Brian P. Coffey1, J. Fred Read2
(1) Exxon-Mobil, Houston, TX
(2) Virginia Tech, Blacksburg, VA
ABSTRACT: Sequence Stratigraphic Model For Paleogene Cool Water Carbonate-Siliciclastic Continental Shelf, North Carolina
Thin sectioned well cuttings through the 0 to 450 m thick Paleogene, North Carolina, integrated with available seismic data, were used to generate a sequence stratigraphic model for these mixed carbonate siliciclastic continental shelf units. Paleogene deposition was initiated by Late Cretaceous deep submergence of the shelf, and generated a distinctive shallow inner shelf, inner shelf break, deep shelf and shelf-continental slope break profile. The Paleogene succession overall consists of deep shelf marls up into bryozoan carbonates, up into siliciclastic units.
During supersequence lowstands, the inner shelf may have been exposed, and lowstand systems tracts evident on the seismic are lobe-shaped siliciclastic (?) units. Extensive hardgrounds formed at supersequence boundaries, whereas on the upper continental slope, erosion by the ancestral Gulf Stream occurred.
Transgressive systems tracts of supersequences on the inner shelf are midshelf bryozoan-echinoderm-facies that backstep onto inner shelf quartzose molluscan facies. On the deep shelf, the ancestral Gulf Stream remolded fine grained sediment units.
Highstand systems tracts on the inner shelf consist of fine wackestone-mudstone and downdip planktonic and spiculitic marls overlain by a progradational bryozoan-echinoderm grainstone and packstone. in near-shore locations. In near-shore locations, sea level fall caused these to be overlain by prograding back-barrier silts and shell beds, coastal sands, and sandy molluscan shoreface deposits. On the deep shelf during highstand, there was intense remolding of fine grained sediment bodies into elongate shelf parallel marl lobes by the ancestral Gulf Stream and local complete removal.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado