Van Itterbeeck Et Al

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Sedimentology of the Upper Cretaceous mammal- and

dinosaur-bearing sites along the Raul Mare and

Barbat rivers, Hatxeg Basin, Romania

Jimmy Van Itterbeecka,), Emanoil Sasaranb, Vlad Codreab,Liana Sasaranb, Pierre Bultyncka,c

aAfdeling Historische Geologie, Katholieke Universiteit Leuven, Redingenstraat 18, 3000 Leuven, BelgiumbCatedra de Geologie-Paleontologie, Universitatea Babesx-Bolyai, Str. Kogalniceanu 1, 3400 Cluj-Napoca, Romania

cDepartement Paleontologie, Koninklijk Belgisch Instituut voor Natuurwetenschappen, Vautierstraat 29, 1000 Brussels, Belgium

Received 21 August 2003; accepted in revised form 22 April 2004

Abstract

Mammal and dinosaur localities in the Hatxeg Basin belonging to the Upper Cretaceous Sanpetru and Densusx-Ciula formations

have been known since the beginning of the last century. Recently, two new exposures with a comparable fauna have been

discovered in the Raul Mare valley. The sediments at these new sites, Totesxti-baraj and Na latx-Vad, have been compared with the

sediments at the previously known Pui site. At all three sites the deposits reflect a fluvial environment with coarse-grained channel

deposits channelized in fine-grained floodplain deposits with calcrete palaeosols. However, the nature of the calcrete palaeosols is

different at the three sites. At Totesxti-baraj and Na latx-Vad, hydromorphic calcic vertisols have been observed, and locally these

grade into groundwater calcretes. At Pui, the calcretes are associated with redbed deposits. Considering the similar

palaeogeographical situation and age of the deposits at the three sites, the difference in soil type should not be interpreted asa climatic difference but rather as a difference in the height of the palaeogroundwater table. The soils at Pui are indicative of

a general semi-arid climate. Those at Totesxti-baraj and Na latx-Vad do not directly reflect the climate, but rather the high seasonal

groundwater table. Differences in palaeohydrology between the sites are reflected in the fossil content with humidity-loving species

only occurring at the Raul Mare sites.

2004 Elsevier Ltd. All rights reserved.

Keywords: Hatxeg Basin; Upper Cretaceous; Continental sedimentology

1. Introduction

During the summers of 2001 and 2002, the Royal

Belgian Institute of Natural Sciences, in collaboration

with the Universitatea Babesx-Bolyai, conducted two

field studies in the Hatxeg Basin. Their main objectives

were the exploration of two new sites along the Raul

Mare River: Totesxti-baraj (Codrea et al., 2002) and

Na latx-Vad (Smith et al., 2002) and new excavations

near the village of Pui along the Barbat River (Fig. 1).

The first fossil discoveries in the Hatxeg Basin were

made as early as the end of the nineteenth century

(Nopcsa, 1900), but it was nearly a century later that the

first studies on microvertebrate remains were conducted

(see Grigorescu et al., 1999 for an overview). The site near

the village of Pui was the first microvertebrate site dis-

covered in the basin. Four multituberculate teeth, the first

from the Upper Cretaceous of Europe, were the most

important discovery (Grigorescu et al., 1985; Grigorescu

and Hahn, 1987; Radulescu and Samson, 1997) after

screen washing less than 100 kg of sediment. In spite of

www.elsevier.com/locate/CretRes

Cretaceous Research 25 (2004) 517e530

) Corresponding author.

E-mail address: [email protected] (J. Van

Itterbeeck).

0195-6671/$ - see front matter 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.cretres.2004.04.004
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the interesting nature of the fossils, no attempts were

made to sieve a larger quantity of sediment. During the

summer of 2001, however, an estimated 2500 kg of sedi-

ments were screen washed at Pui. The residue revealed

a rich assemblage of microvertebrate remains, including

teeth of multituberculates and numerous eggshells.

