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D. A. Lindsey

Publications and source records attributed to D. A. Lindsey.

At least 37 records · Page 2Linked to original sources
USGS1985

Reference section for the Minturn Formation (Middle Pennsylvanian), northern Sangre de Cristo Range, Custer County, Colorado

This reference section of the Middle Pennsylvanian Minturn Formation was measured in the northern Sangre de Cristo Range; the section provides a basis for comparison with the type Minturn and with possibly equivalent strata elsewhere in southern Colorado. The name "Minturn" was first applied to strata of Middle Pennsylvanian age near the town of Minturn in central Colorado (Tweto, 1949, p. 194-228; Tweto and Lovering, 1977, p. 33–53), about 180 km north of the section described, and has been extended to strata of approximately the same age that contain marine limestones in the northern Sangre de Cristo Range (Brill, 1952; Bolyard, 1959; Scott and Taylor, 1974). The Minturn reference section continues upward into the principal reference section of the overlying Pennsylvanian and Permian Sangre de Cristo Formation (Lindsey and Schaefer, 1984), and these two sections together provide a continuous record of upper Paleozoic strata in the northern Sangre de Cristo Range. The reference section was measured by tape and compass in the summer of 1980; observations were recorded on a microcassette tape recorder in the field and transcribed in the office. This method permitted rapid acquisition of data on thickness, mature of contacts, color, grain size, and sedimentary features. These data are shown on the graphic section for each distinct rock unit. Rock units having common attributes or genetic relationships have been grouped together for descriptive and interpretative purposes.

Colorado↗
USGS1984

Measured sections and discussion of the main turbidite member, Middle Pennsylvanian Minturn Formation, northern Sangre de Cristo Range, Custer and Saguache counties, Colorado

Turbidites are sediments deposited by turbid density currents. The turbidites described here are interpreted as prodelta deposits that formed in front of fan deltas and alluvial fans during the uplift of the ancestral Rocky Mountains in Pennsylvanian time. Laterally extensive, lenticular sand bodies deposited by turbidity flows crop out in the Middle Pennsylvanian Minturn Formation in the northern Sangre de Crísto Range, Custer and Saguache Counties, Colo. (figs. 1, 2). One of the turbidite-bearing intervals, informally designated the "main turbidite member," lies 90.6 m above the base of the Minturn; it reaches 150 m in thickness and extends more than 13 km along strike. The internal stratigraphy and sedimentary structures of the main turbidite member are described from the measured sections presented here. The Middle Pennsylvanian Minturn Formation of the Spread Eagle Peak thrust plate (Lindsey, Johnson, and Andriessen, 1983) consists of about 2,000 m of interbedded conglomeratic sandstone, sandstone, siltstone, and lesser amounts of conglomerate, shale, and limestone. The lower 1,500 m of the Minturn is composed mainly of prograding deltaic-alluvial cycles that contain interva1s of prodelta turbidites. The upper 500 m of the Minturn consists of deposits of small deltas and bralded streams interbedded with shallow marine limestones Interpreted as a san-delta deposit (Clark, 1982). Above the Minturn Formation, the Pennsylvanian and Permian Sangre de Cristo Formation consists of more than 1,700 m of coarse conglomerate and sandstone interpreted as an a 11uvialfan deposit (Lindsey and Schaefer, 1984). The main turbidite member is the thickest and most extensive of the intervals of prodelta turbidites in the Minturn Formation. Each turbidite interval is part of a coarsening upward sequence interpreted as a prograding fan delta. A typical prograding cycle consists of prodelta marine shale and siltstone, prodelta turbidite sandstones, delta-front sandstone and conglomerate, and deltaic and alluvial-plain sandstone, siltstone, and shale. Fossils of 1and plants (mostly Calamites, including some in growth position) are locally abundant in deltaic and alluvial sediments of the prograding cycles. The turbidites are regarded as having been deposited offshore from alluvial systems.

