Imbrication and Initial Dip in a Keweenawan Conglomerate Bed

ABSTRACT The source of rhyolitic debris composing conglomerate beds in the Keweenawan lava series of northern Michigan has not been firmly established heretofore. Statistical measurement of imbrication in one bed, the Houghton conglomerate, indicates that the depositing stream flowed from southeast to northwest. The average inclination of pebbles, corrected for the present dip of the bed, is 8° SE. This is compared with the inclinations of imbricated pebbles measured by Krumbein in California flood gravels. In addition, many pebbles in the Houghton conglomerate are inclined at about 40° to bedding it is suggested that these pebbles may have slumped into small scour craters.