The two sites along the Raul Mare have yielded

the richest concentration of mammal remains from

the Upper Cretaceous of Europe: one tooth per

100 kg of sediments for the Totesxti-baraj site (Codrea

et al., 2002) and one per 40 kg of sediments for the

Na latx-Vad site (Smith et al., 2002). In addition to

these microvertebrate remains, Totesxti-baraj is the

richest dinosaur egg nest site in Romania with 11

nests of large megaloolithid eggs (Codrea et al., 2002)

and Na latx-Vad has yielded numerous dinosaur

Fig. 1. A, map of the Hatxeg Basin; inset showing the location of the town Hatxeg, Romania. The grey areas indicate the following sedimentary basins:

I, Rusca Montana ; II, Strei; III, Hatxeg; IV, Petrosxani (modified afterGrigorescu et al. 1994). Two frames locate the more detailed maps of: B, Raul

Mare and C, Barbat valleys. Grey rectangles indicate the location of the exposures.

518 J. Van Itterbeeck et al. / Cretaceous Research 25 (2004) 517e530


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remains concentrated in two pockets (Smith et al.,

2002).

The present paper considers the sedimentology of

these three important fossil sites in combination with the

fossils that have been recovered in order to provide

a palaeoecological interpretation of the sites.

2. General geological setting

The outcrops of the Upper Cretaceous sediments

studied are situated south of the town of Hatxeg. Like

the neighbouring basins (Fig. 1), the Hatxeg Basin is

a South Carpathian, Late Cretaceous, syn-orogenic basin

(see Willingshofer et al., 2001 for details). The South

Carpathians formed in two distinct orogenic phases.

During the Austrian phase (AptianeEarly Albian), the

Severin Basin was subducted and Supragetic nappes were

thrusted over the Getic Domain. The Laramide phase

(TuronianeMaastrichtian) caused the emplacement of

the Supragetic and Getic nappes on the Danubian

Domain and thick-skinned stacking of nappes in the

Danubian Plate. The Hatxeg Basin is located on the Getic

basement and evolved from a piggyback basin to an

extension-related basin, formed during orogenic collapse.

The two tectonic pulses are reflected in the sedimentary

cover of the basin as unconformity-bounded continental

sediments (Grigorescu et al., 1990). The Sanpetru and

Densusx-Ciula formations comprise continental sediments

deposited during andafter the Laramide orogenic pulse in

the central part of the basin.

All the sites described in this paper are generallyconsidered time equivalent of the Sanpetru Formation,

based on the comparable mammal and dinosaur fauna

(Grigorescu et al., 1999; Smith et al., 2002). Fission track

data (Willingshofer et al., 2001) show that the sediments

of the Sanpetru Formation all have a Danubian

Domain origin. The closest outcrops of Danubian rocks

lie within the Retezat Mountains. Palaeocurrent mea-

surements, and the nature of the clasts within the for-

mation (Grigorescu, 1983), also indicate that the Retezat

Mountains were the main source area of the Upper

Cretaceous continental sediments. Based on palynolog-

ical assemblages, the age of the Sanpetru Formation has

been estimated as Late Maastrichtian (Antonescu et al.,

1983), but according toLopez-Martnez et al. (2001), the

arguments for this age estimation are unreliable and need

to be revised. Recently, an Early Maastrichtian age has

been proposed based on palaeomagnetic measurements

(Panaiotu and Panaiotu, 2002).

3. Depositional framework of the Pui site

The exposures of the Pui site are situated in the bed

and the lower part of the banks of the River Barbat,

south of Pui. They are only accessible during the sum-

mer months when the water level is low. Those in

the riverbed are not continuous because recent pebble

lags sometimes cover the reddish Cretaceous sediments.

The thickness of the Quaternary cover varies and as

a consequence the incision of the river is sometimes

too shallow to generate exposures of Cretaceous sedi-ments in the riverbanks. Therefore the stratigraphic

column (Fig. 2) shows some gaps. However, suffi-

cient exposures have been measured to understand

the sedimentary environment. The strata are subhori-

zontal. The sediments are divided into green, coarse-

grained channel deposits and red fine-grained overbank

deposits.

3.1. Green conglomerates and sandstones

At the top of the exposures a conglomerate (mini-

mum thickness 0.3 m) has been observed (Fig. 3A).

Owing to the nature of the exposure, neither the exact

thickness nor the lateral extent of the deposit could be

measured. The maximum clast size is 10 cm, although

the average clast size lies within the pebble fraction. In

the lower part of the stratigraphic column, the green

(5G4/1e5G8/1) coarse deposits are predominantly

sandy. The occurrence of conglomerates is limited to

a basal pebble lag within these sandy deposits,

channelized in the underlying sediments. The conglom-

erates and sandstones are poorly cemented and friable.

