Paper No. 43-8
Presentation Time: 3:40 PM
MAGNETIC FABRIC AND CHANNEL MIGRATION IN THE ACTIVE LEVEE OF THE BENGAL FAN, IODP SITE U1454
Paleocurrent information is necessary to understand the migration of submarine channels and the architecture of channel-levee systems. Anisotropy of magnetic susceptibility (AMS) provides a means to trace paleocurrent directions in cores lacking other sedimentary indicators of flow direction. Here we present AMS results from oriented core collected from a levee of the active submarine channel near 8° N as part of IODP Expedition 354. Turbidites in the levee were deposited in two intervals, separated by a hemipelagic unit (covering the time period between ca. 15 and 25 cal ka BP). Most turbidites in the levee have well-developed oblate to triaxial AMS fabrics characterized by minimum principal AMS axes offset from vertical due to imbrication of sediment particles. Transport directions derived from AMS imbrication (poles to AMS foliation) are generally to the W in the lower levee section deposit, to the S in the hemipelagic unit, and to the SE in the upper levee. The latter direction is approximately consistent with the modern current direction in the active channel. AMS maxima define a similar pattern, suggesting that AMS in the turbidites is due to current-aligned particles. The general W to E shift in paleocurrent directions during levee construction is consistent with downslope meander migration. However, changes in sediment composition and the broader stratigraphic context provided by seismic and acoustic data suggest that other processes may also be important.