Detrital zircon ages from quartzite and metaconglomerate exposed in the Park Range, Front Range, and Sawatch Range of northern and central Colorado reveal new information about age and provenance trends within the Yavapai province of southwestern Laurentia and provide a critical test of regional correlations. Six samples from the three exposure areas—the Lester Mountain area in the Park Range, Coal Creek area in the Front Range, and Collegiate Peaks area in the Sawatch Range—are dominated by Paleoproterozoic detrital zircon that define a relatively narrow range of peak ages between 1772 and 1701 Ma. The unimodal character of most age spectra and the age of the dominant age-probability peaks indicate that the metasedimentary successions were derived largely from local sources within the ca. 1.78–1.70-Ga Yavapai province. Age-probability peaks between 1830 Ma and 2716 Ma are attributed to older source regions to the north and northeast such as the Trans-Hudson orogen, Black Hills, or Wyoming province. However, the percentage of older grains is relatively minor and decreases to almost zero from north to south. Maximum depositional ages constrained by the youngest age populations are 1763 Ma, 1717 Ma, and 1701 Ma for the respective localities from north to south. All of the metasedimentary successions were deformed and metamorphosed after deposition, and quartzite at one locality is intruded by ca. 1672-Ma plutons. On the basis of similarities between outcrop characteristics, structural style, and comparison of detrital zircon age spectra, we correlate the two southern localities with a regional suite of quartzite successions deposited ca. 1.70 Ga following the culmination of the Yavapai orogeny. The northern succession represents an earlier cycle of sedimentation predating ca. 1750-Ma deformation in the northern Yavapai province. The southward progression of ages is consistent with regional tectonic models for the evolution of the Paleoproterozoic accretionary provinces in southern Laurentia, and the multiple cycles of sedimentation suggest that basin formation and collapse were important processes in the tectonic evolution of the continent.
{"title":"Correlating Proterozoic synorogenic metasedimentary successions in southwestern Laurentia: New insights from detrital zircon U-Pb geochronology of Paleoproterozoic quartzite and metaconglomerate in central and northern Colorado, U.S.A.","authors":"James V. Jones, K. Thrane","doi":"10.2113/GSROCKY.47.1.1","DOIUrl":"https://doi.org/10.2113/GSROCKY.47.1.1","url":null,"abstract":"Detrital zircon ages from quartzite and metaconglomerate exposed in the Park Range, Front Range, and Sawatch Range of northern and central Colorado reveal new information about age and provenance trends within the Yavapai province of southwestern Laurentia and provide a critical test of regional correlations. Six samples from the three exposure areas—the Lester Mountain area in the Park Range, Coal Creek area in the Front Range, and Collegiate Peaks area in the Sawatch Range—are dominated by Paleoproterozoic detrital zircon that define a relatively narrow range of peak ages between 1772 and 1701 Ma. The unimodal character of most age spectra and the age of the dominant age-probability peaks indicate that the metasedimentary successions were derived largely from local sources within the ca. 1.78–1.70-Ga Yavapai province. Age-probability peaks between 1830 Ma and 2716 Ma are attributed to older source regions to the north and northeast such as the Trans-Hudson orogen, Black Hills, or Wyoming province. However, the percentage of older grains is relatively minor and decreases to almost zero from north to south. Maximum depositional ages constrained by the youngest age populations are 1763 Ma, 1717 Ma, and 1701 Ma for the respective localities from north to south. All of the metasedimentary successions were deformed and metamorphosed after deposition, and quartzite at one locality is intruded by ca. 1672-Ma plutons. On the basis of similarities between outcrop characteristics, structural style, and comparison of detrital zircon age spectra, we correlate the two southern localities with a regional suite of quartzite successions deposited ca. 1.70 Ga following the culmination of the Yavapai orogeny. The northern succession represents an earlier cycle of sedimentation predating ca. 1750-Ma deformation in the northern Yavapai province. The southward progression of ages is consistent with regional tectonic models for the evolution of the Paleoproterozoic accretionary provinces in southern Laurentia, and the multiple cycles of sedimentation suggest that basin formation and collapse were important processes in the tectonic evolution of the continent.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"42 1","pages":"1-35"},"PeriodicalIF":0.0,"publicationDate":"2012-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.47.1.