A postorogenic volcanic sequence with an intraformational conglomerate, and related granites in the Väderstad region, south central Sweden

Abstract

Abstract A volcanic conglomerate from the province of Östergötland is described. The conglomerate is intraformational in postorogenic Svecokarelian porphyries. In the vicinity of the conglomerate and the volcanics occurs a medium- to coarse-grained, partly foliated granite with rather large quartz crystals. This granite is considered to be the basement of the volcanic conglomerate. The prevolcanic granite is supposed to have weathered to give arkosic material, now appearing as medium- to coarse-grained granite. This material also constitutes the matrix and some of the granitic pebbles of the conglomerate. Other pebbles are finegrained and medium-grained granites and different types of volcanic rocks. The prevolcanic granite and the vulcanism are followed by postvolcanic, complex plutonic intrusions and a hypabyssal activity, which completes a possible postorogenic model. Svecokarelian rocks, postorogenic volcanics and subvolcanics constitute roof pendants of the postorogenic granites.