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Lowrie, A.1, P.A. Dean2, Carol Blanton Lutken3, Erika Geresi3, Tom McGee3
(1) Consultant, Picayune, MS
(2) Consultant, Waveland, MS 
(3) University of Mississippi, University, MS

ABSTRACT: The Lower Mississippi Canyon: Possible Loci of Multiple Mass-Wasting Events

The prominent Mississippi Canyon, central Louisiana, offshore northern Gulf of Mexico, is the result of several mass-wastings starting circa 35,000 to 29,000 yrs. BP and ending some 15,500 yrs. ago. The canyon head-wall commences in the northernmost portion of the Mississippi Canyon Federal Lease Area near the shelfbreak (circa 28o35' N) and the canyon descends to the SE. The slumping thus occurred during and around the Last Glacial Maximum (approximately 24,000 to 17,000 yrs. BP). Along the upper Canyon, there is an eroded channel. Farther south, the Canyon becomes a subsurface feature near 28o05'N; there is seismic evidence for multiple erosion and subsequent infilling phases (cut and fill). The shallowest discrete erosional phase on single channel seismic lies between two salt features, is some 600 ms deep, and 8 to 15 km wide in an E-W trend. 
Deeper and to the east is another zone of apparent cut and fill. The data quality is poor and a unique interpretation is not possible. There may be evidence of several cut and fill phases. Arguing by analogy with the upper Mississippi Canyon, the separate cut-and-fill episodes may record older mass-wastings originating along the paleo-shelfbreak. Prograding sediments from either side of the Canyon are presently encroaching upon the Canyon floor. 
Seismic evidence from this southern extension of the Mississippi Canyon, thus, suggests that perhaps numerous great mass-wasting events have traversed this region. Mississippi Canyon-type mass-wasting events may have been common throughout at least the Quaternary.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.