Chemostratigraphy: a New Approach for the Subregional Correlation of Triassic / Jurassic Sequences of the Barents Sea
Timothy J. Pearce and John H. Martin
Chemostrat Ltd, Welshpool, United Kingdom.
Triassic to Middle Jurassic deltaic to shallow marine sequences from the Western Barents Sea basin are increasingly being targeted for hydrocarbon exploration. However, reservoir quality is strongly influenced provenance, and the lack of well control, marked lateral facies variations and multiple sediment input points all contribute to the difficulty in correlating and ultimately mapping areas with more favourable reservoir quality.
A major chemostratigraphy study has been undertaken to improve the correlation of the Triassic to Middle Jurassic sequences and to aid in reconstructing the history of sediment input into the basin. The succession has been subdivided into five Chemostratigraphic Megasequences termed BMS0 to BMS4, which are further divided into Chemostratigraphic Sequences BCS0 to BCS10. These sequences are again divided into several packages, which are correlated within individual sub-basins such as the Nordkapp and Hammerfest Basins. The chemostratigraphic zonation is largely based on fluctuations in element concentrations that reflect changes in the abundance of feldspar, clay minerals, heavy minerals and opaque minerals (corroborated by data acquired via mineralogical analyses), which themselves ultimately reflect variations in provenance and palaeoclimate.
The study shows chemostratigraphy is a reliable tool for the regional correlation of the Triassic - Lower to Middle Jurassic sequences of the Western Barents Sea area. Furthermore, the technique can be used to revise the existing lithostratigraphy for this area, despite variations in lithology, facies and depositional environment, which highlights the potential of chemostratigraphy as a standard tool for the correlation of these successions. In addition to chemostratigraphic correlation, the geochemical data and selected mineralogical data are used to assist modelling changes in provenance, palaeoenvironment and facies. Furthermore, by mapping lateral variations in the values of selected element ratios, sediment dispersal patterns can also be developed. When sediment dispersal maps are combined with new isopach data, geochemical / mineralogical provenance indicators and sand:shale ratios, sediment input points along basin margins can be identified and the position of source areas inferred. In addition, this approach could employed on equivalent sequences from Eastern Barents and further into the Russian Arctic, but also similar Triassic sequences in the Canadian Arctic.
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia