens, and a

tooth later diagnosed as crocodilian (Singh and Sahni,

1996).

According to Singh and Sahni (1996), preservation

within the Mumbai shales is unique to the Deccan,

being superior to that within most MDP intertrap-

peans. These authors examined the faunal component

of sections at Worli Hill, Amboli and Malabar,

unearthing Shweboemys (Carteremys) leithii skull

and carapace fragments within the latter. This genus

was further documented in MDP sediments at Nagpur,

Marepalli and Kutch (Fig. 1). Similarly, the Mumbai

ostracod genera Mongolianella, Altanicypris, Cypri-

dea (Pseudocypridina), Timiriasevia and Cyprois

were associated with those from MDP intertrappeans

(e.g., Bhatia et al., 1990; Whatley et al., 2003). A new

pelomedusoid turtle species, Sankuchemys sethnai,

has recently been extracted at Amboli (Gaffney et al.,

2003).

Genera common to inland and marginal marine

ecosystems signify that either lagoon waters were

occasionally virtually freshwater, or that central

Indian lakes tended towards brackish. However, Singh

and Sahni (1996) emphasised that dinosaur and fish

taxa, important in several widely distributed MDP

localities, are entirely absent in the Mumbai shales

(Table 6). The lack of fish was attributed to water

turbidity or contamination, conditions frogs were

capable of tolerating (Singh and Sahni, 1996),

although turbid waters of modern coastlines are often

colonised by fish. Even the Mumbai Leptodactylidae

frog Indobatrachus was distinguished from MDP

Pelobatidae and Discoglossidae forms (see also

Khosla and Sahni, 2003, and references therein).

The absence of some important MDP taxa around

Mumbai, despite favourable preservation conditions,

led Blanford (1867) to speculate that the cumulative

effects of previous Deccan volcanism suppressed

rainfall and damaged Mumbai environments to the

extent that most MDP organisms lapsed into extinc-

tion. He interpreted poorly fossiliferous volcaniclas-

tics low in the Malabar and Worli sequences to signify

originally barren ecosystems, and suggested that

Mumbai communities were a replacement biota to

MDP fauna. Sukheswala (1956) reasoned that con-

Table 6

Important organism groups in the Poladpur, Ambenali and Mumbai

Island Formations (based upon a collation of results presented in

Cripps, 2002 and references therein)

Organism Poladpur Ambenali Mumbai

Island

Dinosaur Y Y –

Crocodile – Y Y

Fish Apateodus Y Y –

Lepisosteus Y Y –

Phaerodus Y – –

Pycnodus Y Y –

Ray Y Y –

Stephanodus Y – –

Turtle – Y Y

Frog Y Y Y

Gastropod Lymnaea Y Y –

Paludina Y Y –

Physa Y Y –

Planorbis Y – –

Bivalve Unio – Y –

Ostracod Altanicypris Y Y Y

Bisulocypris – Y –

Candona Y Y –

Cypridea – Y Y

Cyprinotus Y – –

Cypris – – Y

Cyprois Y Y Y

Drawinula Y – –

Eucandona Y – –

Metacyprois Y – –

Mongolianella Y Y Y

Mongolocypris Y – –

Paracypretta Y – –

Paraconadona Y – –

Talicypridea – Y –

Timiriasevia – Y Y

Charophyte Harrisichara – Y –

Microchara Y – –

Peckichara Y Y –

Platychara Y Y –

Stephanochara – Y –

Angiosperm Aquilapollenites Y Y –

Arecaceae Y Y Y

?Betulaceae Y Y –

?Caprifoliaceae Y Y –

?Mimosaceae Y Y –

Gymnosperm ?Araucariaceae Y Y –

Bennettitaceae Y Y –

Ginkgoaceae Y Y –

Pinaceae Y Y –

Podocarpaceae – – Y

Pteridophyte Gleicheniaceae Y Y –

Osmundaceae – Y –

Polypodiaceae – Y –

Salviniaceae Y Y Y

Table 6 (continued)

Organism Poladpur Ambenali Mumba

Island

Algae Acritarcha Y Y –

Botryococcus Y Y Y

Dinoflagellate Y Y –

Zygnemataceae Y Y –


i

temporaneous local, rather than preceding regional,

volcanic activity generated a terrain inhospitable for

Mumbai life. A thick basal greenish ash was thought

to indicate an extended extrusive episode prior to a

period of diminishing volcanism and community

regeneration, represented by upper dark, fossiliferous

shales.

According to Mumbai Trap radiometric dates

(Table 4), the diverse shale communities survived

regional and global K–T boundary events. Bossuyt

and Milinkovitch (2001) detailed archaeobatrachan

frog lineages enduring the Deccan volcanic episode

along the Indian island’s peripheries, and thriving

during the early Tertiary, notwithstanding their

probable confinement along the western fringe by

volcanism to the east and an ocean to the west.

Although many frog groups are environmentally

sensitive, some Leptodactylidae species have broad

physiological tolerances, and today populate habitats

undergoing ecological or climatic disturbances (Kai-

ser, 1997).

2.7. Palaeobotany

Mumbai intertrappean plant megafossils are

uncommon and distinct from those of the MDP

(Blanford, 1867), but have similarly originated from

land plants (Sukheswala, 1956). Bande et al. (1988)

and Bande (1992) found limited Bambusaceae and

Podocarpaceae wood, leaflets of possible Acacia

(Leguminosae) affinity, and seeds similar to Artabo-

trys (Annonaceae). Megafloral remains are allochth-

onous within Mumbai basin facies, and the buoyancy

of such organs as bamboo cane probably assisted their

transportation. Leptodactylidae frog taxa that cur-

rently inhabit marine supra- to intertidal zones and

consume saline marine food must regulate their

osmotic balance (Abe and Bicudo, 1991). It thus

seems plausible that Indobatrachus consumed terri-

genous plant detritus washed down from vegetated


areas, a diet that ostensibly safeguarded the frogs from

any effects of temporary productivity declines driven

by volcanic disturbances (cf. Sheehan and Fastovsky,

1992).

Palynofacies analyses are useful in combination

with sedimentological investigations, potentially

distinguishing environmental transitions before mac-

roscopic change is visible (Tyson, 1985). An amal-

gamation of the ecology of organic matter (OM)

producers, palynodebris transportation, decomposition

prior to burial and alterations during diagenesis ge-

nerates a sediment’s palynofacies characteristics.

According to Cross and Taggart (1982), the principal

factors determining plant fossilisation are tissue

durability, transportation distance, the existence and

persistence of viable preservation sites, and sedimen-

tation rates and consistency. No palynofacies analyses

have previously been performed upon Deccan inter-

trappean floral material.

3. Data collection

3.1. Field observations

(1) Amboli quarry, 19808V03WN; 072850V30WE, 10 m

a.s.l. exposes an intertrappean of z10 m thick-

ness, dipping westward c. 88, terminating in a

junction with basalt above (Fig. 5). Its base is

obscured by the quarry floor (the underlying

flow, occurring c. 3–4 m beneath ground level

here, outcrops to the northeast). Sediments range

from dark grey, flat-laminated shales, through

silts, to pale grey, cross-rippled sands (the latter

occurring exclusively around Jogeshwari).

Coarse grains, rarely present along certain

laminations, include well-rounded c. 0.4 mm

diameter carbonate clasts and rounded quartz

sands (e.g., Fig. 6b). Dark, laminated horizons

(e.g., Bom 4/98 and Bom 12/98; Table 1)

contain pyrite framboids. The majority of units

are planar-bedded, although one chaotically

deposited, coarser layer contains btabletsQ of

flat-laminated sediment. Ripples of 0.1 cm

amplitude by 2 cm wavelength traverse another

upper bedding plane, and some ripple crests

have been transformed into flame structures

(e.g., Fig. 7c). Undulose upper bedding planes

frequently exhibit fine, laterally continuous

organic drapes.

A 1.22-m ash, Bom 1/99, forms a salient,

continuous bed through the section’s centre.

This resistant unit yields virtually unaltered

crystals the potassic mica phlogopite and quartz.

