Phosphorus and organic carbon reservoirs in the Bravaisberget Formation (Middle Triassic), Hornsund, Spitsbergen

• Autorzy: Krajewski K. P.
• Języki publikacji: EN

Abstrakty

EN

The Middle Triassic Bravaisberget Formation at Hornsund, Spitsbergen embraces a coarsening-upwards sequence which is dominated by organic-rich phosphatic silty shale in the lower part (Passhatten Member), and by fine- to medium-grained sandstone in the upper part (Somovbreen and Van Keulenfjorden members). This sequence reflects the development and maintenance of organic-prone phosphogenic shelf depositional system and the overlapped progradation of sandy facies related to land outbuilding and terrigenous sediment supply. The shallowing upward trend in the Formation is recorded by a general change of the nature and content of organic matter, from amorphous fractions of predominantly marine origin in the Passhatten Member (1.5-4 % TOC), to structured terrestrial fractions in the Somovbreen and Van Keulenfjorden Members (0.3-1% TOC). Organic matter in the Formation represents an advanced stage of thermal degradation (Ro = 2.0-2.1% for vitrinite). It is highly carbonized and overmature with respect to oil generation. Phosphate accumulations (5-30% P2O5) are concentrated at recurrent levels in the Passhatten Member, and at the bottom of the Somovbreen Member, where they are associated with sediment condensation, winnowing, and bioturbation. Quantitative calculations of organic carbon and mineral phosphorus show that the Bravaisberget Formation is a prominent reservoir of the two elements in the Hornsund area (524 g TOC and 64 g P per square cm). This also suggests significant expulsion of bitumen from the Formation (in a range of 300 g HC per square cm) during burial history and Tertiary tectogenesis in the West Spitsbergen Fold Belt. Organic-prone and phosphogenic environments responsible for the carbon and phosphorus concentration developed as a result of high biological productivity conditions and enhanced deposition of marine organic matter on the Middle Triassic shelf.

• Wydawca: Instytut Nauk Geologicznych PAN
• Czasopismo: Studia Geologica Polonica
• Rocznik: 2000
• Tom: Vol. 116
• Strony: 175--209

Twórcy

autor

Krajewski K. P.

• Polish Academy of Sciences, Institute of Geological Sciences, ul. Twarda 51/55, 00-818 Warszawa, Poland,