View
225
Download
1
Category
Preview:
Citation preview
Lecture 6:
Sedimentology: a refresher on basinal shales,
turbidites and deep-sea sediments
.
Models of Basin Fill
A digression – why deep-water interests?
Exploration areas in 2000, with deep-water in black
Stow and Mayall, 2000
Stow et al., in Reading’s text 1996
Controls on Deep-Water Sedimentation
TODAY: examine three aspects…….
• Turbidity currents and deep-water sediment dispersal• Submarine fans and sedimentary sequences• Black Shales and fine-grained sedimentation
loftingplume
ramb1<rflow<ramb2
descendingplume
rflow>ramb1
overflow
rflow<ramb
1
underflow
rflow>ramb2
interflow
ramb1<rflow<ramb2
ramb1
ramb2
Hyperpycnal
Hypopycnal
Mesopycnal or
Initiation of turbidity currents
•Slope failure (surge)•Waves/shelf reworking (surging)•Breaching (surging/sustained)•Sustained underflows (fluvial source; sustained)
Kneller & Buckee, 2000
Experimental Density Current
The idealised turbidity current: inception to deposition
...................the Bouma Sequence
Normally graded, very coarse to medium sand (and gravel)without tractional structures, erosive base with sole marks
… representing rapid deposition & turbulence suppression
Medium to fine sand with plane-parallel lamination… representing deposition on upper flow regime plane bed
Very fine sand to coarse silt with ripple cross-lamination, climbing ripples, wavy lamination and/or convolutions
… representing deposition in lower flow regime
Alternation of even silt and mud laminae… representing shear sorting during deposition of fines
Homogenous to finely laminated mud … representing deposition from low-density tail of turbidity current followed by settling from (hemi)pelagic suspension
Proximity to source area
TabcdeTa Tab Tabc
top-missing
downflow sortingthrough deposition
and bypassing
Proximal Distal
velocityaccumulative
depletive
NON-UNIFORM
time
waxingwaning
UNSTEADY STEADY
Temporal changes in velocity Spatial changes in velocity
from Christopher Kendall’s USC website
from Christopher Kendall’s USC website
Stow et al., in Reading’s text 1996
Dispersal of sediment to deepwater
from Christopher Kendall’s USC website
Mud-rich Fan
from Christopher Kendall’s USC website
Sand-rich Fan
from Christopher Kendall’s USC website
Mixed Sand-Mud rich Fan
from Christopher Kendall’s USC website
from Christopher Kendall’s USC website
from Christopher Kendall’s USC website
Chapin et al., 1994
The principal architectural elements in deep-water sedimentary systems
Stow and Mayall, 2000
The principal architectural elements in deep-water sedimentary systems
Stow and Mayall,
2000
The principal architectural elements in deep-water sedimentary systems
Stow and Mayall, 2000
from Christopher Kendall’s USC website
Scales of Hierarchy
from Christopher Kendall’s USC website
Droz et al., 2000
An example: the Zaire Fan
Droz et al., 2000
An example: the Zaire Fan
Stow and Mayall, 2000Erosion on fans
Pyles, 2008
Western Eire- types of facies
Western Eire – Ross Fm model??
Chapin et al., 1994
Western Eire –Ross Fm model??
Pyles, 2008
Western Eire – deep water architecture
Preservation of Organic Matter in Deep Marine Environments
Stow and Mayall, 2000
Wignall, 1994
Depositional processes and products of fine-grained sediments
Wignall, 1994
Oxygen levels in sedimentary environments
Western Eire – black shale
PaleoenvironmentPaleoecologyGeochemistry
References
See GEOL440 Sedimentology lectures (see website)Chapters by Walker and Postamentier in Facies Models Revisited
Chapin, M.A., Davies, P., Gibson, J.L. & Pettingill, H.S. 1994, Reservoir architecture of turbidite
sheet sandstones in laterally extensive outcrops, Ross Formation, western Ireland. In Weimer, P.,
Bouma, A.H. & Perkins, R.F (eds), Submarine fans and turbidite systems, GCSSEPM Foundation
15th Annual Research Conference, 53-68.
Collinson, J.D., Martinsen, O. Bakken, B. and Kloster, A. 1991, Early fill of the western Irish
Namurian Basin: a complex relationship between turbidites and deltas. Basin Research, 3, 223-
242.
Lien, T., Walker, R. & Martinsen, O., 2003. Turbidites in the Upper Carboniferous Ross Formation,
western Ireland: reconstruction of a channel and spillover system. Sedimentology 50: 113-148.
Stow, D.A.V., and Mayall, M. 2000 Deep-water sedimentary systems: New models for the 21st
century, Marine and Petroleum Geology, 17, 125-135.
Stow, D.A.V., Hue. A.-Y. and Betrand, P. 2001 Depositional processes of black shales in deep
water, Marine and Petroleum Geology, 18, 491-498.
Strachan, L.J. 2002 Slump-initiated and controlled syndepositional sandstone remobilization: an
example from the Namurian of County Clare, Ireland. Sedimentology, 49, 25–42.
.
Next week
Carboniferous seafloor communities,
paleoecology and trace fossils
Recommended