PACIFIC RAILROAD SURVEYS (1853–1854): GEOLOGIC INVESTIGATIONS OF WILLIAM PHIPPS BLAKE, THOMAS ANTISELL AND JULES MARCOU IN THE AMERICAN SOUTHWEST

The Pacific Railroad Surveys (PRS) of the U.S. Army Corps of Topographical Engineers were organized to perform a reconnaissance along all the feasible routes for a transcontinental railroad. William Phipps Blake (1826–1910) received his Ph.D. from Yale's Sheffield Scientific School in 1852. From 1853 to 1856 he served as official government geologist for the PRS [the Whipple and Williamson surveys, PRS v. 3 and 5] in the Southwest. Thomas Antisell (1817–1893), trained as a surgeon in Dublin and London, prepared an Irish geology text, joined the “Young Ireland Movement” which necessitated his emigration to the United States where he worked as a surgeon, US Patent Office examiner and as government geologist for the PRS [the Parke survey, PRS v. 7]. Jules Marcou a French student of Élie de Beaumont, was the first professional geologist to run a survey across the whole North American continent, was also a participant in the Whipple survey [see Şengör, A. M. C. 2003, Geological Society of America Memoir 196].

Antisell attributed uplift of the Coast Ranges to two volcanic forces acting in opposition, directed northwards and southwards, that produced a rupture of the superficial strata, and a depression of the land below sea level, in the vicinity of San Francisco. Blake viewed the Rocky Mountains as previously deformed islands in Mesozoic seas and that the Triassic to Cretaceous deposits had been laid down around them, whereas Marcou interpreted the entire uplift simply as the result of a single orogeny, with multiple centers of upheaval and igneous intrusion. Their maps and geologic cross-sections were controlled with detailed topographic surveys addressing railroad grade. This poster provides the major geologic maps and profiles by Antisell, Blake and Marcou between the 34^o and 36^o N parallels, from the Mississippi River to Los Angeles and north to the Bay Area.