A scenario of Mesozoic-Cenozoic ocean circulation over the Blake Plateau and its environs

Abstract

After the continental breakup of North America, Africa, and Europe, a sluggish, wind-driven circulation gyre probably formed in the juvenile North Atlantic basin. Surface flow in the western Atlantic Ocean during the Early Cretaceous likely was northward along the seaward edge of an extensive reef that flourished offshore of North America. Sometime during the Late Cretaceous, the surface circulation in the Gulf of Mexico had evolved into a clockwise rotary pattern as the exchange of water with the Pacific Ocean diminished. By latest Cretaceous time, a vigorous easterly current flowed through the Suwannee Strait of southern Georgia and northern Florida, injecting copious amounts of water and sediment into the western Blake Plateau basin. This flow pattern apparently persisted into Paleocene time. During late Paleocene and early Eocene time, strong northerly flow through the Straits of Florida and across the Blake Plateau was established. This represented the onset of Gulf Stream circulation over the Blake Plateau. The position of the Gulf Stream shifted repeatedly across the northern and central plateau during the Tertiary and Quaternary Periods. The westernmost track was located along the inner Blake Plateau parallel to the Florida-Hatteras Slope; the easternmost track was 500 m lower, bathymetrically, and crossed the central plateau and continental slope just north of the Blake Spur. The Gulf Stream apparently shifted in response to changes in water depth on the Blake Plateau that accompanied global fluctuations of sea level. During rises of sea level, the Gulf Stream drifted westward until it impinged on the Florida-Hatteras Slope and Outer Shelf. During lowerings of sea level, the Gulf Stream was deflected progressively eastward across the central plateau by the Charleston Bump, a prominent bathymetric bulge of the northern Blake Plateau.