No sedimentary structures have been observed withinthese coarse-grained deposits, probably owing to the

poor exposure.

The coarse green deposits represent the channels of

the ancient river. The palaeocurrent data for this site is

limited to one observation, where a single channel was

exposed on both sides of the river. This channel showed

an ENEeWSW orientation indicating a nearly easte

northeastward palaeoflow away from the Retezat source

region. The conglomeratic channel infill represents

a major channel with intense fluvial activity, while the

sandy channel infills represent minor and/or crevasse

channels. The true nature of these channels is difficult to

assess on basis of the available data.

At base of the channels, finger-like bioturbations

occur (Fig. 3C), which were formed after the erosion of

the channel and represent the burrows of organisms

living in the channel substrate. As sediments infilled the

channel, these bioturbations were also infilled with green

sands. Owing to the large number of these burrows, the

base of the sandy deposits is highly irregular (Fig. 3B).

Although previous fossil finds at the Pui site have been

made within the sandy deposits (Grigorescu et al., 1985),

no fossils were found within these facies during our field

work.

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3.2. Red silts with white calcretes

The majority of the outcropping sediments are

massive, red (5YR3/4) and silty. They are very rich in

mica and the clay fraction is dominated by smectites

(G 50%) and illite (G 30%), although small amounts of

chlorite and kaolinite also occur. Throughout the

sequence, white calcareous horizons are present within

the red sediments, ranging from separate calcareous

nodules a few centimetres in diameter (Fig. 3D) to

continuous layers with a maximum thickness of 30 cm

(Fig. 3F).

The red silts represent floodplain sediments deposited

during flood events. Between floods palaeosols de-

veloped on these sediments causing the red colouration

and the formation of calcrete nodules. No slickensides

have been observed in association with these calcrete

horizons. Based on the presence of a calcrete horizon

5

0

15

10

red massive silt, micaceous,

sometimes bioturbated

greenish grey sand, pebbly at the base,locally conglomerate

calcrete nodules, continuous calcrete

layers

not exposed

colour of sediment: green (5G4/1-5G8/1),

red (5YR3/4) and white

mud

ston

e

sand

ston

e

conglo

merate

dinosaur bone

accumulation called

"Pui Dino"

screenwashed layer

containing

gastropods,

mammal teeth and

dinosaur eggshellsFig. 3E

palaeocurrent direction

m

Fig. 3F

Fig. 3A

Fig. 3B Fig. 3D Fig. 3C

Fig. 2. Lithostratigraphic column of the Pui site with the localisation of the photographs ofFig. 3and a detailed sketch of the exposures near themain vertebrate sites.



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and the intense red colouring due to iron oxides, the

palaeosols can be classified as ferric calcisols according

to the classification ofMack et al. (1993). According to

Royer (1999), the presence of calcretes indicates annual

precipitation below 980 mm. Khadkikar et al. (2000)

further refined the range of precipitation for calcretes,

describing from Late Quaternary deposits in India

different associations of calcretes, dated by lumines-

cence, radiocarbon and archaeological techniques, and

linked to a calibrated oxygen isotope record that was

used as a climate proxy. Based on this correlation they

clearly demonstrated a straightforward relationship

between precipitation and calcrete association. Calcretes

associated with vertisols represent subhumid climates

with an annual precipitation of 500e900 mm; those

associated with red beds represent semi-arid climates

with precipitation ranging from 100e500 mm per year;

and those associated with sepiolite or palygorskite

represent arid climates with precipitation ranging from

50e100 mm per year. Ferric calcisols or the association

Fig. 3. Exposures at the Pui site: A, detail of conglomerate facies; B, green pebbly sand (CH) eroded in red silts (FF), base of the green sands (dotted

white line) highly irregular due to bioturbation; C, detail of finger-like bioturbation; D, calcrete horizon in red coloured silts; E, view on the main

fossil locality during the screenwashing; F, overview of the different exposed facies: calcretic palaeosols (P), green sandy channel deposits (CH) and

red silty overbank fines (FF).



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of calcretes with red beds at Pui are indicative of well-

drained conditions in a semi-arid climate.

