A Contribution to the Methodology of Palaeocurrent Determination

Abstract

Palaeocurrent directions in sandstone around Jodhpur (Vindhyan or early Palaeozoic) were determined by measuring direction of cross-bedding, grain orientation, quartz 'c' axis orientation, and also with the help of asymmetrical ripples. A comparison was made of the results derived from these different methods. It was found that there is a fairly good agreement between the directions derived from the study of grain orientation, quartz 'c' axis orientation and cross-bedding. Usually asymmetrical ripples also agree and indicate the general direction of the palaeocurrent; hut occasionally asymmetrical ripples turn out to be climbing ripples and indicate a direction opposite to the true palaeocurrent direction. This paper attempts to correlate the results obtained by different methods and concludes that a fairly good correlation exists between the results obtained by different methods. The grain orientation studies indicate that there is an up-current imbrication of the elongate quartz grain a in general; but in the case of fore-set surface in the cross-bedded strata, they tend to be parallel to the fore-set bedding and therefore develop a down-current imbrication. It is also found that existence of climbing ripples may indicate the necessity of caution and should be used only to assess the depositional strike.