CRUSTAL GROWTH IN SOUTHERN ARIZONA: U
... the craton. Our data suggest that sedimentation within the Pinal block was proximal to the continental margin and occurred later than 1.68 Ga and ended before the intrusion of granitoids at 1.65 Ga. We show that the North American crust grew rapidly and progressively by addition of juvenile but evol ...
... the craton. Our data suggest that sedimentation within the Pinal block was proximal to the continental margin and occurred later than 1.68 Ga and ended before the intrusion of granitoids at 1.65 Ga. We show that the North American crust grew rapidly and progressively by addition of juvenile but evol ...
The western margin of Mexico is ideally - Earth Science
... Collins(2002) as tectonic switching. This “accordion” tectonics may be modified by alongstrike translations. The Cordillera of western North America recordsmost of the global crustal growth during Phanerozoic time, and therefore it serves as a modern/young analog for genesis of the continents in P ...
... Collins(2002) as tectonic switching. This “accordion” tectonics may be modified by alongstrike translations. The Cordillera of western North America recordsmost of the global crustal growth during Phanerozoic time, and therefore it serves as a modern/young analog for genesis of the continents in P ...
Geology - Geostud
... values were determined on the basis of Poisson’s ratios between 0.25 and 0.3 for various lithologies (Christensen, 1996). To obtain realistic synthetic waveforms, each computed waveform is convolved with the observed vertical component. The real ambient noise measured 100–5 s before Pwave arrival wa ...
... values were determined on the basis of Poisson’s ratios between 0.25 and 0.3 for various lithologies (Christensen, 1996). To obtain realistic synthetic waveforms, each computed waveform is convolved with the observed vertical component. The real ambient noise measured 100–5 s before Pwave arrival wa ...
A2 Course Study Guide
... The second phase involves a melt with a variable amount of crystal formation. Many magmas have begun crystallizing long before they are erupted. Thus, lavas erupted at the surface often contain abundant phenocrysts. Typically, they are only millimetres across, but exceptionally they may reach severa ...
... The second phase involves a melt with a variable amount of crystal formation. Many magmas have begun crystallizing long before they are erupted. Thus, lavas erupted at the surface often contain abundant phenocrysts. Typically, they are only millimetres across, but exceptionally they may reach severa ...
Paleogene–early Miocene igneous rocks and geodynamics of the
... and dispersed remains of a Jurassic ophiolite nappe (Wein, 1969; Haas et al., 2000; Csontos and Vörös, 2004). The natural continuation of this unit is found in the Internal Dinarides, and it can be directly correlated to rocks exposed near Zagreb (Fig. 1) (Wein, 1969; Csontos, 1999; Haas et al., 200 ...
... and dispersed remains of a Jurassic ophiolite nappe (Wein, 1969; Haas et al., 2000; Csontos and Vörös, 2004). The natural continuation of this unit is found in the Internal Dinarides, and it can be directly correlated to rocks exposed near Zagreb (Fig. 1) (Wein, 1969; Csontos, 1999; Haas et al., 200 ...
Geology of the Seal Rock Area
... to the North American continent. The terranes were made up of volcanic island archipelagos (arcs) and pieces of ocean crust that originated elsewhere and were moved toward the western edge of North America by tectonic forces. In plate tectonics, slabs or plates of the earth’s crust move slowly atop ...
... to the North American continent. The terranes were made up of volcanic island archipelagos (arcs) and pieces of ocean crust that originated elsewhere and were moved toward the western edge of North America by tectonic forces. In plate tectonics, slabs or plates of the earth’s crust move slowly atop ...
Paleogeographic and tectonic implications of Jurassic sedimentary
... age of extension and development of the angular unconformity between the Upper and Lower Sidewinder volcanic series at ca. 151 Ma. The data suggest that at least part, and possibly all, of the Fairview Valley Formation is late Early Jurassic in age. We correlate the Fairview Valley Formation with Me ...