A dinosaur bone accumulation has been found within

these fine-grained red deposits, consisting of a titano-

saurid humerus and about ten connected vertebrae.

Microvertebrate remains were recovered from red silts

(Fig. 3E) containing abundant gastropods overlying the

calcrete horizon that caps the dinosaur bone accumu-

lation. The gastropod fauna of the Hatxeg Basin has been

described by Antonescu et al. (1983) but is currently

under revision (Pana et al., 2001). The dominance of

typical terrestrial gastropods, mainly represented by

cyclophorid operculae (Pana et al., 2001) at the Pui site,

is consistent with well-drained soil conditions under

a semi-arid climate.

4. Depositional framework of the Totesxti-baraj

and Na latx-Vad sites

Totesxti-baraj and Na latx-Vad are isolated exposures of

Upper Cretaceous continental sediments in the bed of

the Raul Mare River. Exposures in the rest of the

riverbed are no longer accessible because of the

construction of dams, water reservoirs and public works

to improve bank protection; indeed, the continued

accessibility of the two new sites is endangered by such

works. They can be treated together because the same

association of sediments is present at both localities. As

at the Pui site, the exposures are only accessible during

the summer months when the water level is relatively

low; in the winter months they are completely flooded.

The strata strike roughly parallel to the riverbanks

(N40e50(E) and have a nearly vertical dip (75e80(N),

so that an aerial view of the outcrops (Figs. 4, 8A, C)

corresponds to a vertical section. Although no exposures

of Upper Cretaceous sediments had been reported

previously from the Raul Mare valley, their presence

in the subsurface of the valley had been demonstrated in

boreholes (Stancu et al., 1980). Based on the borehole

data, they were divided into three facies: conglomerates,

coarse-grained pale sandstones and fine-grained, clay-

rich, dark sandstones. According to our new observa-

tions on the exposures (Fig. 5), a number of alluvial

depositional facies are recognized; as a result, the

division ofStancu et al. (1980)is refined below.

4.1. Channel facies

The coarsest facies encountered is represented by

yellow medium- to coarse-grained pebbly sands. Al-

though conglomerates were recognized in the borehole,

such facies are not exposed. The sandy deposits, shaded

grey on Fig. 4, display sharp bases eroded into the

underlying sediment. At the base of these deposits, crusts

of iron oxides and hydroxides occur. They almost

certainly developed secondarily at the contact between

the permeable sands and the impermeable fines. The

sands are typically very friable and only locally cemented.

They generally show a fining-upward trend (Fig. 5),

grading up from yellow (10YR9/8), coarse-grained

pebbly sands at the base through trough and planar

N

95

7

6

01

4

8

3

2

1

HG

KB

A

E

F

D

I J

C

channel facies

overbank facies

palaeosol facies

0 200m

exposure covered

7.giF

5.giF

Fig. 4. Aerial views of Totesxti-baraj (upper part) and Na latx-Vad (lower part). The numbered black pentagons indicate the location of the differentfossil finds (all deposited in the collections of the Universitatea Babesx-Bolyai, Cluj-Napoca): AeK, dinosaur nests of Megaloolithus cf. siruguei; 1,

femur of sauropod; 2, 8e9, dinosaur eggs M. cf. siruguei, 3, turtle carapace. The black ovals indicate the fossiliferous pockets with numerous

vertebrate remains: 4, microvertebrates; 5, ornithopod; 10, sauropod. The rectangles indicate the exposure area sketched in Fig. 7and the solid lines

indicate the composite section ofFig. 5.



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Fig. 5. Composite section of the Na latx-Vad site (vertebrate fossils at 11 m and 54 m correspond respectively to locality 4 a


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cross-stratified sands in the middle to greenish-grey

(5GY8/1) horizontally laminated fine-grained sands at

the top. At the base some reworked fragments of

calcretes or overbank fines have been observed together

with unidentifiable wood fragments. The thickness of

these deposits varies mostly from 1.5 to 5 m, although

stacked channel units may have a composite thicknessof 10 m. The lateral dimensions of the individual sand

bodies vary from 20 m to the full length of the outcrop

(400 m). Based on geometry, two types of sand bodies

can be recognized: ribbon-like with a width/depth ratio

of less than 15 and sheet-like with a width/depth ratio

higher than 15 (Friend et al., 1979). Within the sheet-

like sandstone bodies, lateral accretion surfaces occur

(Fig. 7). At one place, a lens-shaped clay plug inter-

calated between two yellow sandy deposits has been

observed (Fig. 9A); its maximum thickness amounts to

1.20 m and it has a lateral extent of ca. 20 m. These

sediments are very rich in organic matter and numerous

palynomorphs have been recovered that are currently

under study. No charophytes or ostracods have been

found. Within this dark coloured clay, organic-stained,

pink sandy lenses occur.

