Jornada Draw fault: a major Pliocene-Pleistocene normal fault in the southern Jornada Del Muerto

TitleJornada Draw fault: a major Pliocene-Pleistocene normal fault in the southern Jornada Del Muerto
Publication TypeJournal Article
Year of Publication1995
AuthorsSeager W.R, Mack GH
JournalNew Mexico Geology
Date Published1995
Call Number00831
Keywordsarticle, articles, geology, earthquake, geology, fault, geology, Pleistocene, geology, Pliocene, journal, journals
AbstractThe north-northwest-trending Jornada Draw fault, 40 mi (64 km) long, has displaced the hinge area of the Jornada del Muerto syncline approximately midway between the Caballo and San Andres Mountains. Downthrown to the east, the fault forms the eastern boundary of the Caballo horst and the west boundary of a broad half graben that underlies the east part of the Jornada del Muerto in this area. Maximum stratigraphic separation of 1,850 ft (564 m) was measured from the central segment of the fault, but this decreases toward its termination to the north and probably also to the south. In spite of the comparatively large, apparent vertical component of slip, physiographic evidence for the fault is subtle because of the extensive low-relief pediment that truncates both hanging-wall and footwall rocks. Local low scarps, a series of playa lakes, and Jornada Draw drainage are its principal physiographic expressions. However, sedimentary and volcanic rock formations ranging in age from Pleistocene to Cretaceous are truncated by the fault, and a basaltic cinder cone was constructed on the fault in late Pliocene time. There is no stratigraphic evidence that the fault developed earlier than Pliocene time. Pliocene-Pleistocene strata of the Camp Rice and Palomas Formations are syntectonic and reach a maximum known thickness of 250 ft (76 m) on the hanging-wall block, although greater thicknesses may be present in the subsurface. Thus, the fault apparently formed late in the history of the Rio Grande rift region of south-central New Mexico, probably to help accommodate growing structural relief between the Caballo uplift and Jornada del Muerto syncline. Most recent movement of 30 ft (9 m) along the fault is estimated to be approximately 0.4 Ma. Quaternary offset locally exceeds 100 ft (30 m). The earthquake potential of this fault is considered to be minimal.
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