... age of extension and development of the angular unconformity between the Upper and Lower Sidewinder volcanic series at ca. 151 Ma. The data suggest that at least part, and possibly all, of the Fairview Valley Formation is late Early Jurassic in age. We correlate the Fairview Valley Formation with Me ...
Mid-Tertiary magamtism in southeastern Arizona
... rhyolite at the summit. The Montana Peak Formation has been correlated with Mesozoic rocks (Wilson and others, 1969) such as the Cat Mountain Rhyolite of the Tucson Mountains (Taylor, 1959), the Salero Formation of the Santa Rita Mountains and the Demetrie Wash Volcanics of the Sierrita Mountains (K ...
... rhyolite at the summit. The Montana Peak Formation has been correlated with Mesozoic rocks (Wilson and others, 1969) such as the Cat Mountain Rhyolite of the Tucson Mountains (Taylor, 1959), the Salero Formation of the Santa Rita Mountains and the Demetrie Wash Volcanics of the Sierrita Mountains (K ...
Did westward subduction cause Cretaceous
... or utilized plate models for the main development of the Cordilleran orogenic belt postulate Neoproterozoic to Cambrian rifting of Laurentia to form a westerly facing passive margin, active until the late Devonian; then 110 m.y., from the Late Devonian to the early Triassic, punctuated by the succes ...
... or utilized plate models for the main development of the Cordilleran orogenic belt postulate Neoproterozoic to Cambrian rifting of Laurentia to form a westerly facing passive margin, active until the late Devonian; then 110 m.y., from the Late Devonian to the early Triassic, punctuated by the succes ...
Alteration of the oceanic lithosphere and its implications for seafloor
... where melt supply is able to keep up with extension at the divergent plate boundary. However, it cannot be applied to much of the crust formed at oceanic ridges spreading at less than 40 mm yr–1 and which comprise nearly 50% of the global mid-ocean ridge system, extending from the Arctic Ocean, alon ...
... where melt supply is able to keep up with extension at the divergent plate boundary. However, it cannot be applied to much of the crust formed at oceanic ridges spreading at less than 40 mm yr–1 and which comprise nearly 50% of the global mid-ocean ridge system, extending from the Arctic Ocean, alon ...
EVOLUTION OF THE NORTH AMERICAN CORDILLERA William R
... Cordilleran margin, Jurassic-Cretaceous accretion of intraoceanic island arcs contributed to the outward growth of the continental block. Beginning in mid-Cenozoic time, impingement of intra-Pacific seafloor spreading systems on the subduction zone at the continental margin gave birth to transform f ...
... Cordilleran margin, Jurassic-Cretaceous accretion of intraoceanic island arcs contributed to the outward growth of the continental block. Beginning in mid-Cenozoic time, impingement of intra-Pacific seafloor spreading systems on the subduction zone at the continental margin gave birth to transform f ...
evolution of the north american cordillera
... Cordilleran margin, Jurassic-Cretaceous accretion of intraoceanic island arcs contributed to the outward growth of the continental block. Beginning in mid-Cenozoic time, impingement of intra-Pacific seafloor spreading systems on the subduction zone at the continental margin gave birth to transform f ...
... Cordilleran margin, Jurassic-Cretaceous accretion of intraoceanic island arcs contributed to the outward growth of the continental block. Beginning in mid-Cenozoic time, impingement of intra-Pacific seafloor spreading systems on the subduction zone at the continental margin gave birth to transform f ...
2200 million years of crustal evolution: the baltic shield
... the view that, in both the low-grade and highgrade terrain, the supracrustal rocks deposited in the period between 2900 and 2700 Ma. There are also good indications for the existence of ensialic crust older than 2900 Ma in the low-grade terrain. The peak of paroxismal activity was reached during the ...
... the view that, in both the low-grade and highgrade terrain, the supracrustal rocks deposited in the period between 2900 and 2700 Ma. There are also good indications for the existence of ensialic crust older than 2900 Ma in the low-grade terrain. The peak of paroxismal activity was reached during the ...