The yellow sandy deposits are interpreted as the main

channels of an ancient alluvial river.Friend et al. (1979)

interpreted ribbon-like sandstone bodies as laterally

stable channels and sheet-like sandstone bodies as

laterally migrating channels. Indeed, lateral accretion

surfaces have only been observed within the sheet-like

sandstone bodies. The co-existence of these two types of

channels is not contradictory. Most of the observed

channels within the exposures are of the laterallymigrating type; the stable channels represent short-

lived channels that were infilled with sediments and

abandoned before the channel could migrate laterally.

At Totesxti-baraj, the exposure conditions did not

allow a reliable palaeocurrent measurement; at Na latx-

Vad, the lateral accretion surfaces, the cross-beds and

the erosional features indicate a northwestern palae-

ocurrent while a northward palaeoflow was measured

in the nearby stratotype of the Sanpetru Formation

(Fig. 6).

The clay plug is interpreted as an abandoned channel

fill. When the channel was isolated from the active

system, it filled with stagnant water, allowing organic

rich clay to accumulate. Short-lived connections between

the abandoned and active channels during flood events

resulted in the invasion of fast flowing sediment-loaded

water into the abandoned channel and the deposition of

the pink sandy lenses. The general fining-upward trend,

the succession of sedimentary structures, the presence of

lateral accretion surfaces, and the general facies associ-

ation are indicative of an ancient fluvial system of mean-

dering character. The observed widths and depths fall

within the ranges of meandering channels (Fielding and

Crane, 1987; Collinson, 1978).

4.2. Levee deposits

The sandy channel deposits wedge out laterally and

pass into dark coloured fines showing intense synsedi-

mentary deformation (Fig. 8D), indicative of a high

sedimentation rate; they have a lateral extension of only

a few metres. Apart from these deformation structures

they are not so different from the overbank fines. Thisfacies is grouped within the overbank facies on Fig. 4

and has not been given a separate code.

These deposits are interpreted as levee accumulations,

based on their limited lateral extent and their association

with the channel sediments. The high rates of deposition

induced from the deformation structures are consistent

with a levee deposit.

4.3. Crevasse channels and splays

Besides the yellow coloured sands, thinner bodies of

silver grey (5Y8/1) fine sands occur within the exposures

(Fig. 8F). Due to their limited thickness this facies, like

the levee deposits, is grouped within the overbank facies

onFig. 4and has not been given a separate code. These

sands occur as laterally continuous sheets that are locally

erosional into the underlying sediments. Often the ero-

sion was checked by the more indurated calcrete horizons

(Fig. 8E). The thickness of these deposits varies between

0.1 and 1 m. The top often shows finger-like burrows,

infilled with the overlying material. These fine- to very

fine-grained sands are uniform in colour, often show

parallel lamination, and are very rich in mica; they have

yielded a few isolated dinosaur eggs (Fig. 4, location 7).

Fig. 6. Palaeocurrent directions at Na latx-Vad and the surrounding

Maastrichtian and Palaeogene continental sediments (modified after

Miha ilescu, 1984).



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The erosion into the underlying sediments at the base

of these deposits represents minor breakthroughs where

crevasse channels cut into the riverbank and levees

during floods. The tabular sand bodies represent

crevasse deltas or splays fed by the crevasse channels.

These sediments cover the low-relief floodplain away

from the main channel.

4.4. Floodplain fines and palaeosols

Dark coloured, mica-rich mudstones (mostly silty)

make up the largest part of the outcrop (Figs. 4, 5, 8F).

The clay fraction of these fines is dominated by smectite

(ca. 85e90%), with minor amounts of illite (ca. 10%)

and chlorite (1%). Calcrete palaeosols occur as white

nodular layers, representing the Bk horizon of the

palaeosol, the soil horizon with calcium carbonate

enrichment. The difference in the number of calcretes

recorded from the Totesxti-baraj and Na latx-Vad sites

(Fig. 4) is due to the different exposure conditions.