Beneath, the uppermost fraction of Bom 8/98

consists of a series of fining-upwards beds.

Fining-upwards cycles throughout this section

tend to be continuous but thin, containing

neither body nor trace fossils. However, small

(1–2 cm) internal moulds of bivalves and

gastropods occur sporadically elsewhere. An

upper bedding plane exposed upon the quarry

floor is pitted by common burrows (cf. Thalas-

sinoides), these being virtually absent in higher

beds. These are subhorizontal, smooth-walled,

pellet back-filled, c. 1.5 cm diameter and 6 cm

length, connecting at triple-junctions. Slightly

oblate features of 1–1.5 cm diameter in Bom 6/

98, viewed in cross section in the quarry face,

initially appear to be higher, slightly com-

pressed, vertical expressions of these horizontal

traces. However, laminations cup underneath

them and, when excavated, their true subspher-

ical rather than cylindrical shape becomes

apparent.

Several ash beds are indistinctly stratified, either

coarsening or fining-upwards. Some layers are

dominated by grains, commonly feldspars, of up

to 1 cm, horizontally aligned in thin, parallel

bands. A coarse carbonate cement envelops the

Bom 1/98 and Bom 2/98 matrices. Crystalline

cement is particularly evident towards the

uppermost basalt. Slickensides both follow and

cross bedding planes. Sediments contacting the

columnar lopolith exposed in the quarry face

exhibit polygonal cracks. In sharp contrast with

many MDP sections, no reddened ashes are

present.

(2) The Worli and Bandra Tunnels are inacces-

sible, hence their overall sedimentological con-

text is impossible to gauge. However, cuttings

reveal that the tunnels pass through similar

lithologies to those present in the Amboli

section, except that the sediments generally lack

cemented layers, being dominated by shale and

OM (Table 1).

Fig. 5. Amboli sedimentary summary log (for detailed log, refer to Cripps, 2002).


Fig. 6. Thin-section micrographs (plane-polarised light). (a) Fine-

grained clay and OM laminae undulating and bifurcating around

coarser ash clasts and cement in silt sample Bom 3/98; (b)

laminations compressed and distorted about a coarse, weathered

pyroclast in ash sample Bom 16.


3.2. Geochemistry

A thorough account of Mumbai clay mineralogy is

given in Singh (2000). To provide comparison, the

mineralogy of Bom 3/99, a spherical clast from

Amboli quarry, was assayed by X-ray diffraction

(XRD) for this work, after preparation using standard

whole-rock and clay-separate methods (Hardy and

Tucker, 1988). The clay separate was subjected to

glycolation and heating, to distinguish between smec-

tites, chlorites and kaolinites. Element concentrations

were established using X-ray fluorescence spectro-

scopy (XRF). Analyses of major elements were

performed on glass discs, and powder pellets were

used for trace element analyses. Losses on ignition

(LOI) were recorded to account for volatile contents.

Two Amboli and two Worli tunnel samples were

chosen for stable carbon isotope composition deter-

mination. Kerogen palynological residues (outlined

next) were prepared for stable carbon isotope analyses

by repeatedly centrifuging dry samples in 9:1 dichlor-

omethane:methanol solvent. Stable isotope ratios were

measured on an elemental analyser-isotope ratio-mass

spectrometer.

3.3. Palynofacies

A sediment’s palynofacies is its content remaining

after maceration in hydrochloric and hydrofluoric

acids (Combaz, 1964). The desired end products of

palynofacies maceration processes are slides clearly

displaying an optimum number of phytoclasts (clasts

of plant origin), with as little accompanying extra-

neous material as possible. Ideally, techniques

employed should not alter the proportions of phyto-

clasts as they occur in their host sediment by biasing

particular grain sizes or types. Standard palynological

processing techniques to produce kerogen slides

(Moore et al., 1991) were followed for the present

study.

4. Results

4.1. Geochemistry

The Amboli spherical clast Bom 3/99 is domi-

nated by calcite, quartz, smectite and feldspar (Fig.

8a). A minor peak at 3.6 2 in the clay separate

diffraction profile (Fig. 8b) denotes the presence of

an ordered super-lattice, produced by two different

minerals alternating regularly, constituting the mixed-

layer clay corrensite. Peak positions confirm the

super-lattice to be chlorite interleaved with a

saponitic smectite (approximately 80:20 chlorite:s-

mectite; Clayton, personal communication). A trace

of kaolinite is evident in the whole-rock profile,

although, interestingly, this clay is unusual in MDP

intertrappeans (Cripps, 2002).

XRF results reveal that, although Amboli ash and

tuff chemistries vary considerably, all the samples

possess elevated Na2O levels (Table 7). The two

Amboli ashes analysed for stable carbon isotopic

composition exhibit marginally lighter d13C values

Fig. 7. Amboli section photographs. (a) Entire section, (b) typical organic-rich shale to marly sandstone bedding cycles, (c) flattened ripples on

upper bedding plane of siltstone.


than the Worli shales (Table 8). The significance of

these findings is discussed in Section 5.

4.2. Palynofacies

Although significant volumes of organic residue

remained after macerating Mumbai intertrappeans,

palynomorphs supplied a negligible contribution.

Spinizonocolpites palm pollen, Azolla water-fern

massulae, Botryococcus algal colonies and various

fungal spores were exceptionally logged in some

shales. While this paucity means that a comprehensive

palynological interpretation is unfeasible, similar

lithologies through the Amboli, Worli and Bandra

sections permit comparisons of their palynodebris

characteristics. Mumbai shales and silty sands are

suited to palynofacies investigations due to their high

concentrations of well-preserved, structured organic

clasts. Seventeen Amboli (Bom), 11 Worli (Wo) and 4

Bandra (B) specimens were examined; samples were

selected to typify the range of sediment types present

(Table 1).

Two hundred phytoclasts were logged for each

sample, and grains allocated 1 of 16 designated

microfloral categories (Table 9; Fig. 9). Palynodebris

percentages are displayed at their stratigraphical

positions through the Amboli sequence in Fig. 10.

Six Amboli ashes proved unproductive (Table 1), and

only one ash horizon macerated trapped significant

quantities of organic clasts (Bom 16/98). By contrast,

Fig. 8. Amboli XRD profiles. (a) Bom 3/99 whole-rock profile, (b) Bom 3/99 clay separate profile. sme=smectite, cal=calcite, qtz=quartz,

feld=feldspar, latt and csme=chlorite:smectite superlattice (corrensite), kao=kaolinite.


all 11 Worli and 4 Bandra samples contained abundant

palynodebris.

Changes in absolute palynodebris abundances

occur with lithology transitions through these beds,

the changes being accompanied by variations in the

relative percentages of some phytoclast categories to

others. For example, taking into account that drops in

angular black clast numbers will force rises in other

category percentages, decreases in small and large

angular black clasts in Worli samples are accompanied

by marked increases in fragments displaying tracheids

(Fig. 9). Following a different trend, low amounts of

angular black clasts in Amboli samples generally

accompany augmented amorphous organic matter

(AOM) and branching leaf-like fragment percentages

(Fig. 10).

Small angular black clasts are consistently present

in high percentages; the largest concentration occurs

in Bom 4/98, a laminated, pyrite-rich bed (Table 9).