Geology of the Dogskin Mountain Quadrangle, northern Walker
... biotite (~10% or greater) and feldspar (~5%) phenocrysts, both 1 mm or less in length. The ash layer also contains conspicuous amounts of petrified wood. Exposed mainly in the southern Fox Range east of Emerson Pass and west of the Buckbrush Spring fault. Unit is ~75 m thick. ...
... biotite (~10% or greater) and feldspar (~5%) phenocrysts, both 1 mm or less in length. The ash layer also contains conspicuous amounts of petrified wood. Exposed mainly in the southern Fox Range east of Emerson Pass and west of the Buckbrush Spring fault. Unit is ~75 m thick. ...
Southern Urals CONTENTS Age and tectonic/structural setting
... signature (REE) of these volcanics is interpreted as either MORB or sub-alkaline depending on which paper you read. These rocks may represent peripheral, early phase spreading and these units are still preserved in the foldbelt. The Tagil zone and the now accreted Sakamara zone shows that the first ...
... signature (REE) of these volcanics is interpreted as either MORB or sub-alkaline depending on which paper you read. These rocks may represent peripheral, early phase spreading and these units are still preserved in the foldbelt. The Tagil zone and the now accreted Sakamara zone shows that the first ...
NWGS NWCS
... called the Wells Creek Volcanic Member of the Nooksack Formation. We designate the type area of the Wells Creek Volcanic Member to be lower Wells Creek, in the vicinity of 48°54’ N, 12T48’ W (Bearpaw Mountain 7.5’ quadrangle). Isolated belemnite molds, pieces of Buchia shell, and (rarely) Buchia has ...
... called the Wells Creek Volcanic Member of the Nooksack Formation. We designate the type area of the Wells Creek Volcanic Member to be lower Wells Creek, in the vicinity of 48°54’ N, 12T48’ W (Bearpaw Mountain 7.5’ quadrangle). Isolated belemnite molds, pieces of Buchia shell, and (rarely) Buchia has ...
modern accretionary processes The Palaeoproterozoic Trans
... Taken at face value, these geochronological constraints suggest that the Manikewan Ocean had formed over a time span of at least 150 Ma before it started to close, which is comparable in duration to most modern oceans. The c. 1.83– 1.80 Ga terminal collision with the Superior Province, which histori ...
... Taken at face value, these geochronological constraints suggest that the Manikewan Ocean had formed over a time span of at least 150 Ma before it started to close, which is comparable in duration to most modern oceans. The c. 1.83– 1.80 Ga terminal collision with the Superior Province, which histori ...
NWGS BC Coast Range
... Jurassic-Early Cretaceous plutonic rocks that characterize the western part of the Coast Mountains south of Prince Rupert (lat. 54°N) are absent from it north of this, so that the plutons which give integrity to the entire belt are of mid-Cretaceous through early Tertiary ages. Subordinate, variably ...
... Jurassic-Early Cretaceous plutonic rocks that characterize the western part of the Coast Mountains south of Prince Rupert (lat. 54°N) are absent from it north of this, so that the plutons which give integrity to the entire belt are of mid-Cretaceous through early Tertiary ages. Subordinate, variably ...
Chapter 4. TTG & Genesis of the Continental Crust
... TTG is an acronym for “tonalite-trondhjemite-granodiorite”. These granitoids, together with greenstone belts, are a typical feature of all Archean terrains. In addition, a rarer feature of Archean terrains is the occurrence of high-Mg diorite-tonalite-granodiorite rocks, collectively called “sanuki ...
... TTG is an acronym for “tonalite-trondhjemite-granodiorite”. These granitoids, together with greenstone belts, are a typical feature of all Archean terrains. In addition, a rarer feature of Archean terrains is the occurrence of high-Mg diorite-tonalite-granodiorite rocks, collectively called “sanuki ...
NJDEP - NJGWS - GMS 15-2, Bedrock Geologic Map of the High
... shale, yellow, red, green, pale brown, and gray shale, and light-gray to pale pinkishgray quartzite. Lower contact lies in a red shale bed approximately 50 to 100 ft above ...
