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Drilling during Leg 47B at Site 398 on the south flank of Vigo Seamount recovered "black shales" and associated relatively organic-rich upper Hauterivian through mid-Cenomanian sediments. This and the recovery of Aptian-Albian "black shales" at two sites on the northern margin of the Bay of Biscay (Scientific Staff—Leg 48, 1976) extends the known area of black shale deposition on the deeper sea floors of the Early Cretaceous North Atlantic. However, the lithology, paleoenvironment, and preservation and source of organic matter in the black shales of the northern North Atlantic (north of the New Foundland fracture zone) differ in important respects from those of dark-colored, organic-rich sediment deposited in other areas of the Early Cretaceous North Atlantic and Tethys. The purpose of this paper is to discuss some of the salient aspects of lithology and paleoenvironment of the Lower Cretaceous sediment of Site 398 and to briefly compare and contrast them with Lower Cretaceous black shale sections in some North Atlantic DSDP sites and Tethyan exposures on land. Although similar organic-rich sedimentary sequences were distributed globally during the Early to Middle Cretaceous (Schlanger and Jenkyns, 1976; Fischer and Arthur, 1977), it is important to avoid general application of a model for paleoenvironment derived from any one region to explain all other occurrences. In this paper, the term "black shale" is used in a general sense to refer to relatively organic carbon-rich (i.e., >0.5 wt. % Corg), dark-colored (dark gray, greenish black, and black) mudstone and marlstone which may or may not be "shale" in the classical sense. "Black shale" sequences rarely consist entirely of darkcolored lithologies; they are often rhythmically interbedded with lighter colored (green to gray) mud, marl, or limestone. The use of Early Cretaceous and Middle Cretaceous here refers to the periods Valanginian-Hauterivian through Albian and CenomanianTuronian, respectively.

North Atlantic Cretaceous Black Shales: The Record at Site 398 and a Brief Comparison with Other Occurrences