οἱ λίθοι κράξουσιν (Luke 19:40)
Flood Geology Challenge #7:
The East Texas Basin is one of the three interior basins of the greater Gulf Coast Basin. It covers the majority of the eastern third of the state of Texas. The history of the basin rightly starts in the early Mesozoic. In the Triassic the basin began rifting with the axis of extension trending NNE-SSW. Around Wood and Upshur Counties, the rift takes an abrupt turn to the east and heads toward Louisiana. Seismic data show the rift and syn-rift geometries, and well data reveal that the Triassic section consists of continental redbeds and volcanoclastics as well as some evaporite (salt) deposits.
Although this was a failed rift (the Gulf of Mexico spreading obviously happened to the south), the axis formed the basin center through much of the Jurassic. In the Jurassic a very expansive evaporite was deposited. It is called the Louann Salt. It was deposited as far north as Hopkins and Franklin Counties, and it has been “squeezed” as far south as the Sigsbee Escarpment in the Gulf of Mexico. This escarpment is easily visible on Google Earth as the transition between relatively shallow to deep water. Immediately above the salt is the well-sorted cross-bedded Norphlet Sandstone. It has characteristics of modern-day desert sands and it is thus interpreted as eolian (or wind-blown sand). Above the Norphlet is the Louark Group which consists of the Smackover Limestone, Buckner Anhydrite and Cotton Valley (Haynesville) Limestone.
As the basin began to subside towards the south during Louark deposition, a small bathymetric relief turned into a shelf margin. Along this shelf margin pinnacle reefs developed in what is now Milam, Robertson and Leon Counties. These reefs can be prolific natural gas producers because of their relatively high porosity. Landward of the pinnacle reef trend the limestone can be a very clean oolitic facies in places. This is very similar to the modern-day carbonate platforms in the Bahamas.
Above the Louark Group is a thick succession of Upper Jurassic clastics. The Bossier Formation is a shale that locally encases sandstones interpreted as part of a prograding deltaic sequence. Numerous core and well log data confirm this interpretation. As this delta prograded over the older carbonate ramp, it triggered the Louann Salt into motion. This sediment loading began to push down and out and start the salt moving vertically up to the sea floor. Where it could keep up with sediment input, the salt formed vertical columns called diapirs. These diapirs are easily seen on seismic data and in some cases even go to the present-day surface where they are mined such as in Van Zandt County.
El Papalote salt diapir in the La Popa Basin, Mexico. This diapir is similar to the ones in the East Texas Basin. The whitish circular object is the gypsum cap to the vertical salt column buried underground. Note the vertical to overturned resistant limestone beds surrounding the diapir. These are local to the diapir, because carbonate growth favored the slightly higher topography of the diapir rather than the flat sea floor around it. These prove that tranquil, not catastrophic, deposition occurred as this salt diapir grew (photo by author).
Above the Bossier deltaic facies is the more sand-rich Cotton Valley Formation and the redbeds of the Travis Peak Formation. From the well and seismic data, one can envision a carbonate shelf that was drown by a delta which prograded out into the basin followed by coastal and then fluvial or terrestrial sand deposition. Intermittently in the sequence the basin flooded back which allowed thin beds of limestone to be deposited.
In the Cretaceous, the shelf margin really began to grow with intensity. A long linear shelf margin reef trend is known in the Pettet (Sligo) and Edwards Formations. The Cretaceous is dominated by carbonate deposition with interbeds of shales and evaporites. Near the salt diapirs, which were growing vertically through this period, reefs would grow as the diapirs made for a nice bathymetric high to nucleate from (see the El Papalote diapir in the picture above). At the end of the Cretaceous, the extensive Austin Chalk Group can be seen throughout the area.
In the early Cenozoic, shales and siltstones dominated the basin as the sediment input system began to prograde out to its present position. Coals are also found in this interval in the Eocene Wilcox Formation. The present-day surface of East Texas is an angular unconformity where middle to upper Tertiary sediments have been eroded down almost completely flat while the layers themselves dip towards the south. This suggests a significant amount of sediment exhumation.
To say that this geologic succession was deposited in a year-long catastrophic Flood would be to ignore the fact that a significant portion of this section cannot be deposited by turbulent sediment-laden waters. The redbeds and eolian sediments are not even deposited by marine waters at all. The reefs in the Jurassic and then in the Cretaceous are obviously in-situ because they map along bathymetric highs, and are thus not random or transported from another location. The two distinct salt packages are the product of shallow marine water and evaporation. The only conceivable place for the Flood to have influenced the geology is in the thick Tertiary sequence, but then you have to explain the coal beds which form from decaying plant material in swamps which are at sea level. If the Flood covered all the mountains it would have had to abate to this level then Flood again, then abate to erode the landscape down to its present level. To be honest, there is no place for the Flood in this geologic succession. Again, that is not to say it did not happen, but it clearly had no geologic influence on the East Texas Basin.
As if this was not enough proof, there is evidence from seismic and well data that the Paleozoic is represented here as well. Below the relatively flat rift sequence of the early Mesozoic, extremely steep dipping beds can be seen which are thrust over each other, then eroded nearly flat at the top. Deep wells have penetrated this section and found that it is extensively metamorphosed. This fits nicely with the geologic interpretation that Gondwanaland (Africa) collided with Laurentia (North America) in the late Paleozoic forming the Ouachita, Ozark and Appalachian Mountains. Here in East Texas, the mountains were eroded nearly flat. Then the story of the East Texas Basin truly begins. Not only is the Flood incapable of producing the geology of the East Texas Basin, it surely cannot explain the basin and tectonics that lie beneath the basin. The Flood fulfilled its purpose, but that purpose was not to produce the geologic layers of the earth.
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