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Title: Storm-generated accumulation of nummulite banks in Eocene of Cairo, Egypt

Abstract

Nummulite banks which are common in neritic and shelf-edge facies in many parts of the Tethyan Eocene have been mainly regarded as reef-type buildups so far. However, stratification and biofabrics of such banks in the middle Eocene around Cairo demonstrate the importance of physical processes in molding nummulitic sediment bodies. Initiation of a nummulite bank at the Giza Pyramids Plateau is localized by a preexisting paleohigh, inherited from Late Cretaceous tectonism. On this submarine swell (about 1 x 1.5 km wide), ecological conditions were optimal for a flourishing Nummulites gizehensis-community, resulting in greater sediment production than in adjacent environments. Growth of the nummulite bank into a sediment body over 30 m (98 ft) in thickness and more than 1 km (.62 mi) in length is strongly enhanced by mechanical concentration of nummulite tests into coquinal packstones. These are interpreted to be a product of storm-generated winnowing. Paleoecological evidence shows that nummulite banks are largely an in-situ lag deposit. Periods of nummulite settlement are episodically disturbed by catastrophic storm events, which result in winnowing and local accumulation of the heavier bioclasts. During shallowing, patch reefs and a back-bank lagoon formed on the landward side of the bank. This facies association maymore » be regarded as a model for hydrocarbon reservoirs. The high intraparticle porosity in nummulite tests (54%) makes the banks a potential reservoir, while adjacent and overlying lagoonal mudstone and wackestone may serve as source and cap rocks.« less

Authors:
Publication Date:
Research Org.:
Univ. of Miami, FL
OSTI Identifier:
6184568
Report Number(s):
CONF-8304200-
Journal ID: CODEN: AAPGB
Resource Type:
Conference
Journal Name:
Am. Assoc. Pet. Geol., Bull.; (United States)
Additional Journal Information:
Journal Volume: 67:3; Conference: Annual AAPG/SEPM/EMD/DPA convention, Dallas, TX, USA, 17 Apr 1983
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 03 NATURAL GAS; EGYPTIAN ARAB REPUBLIC; RESERVOIR ROCK; GEOLOGIC HISTORY; PETROLEUM GEOLOGY; DEPOSITION; NATURAL GAS DEPOSITS; PETROLEUM DEPOSITS; POROSITY; REEFS; RESOURCE POTENTIAL; AFRICA; DEVELOPING COUNTRIES; GEOLOGIC DEPOSITS; GEOLOGIC STRUCTURES; GEOLOGY; MINERAL RESOURCES; RESOURCES; 020200* - Petroleum- Reserves, Geology, & Exploration; 030200 - Natural Gas- Reserves, Geology, & Exploration

Citation Formats

Aigner, T. Storm-generated accumulation of nummulite banks in Eocene of Cairo, Egypt. United States: N. p., 1983. Web.
Aigner, T. Storm-generated accumulation of nummulite banks in Eocene of Cairo, Egypt. United States.
Aigner, T. 1983. "Storm-generated accumulation of nummulite banks in Eocene of Cairo, Egypt". United States.
@article{osti_6184568,
title = {Storm-generated accumulation of nummulite banks in Eocene of Cairo, Egypt},
author = {Aigner, T},
abstractNote = {Nummulite banks which are common in neritic and shelf-edge facies in many parts of the Tethyan Eocene have been mainly regarded as reef-type buildups so far. However, stratification and biofabrics of such banks in the middle Eocene around Cairo demonstrate the importance of physical processes in molding nummulitic sediment bodies. Initiation of a nummulite bank at the Giza Pyramids Plateau is localized by a preexisting paleohigh, inherited from Late Cretaceous tectonism. On this submarine swell (about 1 x 1.5 km wide), ecological conditions were optimal for a flourishing Nummulites gizehensis-community, resulting in greater sediment production than in adjacent environments. Growth of the nummulite bank into a sediment body over 30 m (98 ft) in thickness and more than 1 km (.62 mi) in length is strongly enhanced by mechanical concentration of nummulite tests into coquinal packstones. These are interpreted to be a product of storm-generated winnowing. Paleoecological evidence shows that nummulite banks are largely an in-situ lag deposit. Periods of nummulite settlement are episodically disturbed by catastrophic storm events, which result in winnowing and local accumulation of the heavier bioclasts. During shallowing, patch reefs and a back-bank lagoon formed on the landward side of the bank. This facies association may be regarded as a model for hydrocarbon reservoirs. The high intraparticle porosity in nummulite tests (54%) makes the banks a potential reservoir, while adjacent and overlying lagoonal mudstone and wackestone may serve as source and cap rocks.},
doi = {},
url = {https://www.osti.gov/biblio/6184568}, journal = {Am. Assoc. Pet. Geol., Bull.; (United States)},
number = ,
volume = 67:3,
place = {United States},
year = {Tue Mar 01 00:00:00 EST 1983},
month = {Tue Mar 01 00:00:00 EST 1983}
}

Conference:
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