Resumen de Jurassic and Lower Cretaceous Ostracoda from cost Atlantic Wells, Western North Atlantic Ocean
This paper describes and illustrates 48 species of principally marine Ostracoda from Jurassic and Lower Cretaceous rocks of four of the COST Atlantic wells, western North Atlantic Ocean. A few Cenomanian species are also described. Eleven of the species are new, 23 are assigned to previously described species, and 14 are given affinitive status or are left in open nomenclature.
Six species, three of them new, are from Middle to Upper Jurassic rocks in the COST G-2 well, Georges Bank area. The new Middle or Upper Jurassic species is Pichottia? simonisi, n. sp.; the new Upper Jurassic species are Galliaecytheridea kilenyii, n. sp. and Schuleridea acuminoidea, n. sp.
Five species, only one of which ranges into younger beds, were found from beds of Valanginian or Hauterivian age in the COST wells. A few ostracode species were found in an earlier study in beds assigned to the Berriasian.
Three species, one of which ranges into the Albian, were found in Barremian deposits in the COST wells. Only two COST well ostracode species occur in beds of Aptian age.
The greatest number of early Cretaceous ostracode species in the COST wells (27) occurs in beds of Albian age. Fourteen of these species appear also to range into the Cenomanian in the wells studied. Six of the Albian species are new: Cytherella austinoidea, n. sp., C. nagaseae, n. sp., C. amatoi, n. sp., Cornicythereis bonnermaioides, n. sp,. Curfsina nealei, n. sp., and Cythereis paramahonae, n. sp.
Four species, of which three are limited to this age in the present collection, were obtained from Cenomanian (early Upper Cretaceous) deposits in the COST wells. Two of the Cenomanian species are new: Cytherella comanchoidea, n. sp. and C. dissimiloidea, n. sp.
The large number of Albian species, including those that apparently range into the early Cenomanian, suggests a correlation with the global onlap cycle of Vail et al. (1977) and Haq et al. (1987) that began after a low sea level stand in the Late Aptian and continued through the Albian into the early Cenomanian. The concept is apparently not matched by the pre-Aptian ostracode assemblages in four COST wells studied. The onlap cycle provided widespread shallow marine shelf environments that favored an increase in number of species during the Albian and early Cenomanian Ages.
