The San Pedro Zacapa quadrangle lies along the valley of the Río Ulúa, just southwest of Lago de Yojoa in west-central Honduras. Most of the area lies within the sierras of northern Central America; volcanic ranges and plateaus encroach upon the quadrangle from the south. No pre-Cretaceous rocks are exposed, but a basement of Paleozoic or older low grade metasediments and metavolcanic rocks is known to underlie this region. Very probably a thick section of Jurassic continental clastic strata is also present below the Cretaceous units. The oldest exposed strata belong to the Albian Atima Formation, carbonate shelf deposits of thick-bedded micrite. Late Cretaceous-early Tertiary redbeds of the Valle de Ángeles Group conformably overlie the Atima limestone. The redbeds have been informally divided into three members: a lower member of coarse continental clastic strata, a middle member of Cenomanian shallow marine limestone, and an upper member of fine-grained redbeds with associated gypsum, limestone conglomerate, and coarse metamorphic-rock conglomerate. The Cenomanian limestone member probably is not correlative with the Esquías limestone (which is thought to be Eocene, and does not crop out in the map area). Previous reports included the Cenomanian limestone within the Atima Formation; however, the extensive redbed section separating the limestones makes it apparent that the upper limestone is a part of the Valle de Ángeles Group. After deposition of the Valle de Ángeles limestone member, the region was subjected to late Cretaceous-early Tertiary deformation which produced normal faults and east-trending, broad, open folds in the Atima Formation and lower members of the Valle de Ángeles Group. Limestone conglomerate was shed into the central part of the quadrangle from upfaulted limestone highlands to the northeast. A quartz microdiorite was emplaced at Cerro Lavanderos. To the southeast more severe deformation resulted in the Montaña de Comayagua structural belt, which trends N. 60° W. across central Honduras. Fine-grained andesitic flow rocks of the Matagalpa Formation were erupted subaerially across eroded Mesozoic strata beginning in Oligocene time. These eruptions were probably related to subduction along the Middle America Trench. Following a quiescent period, voluminous mid-Miocene and Pliocene ignimbrites with associated tuffaceous strata and flows were deposited nonconformably over Matagalpa rocks throughout much of northern Central America. The Zacapa area lies to the north of the main accumulations of Padre Miguel ignimbrites; fluviatile tuffaceous strata comprise the bulk of the Padre Miguel Group in the map area. A 400 meter thick pile of basaltic flows was built up around a local eruptive center along the Ulúa fault system. Late Cenozoic normal faulting, primarily along northwest and northeast trends, has occurred almost continuously since Matagalpa time. The Santa Bárbara graben, a major depression with more than 1500 meters of structural relief, extends from the south-central part of the Zacapa quadrangle for thirty-five kilometers to the northwest. North of the map area the graben is bounded by a large horst block which appears to have been uplifted by a deep-seated intrusion. Important silver and base metal mineralization at El Mochito is associated with this intrusion. During Plio-Pleistocene time the Santa Bárbara graben was partially infilled by up to 200 meters of valley fill conglomerate, sandstone, and siltstone derived primarily from Tertiary volcanic units, but including redbed detritus as well. Present-day streams are removing this fill and down-cutting into older units. Minor Quaternary basalt eruptions occurred at the north end of Lago de Yojoa, and within the map area a small Quaternary (?) eruption issued from a fault along the Horconcitos horst. Small pockets of stibnite and impure gypsum are the only deposits of economic interest in the Zacapa quadrangle. / text

No description available.

