This study was conducted to determine the formation history of the protalus ramparts at the base
of the Black Mesa Bysmalith, using climate signals from varnish microlaminations (VML). The oldest
varnish began to accrete on rocks within the ramparts at approximately 267 ka, during the Pre Bull
Lake glaciation. An increased abundance of Mn, as seen by darker layers in the ultra-thin section,
indicates a wetter climatic period. Thus, the ramparts likely formed at the time of the oldest VML.
The formation of ramparts by a long standing snowbank, upon which eroded rocks slide, roll,
bounce, and are deposited at the edge of the snow bank, is the most probable mechanism of
formation.