Large angular black clasts are less concentrated, but

Table 7

Infratrappean and intertrappean major (wt.%) and trace (ppm) element compositions received from XRF analyses (for lithologies, refer to

Table 1)

Sample Bom

1/98

Bom

9/98

Bom

16/98

Bom

23/98

Bom

1/99

Bom

3/99

Other

Deccan

SiO2 60.62 52.13 37.15 71.46 64.59 36.76 42.46

TiO2 0.729 0.544 0.557 0.635 0.751 0.893 1.655

Al2O3 14.25 11.9 3.78 12.09 15.93 9.06 11.01

Fe2O3 5.25 4.5 5.52 3.57 4.24 9.74 11.66

MnO 0.085 0.103 0.161 0.048 0.077 0.19 0.18

MgO 2.43 4.4 11.53 1.5 1.74 6.83 3.78

CaO 3.82 8.43 16.16 1.04 2.3 15.49 13.07

Na2O 5.52 5.66 0.28 3.21 6.89 1.76 0.17

K2O 1.72 1.01 0.05 3.21 1.92 0.41 1

P2O5 0.154 0.077 0.147 0.19 0.107 0.103 0.09

LOI 4.33 11.18 24.34 2.51 1.88 15.38 15.16

Rb 56.8 26.4 2 113 55.5 12.8 34.87

Sr 159 148 155 166 143.6 87.1 106.5

Y 35.1 24.8 18.4 33.3 35.3 26 22.71

Zr 472 420 74 360 582.8 69.1 108.7

Nb 110.6 97.9 10.8 79.1 142.6 9.8 10.58

Ba 500 220 30 919 537 80.6 131.4

Pb 12 10 1 9 14.7 2.1 5.35

Th 23 19 2 17 29.6 0 3.93

U 3 5 0 4 4.9 2.2 1.372

Sc 13 10 17 12 9.8 39.8 30.53

V 217 76 156 103 67 273.4 243.9

Cr 228 222 41 272 212.8 115 111.5

Co 21 7 16 32 9.8 35.1 25.92

Ni 81 24 24 309 3737 58.6 47.15

Cu 51 42 39 56 22.7 58.7 136.7

Zn 57 32 38 74 49.8 51.9 46.12

Ga 14 11 6 11 15.2 15.1 14.9

Mo 0 0 7 1 0.4 0 0.564

As 4 4 4 8 6.7 6.9 3.32

S 232 415 2571 125 424 705 258.8

Other Deccan=mean result obtained from a variety of ash intertrappeans from the Western Ghats, the Krishna–Godavari basin and the Mandla

Lobe (Fig. 1).

Table 8

Results of stable carbon isotope analyses of kerogen samples

(PDB=Peedee belemnite standard)

Sample d13Cx PDB Mean d13Cx PDB Standard

deviation

Bom 5/98 �26.39 �26.68 0.409

�26.97

Bom 16/98 �25.4 �25.58 0.261

�25.77

Wo 2001 �24.78 �24.89 0.148

�24.99

Wo 2850 �24.86 �24.94 0.12

�25.03


follow a similar pattern up the samples. Branching

leaf-like clasts are important in Amboli and Worli

sediments, and Bandra cuttings are dominated by

AOM. Amorphous matter and parenchymatous tissues

are more abundant in Amboli than Worli samples,

while fragments displaying tracheids are only impor-

tant in Worli sediments. As with the small and large

black clasts, branching leaf-like fragments and black

laths typically exhibit angular edges.

Phytoclast colours are recorded in Table 10,

following the thermal maturity scheme of Batten

(1996). Derived plant material is dominantly black-

ened, creating high thermal maturity estimations

Table 9

Relative percentages of palynofacies categories for productive B, Bom and Wo samples

Sample AOM Black

lath (?wood)

Black,

porous

Branching

(?leaf)

Brown,

angular

Brown,

porous

Fungal Large,

black,

angular

Palynomorph

(non fungal)

Parenchyma Small,

black,

angular

Small,

translu t

Subspherical

black

Tracheid Cuticle? Noncellular

membrane

B 3510 51.5 3.5 0 0 0 0 0 8 0 0 33.5 0 3.5 0 0 0

B 3130 68.5 0 0 0 0 0 0 2 0 0 28.5 0 1 0 0 0

B 3000 44.5 3 0 0 0 0 0 11 0.5 0 38 0 0.5 0 0 2.5

B 2800 35 6 0 0 0 0 0 17.5 0 0 41.5 0 0 0 0 0

Bom 20/98 2 3 1 0 0.5 0 0 23 0 70.5 0 0 0 0 0 0

Bom 19/98 60.5 2 0 0 0 0 0 6.5 0 0 31 0 0 0 0 0

Bom 16/98 28 0.5 0 31 0.5 1.5 0 8 0 1.5 20.5 0 0.5 0.5 0 7.5

Bom 15/98 17.5 3.5 0 10.5 0 0 0 14.5 0 3.5 36 8.5 4 0 0 2

Bom 13/98 0.5 6.5 0.5 2.5 0 0 1 26.5 0 0 60 1.5 0.5 0 0 0.5

Bom 12/98 72 2.5 0 0 0 0 0 3.5 0 0 21.5 0.5 0 0 0 0

Bom 10/98 2 0 1 49 0 0 0 10.5 0.5 13 9.5 0 0 0 0 14.5

Bom 8/98 42 1 0 0 0 0 0 11 0 0 45.5 0 0 0 0 0.5

Bom 5/98 0 4.5 19.5 1 0.5 1 0 28 0 0 44.5 0 0 1 0 0

Bom 4/98 8.5 1.5 0 2 0 0 0 12.5 0.5 0 74 0.5 0.5 0 0 0

Bom 3/98 0.5 0 0 0 0 0 0 30 0 0 66.5 1 2 0 0 0

Bom 2/99 47.5 2 8.5 6.5 0 0 0 13 0 0 21 0 1.5 0 0 0

Bom 2/98 0.5 1.5 0 0 1 0 0 19 0.5 0 72 2.5 0.5 2.5 0 0

Bom 1/98 2.5 1.5 0 1.5 0 2 0 12 0.5 0 64.5 11.5 2 2 0 0

Wo 3408 5 1.5 7.5 8.5 4.5 9 1.5 20 0 12 17 3.5 0.5 3 0 6.5

Wo 3128 1.5 4 0 0 24.5 0 0.5 14 0.5 0 25.5 0 1.5 22 3 3

Wo 2850 2 2.5 2.5 19.5 6.5 5 7 9 0 5 24.5 1.5 3 4 0 8

Wo 2736 0 5 0 0 2.5 9 0 11 0 0 30.5 11.5 3 27 0 0.5

Wo 2735 0 5 5 1 1 0 0 24.5 0 0 60.5 0.5 2.5 0 0 0

Wo 2610 1.5 4.5 2.5 15 2.5 6.5 0 8 0 0.5 37 6 5.5 1.5 0 9

Wo 2600 0 6 0 0 4 11.5 0 24 0 0 29.5 0 1 22 1.5 0.5

Wo 2210b 2 7 0 0 3.5 0 0 5 1.5 0 53 16 3 7.5 0.5 1

Wo 2210a 0.5 6 2.5 4.5 6.5 2 0 18.5 0 0 56.5 1.5 1 0.5 0 0

Wo 2100 2.0 30.2 0 1.2 0 0 0.8 12.7 0 0 23.7 0 15.9 6.1 6.9 0.4

Wo 2001 3.5 1.5 0 10.5 1.5 2.5 0 16 0 11.5 34.5 0.5 5.5 1.5 0 11

J.A.Crip

pset

al./Palaeogeography,Palaeoclim

atology,Palaeoeco

logy216(2005)303–332

319

cen

Fig. 9. Relative percentages of palynofacies categories for Bandra (B) and Worli (Wo) samples.


Fig. 10. Distribution of palynofacies types with height through the Amboli section (details given in Table 9). Grey bands mark the positions of

unproductive ashes.


Fig. 10 (continued).


