Turbidites, Redbeds, Sedimentary Structures, and Trace Fossils Observed in DSDP Leg 38 Cores and the Sedimentary History of the Norwegian-Greendland Sea

Abstract

The sedimentary history of the Norwegian-Greenland Sea is typical of rifted-margin ocean basins; it is marked by stratigraphic sequences that (1) were deposited in deeper water through time, as oceanic crust subsided away from the active spreading ridge, and (2) become finer grained and more biogenic through time, as the continental source areas moved farther away from the active spreading ridge during widening of the ocean basin. Nonmarine redbeds above subaerially weathered basalt form the base of the oldest sequences, formed when rifting of the single continent began. Turbidites were subsequently deposited as the rift widened, deepened, and became oceanic. Hemipelagic mudstones were deposited with further widening, and then biogenic calcareous and siliceous oozes were deposited as the influence of the distant continental margins on sedimentation diminished. Finally, ice-rafted glacial deposits blanketed the entire sea floor and all older deposits; the glacial deposits directly overlie newly created Plio-Pleistocene ocean floor near the active spreading ridge. A great variety of sedimentary structures, trace fossils, and related features are found within these stratigraphic sequences, which are complicated by the irregular tectonic history of the Norwegian-Greenland Sea.

Paleoenvironmental Significance of Cenozoic Clay Deposits from the Norwegian Sea: ODP Leg 104

“…Thus the kaolinite/smectite assemblage and the absence of primary clay minerals (illite and chlorite), despite the proximity of micaceous sandstones, suggest these sediments developed as continental soils under a hot and moist climate (Paquet, 1969). This interpretation agrees with that of Nilsen and Kerr (1978), who maintain that lateritic Paleocene soils existed in the Lofoten Basin. Identical assemblages have also been observed in lower Eocene Rockall sediments (DSDP Leg 81, Site 555, Latouche and Maillet, 1984) and Faeroe Iceland Ridge (Parra et al, 1986).…”

Bioturbation and Trace Fossils in Deep Sea Sediments of the Walvis Ridge, Southeastern Atlantic, Leg 74

“…As in many previous studies on deep-sea trace fossils from DSDP cores, diversity is low (Warme et al, 1973 van der Lingen, 1973;Nilsen and Kerr, 1979;Ekdale, 1974Ekdale, , 1978Ekdale, , 1980Chamberlain, 1975). Most traces belong to the ichnogenera Plαnolites, Zoophycos, and Chondrites and a smaller number to Teichichnus.…”

“…Three morphological types can be distinguished, all consisting of densely packed tubes of pyrite the length of which is limited by the core diameter: (1) Cross sections of the burrows show that the tubes were filled primarily with clusters of framboidal pyrite which now are extensively recrystallized, producing a denser structure. It is unlikely that the pyrite has replaced a primary limonite cement within the burrows (as described by Nilsen and Kerr [1979] from pyritized burrows occurring in mudstones of the Norwegian Sea); instead it was probably precipitated at a very early stage of diagenesis within a highly limited reducing microenvironment.…”

Geology and assessment of undiscovered oil and gas resources of the Jan Mayen Microcontinent Province, 2008

“…The unconformity, marked by a basal conglomerate in the Miocene section at drill site 349, is thought to record rift-related uplift and erosion of the Jan Mayen Microcontinent during breakup at the Kolbeinsey Ridge (Talwani and Eldholm, 1977;Gudlaugsson andothers, 1988, Kuvaas andKodaira, 1997). The section at DSDP drill site 350, on the other hand, reflects deposition of coarse-grained turbidites on basalt that are replaced upward by by hemipelagic mudstone, biogenic calcareous and siliceous oozes, and finally by glacial-marine sediments indicative of deposition in a widening oceanic basin on transitional continental crust or oceanic seafloor (Nilsen and Kerr, 1978). Regionally extensive basalts and (or) sills in Miocene deposits appear to cover wide areas of the western part of the microcontinent and diminish the quality of seismic data over much of this part of the province (Gudlaugsson and others, 1988).…”