--> ABSTRACT: Sequence Stratigraphy, Architecture and Reservoir Potential of Late Pleistocene Lagniappe Delta Complex, Southeast of the Modern Mississippi Delta, N.E. Gulf of Mexico, by B. F. Long, V. Kolla, J. Durand, R. H. Fillon; #91020 (1995).

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Sequence Stratigraphy, Architecture and Reservoir Potential of Late Pleistocene Lagniappe Delta Complex, Southeast of the Modern Mississippi Delta, N.E. Gulf of Mexico

B. F. Long, V. Kolla, J. Durand, R. H. Fillon

A multi-disciplinary study based on data from four continuously cored boreholes and all available high-resolution seismic profiles reveal a delta complex (called here Lagniappe Delta complex-LDC) deposited beginning in oxygen isotope stage 8 or before. We report here only on the portion of the LDC deposited since isotope stage 5. This delta complex ranges in thickness from <30 ms in landward areas to about 100 ms in seaward areas, and trends mainly NE-SW, with subsidiary NW-SE trends. The base of this LDC is a well-developed, widespread condensed section that resulted from the maximum flooding of stage 5e. The deltaic succession deposited during stages 5a to 4 is thin and fine-grained. The condensed section of isotope stage 3 is generally week but is more strongly deve oped in the seaward part of the delta than in the landward part. Delta sediments deposited in the isotope stage 2 sequence are thick (up to 100 ms), with coarsening upward grain-size trends. The clinoforms of the LDC dip from <1° SW in landward areas to 7°-10° SW in seaward areas. The topsets and updip portions of the foresets of the delta complex are sand-rich. In addition, sediment wedges derived from updip slumping and erosion (during active delta-growth and abandonment, respectively) overlie the downdip portions of foresets and bottom sets, and may contain mass-transport and gravity-flow deposits that are in part sand-prone. The delta front sediments are overlain by channel (river)-fills with coarse grained deposits up to 20-25 ms thick, having blocky or fining upwa d gamma log shapes. The LDC channel complex essentially consists of four main NE-SW trending channels with subsidiary channels in NW-SE trends. The occurrence of numerous delta lobes within LDC implies autocyclic delta switching in addition to the effects allocyclic sealevel changes. Overlying the LDC, but seaward of the offlap break, there is a wedge shaped onlapping unit (0-15 ms thick) that may represent deepwater deposition subsequent to lobe abandonment during the last sea level rise.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995