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Main Pass and Viosca Knoll, Stratigraphic and Structural Study

J.C. Fluker, III
J.C. Fluker, III
Tenneco Oil Company
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January 01, 1983


This line, east of the Mississippi River Delta in Main Pass and Viosca Knoll areas, trends in a northwest-to-southeast direction as indicated on the location plat.

The line displays thick transgressive and regressive sections of Tertiary and Quarternary clastic sediments deposited in offlapping wedges over carbonate beds of Cretaceous age. Both extensional glide plane faults and salt tectonic structuring can be seen. A piercement salt dome at the southeast end of the seismic profile shows its active growth history by the thinning of section onto it.

The northwestern and southeastern ends of the seismic line show the effect of salt diapirism.

Large down-to-the-north faults appear to be associated with breaks in the Cretaceous carbonate section and are probably the structural weak point that allowed the salt to pierce through the sedimentary column. Increased deposition of sediment into the low side of the faults is observed.

Lystric cults are observed in the center of the line (as labeled) on the northwestern edge of the syncline associated with the salt diapir at the southeastern end of the seismic line. These faults are syndepositional, allowing the build up of sediment on their downthrown side and the movement of sediment basinward.

Prograding sediment wedges are noted above the 2.0 sec time line between shotpoints 445 and 265.

These have been labeled as such and arrows indicate the cycle terminations showing the direction of progradation.

An unconformity/erosional surface (as labeled) is noted above and below the 1.0 sec time line between shotpoints 337 and 277. This is evidenced by the termination of cycles into chaotic event zones. This leaves an impression of a scour and fill feature possibly caused by a gravity flow or turbidity/density current.

Fill patterns can be observed by the onlapping cycle terminations seen between shotpoints 193 and 73.

These onlapping events can be noted from the 4.3 sec to 1.0 sec time lines. The fill patterns provide examples of onlap and prograded fill.

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AAPG Studies in Geology

Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces

A. W. Bally
A. W. Bally
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American Association of Petroleum Geologists
ISBN electronic:
Publication date:
January 01, 1983




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