Where these allow, most calcretes can be traced

throughout the entire length of the exposure. Depending

on the degree of palaeosol development, the colour of

these deposits varies from black (5Y2/1) to reddish

Fig. 7. Sketch with an interpretation of the exposure indicated on Fig. 4(lithofacies codes based onMiall, 1998). Photograph shows details of the

base of a sheet-like sandstone body with lateral accretion surfaces (indicated by white arrows).



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brown (10YR2/2e10R2/2). The more strongly devel-

oped soils give a more reddish hue without ever reaching

true red colours. Associated with the calcrete nodules,

wedge-shaped peds formed by two opposing sets of

concave-up curviplanes with polished surfaces and

slickensides have been observed. The fissures caused

by the curviplanes are typically infilled by calcite

cement, forming mm-thick calcite veins (Fig. 8G).

Based on the combined presence of a calcrete Bk

horizon and wedge-shaped peds with slickensides, the

palaeosols can be classified as vertic calcisols according

to the classification of Mack et al. (1993). As noted

above, according to Khadkikar et al. (2000), calcretes

associated with vertisols (= vertic calcisols) are indica-

tive of subhumid climates with an annual precipitation

ranging from 500e900 mm. However, the relationship

between climate and calcrete development is not so

straightforward.

If a calcrete develops under the influence of the

water table, it does not reflect the palaeoclimate but

rather the palaeogroundwater table (Aslan and Autin,

1996; Slate et al., 1996). Unlike vadose calcretes

(Z developed in well-drained sediments), hydromorphic

calcretes (Z formed within the influence of the ground-

water table) are grey in colour and have a sharp lower

boundary of carbonate accumulation. Vadose calcretes

have a zone of clay accumulation just above the zone

of carbonate accumulation whereas hydromorphic cal-

cretes do not show this relationship (Slate et al., 1996).

The calcretes at the Raul Mare sites typically have

Fig. 8. A, general view of the Totesxti-baraj site, taken from the dam south of the site. Water flows from bottom to top and follows the strike of the

layers. Where the flow crosscuts the layers, faults are present. The location of the faults is indicated by white dotted lines. B, egg nest H ( Fig. 4) at the

top of the Totesxti-baraj site. The black arrow indicates calcrete nodules. C, general view of the Na latx-Vad site, taken from the bridge south of the site,

people in the foreground (white ellipse) are digging out the sauropod pocket ( Fig. 4, locality 10). D, channel (CH) with coarse yellow sands

channelized in dark coloured floodplain fines (FF), black arrows indicating a calcrete horizon that follows the outline of the channel deposit (Na latx-

Vad site). E, detail of a crevasse channel (CS) with erosion into the underlying layers checked by a calcrete horizon (P) at Na latx-Vad site (white

staff = 0.3 m). F, general view of dark coloured floodplain fines (FF) with calcrete palaeosols (P) intercalated with light grey crevasse splay deposits

at Na latx-Vad site (white staff = 1 m). G, detail of concave-up curviplanes with slickensides infilled with calcite veins at the Na latx-Vad site.

Fig. 9. A, general view of clay plug, CH(FF), intercalated between two coarse yellow sandy deposits (CH) at Na latx-Vad site. White arrows indicate

pink sandy deposits within the clay plug (white staff = 1 m). B, fragment of floodplain limestone, white lines encircle microvertebrate remains, black

surfaces are egg shell fragments in top view. C, another fragment of floodplain limestone (Nalatx-Vad site), black lines are egg shell fragments in

lateral cross-section.



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a calcrete horizon, 10 cm thick with sharp upper and

lower boundaries, developed in dominantly grey sedi-

ments. They do not have a zone of clay enrichment at

the top. Therefore the calcretes at Totesxti-baraj and

Na latx-Vad are hydromorphic and reflect a seasonally

fluctuating groundwater table and not necessarily a more

humid climate.Hydromorphic calcretes form in the vadose zone

under the influence of the groundwater table but differ

from groundwater calcretes that are formed completely

within the saturated zone. One calcrete horizon at

Na latx-Vad was found to mimic the concave-up geom-

etry of a channel deposit (Figs 4, 8D), a characteristic

observed in groundwater calcretes (Khadkikar et al.,

1998). The presence of this groundwater calcrete corro-

borates the postulated high groundwater table respon-

sible for the development of the hydromorphic soils.

