Deep circulation in the Weddell Sea is a clockwise gyre, with bottom water formed by mixing along the southern and western margins. Most Antarctic Bottom Water originates here, leaving the Weddell Sea to the east (depths > 4500 m) or to the north (depths 16 m/Ma. Sediments from the deep Weddell Basin are hemipelagic muds with ash laminae and (mainly in the centre of the gyre) distal turbidites derived from the southwest. Thin debris flows occur near seamounts. The hemipelagic muds become coarser from the centre to the edge of the gyre. Winnowing by strong bottom currents is localised along the northern margin of the basin. The absence of diatoms from the Weddell Basin sediments may result from dissolution as well as low productivity. Sediments from Jane Basin consist of alternating diatomaceous and barren hemipelagic muds, considered to represent interglacial and glacial conditions respectively. The diatomaceous sediments contain more silt, suggesting that bottom water flow increases during interglacial periods.