Table

10

Black

woodphytoclastsize,colourandshapestatistics

forproductiveBom

andWosamples(thermal

maturationafterBatten,1996)

Sam

ple

Bom

1/98

Bom

2/98

Bom

3/98

Bom

4/98

Bom

5/98

Bom

10/98

Bom

13/98

Bom

15/98

Bom

16/98

Wo

2001

Wo

2100

Wo

2210a

Wo

2210b

Wo

2600

Wo

2610

Wo

2735

Wo

2736

Wo

2850

Wo

3128

Wo

3408

Phytoclastsize:

Small(b40ım

)~40%

~40%

~40%

~40%

~40%

~40%

~35%

~45%

~45%

~40%

~20%

~40%

~70%

~30%

~45%

~35%

~30%

~30%

~40%

~30%

Medium

(40–80ım

)~40%

~30%

~30%

~35%

~25%

~35%

~35%

~25%

~30%

~25%

~50%

~25%

~25%

~40%

~30%

~40%

~35%

~40%

~45%

~30%

Large(N80ım

)~20%

~30%

~30%

~25%

~35%

~25%

~30%

~30%

~25%

~35%

~30%

~35%

~5%

~30%

~25%

~25%

~35%

~30%

~15%

~40%

Thermal

maturation

66–7

6–7

6–7

75

76

65–6

66

5–6

5–6

56–7

5–6

55

5–6

Pytoclastshape:

Equant(outof50)

41

43

23

43

45

28

42

36

45

34

40

44

34

28

42

41

29

32

33

37

Lath(outof50)

97

27

75

22

814

516

10

616

22

89

21

18

17

13


(Amboli mean 6.3; Worli mean 5.6). E:L ratios

(equant to lath-shaped clasts; Table 10) were received

from counts of 50 black wood grains. Mean E:L ratios

(38.4:11.6 for Amboli, and 35.8:14.2 for Worli) are

similar, equant-shaped grains dominating over lath-

shaped in both sequences. Fig. 11 compares thermal

maturity with black wood shape and size ratios

through the Amboli section. Overall, b40 Am grains

marginally form the greatest black wood size compo-

nent, although there is a relatively even distribution of

b40 Am, 40–80 Am and N80 Am clasts.

5. Interpretation

5.1. Facies

The conspicuous absence of archetypal MDP boles

and calcretes in Mumbai Island intertrappeans high-

lights a general lack of sediment subaerial exposure.

Tectonic adjustments controlled the subaqueous

nature of Mumbai sediments and Traps, allowing

water to flood into the developing shallow basins as

rifting and foundering of the margin progressed.

Slickensides that both follow and cross bedding

planes probably developed during this period of

tectonism. Substantial intertrappean thicknesses are

partly due to the extent of contemporaneous regional

subsidence.

Shale laminations indicate a lack of bioturbation,

suggesting that infauna were unable to exploit these

sediments, possibly due to inadequate interstitial

oxygen levels. The combination of swamp facies

and anoxic laminated sediments implies that water

levels were generally very shallow, yet liable to

stagnation. This was perhaps a consequence of

restricted water mixing through a low-energy column,

the aqueous body being isolated from a fully open

marine influence.

A stratified water column with a high potential

towards basal anoxia may have resulted from a subtly

more dense, brackish layer separating surficial,

aerated freshwater from the sediments, such circum-

stances being liable to occur in partly enclosed,

sheltered lagoons fed by rivers. Shale carbon concen-

trations appear to have been optimised by low clastic

sediment input combined with high terrigenous

organic productivity, and OM decomposition would

Fig. 11. Log of Amboli section palynofacies characteristics.



in turn have depleted oxygen resources. Clastic

sediments are dominated by volcanic material, signi-

fying that sedimentation rates diminished during

nonvolcanic periods. Although OM was largely

introduced, the dearth of eroded clastic material points

to hinterland gradients having been negligible.

Water energy infrequently increased, and undulat-

ing or rippled horizons became deposited above flat-

laminated sediments. Paler, ash-rich units typify

these faintly higher energy facies, the water move-

ment perhaps initiated by ash introductions that

triggered minor density currents. Tablets of flat-

laminated shale in one sandy ash appear to have

been ripped up and reworked after their compaction

but before lithification. Horizons bearing asymmetric

ripples indicate directed flow, potentially having

resulted from such ash-bearing currents progressing

across lagoon floors. Ripple tops were sometimes

preserved flattened or altered into flame structures

during their rapid deposition, dehydration and

collapse (e.g., Fig. 7c).

The Mumbai lagoons were stable environments

that were disrupted by ash eruptions. Rare fine,

laterally continuous organic drapes settled above

rippled layers, as the water reverted to its calm state.

Repetitive pyroclastic influxes established the series

of fining-upwards, ash-rich rhythms through the

Amboli section. The transition from Bom 8/98 to

Bom 1/99 appears to equate to a gradual increase in

pyroclastic activity, culminating in a major local

event. Many ash beds are indurated, their matrix,

having been welded.

Spherical to ovoid objects, constituting Bom 3/99,

lack internal structure, more closely resembling the

coalesced ash bombs described by Sukheswala (1956)

than the spilitic fragments or pillows detailed by Tolia

and Sethna (1990), occurring in an ash rather than a

flow breccia. Laminations cup underneath these

bombs, as though the pyroclasts dropped upon and

depressed unconsolidated sediments. These accre-

tionary lapilli strongly suggest that ejecta cones were

in close proximity to the Amboli lagoon. The

lamination deficit through most ashes probably

resulted from their accelerated, chaotic deposition

styles. Air-fallen and fluvially deposited loose pyro-

clastics were possibly aerated enough to support

burrowing organisms that obscured original bedding

features.

When present, bivalve and gastropod internal

moulds are of small (1–2 cm) sizes. This might be

consequential to oxygen deficiency having stunted

growth and/or caused large proportions of the mollusc

populations to die prior to reaching maturity. The

sizes of feeding traces upon a quarry floor bedding

plane point to excavation by small crustaceans, and

float crustacean claw sample Bom 22/98 (Table 1)

may have originated from this horizon. Subhorizontal

burrowing activity suggests sedimentation rates were

low when organisms exploited the sediments. Their

near absence in higher beds might be consequential to

subsequent ash injections.

The prevalence of shales through the extensive

Worli and Bandra sequences points to continually

low sedimentation rates here, and therefore substan-

tial sedimentation durations. Discrepancies in ash

and Trap frequencies between Amboli and the Worli

and Bandra tunnels indicate that either volcanic

centres were closer to Amboli, or activity was more

intense at the time of Amboli deposition. Worli and

Bandra shales are not as well-cemented as the

Amboli sediments, suggesting cement migrated from

ash horizons. Diagenetic events have altered the

Amboli section, and recrystallisation during lithifi-

cation is particularly evident towards the uppermost

basalt. Polygonal cracks in sediments contacting the

columnar lopolith are likely to have evolved simul-

taneously with the intrusion’s contraction upon

cooling.

5.2. Geochemistry

The XRD profile of a volcanic bomb (Bom 3/99)

exhibited numerous, clearly defined reflection peaks

at positions signifying well-developed corrensite

crystals (Fig. 8). Relatively fresh feldspars produce

peaks; thus, it seems unlikely that sedimentary

processes occurred over an extended enough period

to permit the development of regularly alternating

chlorite:smectite lattices. Rather, increasing diagene-

sis temperatures and durations transformed smectites

into this mixed-layer, chloritic clay, by means of

repeated dissolution and precipitation events. The

ratio of chlorite to smectite (c. 80:20) indicates a

heating event of z100 8C during lithification,

possibly accompanied by a degree of saline fluid

flow (Beaufort et al., 1997; Murakami et al., 1999).


Kaolinite forms a minor contribution to the

volcanic bomb. As weathering continues, smectite

can alter to kaolinite through a succession of

smectite–kaolinite mixed-layer transitions. Its near

absence in weathered Deccan volcanics suggests these

fossilised at early stages of modification. Kaolinite

crystals can, however, grow within substrates sub-

jected to prolonged waterlogging, and while MDP

boles were largely too well-drained to promote its

precipitation, the Mumbai lagoonal basins provided

more favourable precipitation sites. Kaolinite is a

common alteration product of felsic igneous rocks,

and phlogopite micas present through tuff sample

Bom 1/99 may be indicative of a transformation to

more felsic late stage volcanism as the region rifted

and subsided.

The varied chemistries of Amboli ashes are a

reflection of their occasional explosive genesis in

aqueous facies, clastic contamination, element mobi-

lisation prior to lithification and hydrothermal alter-

ation resulting from nearby intrusions. High sodium

levels through these relative to MDP ashes (Table 7)

may be consequential to their deposition in saline

lagoons, although sodium from albites present would

have augmented these concentrations.

