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Stratigraphy of the Cretaceous-Tertiary and Paleocene-Eocene transition rocks of Big Bend National Park, Texas ( USA).

Abstract:

The marine to terrestrial transition in the Big Bend area falls within the Late Cretaceous Aguja Formation, and the Cretaceous-Tertiary boundary falls within the Javelina Formation. No record of a catastrophic event is apparent in the Javelina Formation. The Javelina, Black Peaks, and Hannold Hill Formations and the Big Yellow Sandstone Member of the Canoe Formation record increasing uplift in the region. Volcanism in the Chisos Mountains is the source of upper Canoe Formation sediments. The sequence of changes produced by this trend is gradual and the Javelina through Black Peaks units are not lithostratigraphically distinct at the formation level. The Aguja Formation and the Tornillo Formation are united in the Chilicotal Group (new), which spans the deposits from the first significant influxes of terrestrial sediments, formed as the Cretaceous sea retreated, up to the beginning of local volcanism in the Chisos. The volcanic strata of the upper Canoe Formation are reassigned to the Chisos Formation.-from Authors