SIGNATURE OF A MAFIC VOLCANIC SOURCE IN BARREMIAN TO ALBIAN SANDSTONES ON SPITSBERGEN, NORWAY

The Barremian Helvetiafjellet and Aptian-Albian Carolinefjellet Fms. on Spitsbergen are the uppermost units in a 6 km thick platform cover sequence, and are peripheral to and record the development of the High Arctic Large Igneous Province. Helvetiafjellet Fm. terrestrial strata are in transitional contact with Carolinefjellet marine strata, whose sedimentary structures, facies changes and regional relationships suggest concurrent uplift to the north, a migrating NE-SW oriented shoreline, a storm dominated shallow shelf, and NE to SW longshore drift. Glendonites suggest bottom water <5° C at times. Chamosite oolites, framboidal pyrite, glauconite and shallow siderite/chlorite diagenesis suggest reducing conditions. Petrographic analysis of circa 90 sandstone from three localities indicates the following. Abundant basalt lithics appear in the middle portion of the Barremian Helevtiafjellet Formation. Basalt lithics quickly diminish with stratigraphic ascent, but are replaced with plagioclase grains that comprise up to 40% of the sand in Aptian-Albian Carolinefjellet Fm. strata. Weathered and rounded grains, broken angular grains, and euhedral grains of plagioclase occur in different proportions. Unaltered euhedral grains may represent fresh pyroclastic influx. The amount and character of plagioclase sand fluctuates, but persists in the up to 700 m thick section over distances >150 km suggesting a substantial volume of basalts in the source terrane. Plagioclase grains are mainly absent in coarser grained sands consistent with a fine grained volcanic source and consequent sorting bias. A granitic source is indicated by microcline, perthite, myrmekite, and andalusite grains in Helvetiafjellet and basal Carolinefjellet strata. Following a Hauterivian regression, basalt detritus appears in central Spitsbergen in the Barremian and is undiminished into the Albian. Associated new metamorphic and granitic source input was likely due to LIP associated uplift.