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.

Carbonate, organic carbon, pyrolysis and composition of the extracts at DSDP Holes 76-534A and 44-391

The geochemical studies of Sites 534 and 391 and their comparison allow us to improve the chemical characterization of different geological formations dating from the early Callovian to the Maestrichtian along the continental margin of eastern North America. Three of the formations are favorable for the preservation of organic matter: (1) the unnamed formation (middle Callovian to Oxfordian), (2) the Blake-Bahama Formation (Berriasian to Barremian), and (3) the Hatteras Formation (Aptian to Cenomanian). The organic matter is mainly detrital, except for a few organic-rich layers where a contribution of aquatic material occurs. In these organic-rich layers, the petroleum potential is medium to good. Maturation has not quite reached the beginning of the oil window even for the deepest organic material.

Chemical composition of Fe-Mn nodules and crusts from oceans and seas

Fluorine concentrations were determined ionometrically with an error of 0.02% in iron-manganese materials of the ocean. They were: 0.02-0.04% in ocean iron-manganese nodules, with the exception of two specimens (0.08% and 0.20% F); up to 0.02% in iron-manganese nodules of seas; 0.02-1.17% in ore crusts from ocean seamounts; and 0.02% in ore sediments of the Red Sea. Elevated fluorine content of ore crusts is associated with presence of calcium phosphate inclusions in them. Fluorine is not accumulated during iron-manganese nodule mineralization. Its average concentration in the nodules is half that in host deep-sea sediments.

(Table 1) Chemical composition of Fe-rich layered silicates from the East Korean Rise, Japan Sea

Mineral and chemical compositions of highly ferruginous layered silicates (HLS) of glauconite sands occurred on the East Korean Rise outside volcanic structures and on an unnamed volcano and the Chentsov Volcano have been studied. The use of cluster and discriminant analyses has resulted to more objectively distinguished groups among HLS, and the use of factor analysis - to illustrate correlations between chemical elements in different groups. It has been found that green mineral assemblages of the East Korean Rise are heterogeneous in terms of morphology, composition and origin, and their formation is a complex multistage process including both neoformation and degradation.

Composition and sorption capacity of oceanic and marine ferromanganese nodules

Experimental data obtained show that oceanic and marine ferromanganese nodules and crusts are natural ion-exchangers. Exchange capacity of oceanic ferromanganese aggregates is much higher than that of shallow-water marine ones, whereas reactivities of exchange cations (Na, K, Ca, and Mg) are almost equal in both.

Chemical compositions of monomineral fractions from Fe-Mn crusts and of their host rocks, seamounts of the Sea of Japan

It has been established (with use of analytical electron microscopy) that Fe-Mn crusts from two seamounts of the Sea of Japan consist predominantly of an association of birnessite minerals including Ca-birnessite and clinobirnessite. The latter is represented by twins, which form regular integrowths with 14 Å Ca-birnessite. Ore material from the third seamount (Tarasov submarine volcano) consists only of fibrous todorokite, which forms spherulitic nodules, blocks, and laminar formations. Its chemical composition is close to that of todorokite from the Galapagos rift zone.

Chemical composition of nodules and crusts from the Sea of Japan

Iron-manganese mineralization on seamounts and rises in the Sea of Japan is represented by iron-manganese nodules and crusts. Their chemical composition (major elements and more than 30 trace elements) was studied by a series of analytical methods. According to geochemical comparisons hydrogenic, hydrothermal, and biogenic materials have participated in creation of this mineralization. Contents of Ba and Li, as well as Mo/Pb and Sb/As ratios can be used as indicators of genesis of iron-manganese nodules and crusts along with composition of the rare earth elements.