Upper Permian-Lower Cretaceous clay mineralogy of East Greenland: provenance, palaeoclimate and volcanicity

The clay mineralogy of Upper Permian-Lower Cretaceous mudstones from East G reenland has been investigated by X-ray diffraction (XRD), atomic force mic roscopy (AFM) and thermal analysis in order to evaluate long-term trends in provenance and palaeoclimate and to detect possible Volcanic events. The U pper Permian-Lower Triassic mudstones contain illite, chlorite, vermiculite , kaolinite and illite-smectite (I-S), whereas the Rhaetian-Sinemurian muds tones are dominated by kaolinite. Aalenian-Albian mudstones contain kaolini te and large amounts of I-S with similar to 80% illite layers. Exceptions a re three Kimmeridgian samples, which contain mainly I-S with 30% illite lay ers, and three Upper Barremian-Lower Aptian samples with large amounts of s mectite layers. Discrete clay minerals in the Upper Permian-Jurassic mudsto nes are largely detrital. The smectite-rich I-S probably reflects episodes of volcanic activity in late Jurassic and late Barremian-early Aptian times . This is the first indication of Mesozoic volcanism from the Mesozoic rift basin of East Greenland. The main sediment source during late Permian-earl y Cretaceous times was weathered Precambrian and Caledonian crystalline bas ement. The only possibly climate-induced change is a change from chlorite, illite, vermiculite and kaolinite in Upper Permian-Lower Triassic mudstones to kaolinite and I-S in the Jurassic mudstones and is probably due to an i ncrease in precipitation.