ALBERT

Description: Site 634, drilled during ODP Leg 101, was essentially a reoccupation of Site 98, drilled during DSDP Leg 11 (Hollister, Ewing, et al., 1972, doi:10.2973/dsdp.proc.11.1972; Table 1, Fig. 1). At Site 634, the upper 144 m of sediment was washed in an attempt to reach the Upper Cretaceous target horizon in the time remaining for the cruise (Austin, Schlager, et al., 1986, doi:10.2973/odp.proc.ir.101.1986). Figure 2 illustrates the spatial relationship of Site 98 (2750 m water depth) and Site 634 (2835 m water depth), 0.2 nmi to the northwest. Radiolarians were observed in Site 98 samples from 100 to 240 meters below seafloor (mbsf) during Leg 11, but no detailed biostratigraphic analyses were conducted. Thus, Site 98 presented us an opportunity to sample material correlating with the washed section at Site 634. Samples were taken from Cores 101-634A-2R through 101-634A-4R to study radiolarians, but all proved barren, nor were radiolarians observed in shipboard smear slides. A correlation between Sites 98 and 634 (Fig. 2) suggests that these cores represent the same interval as that recovered in Cores 11-98-10 and 11-98-11, which were also barren. These results are presented separately from other Leg 101 radiolarian studies (Palmer, 1988, datasets: doi:10.1594/PANGAEA.743055) because the Site 98 fauna was predominantly Eocene, while other radiolarian assemblages studied were Oligocene and Miocene.

Description: A major objective of DSDP Leg 95 (New Jersey Transect) was to investigate the effects of eustatic sea-level fluctuation and crustal subsidence on the depositional and erosional patterns of the Atlantic continental margin in the Baltimore Canyon trough area. Deep Sea Drilling Project Sites 612 and 613 were drilled on the New Jersey continental slope and rise during this leg. A more specific goal of Leg 95 was to investigate calcareous and siliceous microfossil biostratigraphy in order to identify biostratigraphic gaps and to intercorrelate the various microfossil zonations for the New Jersey margin. This study of radiolarians from Sites 612 and 613, and from Atlantic Slope Project (ASP) Site ASP 15, demonstrates that although radiolarians occur throughout the Cenozoic section in this region, they are most useful for biostratigraphic control in the upper Paleogene part of the stratigraphic record. Results of this investigation indicate that several biostratigraphic gaps occur in the Cenozoic sedimentary sequence penetrated by the three drill holes. Upper Paleogene radiolarians are well preserved, abundant, and diverse. Although some tropical taxa are rare or absent, sufficient age-diagnostic species are present for biostratigraphic determinations. In comparison, lower Paleogene radiolarians are poorly preserved because pronounced silica diagenesis formed porcellanites in some stratigraphic intervals. The Neogene radiolarians faunas are rare and moderately well preserved at all the sites investigated here. Neogene assemblages are dominated by spongodiscids and porodiscids (similar to faunas of modern cold/temperate shelf waters), and contain few taxa useful for biostratigraphic determinations.

Description: Radiolarians from two sites north of Little Bahama Bank (Sites 627 and 628) are correlated with assemblages from sites on the southeastern U.S. coastal plain and continental shelf and from DSDP Sites 391 and 534 in the Blake-Bahama Basin. Results show that deposition of biogenic silica-rich sediments occurred in this region from the late Oligocene through middle Miocene, although the record is interrupted by unconformities. Radiolarians help constrain the age of a mass-transported deposit at Site 627 that appears to be coeval with the Great Abaco Member of the Blake Ridge Formation.