A detailed geologic investigation was made of the eastern part of the Dairy Ridge Quadrangle and the western part of the Meachum Ridge Quadrangle, Utah. The area is located in north-central Utah in Rich County. It lies between lat. 41°22'30" N. and lat. 41° 28'50" N. and between long. 111° 21'40" W. and long. 111°25'15" W. The area measures 13.8 km in the north-south direction and 5.5 km in the east-west direction. It is on the eastern side of the Wasatch Range about 20 km west-southwest of Randolph, Utah. Stratigraphic units of Precambrian to Cambrian age crop out in the western part of the area, above the Woodruff thrust fault, and dip west. These include the Precambrian Mutual Formation and the Cambrian Geertsen Canyon Quartzite. Units of Pennsylvanian to Jurassic age crop out in the eastern part of the area below the Woodruff thrust fault. They dip west and are overturned to the east. These units include the following: Pennsylvanian Weber Formation, Permian Grandeur Member of the Park City Formation, Permian Phosphoria Formation, Triassic Thaynes Limestone, Triassic Ankareh Formation, Jurassic Nugget Sandstone, and Jurassic Twin Creek Limestone. The Tertiary Wasatch Formation unconformably overlies all older units in places. The Woodruff thrust fault is the major structural feature of the area. Quartzite of the Precambrian Mutual Formation is thrust eastward over the Pennsylvanian Weber Formation as well as over formations of Permian and Triassic ages. The Woodruff thrust fault strikes about N. 20° E. and dips 18° W. to 33° W. Stratigraphic throw is at least 5,800 m. Probable horizontal displacement is tens of kilometers. The stratigraphic units, under the thrust fault, dip west and are overturned to the east. They form the western limb of a large asymmetrical syncline. The overturned units are cut by a west-dipping high-angle thrust fault. The syncline and the thrust faults were produced by the Sevier orogeny which began in latest Jurassic or earliest Cretaceous time. Deformation may have continued into Paleocene time.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Master of Science / Department of Geology / Charles G. Oviatt / The Dyer Mountain quadrangle, located in Utah approximately 200 km east of Salt Lake City and 20 km north of Vernal, lies on the south flank of the east-west trending Uinta anticline. The topography of the area varies from mountain peaks to deep canyons, with rolling hills of uplands in between. The elevation in the quadrangle ranges from 3124 m (10248 ft) at the top of Dyer Mountain to 1835 m (6020 ft) at the lowest point of Big Brush Creek. Most of the northern portion of the quadrangle is vegetated by aspens and pines, whereas the southern part of the quadrangle is covered with sagebrush and grasses. Due to its location on the anticline, the quadrangle contains bedrock that dips gently to the south and southeast. The ages of the rocks within the quadrangle range from the Precambrian Uinta Mountain Group to the Quaternary and Tertiary gravels. Also present are the following formations: Cambrian Lodore; Mississippian Madison, Doughnut, and Humbug; Pennsylvanian Round Valley and Morgan; Pennsylvanian to Permian Weber; Permian Meade Peak Member of the Phosphoria and Franson Member of the Park City; and various Quaternary sediments. The Lodore Formation and the Madison Limestone rest on major unconformities, and the Quaternary and Tertiary gravels overlie the Gilbert Peak erosion surface. The Uinta anticline and southerly dip of the Proterozoic and Paleozoic rocks are a result of Late Cretaceous uplift during the Laramide orogeny; Tertiary rocks within the area show little to no deformation. Limestone and various types of ores have been mined in the quadrangle, and phosphorous is currently being mined for fertilizer production. Several landslides, common at the juncture of the Quaternary and Tertiary gravels and Permian shales, were identified within the quadrangle. An anticline and syncline, trending northwest to southeast, lie in the southeast portion of the quadrangle and transect Big Brush Gorge. Geologic hazards of the area include landslides, erosion and failure of road grades, and cliffs near trails. The karst topography of the area presents dangers of sink holes, and evidence of ceiling collapse is present within Big Brush Cave, a popular destination for tourists and cavers.

The mapped area, in north-central Utah, is centered about 22.6 miles south of Logan, Utah. It measures about 3.8 miles in the north-south direction and 6.6 miles in the east-west direction. Stratigraphic units of Precambrian and Cambrian age underline most of the area. The Precambrian units are as follows: (1) Maple Canyon Formation, (2) Kelley Canyon Formation, (3) Orthoquartzite unit, (4) Argillite unit, (5) Mutual Formation, and (6) Volcanic unit. The Brigham Formation, which overlies the Precambrian volcanic unit, is probably of Cambrian age; however, the lower part may be Precambrian. The overlying Cambrian carbonate unit is not differentiated. The Salt Lake Formation of Tertiary age overlaps older rocks in the valley north of James Peak. The western part of James Peak, east of a major normal fault, consists of east-dipping Precambrian units. The oldest unit, which crops out on the eastern side of Broadmouth Canyon, is the Maple Canyon Formation. The rocks of the eastern part of James Peak also dip generally eastward. A continuous stratigraphic section extends from the Kelley Canyon Formation, exposed in Wolf Creek Canyon, northeastward to the Brigham Formation. The Cambrian carbonate unit seems to overlie the Brigham in normal stratigraphic succession. A thrust fault, which has about 1,000 feet of displacement, is present on the eastern side of James Peak. Another thrust fault, on the southeastern side of James Peak, places the Cambrian carbonate unit on Precambrian units. A block of the Brigham Formation, near the southeastern corner of the area, is thrust over the carbonate unit and the Brigham. The thrust faulting is part of the Laramide Orogeny that occurred late in the Mesozoic Era and early in the Teritary Period. Movement was generally eastward. Normal faulting began early in the Tertiary Period and continues at the present time.

Youthful karst topography and entrenched drainage are two conspicuous geomorphic aids in interpreting the geologic history of the Waco Springs quadrangle. Three high angle, dip slip strike faults of the Balcones system, displaced toward the coast, have off-set all, and exposed most, of the southeastward dipping Comanchean and Gulfian rocks. Broad shallow anticlines are created by a "reversal of dip" on each downthrown fault block. Waco Springs, located in the southwestern part of the map area, has a separate groundwater reservoir from the remainder of the quadrangle, and its discharge is dependent on rainfall concentrated in central Comal County. / text

