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Walden P. Pratt

Publications and source records attributed to Walden P. Pratt.

24 records · Page 2Linked to original sources
USGS1968

Infrared imagery of Lordsburg-Silver City area, New Mexico

Night time infrared imagery of the area between Lordsburg and Silver City, New Mexico, indicates numerous applications of studies of the geology and hydrology of desert regions. Tertiary volcanic rocks consisting of flows and welded tuffs show good tonal contrasts within themselves. Precambrian granites and gneisses appear mottled. Water courses appear as dark streaks, cold water springs as dark patches, and water standing in ponds and reservoirs is bright in contrast to the darker (cooler) surrounding materials.

New Mexico↗
USGS1961

Local evidence of Pleistocene to recent orogeny in the Argentine Andes

Deformed continental sedimentary rocks are exposed in the province of Salta, northwestern Argentina, in one of many intermontane basins of the Puna, a high desert region of subparallel north-trending block-fault ranges. These rocks, formerly thought to be Tertiary but recently dated by fossil diatoms as Pleistocene or younger, comprise several thousand feet of elastics and evaporites interpreted as having accumulated in a structural basin under geologic and climatic conditions much like those of today. They are overlain unconformably by sedimentary rocks and sediments of three distinct depositional periods. The stratigraphic section is as follows: Fan gravels and playa deposits ( Recent ) - Disconformity - Flat-lying lacustrine sandstones and siltstones, minor salines - Angular unconformity - Gently folded conglomerates and sandstones - Angular unconformity - Folded and faulted conglomerate, sandstone, shale, evaporites, and tuffs The basin rocks are folded along north-trending axes and are cut by northeast- to southeast-trending normal faults and by a north-trending reverse fault; the next younger conglomerates and sandstones are gently folded; the two youngest units are undisturbed. The three unconformities, the faults and folds in the older beds, and post-lake-bed faulting of an erosion surface on an adjacent block all indicate intermittent late Pleistocene to Recent local deformation. Neither regional tension nor regional compression can explain both the Pleistocene to Recent movements on the regional block faults and the contemporaneous compressional structures within the basin. The mechanism of horst-wedging, suggested by a current explanation of the analogous ranges of the Great Basin, is proposed as a solution to the dilemma; the horst blocks, forced directly upward along Miocene normal faults, acted as wedges and compressed the sediments accumulating in the graben, creating the pattern of faults and folds now observed. If such structures are ever discovered in the North American Great Basin, as seems reasonable, they should offer new insight into the understanding of basin-and-range structure.

Andes Mountains↗
USGS1957

Core logs from Owens, China, Searles, and Panamint basins, California

Detailed logs of drill cores are presented in this report. The drill cores are of sediments from four basins that were occupied during the Pleistocene by a continuous chain of lakes. Owens Lake basin (one hole, 920 feet) contains fine-grained sediments and includes locally many diatoms and ostracodes. China Lake basin (one hole, 700 feet) contains silt- to sand-sized clastic sediments and some calcite and gaylussite; a few diatoms, ostracodes, and mollusks are present. Searles Lake basin (one hole, 875 feet) contains many layers of gaylussite- or pirssonite-bearing sediments intercalated with beds of halite, trona, and lesser amounts of other minerals peculiar to Searles Lake; the top 120 feet consists of thicker evaporite bodies with a more complex mineralogy. Panamint basin (three holes, 500, 375, and 995 feet) contains clastic deposits ranging from clay to gravel, a small amount of gypsum, anhydrite, a trace of bassanite, and thick bodies of halite in the basin center; a few diatoms and ostracodes are present.

Bulletin↗