Amboli kerogen possesses marginally lower

carbon isotopic signatures than those of Worli

(Table 8). Thermal maturation, induced by local

intrusion emplacement, is one means by which

original Amboli OM d13C could have been low-

ered. Dykes cross-cut intertrappeans offshore Mum-

bai (Sethna, personal communication); if these

imparted a greater influence on Amboli than Worli

sediments, they might additionally have been

responsible for the darker Amboli phytoclast col-

ours (Table 10).

Relative depletions in Mumbai shale 13C through

heating was possibly influenced by a selective

preservation of organic fractions with augmented12C comparative to the total OM. Lipids, the most

stable of plant constituents, are enriched in 12C by

up to 8x compared with other biogenic com-

pounds (Faure, 1986), and their hydrocarbon

composition closely resembles that of petroleum.

Smectitic clays catalyse lipid transformations to

hydrocarbons virtually identical to petroleum

(Faure, 1986), and the offshore Mumbai region is

rich in source rocks.

5.3. Palaeontology

Although molluscs are sporadically distributed

through Amboli shales, no typical MDP genera

(e.g., Physa gastropods, Unio bivalves) were identi-

fied during the present study. Since shale faunal

material possessed high preservation potentials, the

absence of ubiquitous MDP forms almost certainly

reflects their intolerance to marginal marine environ-

ments. Investigations are required to ascertain whether

these genera continued to occupy contemporaneous

MDP Danian, ?Desur Formation palaeoenvironments

(e.g., Singh and Kar, 2002), and thus survived the full

effect of the Deccan episode proximal to the principal

focus of flood basalt activity. Invertebrates which did

inhabit Mumbai lagoons were periodically capable of

exploiting oxygenated surface sediments, as demon-

strated by the pellet back-filled feeding traces.

No macroflora was recovered from the Amboli

section by the present authors, although this sequence

is extremely rich in disseminated plant matter. Parent

plants possibly colonised firm terrain tens of metres

from the low-angled, muddy lagoon shores and,

consequentially, intact plant organs were seldom

fluvially transported into the lagoons.

5.4. Palynofacies analyses

Of the 16 palynofacies categories selected to

represent the Mumbai phytoclasts (Table 9), 14

symbolise land-derived plant fragments which

received their shapes, colours and sizes from their

parent plant and organ varieties and taphonomic

(including sedimentological) effects. (AOM is of

unknown derivation, and fungal remains are virtually

ubiquitous.) To classify the OM according to kerogen

type (Tyson, 1985), these palynofacies are rich in

humic kerogens (higher plant wood and parenchym-

atous tissues), much of this having altered to inertinite

(carbonised black wood). The sapropelic kerogen

component (structureless matter, largely plankton-

derived) is negligible and fusinite (fossil charcoal) is

rare. Any volcanogenic charcoal potentially entered

the open sea due to its slow waterlogging rate (cf.

Nichols et al., 2000).

All phytogenic clasts of known origin are terri-

genous, reflecting deposition proximal to land, shel-

tered from a strong marine influence. The lack of


macroflora, and fragmented nature of wood and leaf

material, infers these are allochthonous phytoclasts,

allowing their characteristics to be applied sedimento-

logically to interpret their transport histories and

depositional environments.

Because the palynodebris were from palynomorph-

releasing plants, the dearth of pollen and spores (Table

9) is unlikely to reflect low productivity, and

sporopollenin-walled grains doubtfully degraded prior

to wood and leaves. Whereas larger, more massive

phytoclasts settled upon lagoon floors near river

mouths, palynomorphs, particularly those trapping

air, probably floated into the marine realm. This

would necessitate slight horizontal water movements

within the lagoon. Nonetheless, shales trap rare palm

pollen, water-fern massulae, algal colonies and fungal

spores, these grains also occurring in MDP intertrap-

peans (Cripps, 2002). Well preserved, seemingly

autochthonous Botryococcus algae conceivably

bloomed following seasons of high rainfall, within

negligible salinity surficial layers of density- and

salinity-stratified lagoons.

Through the Amboli sequence, depletions in

angular clasts correspond to rises in AOM and/or

branching leaf-like fragments (Fig. 10), these

changes normally accompanying transitions into

shale facies (Table 1). Large angular clasts (e.g.,

Bom 13/98) accumulated when high runoff volumes

rapidly transported palynodebris to the basins. Bom

4/98 has the most small angular black clasts. A

lower velocity waterway would permit palynodebris

darkening through oxidation during protracted transit

times, selectively entraining finer grains, without

promoting significant rounding. High AOM percen-

tages in the Bandra samples and Bom 12/98, as well

as a relatively large concentration of parenchyma in

Bom 20/98, signify periods of diminishing river

currents, during which only the lightest material

reached the lagoons.

Large black angular clast abundances mimic the

trend of their small counterparts, implying that black

clast percentages are predominantly associated with

preservation effects. At Worli, negative correlations of

palynodebris exhibiting tracheids to angular black

clasts (Fig. 9) are likely to have resulted from runoff

fluctuations vertically displacing the oxygen mini-

mum zone. Palynodebris displaying tracheids

increased in importance when this zone rose, while

falls increased biodegradation, deteriorating ultra-

structural details and blackening palynodebris.

Branching leaf-like material forms the second most

common structured palynodebris type after angular

black clasts. Worli sediments appear to have accumu-

lated in a more distal setting than the Amboli

intertrappeans, typically beneath the oxygen-mini-

mum zone, with many particles exhibiting tracheids

or leaf ultrastructures. The presence of leafy material

in many Amboli and Worli sediments indicates that

the decay of vast quantities of introduced leaves

exhausted oxygen supplies, leaving much of the litter

to become buried beneath muds (e.g., Bom 10/98).

Bom 16/98, the only productive ash bed, contains a

disproportionately high percentage of leaf-like mate-

rial, and this is mostly pale. It is plausible that

pyroclastic debris fell into a river, charging the water

with sediment until it breached its banks, overwhelm-

ing and incorporating leafy floodplain plants. Upon

entering the lagoon, the prompt and chaotic dumping

of this material prohibited organic biodegradation.

Bom 16/98 phytoclast distributions are very different

to those of adjacent samples (Figs. 10 and 11), due to

its distinct deposition style. Diluted palynodebris

concentrations in other ash horizons have resulted

from extremely rapid ash accumulation rates. The

Amboli logs do not exhibit a constant palynofacies

evolution timeline (Figs. 10 and 11) because of

substantial disparities in shale and ash deposition

rates and compaction extents.

Although palynofacies data cannot delineate suc-

cessional seres following pyroclastic events, low OM

concentrations would be anticipated after catastrophic

eruptions, and these are not apparent above Amboli

extrusives. Ash Bom 16/98 terminates in black shales,

and Bom 10/98 is a very productive bed occurring

above ash Bom 9/98. It appears that Amboli vicinity

ash-falls were localised phenomena, imparting mini-

mal disturbance upon plant-life in the surrounding

watershed. The manifest lack of a consistent paly-

noclast distribution pattern following ash emplace-

ments is perhaps due to the erratic natures of the

fluvial and aerial transport mechanisms.

Minimal sorting has led to black wood exhibiting

angular shapes and notable size ranges through the

three sequences. It is thus surmised that much of the

parent vegetation grew behind the lagoon shores,

separated by stretches of muddy coastline. The


dominance of equant- over lath-shaped phytoclasts is

a reflection of debris buoyancy. Laths remain in

suspension longer than equant grains, their high

surface area to weight ratios retarding settling through

the water column (Tyson and Follows, 2000).

Palynofacies in which laths become increasingly

significant (e.g., Bom 3/98, Wo 2600) delineate times

of low lagoon energy, when sediment barriers to the

sea developed. The marginally lower mean E:L ratio

for Worli than Amboli suggests that Worli sedimenta-

tion occurred slightly further from river mouths.

Most phytoclasts have high thermal maturities (6.3

Amboli mean, 5.6 Worli mean; Fig. 11; Table 10).

While colour differences between palynodebris are

influenced by variations in OM type and pre-burial

oxidation (McArthur et al., 1992), diagenetic heating

by intrusions was important around Mumbai.