The northern part of the Oxford Quadrangle, Idaho, includes parts of the Bannock Range to the west and the Portneuf Range to the east. These ranges are separated by Marsh Valley to the north and Cache Valley to the south. Red Rock Pass, the outlet of glacial Lake Bonneville, divides the two valleys. The mapped area is north of Preston, Idaho, and south of Downey, Idaho. The north-south dimension of the mapped area is 5.2 miles and the east-west dimension is 6.4 miles. The stratigraphic units, within the mapped area, are Precambrian, Paleozoic, and Cenozic in age. The oldest rock unit is the Pocatello Formation of late Precambrian age. Other Precambrian units, in ascending order, are the Papoose Creek Formation and the Caddy Canyon Quartzite. The Precambrian units are dominantly argillite and quartzite with some extrusive and intrusive metaigneous rocks. The Cambrian formations, in ascending order, are the Langston, Ute, Blacksmith, Bloomington, Nounan, and St. Charles Formations. The Cambrian units are dominantly limestone and dolomite, with interbedded shale. Ordovician formations consist of the basal Garden City Formation which is limestone and the Swan Peak Formation which is quartzite. The Tertiary Salt Lake Formation is dominantly tuff and conglomerate. The Quaternary is represented by colluvial deposits, Lake Bonneville Group, and alluvial deposits. Major structural features, within the mapped area, are thrust faults and normal faults. A major thrust fault places Middle Cambrian rocks on Precambrian rocks and eliminates a significant part of the stratigraphic column. Thrust faults are also present between Papoose Creek Formation and Caddy Canyon Quartzite, Bloomington and Nounan Formations, St. Charles and Garden City Formations, and Garden City and Swan Peak Formations. The evidence, within the mapped area, indicates eastward thrusting. The normal faults postdate the thrust faults and offset Salt Lake Formation. The normal faults generally trend north-northwest. These structural features are the result of two separate events. The thrust faulting and related deformation is late Jurassic to Eocene in age. The Basin and Range normal faulting began in late Eocene and continued to Holocene.

The Smithfield 7.5' quadrangle is located about 13.8 kilometers (8.6 miles) south of the Utah-Idaho State Line and occupies the central portion of the eastern side of Cache Valley, Utah. The mapped area contains more than 55 square miles. The Bear River Range on the eastern side of the quadrangle contains stratigraphic units ranging from Precambrian to Quaternary age. Cache Valley contains deposits of Tertiary and Quaternary age. Quaternary units in the Smithfield quadrangle are subdivided into thirty-two map units based on age and genesis. Five ages of Quaternary units are identified, and these units are assigned to one of fourteen genetic types. The East Cache fault zone is mapped along the western edge of the Bear River Range. Early Quaternary time was principally a period of pediment formation, followed by normal faulting, erosion, and alluvial-fan deposition. Cache Valley was later occupied by a pre-Bonneville cycle lake which is tentatively correlated with the Little Valley lake cycle. This lacustrine cycle was followed by more erosion and alluvial-fan deposition. The current Cache Valley landscape is dominated by the sediments and geomorphic features of Pleistocene Lake Bonneville. Alluvial-fan deposition has been the principal geologic process in post-Lake Bonneville time. Geologic hazards in the Smithfield quadrangle include flooding, landslides, debris flows, rock fall, problem soils, shallow ground water, earthquake ground shaking, surface fault rupture, and liquefaction. Some of the areas affected by these hazards and measures for mitigating the hazards are identified. Bonneville lake cycle fine-grained offshore deposits and the Tertiary Salt Lake Formation are the primary geologic units susceptible to landsliding.

The study area encompasses a region of about 80 square kilometers, centered about Corbett, Oregon. Sieve analyses suggest that the Troutdale Formation is composed of a conglomerate, a coarse-grained sandstone, and a siltstone lithofacies. Measured sections data show that 56 to 60 percent of the Troutdale Formation's exposures are composed of the conglomerate lithofacies. The coarsegrained sandstone lithofacies makes up 34 to 38 percent, while the siltstone lithofacies makes up only 4 to 8 percent. Pebble count data show that the representation of basalt varies from 69 to 100 percent, with an average of 85 percent, while quartzite varies from 0 to 25 percent, with an average of 9 percent. Geochemical data show that at least one formal member and two informal members of the Columbia River Basalt Group (Frenchman Springs, Grande Ronde High Mg, and Grande Ronde Low Mg) compose part of the detritus. The geochemical data also show that rocks of the Boring Lavas or similar lavas are intercalated with the Troutdale Formation, high in the section. Grain mount petrographic data show that volcanic rock fragments are the dominant component in the coarse sand fraction of the Troutdale Formation. Many of the volcanic rock fragments contain brown glass with an index of refraction of 1.583 +/- 0.001, which indicates a mafic composition {silica content of 50 +/- 1 percent). The representation of volcanic rock fragments varies from 29 to 98 percent, with an average of 75 percent. Sedimentary rock fragments, such as chert, vary from 0 to 17 percent, with an average of 5 percent. Biotite ranges from 0 to 12 percent, with an average of 2 percent. Two-thirds of the samples which contain sedimentary rock fragments also contain biotite. Orthopyroxene varies from 0 to 18 percent, with an average of 5 percent. 2 The samples with the three greatest amounts of orthopyroxene do not contain sedimentary rock fragments or biotite.