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311582","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hauge (2013) claims to present a better model for the South Fork Fault System (SFFS) involving multiple movement events, yet he offers minimal evidence to support his fault timing and interpretation of non-catastrophic emplacement. In addition, he provides little data in terms of an emplacement mechanism for the SFFS. Likewise, his model (Beutner and Hauge, 2009) requires an unusual, concealed, linking fault between the Heart Mountain Fault System (HMFS) and SFFS that cuts downward approximately 1,500 m into underlying rocks. Hauge points out that Pierce and Nelson's (1969) cross section A–A' (east of Castle Tear Fault and south of Sheep Mountain) shows no evidence of folding of the HMFS by the underlying SFFS. However, Pierce and Nelson (1969) drew their cross section where they placed no orientation data on the south edge of Sheep Mountain, a carbonate block emplaced by the HMFS. Therefore, they assumed no folding or displacement had occurred within the allochthonous block. In contrast, limited published orientation data were collected by Stevens (1938) and shown on the southeast edge of his map of Sheep Mountain. Stevens placed northwesterly and westerly dips along the southeast edge of the allochthon consistent with his orientation data in the underlying Mesozoic rocks. He interpreted (in cross section A–A') that subsequent movement of the SFFS folded the Sheep Mountain allochthon (as part of the HMFS). Clarey (2012) also interpreted that the observed folding of the …
{"title":"South Fork Fault as a gravity slide: Its break-away, timing, and emplacement, northwestern Wyoming, U.S.A.: REPLY","authors":"T. Clarey","doi":"10.2113/GSROCKY.48.1.67","DOIUrl":"https://doi.org/10.2113/GSROCKY.48.1.67","url":null,"abstract":"Hauge (2013) claims to present a better model for the South Fork Fault System (SFFS) involving multiple movement events, yet he offers minimal evidence to support his fault timing and interpretation of non-catastrophic emplacement. In addition, he provides little data in terms of an emplacement mechanism for the SFFS. Likewise, his model (Beutner and Hauge, 2009) requires an unusual, concealed, linking fault between the Heart Mountain Fault System (HMFS) and SFFS that cuts downward approximately 1,500 m into underlying rocks.\u0000\u0000Hauge points out that Pierce and Nelson's (1969) cross section A–A' (east of Castle Tear Fault and south of Sheep Mountain) shows no evidence of folding of the HMFS by the underlying SFFS. However, Pierce and Nelson (1969) drew their cross section where they placed no orientation data on the south edge of Sheep Mountain, a carbonate block emplaced by the HMFS. Therefore, they assumed no folding or displacement had occurred within the allochthonous block. In contrast, limited published orientation data were collected by Stevens (1938) and shown on the southeast edge of his map of Sheep Mountain. Stevens placed northwesterly and westerly dips along the southeast edge of the allochthon consistent with his orientation data in the underlying Mesozoic rocks. He interpreted (in cross section A–A') that subsequent movement of the SFFS folded the Sheep Mountain allochthon (as part of the HMFS). Clarey (2012) also interpreted that the observed folding of the …","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"48 1","pages":"67-69"},"PeriodicalIF":0.0,"publicationDate":"2012-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.48.1.67","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68312141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-09-21DOI: 10.2113/GSROCKY.46.2.111
W. A. Sullivan, R. Beane, E. N. Beck, W. Fereday, A. M. Roberts-Pierel
A system of subvertical, northeast-striking shear zones collectively called the Cheyenne belt comprises the fundamental boundary between the Archean Wyoming province and the Paleoproterozoic Colorado province in the Medicine Bow Mountains of southeastern Wyoming. These shear zones are generally interpreted as a mid-crustal thrust system rotated to its present-day subvertical orientation during late-stage, orogen-scale folding. However, the map geometry, presence of large domains of S tectonites, and vertical mineral lineations closely match numerical simulations of transpressional shear zones. This transpression hypothesis is tested using two detailed case studies that integrate detailed geologic mapping, kinematic analyses of S and L-S tectonites, quartz crystallographic fabric analyses, and deformation mechanism analyses of shear zones in the western part of the Medicine Bow Mountains. These data point toward general shear deformation that accommodated two coeval deformation components: (1) southeast-side-up, dip-slip or southeast-side-up/dextral, oblique-slip motion and (2) foliation-normal shortening. According to the broadest definition, these are transpressional shear zones. However, the strike-slip component is small, and these data do not require any significant oblique plate motion during the formation of the Cheyenne belt shear zones. The lack of evidence for overprinting of initial southeast-side-up fabrics by horizontal shortening, the near parallelism of the subvertical shear zones throughout the upper and middle crust, and the presence of subvertical mafic dike swarms in Archean basement rocks immediately adjacent to the Cheyenne belt all indicate that the Cheyenne belt shear zones were not rotated into their present-day subvertical orientations during late-stage deformation. Instead, we interpret the shear zones as a ∼1,750-Ma steeply dipping stretching fault system between the penetratively deformed young, hot, rheologically weak rocks of the Colorado province and the old, cold, rheologically strong Archean rocks north of the belt.
