FOLDS PRODUCED BY GRAVITY SPREADING OF A BANDED RHYOLITE LAVA FLOW

Recumbent folds near the top of the Minyon Falls banded rhyolite flow, in northeastern New South Wales, Australia, indicate lateral radial e xtension of lava as it flowed from the vent under the influence of gra vity. These structures occur near the vent of the flow and differ from the upright folds commonly observed near the tops of lava flows. Fart her from the vent, the fold patterns indicate lateral radial shortenin g and shearing as the spread of lava was impeded. Interpretation of th e folds leads to a kinematic model of coaxial flow near the vent gradi ng to simple shear and sub-simple shear away from the vent.