Preliminary map showing known and suspected active faults in western Montana

Abstract

UNITED STAVES i'-EPAJlTMErT OF THE INTERIOR GEOLOGICAL SURVEY Pre3.iiui.nary map shoeing known and suspected active faults in western liontana Compiled by Irvinj; J. Witkind Open-file report 75-285 1975This report is preliminary and has not been edited or reviewed for conformity v?ith U.S. Geological Survey standards and nomenclature.

Data for Quaternary faults in western Montana

“…The first comprehensive compilation of late Cenozoic faults was by Pardee (1950 #46), and for many faults, this report is still the only source of information. The earliest compilations that included fault locations on a topographic base maps were by Witkind (1975 #320;1975 #819;1975 #317) for Montana and adjacent states; these maps were subsequently incorporated into the National compilation of Howard and others (1978 #312). Later, Johns and others (1982 #259) compiled data for most of the southern part of the State of Montana and maps of Stickney and Bartholomew (1987 #242;written commun.…”

“…1992 #556) were a derivative product showing those faults in Johns and others that demonstrated evidence of late Quaternary movement (i.e., field reconnaissance suggested scarps on alluvium were present). The faults that Witkind (1975 #320;1975 #819;1975 #317) interpreted to be late Cenozoic in age are not included in this compilation because they generally lack evidence of movement young enough to meet the standards of this compilation. However, the structure is included in this report if more recent studies suggest that the fault was active during the Quaternary.…”

“…References to the same structure shown in compilations by others are included in "Comments". The three principle compilations of Quaternary faults in Montana include Witkind (1975 #317), Johns and others (1982 #259), and Stickney and Bartholomew (1987 #242) and are cited extensively through this compilation.…”

“…Comments: Refers to number 104 (unnamed fault) of Witkind (1975 #320) and number 11 (Deadman fault) of Witkind (1975 #317).…”

Evaluation of a hydrothermal anomaly near Ennis, Montana

“…Displacement and eastward tilting of Pleistocene to Holocene colluvium and alluvium, with the formation of triangular facets and a discontinuous scarp that extends 64 km along the west flank of the Madison Range in and south of the study area, indicate recent movement on the Madison fault (Pardee, 1950, p. 369;Witkind, 1975). The study area is within an active earthquake zone (Smith and Sbar, 1974, fig.…”