Cenozoic radiolaria in the western North Atlantic

Eight Cenozoic radiolarian zones were recognized in samples from two holes at Site 603, drilled on the lower continental rise off North America during Leg 93 of the Deep Sea Drilling Project. Paleocene to early Eocene radiolarian zones (Bekoma bidartensis, Buryella clinata, and Phormocyrtis striata striata zones) and early to late Miocene radiolarian zones (Calocycletta costata, Dorcadospyris alata, Diartus petterssoni, and Didymocyrtis antepenultima zones) were recognized in sediments from Holes 603 and 603B. In addition, a new Paleocene Bekoma campechensis radiolarian Zone is defined by the interval between the first morphotypic appearance of B. campechensis and the B. campechensis-B. bidartensis evolutionary transition. This zone is immediately below the B. bidartensis Zone of Foreman (1973), and has previously been discussed as a Paleocene "unnamed zone" by other investigators. A hiatus between Neogene and Paleogene sequences was also recognized in the radiolarian faunas.

Fossil manganese deposits buried within DSDP/ODP cores, Legs 1-126

Probable in-situ manganese deposits larger than 1 cm in diameter buried in ODP/DSDP cores were selected for study after examining previous descriptions of the manganese deposits in site reports and the ODP data base. Most of the selected samples from 11 cores occur at or just above sedimentary hiatuses or in slowly deposited sediments and are overlain by rapidly deposited sediments of biogenic, terrigenous or volcanogenic origin. The changes in sedimentation recorded in the lithostratigraphic sections around these deposits are closely related to changes in tectonic evolution, deep water circulation or biological productivity at the sites. The similarity in composition and structure of the buried deposits to those of the modern manganese nodules and crusts with no evidence of post-depositional change suggest that buried manganese deposits may be used as indicators of past sedimentary conditions during which they formed. Their major components are hydrogenetic and earlydiagenetic manganese minerals as well as detrital minerals. The characteristics of these manganese deposits suggests that similar processes of deposition have taken place since the Paleogene or older.

Nd-Sr isotopes in fossil fish debris from IODP Exp302

Strontium and neodymium radiogenic isotope ratios in early to middle Eocene fossil fish debris (ichthyoliths) from Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302) help constrain water mass compositions in the Eocene Arctic Ocean between 55 and 45 Ma. The inferred paleodepositional setting was a shallow, offshore marine to marginal marine environment with limited connections to surrounding ocean basins. The new data demonstrate that sources of Nd and Sr in fish debris were distinct from each other, consistent with a salinity-stratified water column above Lomonosov Ridge in the Eocene. The 87Sr/86Sr values of ichthyoliths (0.7079 - 0.7087) are more radiogenic than Eocene seawater, requiring brackish to fresh water conditions in the environment where fish metabolized Sr. The 87Sr/86Sr variations probably record changes in the overall balance of river Sr flux to the Eocene Arctic Ocean between 55 and 45 Ma and are used here to reconstruct surface water salinity values. The eNd values of ichthyoliths vary between -5.7 and -7.8, compatible with periodic (or intermittent) supply of Nd to Eocene Arctic intermediate water (AIW) from adjacent seas. Although the Norwegian-Greenland Sea and North Atlantic Ocean were the most likely sources of Eocene AIW Nd, input from the Tethys Sea (via the Turgay Strait in early Eocene time) and the North Pacific Ocean (via a proto-Bering Strait) also contributed.