4.5. Taphonomy

With the exception of a few isolated eggs, all fossils

were found within the floodplain fines. In the following

section the taphonomy of the different fossil groups is

discussed for the Raul Mare sites.

4.5.1. Dinosaur eggs

As in the Provence Basin (Cojan, 1999; Cojan et al.,

2003), all the egg nests are associated with the Bkhorizon of the carbonate-rich palaeosols (Fig. 8B). The

palaeosol development postdates the nesting as calcar-

eous nodules can be observed within the eggs. The

excellent preservation of the eggs can be attributed tothe calcic environment of the Bk horizon and the large

number of egg nests recovered from the two sites

indicates that they were preferential nesting sites. All the

complete eggs found at both sites can be attributed to

the oospecies Megaloolithus cf. siruguei. Megaloolithus

sirugueiVianey-Liaud et al. (1994)is an oospecies with

an enhanced permeability. Successful incubation of this

type of egg requires the limitation of water loss to the

environment by evaporation. Different strategies to pre-

vent water loss exist: burial of the nest, or nesting in a

humid environment with a water-saturated atmosphere.

Nests of this type of egg are known from waterlogged

environments (Lopez-Martnez et al., 2000). The pres-

ence of this oospecies is thus another argument for a high

groundwater table at the sites in the Raul Mare valley.

4.5.2. Microvertebrate remains

The microvertebrate remains at the Totesxti-baraj site

were recovered from the dark coloured fines capping the

calcrete horizon of nest B (Fig. 4). At Na latx-Vad,

a pocket of such remains has yielded a rich fauna

of mammals. The vertebrate bones were recovered

from sediments composed mainly of eggshell debris,

a continental coquina (Fig. 9B, C). The lower part is

cemented into a true limestone, whereas the upper part,

less rich in eggshell debris, consists of black marl. As

a large number of dinosaur egg nests have been found at

the Raul Mare sites, the coquina could represent the

remains of a trampled nest, but this seems unlikely since

the dominant eggshell type in the coquina is the ornithoid

basic shell type and not M. cf. siruguei as could beexpected (Smith et al., 2002), and such a hypothesis does

not explain the associated concentration of microverte-

brate remains.

Limestone lenses of similar dimensions (2!2!0:3 m)

rich in microvertebrate remains have been described

from the Clarks Fork Basin, Wyoming (Bloch and

Boyer, 2001; Bowen and Bloch, 2002). These so-called

floodplain limestones were formed in ponded waters

atop groundwater-influenced soils on the floodplain,

into which microvertebrates were washed during epi-

sodic floods. In ponds, the conditions are ideal to

preserve the concentrated microvertebrate remains.

They are protected in the water from solar radiation

and repeated wetting and drying, and the calcareous

sediments in the ponds protect them from corrosion due

to acidic soil solutions.

A similar genesis is postulated for the vertebrate-rich

limestone lens at the Na latx-Vad site. The presence of

ponded water on the floodplain is highly probable

considering the, at least seasonally, high groundwater

table. The completeness of the skeletons retrieved from

the floodplain limestones of the Clarks Fork Basin is

highly variable, although complete and fairly complete

skeletons occur quite frequently (Bloch and Boyer,

2001). At Na latx

-Vad, only one limestone block has beenfound. The microvertebrate remains recovered from this

block are still being studied but they clearly represent

incomplete skeletons of different fossil taxa. They were

probably washed into the pond as disarticulate remains

and not as complete skeletons as is the case for the

Clarks Fork Basin limestones (Bloch and Boyer, 2001).

Gingerich (1987) mentioned the occurrence of

broken eggshells throughout a limestone lens in the

Clarks Fork Basin, as is the case for the Na latx-Vad

limestone. The freshwater limestones in the Clarks

Fork Basin represent unique habitats and have yielded

fossil assemblages that are different from those found

on the surrounding floodplain. Further study of the

microvertebrate remains and the eggshell debris of the

Na latx-Vad limestone lens will complete the faunal as-

semblage of the site and provide a better impression of

the biodiversity at the site during the Late Cretaceous.

