Nature of Silica Phases in Deep Sea Cherts of the North Atlantic

Abstract

THE cherts recovered from drill cores at several sites in the North Atlantic during Legs 1 and 2 of the Deep Sea Drilling Project1 (Fig. 1) are Upper Jurassic to Middle Eocene in age and occur in a wide variety of sediment types, including radiolarian oozes, nannoplankton chalks, foraminiferal silts and zeolitic clays2,3. The unexpected discovery of these highly siliceous rocks over a large area of the North Atlantic and their possible correlation with the seismic reflector Horizon A (ref. 4) raise several interesting problems concerning the palaeoceanography of the Atlantic during late Mesozoic and Cainozoic time. These have been briefly discussed by Peterson et al.3 and Gartner5 and will not be further discussed here.