The tonalite–trondhjemite–granodiorite (TTG)
... zircon sensitive high-resolution ion microprobe (SHRIMP) date of 2952 ± 4 Ma, and a granodiorite dike within the supracrustal sequence at Hazelton Peak was intruded at 2949 ± 5 Ma (Frost and Fanning 2006). A layered tonalite gneiss from the E-1 gneisses of Barker (1982) is somewhat younger, at 2886 ...
... zircon sensitive high-resolution ion microprobe (SHRIMP) date of 2952 ± 4 Ma, and a granodiorite dike within the supracrustal sequence at Hazelton Peak was intruded at 2949 ± 5 Ma (Frost and Fanning 2006). A layered tonalite gneiss from the E-1 gneisses of Barker (1982) is somewhat younger, at 2886 ...
Carbonates and associated sedimentary rocks of the Upper Visgan
... the Cape Breton Highlands. They also underlie large areas in the Sydney Basin and in central parts of the island. These strata range in age from latest Devonian to latest Carbonif erous (Bell and Howie, 1990) and provide the local record of sedimentation in this portion of the Maritimes Basin as de ...
... the Cape Breton Highlands. They also underlie large areas in the Sydney Basin and in central parts of the island. These strata range in age from latest Devonian to latest Carbonif erous (Bell and Howie, 1990) and provide the local record of sedimentation in this portion of the Maritimes Basin as de ...
characterization and reconstruction of the tea cup porphyry system
... Volcanics and broadly correlative units were deposited at this time. A period of tectonic quiescence and erosion took hold after Laramide time until ~25 Ma, when extension began to dismember the Laramide porphyry systems and surrounding rocks (Howard and Foster, 1996). Locally, areas in the Northern ...
... Volcanics and broadly correlative units were deposited at this time. A period of tectonic quiescence and erosion took hold after Laramide time until ~25 Ma, when extension began to dismember the Laramide porphyry systems and surrounding rocks (Howard and Foster, 1996). Locally, areas in the Northern ...
Chapter 5
... on surface bacteria and fallen particles of organic sediment. Note that the surface of the sediment is not always smooth. Where bottom currents are swift and persistent, they can cause ripples like those on a streambed (Figure 5.3). The extraordinary thickness of some layers of marine sediment can b ...
... on surface bacteria and fallen particles of organic sediment. Note that the surface of the sediment is not always smooth. Where bottom currents are swift and persistent, they can cause ripples like those on a streambed (Figure 5.3). The extraordinary thickness of some layers of marine sediment can b ...
The Picuris Formation - New Mexico Geological Society
... stratigraphic nomenclature of the study area is extraordinarily complex......due to interfingering of distantly and locally derived nonmarine units of widely differing provenance and lithology. There are many examples of published geologic maps with different stratigraphic units mapped in the same pl ...
... stratigraphic nomenclature of the study area is extraordinarily complex......due to interfingering of distantly and locally derived nonmarine units of widely differing provenance and lithology. There are many examples of published geologic maps with different stratigraphic units mapped in the same pl ...
Geology of the Corona South quadrangle and the Santa Ana
... The rejriou in jreneral eonsists of alluviated valleys separated hy rather narrow mountain raufies, whicli trend northwestward. The tlat lanils are mostly less tiian 1, ;")()() feet above sea level and slope jrently up to the bases of the mountain raiifres. The mountains rise sharply above the alluv ...
... The rejriou in jreneral eonsists of alluviated valleys separated hy rather narrow mountain raufies, whicli trend northwestward. The tlat lanils are mostly less tiian 1, ;")()() feet above sea level and slope jrently up to the bases of the mountain raiifres. The mountains rise sharply above the alluv ...
Stratigraphy and Host Rock Controls of Gold Deposits of the
... 1994 has been achieved from these large, disseminated gold deposits hosted by carbonate strata of the Devonian-Silurian Roberts Mountains Formation and the Devonian Popovich Formation. Host rocks are composed of silty limestone with intercalated biogenic debris that were deposited along the western ...
