Climate induced changes in the circulation and dispersal patterns of the fluvial sources during late Quaternary in the middle Bengal Fan

From a transact along 15‡N latitude in the middle Bengal Fan, temporal and spatial variations in the granulometric parameters and clay minerals in¹⁴C dated box cores from the eastern, the central and the western regions were studied to determine climate induced changes in the hydrography. Clay assemblages have spatial and temporal changes and are markedly different in the eastern and the western bay. From a high abundance of the clay smectite, which has its major source in the Deccan Basalt in peninsular India, it is inferred that the western bay is predominantly a depocenter of ‘peninsular sources”. The eastern and the central regions of the bay, however, mostly receive sediments of the ‘Himalayan source’. Related to unstable climate, the reported dominant illite-chlorite (I + C) assemblage in the eastern region of the bay (I + C > 60% smectite <15%), between 18 and 12.6 ka BP, points to a predominant supply from the Himalayan sources through equatorwards dispersal by the winter hydrography. Higher smectite, and reduced clays of the Himalayan sources (smectite > 25%; I + C > 45%) are reported also after 12.5 ka BP from the eastern bay. These are interpreted as evidences of an intensified SW monsoon and associated change in the dispersal pattern by stronger summer monsoon hydrography which supports across bay dispersal by anticyclonic gyre. The influence of climate on hydrographic changes is consistent during the short events of arid climate (weak NE monsoon) in Holocene in core 31/1 (western bay), in which the enhanced contents of the clays of the Himalayan sources are observed (smectite < 40% I + C > 50%). These findings have implications for climate regulated influence of fluvial processes over the areas, hitherto, considered unaffected by the Indian peninsular fluvial sources     

The use of GPS for marine positioning in Germany—requirements,experience, and concepts

Abstract

While beginning to establish a German Civil GPS Information and Observation Service in 1990, the actual and (near) future GPS market in Germany was analyzed. In addition, the feasibility of using GPS for water authority tasks has been studied during past years. Typical capabilities in this area are real‐time positioning for hydrographic surveying (kinematic application) and precise transfer of levels to tide gauges and verification at offshore positions.

The article describes the user interests, the requirements, some of the test campaigns, and the derived concepts for future applications.