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R.E. Wilcox

Publications and source records attributed to R.E. Wilcox.

11 recordsLinked to original sources
USGS2017

Age of the last major scabland flood of the Columbia Plateau in eastern Washington

Pumice layers of set S from Mount St. Helens can be correlated with certain ash beds associated with young flood deposits of the channeled scabland. The correlation points to an age of about 13,000 14 C yr B.P. for the last major flood to have crossed the scabland. Until recently, the last major episode of flooding was thought to be closer to 20,000 yr B.P., an age inferred chiefly from the relation of the flood to glacial events of the northern Rocky Mountains. Several investigations within the last few years have suggested that the last major flood occurred well after 20,000 yr B.P. Tentative correlations of ash beds of the scabland with set S pumice layers, the relations of flood and glacial events along the northwestern margin of the Columbia Plateau, and a radiocarbon date from the Snake River drainage southeast of the plateau all indicate an age much younger than 20,000 yr. The postulated age of about 13,000 yr B.P. is further supported by a radiocarbon date in the Columbia River valley downstream from the scabland tract. Basal peat from a bog on the Portland delta of Bretz, which is a downvalley deposit of the last major scabland flood, has been dated as 13,080 ± 300 yr B.P. (W-3404).

Washington↗
USGS2014

Activity of Parícutin volcano from December 1, 1946 to March 31, 1947 patterns

A record of the activity of Parícutin Volcano, Michoacán, Mexico, is shown in the diagram of eruptive characteristics, Figure 1, covering the period December 31, 1946 to March 31, 1947, and is supplemented by the maps of the areal extent of the lava flows, Figures 2 and 3. This continues the previous record for the period from September 18 to November 30, 1946 [Trans. Amer. Geophys. Union, v. 28, no. 4, pp. 567–572, 1947], and reference is made to that report for explanatory discussion of the diagram of eruptive characteristics and for general information concerning the methods of investigation. As shown in Figure 1, the periods of predominantly heavy pyroclastic eruption occurred December 16 to February 14 and March 15 to 28. The periods of greater effusion of lava occurred December 1 to 20 and January 22 to February 25.

Parícutin, Michoacán↗
USGS1992

The Pearlette family ash beds in the Great Plains: Finding their identities and their roots in the Yellowstone country

For many years the numerous deposits of so-called 'Pearlette volcanic ash' in the Great Plains region of the United States were considered to be the remnants of the same volcanic event, and were used as a time-stratigraphic marker of probable Middle Pleistocene age. Although a few early workers had suggested that more than one air-fall event might be represented among the Pearlette occurrences, it was not until the latter half of the present century, after identification of volcanic ash beds by detailed chemical and mineralogical methods had been developed, that it could be established that the 'Pearlette family' of volcanic ashes included three ash beds of subtly differing characteristics. Development of isotopic methods of age determination has established that the ages of the three are significantly different (2.09, 1.29, and 0.60 Ma). The area of distribution of the Pearlette family ash beds was found to include not only the Great Plains, but also to extend across the Rocky Mountain and the Basin and Range provinces to the Pacific Ocean. The search for the sources of these three similar appearing ash beds, facilitated greatly by information gained from concurrent mapping projects underway in areas of major Late Cenozoic volcanic activity in western United States, ultimately led to the sites of the caldera-forming eruptions in the Yellowstone National Park region. ?? 1992.

Quaternary International↗
USGS1986

Deglaciation of the mountainous region of northwestern Montana, U.S.A., as indicated by late Pleistocene ashes

During the late Wisconsin glaciation, the mountainous regions of northwestern Montana were covered by glacial ice. Marias Pass, on the Continental Divide immediately south of Glacier National Park, was covered by a local ice field. This ice and that from other glaciers to the north and south flowed eastward onto the plains of Montana to form the Two Medicine Glacier, a large piedmont glacier that extended 55 km beyond the mountain front. The presence of the Glacier Peak G ash and the underlying St. Helens Jy ash in laminated lake sediments near Marias Pass indicates that in this region the Continental Divide was ice free before about 11,400 BP. Macrofossils, pollen, and spores in these same sediments indicate establishment of shrubs, herbs, and scattered conifers by that time. At Sun River Canyon, about 90 km south of Marias Pass, glaciers also flowed beyond the mountain front onto the plains to form the Sun River Glacier, another large piedmont glacier that extended beyond the mountain front for 25 km. The presence of the Glacier Peak G ash in a postglacial alluvial fan indicates that glacial ice had receded upvalley from the canyon mouth and that the Sun River Glacier no longer existed by 11,200 BP.

Montana↗
USGS1964

Volcanic ash from Mount Mazama (Crater Lake) and from Glacier Peak

New petrographic and chemical data indicate that the great Mount Mazama eruption at Crater Lake, Oregon, about 6600 years ago was the source of most ash which has been called "Glacier Peak" and of some ash called "Galata." Glacier Peak volcano in Washington was itself the source of an older ash deposit, perhaps very late glacial or early postglacial in age.

Oregon, Washington↗