JURASSIC CALCAREOUS NANNOFOSSILS FROM PRERIFT SEDIMENTS DRILLED DURING ODP LEG 173, IBERIA ABYSSAL PLAIN, AND THEIR IMPLICATIONS FOR RIFT TECTONICS

CONCHEYRO, A.; WISE, S

Proceedings of the Ocean Drilling Program, Scientific Results

Texas A&M University

Año: 2001 vol. 173 p. 1 - 24

0884-5891

Upper Jurassic calcareous nannofossil assemblages have been studied from strata cored over basement blocks now buried under the Iberia Abyssal Plain (Ocean Drilling Program Leg 173 Sites 1065 and 1069). The youngest Jurassic assemblages at each site are Tithonian in age, the same as those at nearby Leg 149 Site 901, an age that predates the breakup of the Iberia continental margin. The paucity of the assemblages, the prevalence of coccospheres, and the relatively high organic contents of the fine clastic sediments in which they occur are characteristic of a restricted interior basin that had little communication with the open ocean. During the major rifting episode (a Berriasian event), the Jurassic sequences were dispersed along with their underlying blocks of presumed continental crust across the ocean?continent transition of the Iberia Abyssal Plain, probably as a result of detachment faulting.