6. Discussion

Mumbai palynofacies are the products of tectonic

and igneous activity, the proximity of plant commun-

ities, runoff volumes and velocities, airborne particle

Fig. 12. Palaeogeographical reconstruction of Amboli, Worli and Bandra d

Singh and Sahni (1996); flora based upon current work, Bande (1992) an

fluxes and lagoon oxygen levels. The latter fluctuated

consequential to depth changes, salinity stratification,

turbulence and OM additions. Palynodebris sedimen-

tological and preservational responses to environ-

mental transformations produced the palynofacies

patterns present. Mumbai intertrappean phytoclasts

were deposited in extensive lagoons which experi-

enced mild horizontal currents but insignificant

vertical mixing.

Forests persistently occupied river watersheds

draining into the lagoons, on the solid, gently sloping

hinterland beyond their muddy shores, regardless of

sporadic regional pyroclastic volcanism. Terrigenous

OM was supplied by rivers following precipitation.

Although the Amboli, Worli and Bandra sections may

not be contemporaneous, their depositional facies are

likely to have coexisted concurrently in adjacent areas

(Fig. 12). Worli and Bandra sediments accumulated

further from the mouths of palynodebris-bearing

rivers and ash cones than those at Amboli.

Megaflora is scarce, although large land plant

organs have been identified (e.g., Podocarpaceae

wood; Bande, 1992). Sizeable fragments, such as

logs, would be most effectively transported by an

epositional environments (aerial view, not to scale). Fauna based on

d Bande et al. (1988).


aggressive, erosive drainage system. At Mumbai,

however, megafloral remains were deconstructed

through biological activity into smaller fragments,

light enough to be suspended in distributaries mean-

dering down the low-gradient back-shores to the

lagoons.

Charcoal is uncommon in Mumbai palynofacies,

although it might be anticipated in volcanic regions

(e.g., Uhl et al., 2004). Molten lava could promote

the vaporisation and/or aerobic ashing of flora it

advanced upon, rather than anaerobic charcoalifica-

tion. Sedimentological and geochemical evidence

points to Mumbai activity being more explosive

than previous MDP tholeiitic eruptions; Mumbai

surges presumably had lower expulsion temperatures

than those of mafic effusions, and potentially cooled

before contacting plants, as documented at Merapi,

Java by Kelfoun et al. (2000). OM was infrequently

scorched either within airborne plumes or by

volcanic bombs. Eruptions doubtless uprooted or

smothered plants, killing those worst affected, and

forcing others to defoliate. However, the palynofa-

cies reveal that few burned and, more importantly, a

significant percentage survived to produce both OM

and later generations.

Paroxysmal volcanic explosions repeatedly show-

ered Mumbai coasts, and organisms at bground zeroQmust have been subjected to serious environmental

trauma. However, palaeontological evidence con-

firms the establishment of enduring communities of

remarkable diversity and sensitivities. As well as the

magnitudes of volcanic impacts decreasing with

radial distance from ash vents, effects would be

dependent upon the direction of pyroclastic flow and

plume movements. Refugia clear of gravity flow

drainage routes and upwind of plumes could have

remained comparatively unscathed. Pyroclastic

releases can decouple into flows and clouds (cf.

Kelfoun et al., 2000) that generate at least two

deposits, and fluvial reworking into further accumu-

lations is possible. In such ways, one Mumbai

expulsion might be represented by several lagoon

layers, giving the semblance of more frequent

eruptions than actually prevailed.

If ashes did not reach Worli and Bandra because

pyroclastics were transported in negligible distances,

eruptions would have been of an inadequate magni-

tude to have injected materials into the stratosphere.

Hence, it is rational to conclude that no long-term

climatic ramifications resulted. Negi et al. (1993)

proposed that an offshore Mumbai extraterrestrial

impact triggered Deccan volcanism, and argued for a

bimodal origin for the K–T boundary extinctions. The

palaeontology of intertrappeans near the focus of this

alleged bolide cataclysm demonstrably contradicts

this. The establishment of a varied biota shortly after

the MDP eruptions calls into question their efficacy

regarding environmental devastation. These data add

credence to models implicating the Chicxulub impact

as the main cause of organism turnover at the K–T

boundary.

7. Conclusions

! This work highlights the imperative for future

investigators to identify irrefutable K–T bounda-

ries within the main Deccan tholeiitic succession,

and thereby divide intertrappeans into pre- and

post-boundary environments. Tertiary Deccan

intertrappeans are extremely scarce (e.g., Singh

and Kar, 2002), and the Danian Mumbai Island

Formation possesses facies and organisms that are

highly distinctive from all known MDP sediments.

! Mumbai facies are dominantly subaqueous, the

sediments being significantly more organic-rich

than those of the MDP. This is due to their coastal

palaeoenvironments having undergone syndeposi-

tional subsidence, although it may additionally

reflect the influence of an increasingly humid

Danian climate. Crustal extension supplied path-

ways for intrusions which heated basin sediments,

and created the Mumbai gravity high.

! Mumbai ecosystems represent the legacy of global

K–T boundary phenomena combined with local

and preceding intense regional Deccan flood basalt

activity. Numerous pyroclastic eruptions influ-

enced lagoon intertrappean accumulation; how-

ever, no evidence exists for extensive wildfires

ensuing or for floral mass mortality events. Rather,

abundant plant material entered the lagoons

throughout this active period.

! Based upon the current findings, the authors stress

a need to reassess the palaeoenvironments of other

continental flood basalt provinces that are tempo-

rally correlated with ecological crises.


Acknowledgements

The authors would like to thank the reviewers for

their constructive criticisms, and K.V. Subbarao (IIT

Mumbai) and A. Sahni (Panjab University) for their

invaluable comments and field support. Cuttings from

the Worli and Bandra tunnels were kindly donated to

this investigation by S.F. Sethna (St. Xavier’s

College). We are indebted to V. Pearson, J. Watson,

M. Sephton (Open University), R. Williams and T.

Clayton (University of Southampton) for their advice

and assistance with various analyses. This work was

conducted during the tenure of a project funded by the

Natural Environment Research Council.

References

Abe, A.A., Bicudo, J.E.P.W., 1991. Adaptations to salinity and

osmoregulation in the frog Thoropa miliaris (Amphibia,

Leptodactylidae). Zool. Anz. 227, 313–318.

Balasubrahmanyan, M.N., Snelling, N.J., 1981. Extraneous argon in

lavas and dykes of the Deccan volcanic province. In: Subbarao,

K.V., Sukheswala, R.N. (Eds.), Deccan Volcanism and Related

Flood Basalt Provinces in Other Parts of the World, Geological

Society of India Memoir, vol. 3, pp. 259–264.

Bande, M.B., 1992. The Palaeogene vegetation of peninsular India

(Megafossil evidences). Palaeobotanist 40, 275–284.

Bande, M.B., Chandra, A., Venkatachala, B.S., Mehrotra, R.C.,

1988. Deccan Intertrappean floristics and its stratigraphic

implications. In: Maheshwari, H.K. (Ed.), Palaeocene of India.

Indian Association of Palynostratigraphers, Lucknow, India,

pp. 83–123.

Batten, D.J., 1996. Palynofacies and palaeoenvironmental inter-

pretation. In: Jansonius, J., McGregor, D.C. (Eds.), Palynol-

ogy: Principles and Applications. American Association of

Stratigraphic Palynologists Foundation, Salt Lake City, Utah,

pp. 1011–1064.

Beane, J.E., Turner, C.A., Hooper, P.R., Subbarao, K.V., Walsh,

J.N., 1986. Stratigraphy, composition and form of the Deccan

basalts, Western Ghats, India. Bull. Volcanol. 48, 61–83.

Beaufort, D., Baronnet, A., Lanson, B., Meunier, A., 1997.

Corrensite: a single phase or a mixed-layer phyllosilicate in

the saponite-to-chlorite conversion series? A case study of

Sancerre–Couy deep drill hole (France). Am. Mineral. 82,

109–124.

