Petrography and geochemistry of siliciclastic rocks from the Central Tertiary Basin of Svalbard - implications for provenance, tectonic setting and climate

作者：Schlegel Andreas^*; Lisker Frank; Doerr Nina; Jochmann Malte; Schubert Karsten; Spiegel Cornelia

来源：Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften, 2013, 164(1): 173-186.

DOI：10.1127/1860-1804/2013/0012

• siliciclastic rocks
• petrographic analysis
• geochemical composition
• provenance
• tectonic setting
• palaeoclimate
• Svalbard

The petrographic and geochemical compositions of Palaeocene and Eocene shales, silt-and sandstones from two boreholes of the Central Tertiary Basin of Svalbard (CTB) were studied for gaining information on provenance, tectonic and climatic conditions during sediment deposition. The transition from arkosic sandstone compositions in the lowermost Palaeocene to litharenites in the upper Palaeocene and Eocene strata points to a trend of increasing maturity. The Palaeocene sandstones of the Firkanten, Basilika and Grumantbyen formations are characterised by a significantly higher feldspar contents (18-25 vol. %) and a better preservation of the feldspar grains, as compared to the sandstones of the Palaeocene to Eocene Batfjellet and Aspelintoppen formations (13-14 vol. %). These contain relict feldspar mostly replaced by illite and kaolinite. Moreover, kaolinite is missing in the older Palaeocene sandstones. The older (Palaeocene) and younger (Palaeocene to Eocene) strata differ not only regarding their petrography, but also with respect to their geochemical compositions: Compared to the Palaeocene to Eocene sandstones, the older Palaeocene sandstones are characterised by higher contents of SiO2, K2O, Na2O, Ba and Sr, higher K/Rb ratios, and by lower values of Al2O3, MgO, Rb/Sr ratios and chemical index of alteration (CIA). By contrast, the Palaeocene to Eocene shales and siltstones show typically higher values of CIA, Al2O3, Fe2O3 and MgO and lower SiO2 contents. These mineralogical and geochemical differences are presumably not resulting from a changed provenance or tectonic regime. Instead, it seems more likely that they indicate a change of chemical weathering conditions between the deposition of the older Palaeocene and the younger Palaeocene to Eocene strata.

• 出版日期2013-3