Distinction of Glacial and Interglacial Cycles in Feni and Gardar Drifts, North Atlantic: ABSTRACT

Abstract

The Feni and Gardar drifts of the North Atlantic are thought to represent large accumulations of current-deposited material and should record changes through time in direction and intensity of overflows in the Norwegian Sea and Iceland-Faereo Ridge, respectively. Both drifts were drilled by DSDP Leg 94. Initial shipboard examination revealed no visual differences between these sediments and typical pelagic North Atlantic sediments. Fourier shape analysis on quartz silts, augmented by SEM, showed that each sample consists of a mixture of 3 grain populations. One grain type is covered with surface fractures unmodified by subsequent abrasion. Lack of such abrasion and the fact that the abundance of these grains varies independently of other shape types suggest a glacial-ice afted origin. A second shape family is covered with irregular, platy silica overgrowths, typical of diagenesis in a poorly sorted, clay-rich environment and is likely the product of erosion of submarine lutites. A third grain type, plastered with fine-grained silica, is characterized by protuberences and indentations typical of primary continental source terranes. These last 2 grain types vary inversely with one another, implying that at glacial maxima, bottom currents deposited first-generation continental material, but at glacial minima, they eroded material from the sea bottom and redeposited it as drift sediments. End_of_Article - Last_Page 252------------