Bhatia, S.B., Prasad, G.V.R., Rana, R.S., 1990. Deccan volcanism: a

Late Cretaceous event: conclusive events of ostracodes. In:

Sahni, A., Jolly, A. (Eds.), Cretaceous Event Stratigraphy and

Correlation of the Indian Non-marine Strata. International

Geological Correlation Project, Chandigarh, pp. 47–49.

Biswas, S.K., 1991. Stratigraphy and sedimentary evolution of the

Mesozoic Basin of Kutch, western India. In: Tandon, S.K.,

Pant, C.C., Casshyap, S.M. (Eds.), Sedimentary Basins of

India. Tectonic Context. Gyanodaya Prakashan, Nainital, India,

pp. 74–103.

Blanford, W.T., 1867. On the Traps and intertrappean beds of

western and central India. Mem. Geol. Surv. India 6, 137–162.

Blanford, W.T., 1872. Sketch of the geology of the Bombay

presidency. Rec. Geol. Surv. India 5, 82–102.

Bossuyt, F., Milinkovitch, M.C., 2001. Amphibians as indicators of

Early Tertiary bout of IndiaQ dispersal of vertebrates. Science

292, 93–95.

Chatterjee, S., Rudra, D.K., 1996. KT events in India: impact,

rifting, volcanism and dinosaur extinction. Mem. Queensl. Mus.

39, 489–532.

Chiplonkar, G.W., 1940. A new species of fossil frog from the Inter-

Trappean beds of Worli Hill, Bombay. J. Bombay Nat. Hist.

Soc. J. 40, 799–804.

Combaz, A., 1964. Les palynofacies. Rev. Micropaleontol. 7,

205–218.

Courtillot, V., Besse, J., Vandamme, D., Montigny, R., Jaeger, J.-J.,

Cappetta, H., 1986. Deccan flood basalts at the Cretaceous/

Tertiary boundary? Earth Planet. Sci. Lett. 80, 361–374.

Cox, K.G., Hawkesworth, C.J., 1984. Relative contribution of crust

and mantle to flood basalt magmatism, Mahabaleshwar area,

Deccan Traps. Philos. Trans. R. Soc. Lond., A 310, 627–641.

Cox, K.G., Hawkesworth, C.J., 1985. Geochemical stratigraphy of

the Deccan Traps at Mahabaleshwar, Western Ghats, India, with

implications for open system magmatic processes. J. Petrol. 26,

355–377.

Cripps, J.A., 2002. Environmental impact of Deccan Trap flood

basalt volcanism: assessment of regional floral responses to late

Cretaceous–early Tertiary activity. PhD thesis, The Open

University, Milton Keynes, UK, 502 pp.

Cross, A.T., Taggart, R.E., 1982. Causes of short-term sequential

changes in fossil plant assemblages; some considerations based

on a Miocene flora of the Northwest United States. Ann. Mo.

Bot. Gard. 69, 676–734.

Deshmukh, S.S., 1982. Volcanological and petrological appraisal on

Deccan basalts. Science Lecture Series, vol. 1. Gondwana

Geological Society, India, pp. 30–56.

Deshmukh, S.S., 1984. Geological and petrographic studies of the

Deccan basalt flows and intercalated volcanoclastic beds

encountered in drill holes in Bombay city and harbour areas.

Rec. Geol. Surv. India 113, 33–51.

Dessai, A.G., Bertrand, H., 1995. The bPanvel flexureQ along the

western Indian continental margin: an extensional structure

related to Deccan magmatism. Tectonophysics 241, 165–178.

Devey, C.W., Lightfoot, P.C., 1986. Volcanological and tectonic

control of stratigraphy and structure in the western Deccan

Traps. Bull. Volcanol. 48, 195–207.

Devey, C.W., Stephens, W.E., 1991. Tholeiitic dykes in the

Seychelles and the original spatial extent of the Deccan.

J. Geol. Soc. Lond. 148, 979–983.

Duncan, R.A., Pyle, D.B., 1988. Rapid eruption of the Deccan

flood basalts at the Cretaceous/Tertiary boundary. Nature 333,

841–843.

Erwin, D.H., Vogel, T.A., 1992. Testing for the causal relationships

between large pyroclastic volcanic eruptions and mass extinc-

tions. Geophys. Res. Lett. 19, 893–896.


Faure, G., 1986. Principles of Isotope Geology. Wiley-Europe,

Chichester, UK. 589 pp.

Gaffney, E.S., Sahni, A., Schleich, H., Singh, S.D., Srivastava, R.,

2003. Sankuchemys, a new side-necked turtle (Pelomedusoides :

Bothremydidae) from the Late Cretaceous of India. Am. Mus.

Novit. 3405, 1–10.

Gombos, A.M., Powell, W.G., Norton, I.O., 1995. The tectonic

evolution of western India and its impact on hydrocarbon

occurrences—an overview. Sediment. Geol. 96, 119–129.

Hardy, R., Tucker, M.E., 1988. X-ray powder diffraction of

sediments. In: Tucker, M.E. (Ed.), Techniques in Sedimentol-

ogy. Blackwell Science, Oxford, UK, pp. 191–228.

Hildebrand, A.R., Penfield, G.T., Kring, D.A., Pilkington, M.,

Camargo, A., Jacobsen, S.B., Boynton, W.V., 1991. Chicxulub

crater—a possible Cretaceous Tertiary boundary impact crater

on the Yucatan Peninsular, Mexico. Geology 19, 867–871.

Hofmann, C., Feraud, G., Courtillot, V., 2000. 40Ar/39Ar dating of

mineral separates and whole rocks from the Western Ghats lava

pile: further constraints on duration and age of the Deccan traps.

Earth Planet. Sci. Lett. 180, 13–27.

Hooper, P.R., 1990. The timing of crustal extension and the eruption

of continental flood basalts. Nature 345, 246–249.

Hooper, P.R., 1999. The winds of change: the Deccan traps, a

personal perspective. In: Subbarao, K.V. (Ed.), Deccan Volcanic

Province, Memoir of the Geological Society of India, vol. 43,

pp. 153–165.

Kaiser, H., 1997. Origins and introductions of the Caribbean

frog, Eleutherodactylus johnstonei (Leptodactlidae): manage-

ment and conservation concerns. Biodivers. Conserv. 6,

1391–1407.

Kaneoka, I., 1980. 40Ar–39Ar dating on volcanic rocks of the

Deccan Traps, India. Earth Planet. Sci. Lett. 46, 233–343.

Kaneoka, I., Haramura, H., 1973. K–Ar ages of successive lava

flows from the Deccan Traps, India. Earth Planet. Sci. Lett. 18,

229–236.

Kaneoka, I., Iwata, N., Takigami, Y., 1997. 40Ar–39Ar dating:

investigation of some technical problems and its application to

the Deccan Traps rocks and a unique meteorite from Antarctica.

Sci. Rep. Res. Inst., Tohoku Univ., Ser. A—Phys. Chem. Metall.

45, 47–51.

Kelfoun, K., Legros, F., Gourgaud, A., 2000. A statistical study of

trees damaged by the 22 November 1994 eruption of Merapi

volcano (Java, Indonesia): relationships between ash-cloud

surges and block-and-ash flows. J. Volcanol. Geotherm. Res.

100, 379–393.

Khosla, A., Sahni, A., 2003. Biodiversity during the Deccan

volcanic eruptive episode. J. Asian Earth Sci. 21, 895–908.

Lightfoot, P.C., Hawkesworth, C.J., Sethna, S.F., 1987. Petrogenesis

of rhyolites and trachytes from the Deccan Trap: Sr, Nd and Pb

isotope and trace element evidence. Contrib. Mineral. Petrol. 95,

44–54.

McArthur, J.M., Tyson, R.V., Thomson, J., Mattey, D., 1992. Early

diagenesis of marine organic-matter—alteration of the carbon

isotopic composition. Marine Geol. 105, 51–61.

Mitchell, C., Widdowson, M., 1991. A geological map of the

southern Deccan Traps, India and its structural implications.

