Improved Correlation using High-resolution Element Chemical Analyses of the Triassic Succession from the IKU Shallow Cores, Southwestern Barents Sea

Carsten Elfenbein

This study investigates the feasibility of high-resolution correlation of chemostratigraphic units on a semi-regional scale based on non-destructive measurement of element ratios in rock samples. Semi-quantitative analysis of 50 chemical elements using Avaatech XRF core scanner has been performed on the IKU shallow cores of the Triassic succession of the southwestern Barents Sea. The analysis was performed on areas of 10 mm x 12 mm at intervals mainly between 2 and 20 cm. The sampled stratigraphy ranges from the Permian/Triassic boundary, through the Early, Middle, and Late Triassic and into the Jurassic. The chosen cores cover palaeo-depositional environments of distal and proximal settings, predominantly from the Havert, Klappmyss, Kobbe, Snadd, and Fruholmen formations or their equivalents from locations on the Finnmark Platform, the Svalis Dome, Nordkapp Basin, and the Bjarmeland Platform. Element chemical variations in sediments reflect variations in sediment provenance areas and depositional environment. So far, palaeogeographic reconstructions of the Triassic succession in the southwestern Barents Sea have documented a southern (Fennoscandian) provenance area dominated by quartz arenitic sandstones and an easterly provenance (Uralides) dominated by very feldspar-rich sandstones. The distributions of elements indicative of palaeo-depositional environments depend on redox conditions during deposition (formed during anoxia as pyrite (Fe, S), native sulphure (S)) and are modified by early diagenetic mineralization processes like carbonate cementation (Ca, Mg, Fe), phosphorite (abundant in the Anisian), and clay mineral formation as glauconite (Fe, Al, K, Si) and chamosite (Fe, Mg, Al, Si). Other elements (e.g. Uranium and Thorium) can be linked to organic matter content. Variations of selected element ratios which are in common for the different locations are used to derive correlative units. These are compared to the biostratigraphic data and the potential for a refinement of established time frameworks is discussed with basis on the combination of biostratigraphy and chemostratigraphy. In addition, the chemostratigraphic signature and the observed variations along “time-lines” are explained by the variable spatial influence of different sediment provenances and palaeo-oceanographic conditions. We expect a significant improvement of the confidence in palaeo-geographic reconstruction for the investigated formations based on high-resolution chemostratigraphy, as well as a better understanding of the formation of stratigraphically relevant boundaries.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013