... 1994 has been achieved from these large, disseminated gold deposits hosted by carbonate strata of the Devonian-Silurian Roberts Mountains Formation and the Devonian Popovich Formation. Host rocks are composed of silty limestone with intercalated biogenic debris that were deposited along the western ...
GEOLOGY OF PRE-MESOZOIC BEDROCK OF THE AMHERST
... Connecticut Valley border fault and on the west by an unconformity in places and in other places by east-dipping normal faults of small displacement (Wheeler, 1937; Krynine, 1950). The northern basin, called the Montague (Emerson, 1917; Goldstein,1976) or Deerfield basin (Chandler, 1978), extends 24 ...
... Connecticut Valley border fault and on the west by an unconformity in places and in other places by east-dipping normal faults of small displacement (Wheeler, 1937; Krynine, 1950). The northern basin, called the Montague (Emerson, 1917; Goldstein,1976) or Deerfield basin (Chandler, 1978), extends 24 ...
Papers presented to the Conference on Heat and Detachment in
... Reconnaissance field work has led to the recognition of extensive Early Tertiary gneiss and schist which are distinguished by weakly developed to highly conspicuous northeast to east-trending stretching lineation commonly accompanied by low-dipping foliation. This structural fabric has been imposed ...
... Reconnaissance field work has led to the recognition of extensive Early Tertiary gneiss and schist which are distinguished by weakly developed to highly conspicuous northeast to east-trending stretching lineation commonly accompanied by low-dipping foliation. This structural fabric has been imposed ...
Sedimentology of Middle Precambrian Animikean Quartzites
... consists of more than 5000 feet of dark slate and graywacke, with lesser amounts of amphibolite, agglomerate, iron-formation and quartzite. C. E. Dutton (1964) has interpreted the two units to be in separate northwest-southeast trending fault blocks of Michigamme Slate (fig. 1). Because they crop ou ...
... consists of more than 5000 feet of dark slate and graywacke, with lesser amounts of amphibolite, agglomerate, iron-formation and quartzite. C. E. Dutton (1964) has interpreted the two units to be in separate northwest-southeast trending fault blocks of Michigamme Slate (fig. 1). Because they crop ou ...
Memoir 36: Geology of Organ Mountains and southern San Andres
... describe sections of Paleozoic rocks that had not been described in detail or subdivided into up-to-date stratigraphic units, and finally 3) to investigate relationships between the Organ batholith and volcanic rocks in the southern Organ range, which recently were shown to be of the same age. Durin ...
... describe sections of Paleozoic rocks that had not been described in detail or subdivided into up-to-date stratigraphic units, and finally 3) to investigate relationships between the Organ batholith and volcanic rocks in the southern Organ range, which recently were shown to be of the same age. Durin ...
NWGS Methow
... of the Methow block, that are 10 times greater than most geologists believe probable. Years of looking at the landscape, consideration of the Pleistocene history, and computer visualization of the regional topography have reawakened questions about the topographic evolution of the North Cascades, qu ...
... of the Methow block, that are 10 times greater than most geologists believe probable. Years of looking at the landscape, consideration of the Pleistocene history, and computer visualization of the regional topography have reawakened questions about the topographic evolution of the North Cascades, qu ...
Normal faulting in the upper plate of a metamorphic core complex
... the upper plate that might provide significant insight into the development of the NSRD and metamorphic core complexes. The northern Snake Range has perhaps the best exposures of upper plate rocks of any core complex, and these rocks are characterized by a straightforward and easily mappable stratig ...
... the upper plate that might provide significant insight into the development of the NSRD and metamorphic core complexes. The northern Snake Range has perhaps the best exposures of upper plate rocks of any core complex, and these rocks are characterized by a straightforward and easily mappable stratig ...
Geologic Map and Cross Sections of the Embudo Fault Zone in the
... geologic and hydrogeologic complexities in both the basin-fill deposits and the bedrock. Although sections of the Embudo fault zone are locally exposed in the bedrock of the Picuris Mountains and in the late Cenozoic sedimentary units along the top of the Picuris piedmont, the full proportions of ...
