Sequence stratigraphy and composition of late quaternary shelf-margin deltas, Northern Gulf of Mexico

Journal Article · Mon Apr 01 04:00:00 EST 1996 · AAPG Bulletin

OSTI ID:249785

Morton, R A ^[1]; Suter, J R ^[2]

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1. Univ. of Texas, Austin, TX (United States)
2. Conoco Inc., Houston, TX (United States)

High-resolution seismic profiles and foundation borings from the northwestern Gulf of Mexico record the physical attributes and depositional histories of several late Quaternary sequences that were deposited by wave-modified, river-dominated shelf-margin deltas during successive periods of lowered sea level. Each progressively younger deltaic sequence is thinner and exhibits a systematic decrease in the abundance and concentration of sand, which is attributed to a shift in the axes of trunk streams and greater structural influence through time. Our study shows that (1) contemporaneous structural deformation controlled the thickness of each sequence, the oblique directions of delta progradation, the axes of major fluvial channels, and the geometries of delta lobes at the shelf margin; (2) sedimentation was rapid in response to rapid eustatic fluctuations and structural influence; (3) boundaries of these high-frequency sequences are the correlative conformities of updip fluvial incision and coincide with downlap surfaces at the shelf margin; (4) the downlap surfaces are not true surfaces, but zones of parallel reflections that become progressively higher and younger in the direction of progradation; (5) the downlap zones are composed of marine muds that do not contain the high concentrations of shell debris expected in condensed sections; (6) possible paleosols capping the two oldest sequences are regressive surfaces of subaerial exposure that were preserved during transgressions; and (7) no incised valleys or submarine canyons breach the paleoshelf margin, even though incised drainages were present updip and sea level curves indicate several periods of rapid fall.

• OSTI ID: 249785
• Journal Information: AAPG Bulletin, Journal Name: AAPG Bulletin Journal Issue: 4 Vol. 80; ISSN 0149-1423; ISSN AABUD2
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
CONTINENTAL SHELF
EXPLORATION
GEOMETRY
GULF OF MEXICO
PETROLEUM
QUATERNARY PERIOD
RESERVOIR ROCK
SEDIMENTATION
SEISMIC SURVEYS
STRATIGRAPHY