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

Conference · Fri Mar 01 00:00:00 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-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

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