Colorado↗
USGS1981

Upper Oligocene evaporites in basin fill of Sevier Desert region, western Utah

The basin fill beneath the Sevier Desert of western Utah contains evaporites that were deposited in a broad closed basin. All of the basin fill penetrated by the Gulf Oil 1 Gronning contains abundant volcanic detritus and its alteration products of Cenozoic age. Fission-track dating of tuffaceous sandstone yields ages of 26-28 m.y. Fossil pollen from mudstone in the evaporite-bearing strata includes forms no older than late Oligocene, in good agreement with the fission-track ages. Thus the age of evaporites is late Oligocene and younger. Anhydrite is present throughout approximately 900m of volcaniclastic rocks in the lower part of the section cut by the Gulf hole. Fossil pollen are indicative of an arid to semiarid flora.-from Authors

Utah↗
USGS1980

The distribution and mobility of uranium in glassy and zeolitized tuff, Keg Mountain area, Utah, U.S.A.

The distribution and mobility of uranium in a diagenetically altered, 8 Ma old tuff in the Keg Mountain area, Utah, are modelled in this study. The modelling represents an improvement over similar earlier studies in that it: (1) considers a large number of samples (76) collected with good geologic control and exhibiting a wide range of alteration; (2) includes radiometric data for Th, K and RaeU (radium equivalent uranium) as well as U; (3) considers mineralogic and trace-element data for the same samples; and (4) analyzes the mineral and chemical covariation by multivariate statistical methods. The variation of U in the tuff is controlled mainly by its primary abundance in glass and by the relative abundance of non-uraniferous detritus and uraniferous accessory minerals. Alteration of glass to zeolite, even though extensive, caused no large or systematic change in the bulk concentration of U in the tuff. Some redistribution of U during diagenesis is indicated by association of U with minor alteration products such as opal and hydrous Fe-Mn oxide minerals. Isotopic studies indicate that the zeolitized tuff has been open to migration of U decay products during the last 0.8 Ma. The tuff of Keg Mountain has not lost a statistically detectable fraction of its original U, even though it has a high (??? 9 ppm) trace U content and has been extensively altered to zeolite. Similar studies in a variety of geological environments are required in order to identify the particular combination of conditions most favorable for liberation and migration of U from tuffs. ?? 1980.

Chemical Geology↗
USGS1980

U-Pb ages of uraniferous opals and implications for the history of beryllium, fluorine, and uranium mineralization at Spor Mountain, Utah

The U-Pb isotope systematics of uraniferous opals from Spor Mountain, Utah, were investigated to determine the suitability of such material for geochronologic purposes, and to estimate the timing of uranium and associated beryllium and fluorine mineralization. The results indicate that uraniferous opals can approximate a closed system for uranium and uranium daughters, so that dating samples as young as ∼1 m.y. should be possible. In addition, the expected lack of initial 230 Th and 231 Pa in opals permits valuable information on the initial 234 U/ 238 U to be obtained on suitable samples of ≲10 m.y. age. The oldest 207 Pb/ 235 U apparent age observed, 20.8 ± 1m.y., was that of the opal-fluorite core of a nodule from a beryllium deposit in the Spor Mountain Formation. This age is indistinguishable from that of fission-track and K-Ar ages from the host rhyolite, and links the mineralization to the first episode of alkali rhyolite magmatism and related hydrothermal activity at Spor Mountain. Successively younger ages of 13 m.y. and 8–9 m.y. on concentric outer zones of the same nodule indicate that opal formed either episodically or continuously for over 10 m.y. Several samples of both fracture-filling and massive-nodule opal associated with beryllium deposits gave 207 Pb/ 235 U apparent ages of 13–16 m.y., which may reflect a restricted period of mineralization or perhaps an averaging of 21−and<13−m.y. periods of opal growth. Several samples of fracture-filling opal in volcanic rocks as young as 6 m.y. gave 207 Pb/ 235 U ages of 3.4–4.8 m.y. These ages may reflect hot-spring activity after the last major eruption of alkali rhyolite.

Utah↗