J. Geophys. Soc. Lond. 148, 495–505.

Moore, P.D., Webb, J.A., Collinson, M.E., 1991. Pollen Analysis.

Blackwell Science, Oxford, UK. 216 pp.

Murakami, T., Sato, T., Inoue, A., 1999. HRTEM evidence for the

process and mechanism of saponite-to-chlorite conversion

through corrensite. Am. Mineral. 84, 1080–1087.

Negi, J.G., Agrawal, P.K., Singh, A.P., Pandey, O.P., 1992. Bombay

gravity high and eruption of Deccan flood basalts (India) from a

shallow secondary plume. Tectonophysics 206, 341–350.

Negi, J.G., Agrawal, P.K., Pandey, O.P., Singh, A.P., 1993. A

possible K–T boundary bolide impact site offshore Bombay and

triggering of rapid Deccan volcanism. Phys. Earth Planet. Inter.

76, 189–197.

Nichols, G.J., Cripps, J.A., Collinson, M.E., Scott, A.C., 2000.

Experiments in waterlogging and sedimentology of charcoal:

results and implications. Palaeogeogr. Palaeoclimatol. Palae-

oecol. 164, 43–56.

Owen, R., 1847. On the Batracholites, indicative of a small species

of frog (from Bombay). Q. J. Geol. Soc. Lond. 3, 224–225.

Pandey, O.P., Agrawal, P.K., 2000. Thermal regime, hydrocarbon

maturation and geodynamic events along the western margin of

India since late Cretaceous. J. Geodyn. 30, 439–459.

Pope, K.O., Baines, K.H., Ocampo, A.C., Ivanov, B.A., 1994.

Impact winter and the Cretaceous–Tertiary extinctions—results

of a chicxulub asteroid impact model. Earth Planet. Sci. Lett.

128, 719–725.

Rampino, M.R., Stothers, R.B., 1988. Flood basalt volcanism

during the past 250 million years. Science 241, 663–668.

Sabale, A.B., Vishwakarma, L.L., 1996. Zeolites and associated

secondary minerals in Deccan volcanics: study of their

distribution, genesis and economic importance. Gondwana

Geol. Mag. Spec., Vol. 2, 511–518.

Sen, G., 2001. Generation of Deccan Trap magmas. Proc. Indian

Acad. Sci., Earth Planet. Sci. 110, 409–431.

Sethna, S.F., 1999. Geology of Mumbai and surrounding areas and

its position in the Deccan volcanic stratigraphy, India. J. Geol.

Soc. India 53, 359–365.

Sethna, S.F., 2003. The occurrence of acid and intermediate rocks in

the Deccan volcanic province with associated high positive

gravity anomalies and their probable significance. J. Geol. Soc.

India 61, 220–222.

Sharma, R.K., Pandit, M.K., 1998. Ignimbrite deposits from North

of Mumbai in western part of Deccan flood basalt province,

India. J. Geol. Soc. India 51, 813–815.

Sheehan, P.M., Fastovsky, D.E., 1992. Major extinctions of land-

dwelling vertebrates at the Cretaceous–tertiary boundary, east-

ern Montana. Geology 20, 556–560.

Sheth, H.C., Ray, J.S., 2002. Rb/Sr–87Sr/86Sr variations in Bombay

trachytes and rhyolites (Deccan Traps): Rb–Sr isochron, or AFC

process? Int. Geol. Rev. 44, 624–638.

Sheth, H.C., Pande, K., Bhutani, R., 2001a. 40Ar–39Ar ages of

Bombay trachytes: evidence for a palaeocene phase of Deccan

volcanism. Geophys. Res. Lett. 28, 3513–3516.

Sheth, H.C., Pande, K., Bhutani, R., 2001b. 40Ar–39Ar age of a

national geological monument: the Gilbert Hill basalt, Deccan

traps, Bombay. Curr. Sci. 80, 1437–1440.

Singh, S.D., 2000. Petrography and clay mineralogy of intertrap-

pean beds of Mumbai, India. J. Geol. Soc. India 55, 275–288.


Singh, R.S., Kar, R.K., 2002. Palaeocene palynofossils from the

Lalitpur Intertrappean Beds, Uttar Pradesh, India. J. Geol. Soc.

India 60, 213–216.

Singh, S.D., Sahni, A., 1996. Bombay inter-trappeans: new data on

age and faunal affinities. Contributions to the XV Indian

Colloquium on Micropalaeontology and Stratigraphy, Dehra

Dun, India, pp. 465–469.

Subbarao, K.V., Sukheswala, R.N., 1979. Deccan volcanism and

related basalt provinces in other parts of the world: field guide

for excursions—Bombay and Khandala. International Group

Symposium. 29 pp.

Sukheswala, R.N., 1956. Notes on the field occurrence and

petrography of the rocks of the Bombay Island, Bombay. Trans.

Min., Geol. Metall. Inst. India 50, 101–126.

Sukheswala, R.N., Awate, G.S., 1957. Correlation of the ash beds

occurring in the western parts of Salsette Island, Bombay.

J. Univ. Bombay, 48–52.

Sweet, A.R., Braman, D.R., Lerbekmo, J.F., 1999. Sequential

palynological changes across the composite Cretaceous–Tertiary

(K–T) boundary claystone and contiguous strata, western

Canada and Montana, USA. Can. J. Earth Sci. 36, 743–768.

Tandon, S.K., 2002. Records of the influence of Deccan volcanism

on contemporary sedimentary environments in central India.

Sediment. Geol. 147, 177–192.

Tolia, N., Sethna, S.F., 1990. Lopolithic intrusion of basalt in the

intertrappeans at Amboli Hill, Jogeshwari, Bombay. J. Geol.

Soc. India 35, 524–528.

Tyson, R.V., 1985. Palynofacies and sedimentology of some late

Jurassic sediments from the British Isles and northern North

Sea. PhD thesis, The Open University, Milton Keynes, UK.

Tyson, R.V., Follows, B., 2000. Palynofacies prediction of distance

from sediment source: a case study from the Upper Cretaceous

of the Pyrenees. Geology 28, 569–571.

Uhl, D., Lausberg, S., Noll, R., Stapf, K.R.G., 2004. Wildfires in the

Late Palaeozoic of Central Europe—an overview of the

Rotliegend (Upper Carboniferous–Lower Permian) of the

Saar–Nahe Basin (SW Germany). Palaeogeogr. Palaeoclimatol.

Palaeoecol. 207, 23–35.

Vajda, V., Raine, J.I., Hollis, C.J., 2001. Indication of global

deforestation at the Cretaceous–Tertiary boundary by New

Zealand fern spike. Science 294, 1700–1702.

Vandamme, D., Courtillot, V., 1992. Paleomagnetic constraints on

the structure of the Deccan Traps. Phys. Earth Planet. Inter. 74,

241–261.

Vandamme, D., Courtillot, V., Besse, J., Montigny, R., 1991.

Palaeomagnetism and age determinations of the Deccan Traps,

India—results of a Nagpur–Bombay traverse and review of

earlier work. Rev. Geophys. 29, 159–190.

Whatley, R.C., Bajpai, S., Whittaker, J.E., 2003. The identity of the

non-marine ostracod Cypris subglobosa Sowerby from the

intertrappean deposits of peninsular India. Palaeontology 46,

1281–1296.

Widdowson, M., 1997. Tertiary palaeosurfaces of the SW Deccan,

western India: implications for passive margin uplift. In:

Widdowson, M. (Ed.), Palaeosurfaces: Recognition, Recon-

struction and Palaeoenvironmental Interpretation, Geological

Society of London Special Publication 120, pp. 221–248.

Widdowson, M., Pringle, M.S., Fernandez, O.A., 2000. A post K–T

boundary (Early Palaeocene) age for Deccan-type feeder dykes,

Goa, India. J. Petrol. 41, 1177–1194.

Documents

Coastal ecosystem responses to late stage Deccan Trap ... · Coastal ecosystem responses to late stage Deccan Trap volcanism: the post K–T boundary (Danian) palynofacies of Mumbai