Geology of Tumbledown Mountain
— Philip B. King

Tumbledown Mountain is a steep-sided, west-projecting spur of Beach Mountain, 11 km north-northwest of Van Horn, Texas (fig. 1). An account of its geology seems worthwhile, as the locality will be visited during the New Mexico Geological Society Field Conference. Moreover, its excellent rock exposures epitomize many of the earlier geological events in the Van Horn area.

This account is based on observations that I made half a century ago, between 1933 and 1939 (King and Flawn, 1953; King, 1965),and I have made only brief visits there since then. I am aware that more recent work has been done in the area, including prospecting for talc. Nevertheless, I doubt that this later work materially changes the conclusions that I reached during my earlier survey.