A late Eocene erosion sudace of low relief, which extended throughout south-central Colorado, provides a post-Laramide, pre-Oligocene, regional structural datum. The age and geomorphic character of the sudace are documented for an area of more than 10,400 km2 in the southern Front Range, Rampart Range, South Park, Thirtynine Mile volcanic field, southern Mosquito Range, upper Arkansas River val...

Three new genera and four new species of omomyid primates constitute the first record of the Primates from upland middle Eocene rocks of Wyoming. One of these, Strigorhysis, gen. nov., possesses broadly basined molars with highly crenulated enamel which probably indicates a good deal of tough vegetable matter in its diet. Each of the new genera could have descended from known Wasatchian or earl...

the kuh shah prospecting area is located in tertiary volcano-plutonic belt of the lut block. more than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. the intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hy...

Tertiary meteoric hydrothermal systems have altered the rocks exposed over more than S% of the land surface of the northwestern United States and southern British Columbia, including at least 25,000 1m? in Idaho. The systems typically involved convective circulation of fluid derived from ordinary meteoric groundwater& around crystallizing, calc-alksline, epizonal plutons eiiiP.laced into coeval...

Newly discovered xenoliths within Pliocene and Quaternary intermediate volcanic rocks from southern Peru permit examination of lithospheric processes by which thick crust (60–70 km) and high average elevations (3–4 km) resulted within the Altiplano, the second most extensive orogenic plateau on Earth. The most common petrographic groups of xenoliths studied here are igneous or meta-igneous rock...