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The lower Tuscaloosa and Dantzler formations of east-central Louisiana and southeastern Mississippi are excellent examples of fluvial-deltaic sediments deposited in a semiarid climate. This deltaic deposition was subsequently slowly transgressed by the sea, and deposition of the middle marine Tuscaloosa occurred.
The Lower Cretaceous Dantzler sediments were deposited in a down-dip stranded (dry) basin (Perry basin) contemporaneous with uplift and erosion of the land to the north. Sedimentation continued in this manner throughout deposition of the lower Tuscaloosa. By this means the basins were filled with sediment, and deltas were built seaward of the older Edwards shelf edge. As the sea continued to transgress during deposition of the middle Tuscaloosa, all fluvial-deltaic deposition was restricted to the far updip areas. The result of this marine transgression and sediment deposition has been a tripartite relationship of depositional environments. Observations from electric logs, cores, and cuttings indicate a typical depositional sequence consists of a basal braided channel complex overlain by meander-belt point bars and topped by overlapping, shallow-marine, nearshore bars. Facies and depositional interpretations indicate that the lower Tuscaloosa and Dantzler are facies equivalents of one another and, as such, form a time-transgressive unit which spans the Upper-Lower Cretaceous boundary.
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