3. CALCAREOUS NANNOFOSSILS FROM LEG 156, NORTHERN BARBADOS RIDGE COMPLEX ¹

Yan Xu ² and Sherwood W. Wise, Jr.²

ABSTRACT

Oligocene to lower Pleistocene calcareous nannofossils were recovered at Ocean Drilling Program Leg 156 Sites 948 and 949 on the frontal portion of the Barbados Ridge accretionary complex. Upper Miocene to lower Pliocene and lower Pleistocene nannofossils are generally well preserved, but those of the lower to middle Miocene are absent or poorly preserved as a result of intense dissolution. Oligocene sediments, introduced as turbidites, contain well-preserved nannofossils.

A important finding is a nannofossil stratigraphic inversion in the upper part of the cored section at Hole 949B, where lower Pliocene to upper Miocene sediments (Zones CN9 and 10) lie stratigraphically below those of middle Miocene Zone CN7. This, in conjunction with discontinuities in index properties, acoustic impedance, and pore-water composition, suggests the presence of a reverse fault formed by imbricate thrusting within the unrecovered interval of Core 156-949B-6X.

¹ Shipley, T.H., Ogawa, Y., Blum, P., and Bahr, J.M. (Eds.), 1997. Proc. ODP, Sci. Results,156: College Station, TX (Ocean Drilling Program).
² Department of Geology, Florida State University, Tallahassee, Florida 32306-2630, U.S.A. yanxu@garnet.ains.fsu.edu