Development of Hollendardalen Formation (Svalbard); with emphasis on sedimentological and petrographical analysis.

Abstract

Hollendardalen Fm. is a shallow marine sandstone unit in the Van Mijenfjorden Group within the Central Basin on Spitsbergen. No detailed systematic mapping, sedimentological or petrographic studies of Hollendardalen Fm. have been conducted before this study. The sedimentological logs display an upwards shallowing development through the Hollendardalen Fm. Internally Hollendardalen Fm. consists of two upwards coarsening parasequences, which have been recognized throughout the basin. The thickest sediment accumulations are found in the west, with a decreasing development eastwards. Observed structures, lithology and stacking of sedimentary units within the Hollendardalen Fm. indicate a depositional environment of wave and tide dominated delta. Paleocurrent measurements indicate a northwestern infill in western areas, progressing to a northeastern infill direction in the east. K-feldspar/plagioclase ratio increases from 0,08 in west to 0,51 in east. This is probably a result of a source rock enriched in K-feldspar relative to plagioclase located north in the basin feeding the eastern areas. This is further supported by an increase in the total feldspar/total clay ratio from proximal parts in the west to distal parts in the east. Heavy mineral assemblages in Grumantbyen, Hollendardalen and Battfjellet formations are not similar. These observed differences indicate that there are different types of parent rocks feeding the system. Change in provenance source between Grumantbyen Fm. and Hollendardalen Fm. is related to a change in regional provenance from an eastern sediment source for Grumantbyen Fm. and a western source for Hollendardalen Fm. Unroofing of source rock under the rising West Spitsbergen Orogen give an explanation for heavy mineral differences between Hollendardalen and Battfjellet formations.