Micropaleontology and Mineral magnetic evidences of the Holocene mudflats of Navlakhi, Gulf of Kachchh

Abstract

A combination of foraminiferal and mineral magnetic analyses has been used to reconstruct the depositional environment of the clays from a 3.5 m shallow core of the mudflats of Gulf of Kachchh. The overall foraminiferal assemblage is related to the Early Holocene high sea level. The quantitative analyses of the two most common families viz., Nonionidae and Elphidiidae of the clays established definite relations between the counts of Elphidiidae and the values of magnetic parameters. The relatively lower values of ARM/SRIM, S-ratio and χ correspond to the lower counts of Elphidiidae inferring low discharge periods during drier climates of weaker monsoons. Similarly, high values of magnetic parameters correspond to the higher counts of Elphidiidae inferring high discharge periods of wetter climates of stronger monsoons. During wet periods of monsoonal reinforcements occurring at the early and middle (?) Holocene, it is postulated that there is an overall reduction in magnetic grain size as reflected in higher values of ARM/SIRM, low haematite content from high S-ratio values and increase in percentage abundance of the micro-fauna of Elphidiidae and vice versa.