... geologic and hydrogeologic complexities in both the basin-fill deposits and the bedrock. Although sections of the Embudo fault zone are locally exposed in the bedrock of the Picuris Mountains and in the late Cenozoic sedimentary units along the top of the Picuris piedmont, the full proportions of ...
bureau of geology - Department of Geosciences
... of shear are given by Berthe and others (1979), Simpson and Schmid (1983), and Lister and Snoke (1984). ...
... of shear are given by Berthe and others (1979), Simpson and Schmid (1983), and Lister and Snoke (1984). ...
Miocene Landscape Evolution and Geomorphologic Controls on
... and 9.4 Ma (Bissig et al., 2001). Among productive deposits, those of the Tambo district, close to the southern limit of the belt (Deyell et al., 2000, and in press), are entirely of high-sulfidation type, a characteristic shared by the multiple centers of the large Pascua-Lama and Veladero prospect ...
... and 9.4 Ma (Bissig et al., 2001). Among productive deposits, those of the Tambo district, close to the southern limit of the belt (Deyell et al., 2000, and in press), are entirely of high-sulfidation type, a characteristic shared by the multiple centers of the large Pascua-Lama and Veladero prospect ...
The ancestral Cascades arc: Cenozoic evolution of the central
... the southern Sierra compared to the extensive volcanic cover to the north. All these data taken together suggest that the “future plate boundary” represented by the transtensional western Walker Lane belt was born in the axis of the ancestral Cascades arc along the present-day central Sierran range ...
... the southern Sierra compared to the extensive volcanic cover to the north. All these data taken together suggest that the “future plate boundary” represented by the transtensional western Walker Lane belt was born in the axis of the ancestral Cascades arc along the present-day central Sierran range ...
Hydrogeology of the coastal plain between
... closure of the Mines Department Drilling Branch. Drilling was recommenced in the southern half of the original project area, between Cervantes and about 20 km north of Leeman, in 1993. This report includes the results from sites LS1–17. ...
... closure of the Mines Department Drilling Branch. Drilling was recommenced in the southern half of the original project area, between Cervantes and about 20 km north of Leeman, in 1993. This report includes the results from sites LS1–17. ...
Landform evolution in the Nagar region, Hispar Mustagh Karakoram
... Himalaya and the Karakoram, which occurred mostly in the Late Cainozoic (Gansser 1964, 1983) a#er the time span of orogenic movements of the nappe character and a#er intervals of regional high-pressure and/or high-temperature rocks metamorphism. Zones of deep-seated igneous rocks in the eastern Kara ...
... Himalaya and the Karakoram, which occurred mostly in the Late Cainozoic (Gansser 1964, 1983) a#er the time span of orogenic movements of the nappe character and a#er intervals of regional high-pressure and/or high-temperature rocks metamorphism. Zones of deep-seated igneous rocks in the eastern Kara ...
54. Regional Geology of the Goban Spur Continental Margin
... synthesis of the Goban Spur passive continental margin. The thin sediment sequence overlying basement is divided into three seismostratigraphic sequences. The lowest of these, sequence 3, occurs in fault-bounded basins, often wedgeshaped in cross-section. Intraformational reflector geometry shows th ...
... synthesis of the Goban Spur passive continental margin. The thin sediment sequence overlying basement is divided into three seismostratigraphic sequences. The lowest of these, sequence 3, occurs in fault-bounded basins, often wedgeshaped in cross-section. Intraformational reflector geometry shows th ...
Chapter 2
... collision. Previously existing geologic structures and differences in depositional history along the system produce a variety of features that are characteristic of large-scale continent/continent convergence and whose recognition may be useful in the study of other similar systems. Western North Am ...
... collision. Previously existing geologic structures and differences in depositional history along the system produce a variety of features that are characteristic of large-scale continent/continent convergence and whose recognition may be useful in the study of other similar systems. Western North Am ...
M116 Tuscarora text - University of Nevada, Reno
... Published reconnaissance and our new work indicate that the Tuscarora volcanic field includes several volcanic centers that were active during an intense period of magmatism between about 39.9 and 39.3 Ma (Berger and ...
