Ostracoda of Cretaceous-Tertiary Contact Sections in Central Texas

摘要: ABSTRACT At the Littig Quarry in Travis County, Texas, Navarro claystones yield sparse ostracode assemblages with low species diversity and equitability, dominated by Haplocytheridea, that suggest stressful coastal environments rapid sedimentation. The overlying Midway glauconitic are fully marine, moderately diverse, characteristically Paleocene but sparse, except three condensed zones, lowest of which marks disconformable contact. Walkers Creek Milam richer normal-marine, nearshore aspect, moderate Cytherella. They belong to "Cythereis" lixula interval-zone Hazel Brouwers (1982) perhaps not very youngest part. zone at base yields a fauna high diversity, either younger or further offshore than Littig, few reworked specimens Cretaceous species. On Brazos River Falls aspect equitability; they upper part zone. A barren sandstone ledge turbidite deposit (Kocurek Hansen, 1982) disappear. above this have fragmentary assemblages, gradually become more abundant, better preserved less equitable upward, reflecting somewhat conditions intense naticid predation. Brachycythere plena, Bairdoppilata suborbiculata, other characteristic appear one through 3-m transitional interval, as holdover disappear, until is established.