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Abstract: Geologic Study of Upper Cretaceous (Cenomanian) Buda Limestone Outliers in Northeast Texas

Donald F. Reaser, William C. Dawson

Buda Limestone is the youngest Cretaceous unit within the Comanche Series, a major cycle of deposition in Texas. The top of the Buda is a submarine discontinuity in the Gulf Coast area. In northeast Texas, the formation is absent by erosion or thinned to a few meters or less. Erosional remnants of Buda crop out at several places in Denton County near Grapevine Lake. There the hard, 0.5-meter fossiliferous limestone yields a variety of mollusks including ammonites, bivalves, and gastropods as well as calcareous algae, bryozoans, corals, and echinoids. The upper part of the rock is marked by large (2.5 cm in diameter), thalassinoidean-type burrows that are filled with iron oxide "piped" downward from the superjacent Woodbine Sandstone. At some places near Bolo Point, the ro k is bored by the bivalve Gastrochaena and encrusted by the hexacoral Orbicella=Montastrea; these features suggest the development of a hard ground in this area. Petrographically, the Buda ranges from a glauconitic, mollusk-echinoderm biomicrite to a bryozoan-coral-bearing biomicrite.

The Buda was deposited on the upper part of a shallow shelf in highly aerated water. Samples from the Buda near Bolo Point have ^dgr18O values that range from -4.62 to -5.32 (PDB) and ^dgr13C values that range from -1.32 to -1.79 (PDB). These data are characteristic of average Phanerozoic marine limestones. Tentative plate reconstructions by Kraus suggest that Buda in north Texas was transported more than 36° (3,370 km) westward and 3° (330 km) northward from the deposit during the last 98 million years.

AAPG Search and Discovery Article #90955©1995 GCAGS 45th Annual Meeting and Gulf Section SEPM, Baton Rouge, Louisiana