Seismic and geologic characteristics of drowning events on carbonate platforms
- Amoco Production Co., Houston, TX (United States)
- Nanhai East Oil Corp., Guangzhou (China)
Carbonate platform drowning events are recorded in Upper Jurassic-Lower Cretaceous carbonates of the Baltimore Canyon area, offshore US East Coast, and lower Miocene carbonates of the Pearl River Mouth Basin, offshore People's Republic of China. Cursory examination of seismic data from both areas would indicate that the platforms fit the classic definition of a drowning unconformity. However, detailed lithologic and paleontologic data indicate that the depositional/erosional hiatuses vary widely in each area, from 0-25 m.y. in the Baltimore Canyon area, to a condensed section with no hiatus in the Pearl River Mouth Basin. The sedimentary sequence produced during drowning in both areas is gradational with underlying shallow platform carbonates and, in some places, overlying deeper marine limestones and shales. The generalized facies models proposed for drowning events suggest that they may appear as instantaneous or gradual changes in geologic and seismic data. Because of this resolution problem, a distinction should be made between seismically and geologically defined unconformity surfaces. The geologic characteristics of drowning events on carbonate platforms include a gradational lower (and sometimes upper) contact, chemical sedimentation (glauconite, phosphate), open-marine shelf sediments, and a variable hiatus at the upper boundary. Data from isolated open-ocean atolls (Pearl River Mouth Basin) indicate that they respond differently to drowning, showing an asymmetric decrease in shallow platform environments as drowning occurs. Proper recognition by a geoscientist of the seismic and geological characteristics of drowning events can lead to better reservoir and seal estimates, and the correct reconstruction of the depositional, tectonic, and eustatic histories of an area.
- OSTI ID:
- 5848350
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Vol. 74:10; ISSN AABUD; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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030200 -- Natural Gas-- Reserves
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58 GEOSCIENCES
580000 -- Geosciences
ASIA
ATLANTIC OCEAN
BALTIMORE CANYON
CARBONATE ROCKS
CENOZOIC ERA
CHINA
CRETACEOUS PERIOD
DEPOSITION
EXPLORATION
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOLOGIC TRAPS
GEOLOGY
GEOPHYSICAL SURVEYS
JURASSIC PERIOD
LITHOLOGY
MESOZOIC ERA
MINERAL RESOURCES
MIOCENE EPOCH
PETROLEUM DEPOSITS
PETROLEUM GEOLOGY
RESERVOIR ROCK
RESOURCES
ROCKS
SEAS
SEDIMENTARY BASINS
SEDIMENTARY ROCKS
SEISMIC SURVEYS
STRATIGRAPHY
SURFACE WATERS
SURVEYS
TERTIARY PERIOD