4.5.3. Invertebrates

Numerous gastropods have been recovered from the

microvertebrate horizons at Totesxti-baraj and Na latx-

Vad. No cyclophorid operculae, the dominant element

in the gastropod assemblage of Pui, were recognized

within these assemblages.



13/14

4.5.4. Dinosaurs

Dinosaur finds in the Hatxeg Basin often consist of

disarticulated, isolated bones. Accumulations of disar-

ticulated bones of several dinosaur taxa have been found

locally in so-called fossiliferous pockets (Grigorescu,

1983). The dinosaur remains from the Na latx-Vad site

were also recovered from two different pockets. As inthe case of those described by Grigorescu (1983), they

contain mostly disarticulated bones. On the other hand,

they are smaller (2!1:5!0:5 m), and the bones in each

pocket seem to belong to a single, incomplete specimen;

the small and fragile bones are missing.

The two monospecific pockets at the Na latx-Vad site

represent the fossilized remains of two dinosaur

carcasses. The time between death and burial of these

animals was long enough to allow the disarticulation of

the skeleton by decay and scavenging but short enough

to allow good preservation of the bones. During the

flood event following the death of the animal the small

bones were washed away and the larger bones were

buried under the flood sediments.

5. Discussion and conclusions

The sediments at the Pui and the Raul Mare sites

represent a fluvial environment with coarse-grained

channel deposits eroded into floodplain fines with

calcrete palaeosols. The most distinctive difference

between the sites is the colour of the sediments and

the calcrete associations. The ferric calcisols at the Pui

site are indicative of a semi-arid climate with an annualprecipitation of 100e500 mm. The vertic calcisols at the

Raul Mare sites are hydromorphic and, therefore, not

representative of a more humid climate compared to the

Pui site, but of a seasonally high palaeogroundwater

table, its occurrence reflecting a combination of climatic

and topographic factors.

All of the sites described in this paper are generally

considered to be time equivalent to the Maastrichtian

Sanpetru Formation, based on the comparable mammal

and dinosaur faunas. The palaeolatitude of the Hatxeg

Basin during the Late Cretaceous varied between 21 and

29(N (Patrascu et al., 1993; Panaiotu and Panaiotu,

2002). According to Mack and James (1994), these

latitudes correspond to the dry subtropical zone in

which soil formation is dominated by the accumulation

of calcium carbonate in the Bk horizon, a soil type

present at both sites. Time equivalent deposits in the

same palaeogeographic position, as for the three sites

studied, are most likely to have been accumulated under

the same palaeoclimate. Therefore, the different calcrete

associations at the sites must be interpreted as resulting

from a difference in height of the palaeogroundwater

table, which had a significant influence on the occur-

rence and the preservation of fossil taxa. The high

groundwater table at the Raul Mare sites made them

ideal nesting grounds for the water-loving oospecies

Megaloolithus cf. siruguei; its abundant occurrence

makes Totesxti-baraj the richest dinosaur egg-nest site

of Romania. The high groundwater table also generated

ideal conditions for the preservation of microvertebrate

remains in floodplain ponds at the Na latx

-Vad site, wherethe richest concentration of mammal remains in the

Upper Cretaceous of Europe is found.

Acknowledgements

We greatly appreciate the time and effort of all the

participants in the field: Cristina Fa rcasx, Steffi M., Paul

Grovu, Paul Dica, Virgil Benedek, Cladiu Chendesx,

Sergiu Hosu, Suzanne Watrin, Ge raldine Garcia, Stijn

Goolaerts, Pascal Godefroit, and Thierry Smith. JVI is

a Research Assistant of the Fund for Scientific Re-

search, Flanders, Belgium (FWO, Vlaanderen) and

thanks his supervisor, Prof. Noel Vandenberghe, whose

constructive comments improved the paper significantly.

The field work was supported in particular by travel

grants from the Dirk Vogel Fonds, KUL to JVI. Field

vehicles were kindly provided by Fabricom NV (2001)

and Ford NV (2002). This paper is a contribution to

research project MO/38/004, financially supported by

the Belgian Federal Office for Scientific, Technical and

Cultural Affairs (DWTC-SSTC). J.R. Ineson and D.J.

Horne are kindly thanked for their reviews of the

original manuscript.

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