Sedimentary development of the Louisiana continental shelf related to sea level cycles: Part I—sedimentary sequences |
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Authors: | James M Coleman Harry H Roberts |
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Institution: | (1) Coastal Studies Institute, School of Geoscience, Louisiana State University, 70803 Baton Rouge, LA |
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Abstract: | Cyclic sequences occur worldwide in nearly every stratigraphic sequence; they are particularly well developed in marine deposits
associated with large river systems. Superimposed on those cycles attributed to shifting sites of deposition are those related
to high-frequency sea level changes. The large data base for this study (including 471 deep foundation borings, thousands
of line kilometers of high-resolution seismic, and sedimentological and dating analyses) represents the most complete information
on high-resolution chronostratigraphy and lithostratigraphy that is available on any modern continental shelf/upper slope.
These data are used to document sedimentological characteristics and spatial depositional patterns during three complete sea
level cycles over the entire continental shelf/upper slope of offshore Louisiana.
Sedimentation during periods of high sea level is characterized by: 1) thin, slowly accumulated depositional sequences, referred
to as condensed sections, 2) calcareous-rich deposits, including hemipelagic sediments and shell hashes, and 3) wide lateral
continuity. Sedimentation during periods of low sea level is characterized by; 1) variable-thickness, rapidly accumulated
sequences referred to as expanded sections, 2) coarse-grained elastic deposits, including abundant sands and gravels, and
3) well-defined depositional trends.
Even though the data set covers only a short period of geologic time (240 000 yrs), these high frequency events are responsible
for the deposition of excellent reservoir-quality facies in well-defined and predictable trends. |
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