Paleoenvironmental analysis of Early Miocene (Po/Pl boundary) foraminifera of north Westland and north-west Nelson 

Clark, C.; DSIR New Zealand Geological Survey, 

1982 

 

 

Report 

Nathan (1978) outlining the geological history of the Westland region states that an extensive unconformity recognised throughout Westland and north-west Nelson represents a period of uplift and erosion, during Otaian or early Altonian times, that has removed lower and middle Tertiary shelf sediments presumed to have originally covered the region. Otaian-Altonian (Po/Pl) sediments not removed by this period of erosion have been preserved at only a few localities in north Westland, north-west Nelson and at localities offshore. Currently S. Nathan, NZGS Christchurch, is undertaking a major study of the West Coast Basin as part of the NZGS Cretaceous-Cenozoic Sedimentary Basins Project. The limited exposure of lower-middle Tertiary sediments hampers efforts to determine paleoenvironmental conditions. This study is an investigation of foraminiferal assemblages from 16 localities dated as very close to the Otaian-Altonian boundary or early Altonian. It aims to develop a paleoenvironmental model of the Po/Pl boundary period through north Westland and north-west Nelson. If successful the model would complement other studies, providing a basis for extrapolation of Po/Pl sequences across areas where sediments are missing, particularly southward into south Westland, and establishing a geographic framework for the selective preservation of Po/Pl sediments. A specific target of the study is to establish if foraminiferal assemblages can identify a deep water basin surrounded by shallower sediments in the Murchison region, as suggested by S. Nathan. This study also aims to extend knowledge of New Zealand early Miocene benthic assemblages. It is the fifth such project following on the work of Scott (1970) at Kaipara, Scott (1971) Western Nelson, Hayward (1979) North Auckland and Topping (1978) North Wanganui Basin. 

 

benthos; foraminifera; north westland; nzms262 09; otiran glacial; lower miocene; nzms262 10; north-west nelson; altonian; nzms262 11; paleoenvironment; boundaries; paleontology; Biogeophysical