Discovery of an aborted reversal (geomagnetic excursion) in the Late Pleistocene sediments of Pinjor Dun, NW Himalaya

We report here the occurrence of an aborted reversal (geomagnetic excursion) in the Late Pleistocene sediments of Pinjor Dun near Chandigarh, NW Himalaya. The event discovered at ~697.5 cm level from the base of Kiratpur section corresponds to the OSL date of 40±5 Ka coinciding with the Laschamp excursion and palaeointensity minima elsewhere. The Pinjor Dun sediments are deposited at a high rate of sedimentation that enables quite enlarged records of remanent geomagnetic field, hence suitable for further high resolution study of the excursion (under progress) to extend its utility as a stratigraphic marker in the Quaternary sediments at the foothills of the Himalaya

Interrelation between factors controlling sediment yield in the largest catchment of Peninsular India

The catchment area of the Godavari in Peninsular India shows complex heterogeneous morphologic, climatic, and geological settings. Although the sub-basins of the Godavari indicate a great spatial variation in sediment yield, the role of such morpho-climatic heterogeneity in the sediment yield variation is poorly understood. This study aims to analyze the role of geomorphology, lithology, precipitation, and land use on spatial sediment yield variation in the Godavari basin. Using digital topography data, with the aid of a Geographical Information System (GIS), we delineated 25 sub-basins based on gauging station locations and showed a wide variation of sediment yield, ranging from 28 to 3404 t km−2 yr−1. Several geomorphic attributes were found to be co-dependent; then, we utilized the partial least-square regression (PLSR) technique to recognize the relationship between controlling factors with sediment yield and established a predictive model. Furthermore, we quantitatively determined the most important first-order controlling factors using variable importance for the projection (VIP) method. The results of PLSR and VIP revealed that among 20 geomorphic variables, plan curvature (VIP = 1.61), profile curvature (1.61), LS factor (VIP = 1.51), topographic ruggedness index (VIP = 1.51), slope (VIP = 1.51), topographic wetness index (VIP = 1.29), and steepness index (VIP = 1.06) exert first-order control in sediment yield variation. Moreover, Mesozoic and Precambrian rocks in agricultural, forested, and bare-ground environments collectively play a crucial role under the influence of differential rainfall patterns in the spatial variation of sediment yield as indicated by VIP values higher than 1. Our optimal PLSR model explained 62% of the total variance in average sediment yield with a moderate predictive ability value (Q2 = 0.46). The insights obtained from the results of this study can be utilized for basin-specific erosion and hydrological modeling in a similar environment. Moreover, this study can be helpful to planners and policymakers for better erosion management and soil–water conservation measures in the Godavari basin

Magnetic fabrics indicating Late Quaternary seismicity in the Himalayan foothills

Abstract The anisotropy of magnetic susceptibility (AMS) study was performed on soft sediment samples from a trenched fault zone across the Himalayan frontal thrust (HFT), western Himalaya. AMS orientation of K min axes in the trench sediments is consistent with lateral shortening revealed by geometry of deformed regional structures and recent earthquakes. Well-defined vertical magnetic foliation parallel to the flexure cleavage in which a vertical magnetic lineation is developed, high anisotropy, and triaxial ellipsoids suggest large overprinting of earthquake-related fabrics. The AMS data suggest a gradual variation from layer parallel shortening (LPS) at a distance from the fault trace to a simple shear fabric close to the fault trace. An abrupt change in the shortening direction (K min ) from NE-SW to E-W suggests a juxtaposition of pre-existing layer parallel shortening fabric, and bendingrelated flexure associated with an earthquake. Hence the orientation pattern of magnetic susceptibility axes helps in identifying co-seismic structures in Late Holocene surface sediments