Hatteras Deep-sea Fan

Abstract

ABSTRACT In the northwest Atlantic Ocean, at depths of 5200 m to 5250 m, the solitary feeding channel of the now extinct Hatteras Canyon disgorges into a braided network of channels and levees with 10 to 30 m of relief forming a fan that feeds onto the Hatteras Abyssal Plain. Piston coring and bottom photography within a 25 by 25 km area of the Hatteras Fan shows that the upper 6 m of sediment of the channels' floors consist of 10 cm to 2 m thick beds of well sorted and often graded subarkosic sand and gravel interbedded with laminated silts and clays. Cores taken on the levees consist mostly of laminated clays and silts with few or no sand layers. Layers of conglomeratic, glauconitic, pebbly mud occur in some high, presumably relict, levee banks. The present distribution of channels and levees suggest that the deep channels on the western portion of the fan were the most recently active while those on the topographically higher system to the northeast are relict. Petrographic analyses of over 100 impregnated grain thin-sections of sand layers reveal that the sands of the Hatteras Fan have a homogenous character and belong to a single compositional suite. The terrigenous fraction consists predominantly of monocrystalline quartz (30-70%) polycrystalline quartz (0-13%), mainly igneous and stretched metaquartz, feldspar (6-30%, potassic varieties prevalent) and minor amounts of rock fragments (3-10%). Skeletal components (molluscs 10-25%, algae 0-7%, forams 0-30%) are prevalent in the carbonate fraction, while nonskeletal components include ooids (04%) pellets (0-3%) and biomicrites (0-9%). The character of the terrigenous fraction suggests the sands are derived from Appalachian piedmont crystalline rocks, probably mainly from north of Cape Hatter s, while a more southerly source is suggested for carbonate grains such as ooids which occur in abundance south of Cape Lookout in outcropping continental shelf rocks.