... Published reconnaissance and our new work indicate that the Tuscarora volcanic field includes several volcanic centers that were active during an intense period of magmatism between about 39.9 and 39.3 Ma (Berger and ...
Pull-apart basins at releasing bends of the sinistral Late Jurassic
... need to lump all of the basins into one region of extension with minimum principal stress oriented orthogonal to the Cordilleran magmatic arc. One argument against the borderland rift model is the presence of a belt of thick, Upper Jurassic conglomerate in northern Sonora (Fig. 1), separate from the ...
... need to lump all of the basins into one region of extension with minimum principal stress oriented orthogonal to the Cordilleran magmatic arc. One argument against the borderland rift model is the presence of a belt of thick, Upper Jurassic conglomerate in northern Sonora (Fig. 1), separate from the ...
FRICTIONAL PROPERTIES OF NATURAL FAULT GOUGE FROM A
... A second class of explanations rely on the recognition that Andersonian principles may not strictly apply in cases where the fault zone is anomalously weak. Two of the most common explanations for weak fault zones are elevated pore pressures within the fault zone [Rice, 1992], and/or the presence o ...
... A second class of explanations rely on the recognition that Andersonian principles may not strictly apply in cases where the fault zone is anomalously weak. Two of the most common explanations for weak fault zones are elevated pore pressures within the fault zone [Rice, 1992], and/or the presence o ...
Nappes of the southern Tien Shan
... The southern Tien Shan is a folded area with widespread Paleozoic nappes. The ensembles of nappes distributed in Uzbekistan, Tajikistan, Kyrgyzstan, and China are described, and their structural similarity and distinctions in different parts of the area are shown. Nappes of the southern Tien Shan oc ...
... The southern Tien Shan is a folded area with widespread Paleozoic nappes. The ensembles of nappes distributed in Uzbekistan, Tajikistan, Kyrgyzstan, and China are described, and their structural similarity and distinctions in different parts of the area are shown. Nappes of the southern Tien Shan oc ...
Geology of the Death Valley area
The exposed geology of the Death Valley area presents a diverse and complex set of at least 23 formations of sedimentary units, two major gaps in the geologic record called unconformities, and at least one distinct set of related formations geologists call a group. The oldest rocks in the area that now includes Death Valley National Park are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. These rocks were intruded by a mass of granite 1400 Ma (million years ago) and later uplifted and exposed to nearly 500 million years of erosion.Marine deposition occurred 1200 to 800 Ma, creating thick sequences of conglomerate, mudstone, and carbonate rock topped by stromatolites, and possibly glacial deposits from the hypothesized Snowball Earth event. Rifting thinned huge roughly linear parts of the supercontinent Rodinia enough to allow sea water to invade and divide its landmass into component continents separated by narrow straits. A passive margin developed on the edges of these new seas in the Death Valley region. Carbonate banks formed on this part of the two margins only to be subsided as the continental crust thinned until it broke, giving birth to a new ocean basin. An accretion wedge of clastic sediment then started to accumulate at the base of the submerged precipice, entombing the region's first known fossils of complex life. These sandy mudflats gave way about 550 Ma to a carbonate platform which lasted for the next 300 million years of Paleozoic time.The passive margin switched to active margin in the early-to-mid Mesozoic when the Farallon Plate under the Pacific Ocean started to dive below the North American Plate, creating a subduction zone; volcanoes and uplifting mountains were created as a result. Erosion over many millions of years created a relatively featureless plain. Stretching of the crust under western North America started around 16 Ma and is thought to be caused by upwelling from the subducted spreading-zone of the Farallon Plate. This process continues into the present and is thought to be responsible for creating the Basin and Range province. By 2 to 3 million years ago this province had spread to the Death Valley area, ripping it apart and creating Death Valley, Panamint Valley and surrounding ranges. These valleys partially filled with sediment and, during colder periods during the current ice age, with lakes. Lake Manly was the largest of these lakes; it filled Death Valley during each glacial period from 240,000 years ago to 10,000 years ago. By 10,500 years ago these lakes were increasingly cut off from glacial melt from the Sierra Nevada, starving them of water and concentrating salts and minerals. The desert environment seen today developed after these lakes dried up.