Evidence for deep-water evaporite deposition in the Miocene Kareem Formation, Gemsa basin, eastern Egypt

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:7158697

May, J A; Stonecipher, S A; Steinmetz, J C ^[1]; Dyess, J N ^[2]

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1. Marathon Oil Co., Littleton, CO (United States)
2. Marathon Petroleum Egypt, Maadi (Egypt)

The correct interpretation of intercalated Miocene siliciclastics and evaporites of Gemsa basin is crucial for understanding early rift tectonics of the Gulf of Suez, pinpointing the timing of isolation of the Gulf from the Mediterranean, and developing exploration plays. Evaporites of the Kareem Formation comprise celestites and massive, 'chicken-wire,' and laminated anhydrites. Although previously interpreted as sabkha deposits; sedimentologic, petrographic, and paleontologic analyses indicate these evaporites more likely formed in a submarine setting. Marls that encase the evaporites contain a diverse and abundant assemblage of nannoplankton, planktonic foraminifera, diatoms, pteropods, and fish scales indicative of basinal deposition. Associated turbidites also denote deep-water sedimentation. The paucity of benthic diatoms and foraminifera, plus the presence of unburrowed shales, phosphate nodules, early ferroan carbonate cements, and authigenic pyrite, suggest periodic anoxic, or at least disaerobic, bottom waters. These sequences probably represent partial isolation of the Gulf of Suez by middle Miocene, producing periodic basin restriction and evaporative drawdown. Episodes of increasing salinity likely caused the progressive decreases in foram abundance and diversity in marls beneath the anhydrites, culminating in subaqueous evaporite formation. Diverse, indigenous nannoplankton assemblages from shale seams within the anhydrites suggest Gemsa basin was stratified; shallow open-marine conditions coexisted with anhydrite crystallization from deeper hypersaline waters.

• OSTI ID: 7158697
• Report Number(s): CONF-910403--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200 -- Petroleum-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580000* -- Geosciences
AFRICA
ALKALINE EARTH METAL COMPOUNDS
ANHYDRITE
CARBONATE MINERALS
CARBONATE ROCKS
CENOZOIC ERA
DEPOSITION
DEVELOPING COUNTRIES
DOLOMITE
EGYPTIAN ARAB REPUBLIC
EVAPORITES
EXPLORATION
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GULF OF SUEZ
LIMESTONE
MIDDLE EAST
MINERAL RESOURCES
MINERALOGY
MINERALS
MIOCENE EPOCH
ORIGIN
OXYGEN COMPOUNDS
PALEONTOLOGY
PETROGRAPHY
PETROLEUM DEPOSITS
PRECIPITATION
RED SEA
RESOURCES
RIFT ZONES
ROCKS
SEAS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
STRONTIUM COMPOUNDS
STRONTIUM SULFATES
SULFATE MINERALS
SULFATES
SULFUR COMPOUNDS
SURFACE WATERS
TERTIARY PERIOD