Geology Reports⌕ Search

Geology topics

Michael N. Machette

Publications and source records attributed to Michael N. Machette.

45 records · Page 3Linked to original sources
USGS1980

Integrated uranium system in the Marysvale volcanic field, west-central Utah

Uranium in the Marysvale volcanic field is known to occur in several geologic environments, and is hypothesized to occur in others. Together the known and hypothetical occurrences range from a source in rhyolite magma, through porphyry-type deposits, hydrothermal vein deposits, dispersed hydrothermal deposits, and after transport in ground and surface water, to roll-front or sedimentary trap-deposits in basin-fill sediments. To date, only the hydrothermal vein environment has been productive, but billions of pounds of uranium were available in all other environments, and if proper circumstances occurred, significant concentrations probably exist there too. The intracaldera fill of the Mount Belknap caldera and sediment-filled basins adjoining the Tushar Mountains are especially favorable for the undiscovered uranium that may be expected.

Utah↗
USGS1978

Dating Quaternary faults in the southwestern United States by using buried calcic paleosols

Calcareous soils are widespread on upper Pliocene to upper Pleistocene unconsolidated surflcial deposits in semiarid portions of the southwestern United States. Where these soils are related to faults, the soils may provide a means for quantitatively estimating timing and amounts of Quaternary faulting. Soil age estimates are based on the amount of pedogenic CaCO 3 (g/cm 2 -soil column) that has accumulated from soil processes, whereas rates of calcic-soil formation were calibrated by the K-Ar dating method, tephrochronology, vertebrate paleontology, and regional soil studies. The County Dump fault, west of Albuquerque, N. Mex. cuts a 500 000-yearold datum, the Llano de Albuquerque. The downdropped block of this fault contains a sequence of faulted younger deposits and intercalated calcic paleosols. Soil ages, and hence fault ages, can be calculated by measuring the total pedogenic calcium carbonate content in a section of buried paleosols and by using an independently established maximum soil formation rate of 0.35 g CaCO 3 • cm -2 • 10 -3 yr -1 for the Albuquerque area. This particular fault segment has had four discrete episodes of movement in the past 500 000 yr, the most recent of which occurred about 20000 yr B.P. Recurrence intervals on the segment are 90 000-190 000 yr, but the composite recurrence interval for all fault movements in this area may be less by several orders of magnitude. This technique of quantifying soil properties and calculating ages of relict soils can be used to estimate ages of Quaternary deposits and associated surfaces, to correlate such features over broad regions, and to analyze regional trends in calcic-soil formation.

New Mexico↗
USGS1977

Calcic soils and calcretes in the southwestern United States

Secondary calcium carbonate of diverse origins, 'caliche' of many authors, is widespread in the southwestern United States. 'Caliche' includes various carbonates such as calcic soils and products of groundwater cementation. The term 'caliche' is generally avoided in this report in favor of such terms as calcrete, calcic soils, and pervasively cemented deposits. Criteria for the recognition of various types of calcrete of diverse origins include field relations and laboratory data. Calcic soils provide a comprehensive set of characteristics that aid in their recognition in the field. These characteristics include a distinctive morphology that is zoned horizontally and can frequently be traced over tens to hundreds of square kilometers. The major process in the formation of pedogenic calcrete and calic soils is the leaching of calcium carbonate from upper soil horizons by downward percolating soil solutions and reprecipitation of the carbonate in alluvial horizons near the base of the soil profile. The formation of pedogenic calcrete involves many factors including climate, source of carbonate, and tectonic stability of the geomorphic surface on which the calcrete is deposited. Most of the carbonate in pedogenic calcrete is probably derived from windblown sand, dust, and rain. Calcic soils and pedogenic calcretes follow a six-stage sequence morphologic development and is based on a classification devised by Gile, Peterson and Grossman in 1966. The .six morphologic stages of carbonate deposition in soils are related to the relative age of the soil and are as follows: I. The first or youngest stage includes filamentous or faint coatings of carbonate on detrital grains. II. The second stage includes pebble coatings which are continuous; firm carbonate nodules are few to common. III. The third stage includes coalesced nodules which occur in a friable or disseminated carbonate matrix. IV. The fourth stage includes platy, firmly cemented matrix which engulfs nodules; horizon is plugged to downward moving solutions. V. The fifth stage includes soils which are platy to tabular, dense, strongly cemented. A well-developed laminar layer occurs on the upper surface. VI. The sixth and most advanced stage is massive, multilaminar, and strongly cemented calcrete with abundant pisoliths, the upper surface of which may be brecciated. Pisoliths may indicate many generations of brecciation and reformation. In general calcic soils include stages I through III and are friable to moderately indurated; whereas pedogenic calcretes include stages IV through VI and are dense and strongly indurated. In a single pedon the morphologic stage of carbonate deposition decreases downward in the profile. The stage of development may be used in local regions for correlation and determination of relative ages of soils and geomorphic surfaces. Some structures observed in pedogenic calcretes may be present in other types of calcrete but the horizontal zonation typical of deposits of soil processes is absent. Laminar structure in particular is not restricted to pedogenic deposits and is common in many varieties of calcrete. Very little chemical change occurs in the noncalcareous nonclayey fractions of calcretes with age; but clay minerals within calcretes undergo a complex history of authigenesis. There is a depletion of magnesium in the calcareous portion and an enrichment of magnesium in the clayey portion of a calcrete with age. In keeping with this relationship, montmorillonite, or mixed layer montmorillonite-illite, is common in younger calcretes; whereas the high magnesium-silicate clays, sepiolite and palygorskite, are common in older calcretes. This indicates that the magnesium depleted from the carbonate is redistributed authigenically in clay minerals. The mobility of carbonate introduces many problems in attempts to date calcretes directly. Although the relative ages of soils within a province may be determined by quant

Open-File Report↗