... shale, yellow, red, green, pale brown, and gray shale, and light-gray to pale pinkishgray quartzite. Lower contact lies in a red shale bed approximately 50 to 100 ft above ...
Geol.Soc Australia Spec Publ.22 2003
... to have been divided into two parts: an eastern active margin and a western rifted margin, with the boundary roughly along the Tasman Line. East of the line in Australia, rocks of the Tasman Orogen are thought to largely overlie Cambrian or Ordovician oceanic crust (Aitchison et al. 1992) and to hav ...
... to have been divided into two parts: an eastern active margin and a western rifted margin, with the boundary roughly along the Tasman Line. East of the line in Australia, rocks of the Tasman Orogen are thought to largely overlie Cambrian or Ordovician oceanic crust (Aitchison et al. 1992) and to hav ...
as a PDF - University of Innsbruck
... by marly intercalations and arenaceous bioclastic limestones of the Plöcken Formation which presumably corresponds to the graptolite zone of Gl. persculptus (SCHÖNLAUB, 1996). If so, it may have lasted during the early and middle Hirnantian Stage for not more than 0.5 to 1 million years. It resulted ...
... by marly intercalations and arenaceous bioclastic limestones of the Plöcken Formation which presumably corresponds to the graptolite zone of Gl. persculptus (SCHÖNLAUB, 1996). If so, it may have lasted during the early and middle Hirnantian Stage for not more than 0.5 to 1 million years. It resulted ...
An explanation of the landforms and geology between Broken Hill
... The tour route generally passes across the sand and gravel products resulting from the prolonged erosion of this ancient continent. Central Australia is relatively flat, because the ancient rocks which make up the crust have been planed downward by hundreds of millions of years of erosion by wind, w ...
... The tour route generally passes across the sand and gravel products resulting from the prolonged erosion of this ancient continent. Central Australia is relatively flat, because the ancient rocks which make up the crust have been planed downward by hundreds of millions of years of erosion by wind, w ...
Sa˜o Luıs Craton and Gurupi Belt
... 2150 Ma and a late collisional phase at 2080 + 20 Ma. Geological, geochronological and isotopic evidence, along with palaeogeographic reconstructions, strongly suggest that these Brazilian terrains were contiguous with the West African Craton in Palaeoproterozoic times, and that this landmass appare ...
... 2150 Ma and a late collisional phase at 2080 + 20 Ma. Geological, geochronological and isotopic evidence, along with palaeogeographic reconstructions, strongly suggest that these Brazilian terrains were contiguous with the West African Craton in Palaeoproterozoic times, and that this landmass appare ...
Article
... geometry [1], which the Devonian and Triassic sample sets show in Fig 4. The recycled Devonian sample set is dominated by Precambrian ages with good correlation to the “Cordilleran supersource I”, with lesser fractions derived from Paleozoic arcs. Detrital zircons from the exotic Devonian sample set ...
... geometry [1], which the Devonian and Triassic sample sets show in Fig 4. The recycled Devonian sample set is dominated by Precambrian ages with good correlation to the “Cordilleran supersource I”, with lesser fractions derived from Paleozoic arcs. Detrital zircons from the exotic Devonian sample set ...
Geological history of Earth
The geological history of Earth follows the major events in Earth's past based on the geologic time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System.Earth was initially molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as the result of a Mars-sized object with about 10% of the Earth's mass impacting the planet in a glancing blow. Some of this object's mass merged with the Earth, significantly altering its internal composition, and a portion was ejected into space. Some of the material survived to form an orbiting moon. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from comets, produced the oceans.As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke apart. They migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600 to 540 million years ago, then finally Pangaea, which broke apart 180 million years ago.The present pattern of ice ages began about 40 million years ago, then intensified at the end of the Pliocene. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40,000–100,000 years. The last glacial period of the current ice age ended about 10,000 years ago.