Steven R. May

University of Texas at Austin | UT · Department of Geological Sciences

We present the first description of Jurassic vertebrate fossils from Texas. The vertebrate specimens were collected from the Upper Jurassic Malone Formation in the Malone Mountains of western Texas. The specimens are fragmentary and not particularly diagnostic, but probably represent elements of plesiosaurians. One specimen is similar to the caudal...

In order to test for paleoenvironmental and paleoecological parameters important in dinosaur evolution, thirty-four fragments of dinosaur eggshell, paleosol carbonates from six localities, and calcite crystals from inside a dinosaur femur were collected from the Campanian to Maastrichtian Baruungoyot and Nemegt formations, Gobi Desert, Mongolia. Th...

Fossil vertebrates from the Alturas Formation in northern California have previously been considered important for defining the age of the boundary between the Hemphillian and Blancan North American Land Mammal Ages. Diatomaceous mud-stone of the upper Alturas Formation contain fossil mammals including the arvicoline rodent Mimomys (Ogmodontomys) s...

The Bench 19 Bonebed at Bentiaba, Angola, is a unique concentration of marine vertebrates preserving six species of mosasaurs in sediments best correlated by magnetostratigraphy to chron C32n.1n between 71.4 and 71.64 Ma. The bonebed formed at a paleolatitude near 24°S, with an Atlantic width at that latitude approximating 2700 km, roughly half tha...

Tectonostratigraphic assemblages record phases of basin history during which the fundamental controls of tectonic setting, sub sidence style, and basin geometry are relatively similar. Because these fundamental controls, in combination with climate and eustasy, influence paleogeography and sediment-dispersal patterns, they should also yield similar...

A high-flux, Late Cretaceous magmatic event in the western United States has been tested as a zircon source for high-resolution chronostratigraphic correlation in coeval sedimentary rocks in northwest Wyoming. Thirteen samples of Cenomanian-Coniacian sandstone in the Bighorn Basin yielded more than 1200 U/Th/Pb detrital zircon ages from the Mowry S...

The Horned Toad Formation includes five lithostratigraphic members that record alluvial fan, fluvial, lake margin, and lacustrine deposition within a relatively small basin just south of the active Garlock fault during the late Miocene to early Pliocene. These sediments experienced northwest-southeast contractional deformation during the Pliocene-P...

Each of the Earth's approximately 900 sedimentary basins is a unique result of geologic, hydrologic, atmospheric and biologic processes. The interaction of these processes results in complex histories that are palaeogeographically linked within tectonic provinces. Process-based genetic analysis provides the fundamental framework for predicting the...

Volume interpretation and visualization technologies are having a significant impact on upstream geoscience and engineering activities at ExxonMobil. From regional exploration to mature field development, from seismic interpretation to detailed well planning, from macroscopic to microscopic scales, volume interpretation and visualization technologi...

Upper Miocene sedimentary rocks of the Ridge basin provide an opportunity to evaluate the relationship between tectonics, subsidence history, and basin fill in an extensional strike-slip setting. Cyclicity of strata within the Ridge basin, which is expressed by the progradational members of the Ridge Route Formation and retrogradation within the Vi...

The Ridge basin contains as much as 14 km of Mio-Pliocene marine and nonmarine sedimentary fill. Pliocene to Holocene deformation, uplift, and dissection of this basin provide an opportunity to study stratal geometry and sedimentary facies in what is commonly cited as a classic "strike-slip' basin. Newly acquired seismic data from the northern Ridg...

Stratigraphic, petrologic, and isotopic data indicate that parts of the Coast Plutonic Complex and the North Cascade Range have been tilted northeast-side-up by angles of ˜30° about north-northwest-trending axes. These tilts can account for discordant paleomagnetic directions observed in mid-Cretaceous plutons from these regions without large-scale...

The North American apparent polar wander (APW) path indicates an episode of unusually rapid absolute northward motion of western North America between 150 and 135 Ma. During this time the northward component of absolute motion of points along the Washington-Oregon-California coast was in excess of 150 km/m.y. and perhaps as high as 230 km/m.y. We b...

The purpose of this paper is to review the progress made over the past four years in studies of Phanerozoic and Precambrian polar wander, with an emphasis on the contributions made by U.S. scientists. We perceive a general theme embracing the notion that the accuracy of cratonic “reference poles” and therefore of apparent polar wander (APW) paths i...

A new Jurassic apparent polar wander (APW) path for North America is developed. Various techniques for constructing APW paths, and the relation between the paths and geologic time scales are described. The paleomagnetic Euler pole technique is utilized to analyze the geology and distribution of nine reliable Jurassic and Early Cretaceous reference...

Paleomagnetic study of Middle Jurassic volcanic and volcaniclastic rocks in southeastern Arizona yields a paleomagnetic pole located at 61.8°N, 116.0°E (k=49.6, alpha95=6.2°). These rocks from corral Canyon represent an autochthonous segment of the Jurassic Cordilleran magnetic arc and were deposited directly on Upper Paleozoic carbonates of the cr...

A fundamental limiting factor in the precision of magnetostratigraphic correlation is stratigraphic completeness. Sadler [1981] has suggested a method by which the expected completeness of any given stratigraphic section can be calculated given the thickness, duration, and depositional environment. The technique is probabilistic and requires the in...

Paleomagnetic samples were collected from 15 sites in the early Cretaceous Puente Piedra Formation near Lima, Peru. This formation consists of interbedded volcanic flows and marine sediments and represents the oldest known rocks of the Andean coastal province in this region. The Puente Piedra Formation is interpreted as a submarine volcanic arc ass...

The Mount Eden fauna, first described by Childs Frick in 1921, is an important late Hemphillian mammalian fauna from the San Timoteo Badlands of southern California. Identification of Repomys maxumi May, an early hypsodont cricetid rodent, and the results of geomagnetic-polarity determinations indicate that this fauna correlates with the lower reve...

Repomys is a new genus of hypsodont cricetine from the late Neogene of California and Nevada. Three new species define its known temporal and geographic distribution: Repomys gustelyi n. sp. (type species), late Hemphillian, Mojave Desert, California; Repomys maxumi n. sp., early Blancan, San Francisco Bay area, California; and Repomys panacaensis...

Thesis (Ph. D. - Geosciences)--University of Arizona, 1985. Includes bibliographical references (leaves 214-227).

Thesis (Ph. D. - Geosciences)--University of Arizona, 1985. Bibliography: leaves 214-227. Microfiche. s