{"title":"Testing the transpression hypothesis in the western part of the Cheyenne belt, Medicine Bow Mountains, southeastern Wyoming","authors":"W. A. Sullivan, R. Beane, E. N. Beck, W. Fereday, A. M. Roberts-Pierel","doi":"10.2113/GSROCKY.46.2.111","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.2.111","url":null,"abstract":"A system of subvertical, northeast-striking shear zones collectively called the Cheyenne belt comprises the fundamental boundary between the Archean Wyoming province and the Paleoproterozoic Colorado province in the Medicine Bow Mountains of southeastern Wyoming. These shear zones are generally interpreted as a mid-crustal thrust system rotated to its present-day subvertical orientation during late-stage, orogen-scale folding. However, the map geometry, presence of large domains of S tectonites, and vertical mineral lineations closely match numerical simulations of transpressional shear zones. This transpression hypothesis is tested using two detailed case studies that integrate detailed geologic mapping, kinematic analyses of S and L-S tectonites, quartz crystallographic fabric analyses, and deformation mechanism analyses of shear zones in the western part of the Medicine Bow Mountains. These data point toward general shear deformation that accommodated two coeval deformation components: (1) southeast-side-up, dip-slip or southeast-side-up/dextral, oblique-slip motion and (2) foliation-normal shortening. According to the broadest definition, these are transpressional shear zones. However, the strike-slip component is small, and these data do not require any significant oblique plate motion during the formation of the Cheyenne belt shear zones.\u0000\u0000The lack of evidence for overprinting of initial southeast-side-up fabrics by horizontal shortening, the near parallelism of the subvertical shear zones throughout the upper and middle crust, and the presence of subvertical mafic dike swarms in Archean basement rocks immediately adjacent to the Cheyenne belt all indicate that the Cheyenne belt shear zones were not rotated into their present-day subvertical orientations during late-stage deformation. Instead, we interpret the shear zones as a ∼1,750-Ma steeply dipping stretching fault system between the penetratively deformed young, hot, rheologically weak rocks of the Colorado province and the old, cold, rheologically strong Archean rocks north of the belt.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"111-135"},"PeriodicalIF":0.0,"publicationDate":"2011-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.2.111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-09-01DOI: 10.2113/GSROCKY.46.2.137
Susana Palamarczuk, N. Landman
The Upper Cretaceous Pierre Shale and Bearpaw Shale contain rich assemblages of dinoflagellates. We analyzed nine samples from the Baculites compressus – B. cuneatus Zones in Montana, South Dakota, and Colorado. According to the ammonite zonation of the Western Interior of North America, these zones represent the middle part of the upper Campanian. Dinoflagellate cysts include Alterbidinium acutulum, Cordosphaeridium fibrospinosum, Hystrichodinium pulchrum, Isabelidinium cooksoniae, Laciniadinium firmum , members of the Microdinium group Odontochitina operculata, Oligosphaeridium pulcherrimum, Palaeohystrichophora infusorioides, Palaeoperidinium pyrophorum, Phelodinium tricuspe , members of the Spiniferites group, Spongodinium delitiense , and Xenascus ceratioides . Variation in species composition among samples may indicate slight differences in environment and/or age. The environment and proximity of samples to the paleoshoreline was evaluated based on the ratio of marine to terrestrial palynomorphs and the relative abundance of dinoflagellate cysts versus other organic-walled remains. Our results suggest that the samples from Colorado were deposited in a nearshore environment, the samples from southwestern South Dakota and Montana in an offshore environment, and the sample from eastern South Dakota in an offshore environment far from shore. These results agree with previous interpretations about the position of the shoreline based on the distribution of litho- and biofacies.
{"title":"Dinoflagellate cysts from the upper Campanian Pierre Shale and Bearpaw Shale of the U.S. Western Interior","authors":"Susana Palamarczuk, N. Landman","doi":"10.2113/GSROCKY.46.2.137","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.2.137","url":null,"abstract":"The Upper Cretaceous Pierre Shale and Bearpaw Shale contain rich assemblages of dinoflagellates. We analyzed nine samples from the Baculites compressus – B. cuneatus Zones in Montana, South Dakota, and Colorado. According to the ammonite zonation of the Western Interior of North America, these zones represent the middle part of the upper Campanian. Dinoflagellate cysts include Alterbidinium acutulum, Cordosphaeridium fibrospinosum, Hystrichodinium pulchrum, Isabelidinium cooksoniae, Laciniadinium firmum , members of the Microdinium group Odontochitina operculata, Oligosphaeridium pulcherrimum, Palaeohystrichophora infusorioides, Palaeoperidinium pyrophorum, Phelodinium tricuspe , members of the Spiniferites group, Spongodinium delitiense , and Xenascus ceratioides . Variation in species composition among samples may indicate slight differences in environment and/or age. The environment and proximity of samples to the paleoshoreline was evaluated based on the ratio of marine to terrestrial palynomorphs and the relative abundance of dinoflagellate cysts versus other organic-walled remains. Our results suggest that the samples from Colorado were deposited in a nearshore environment, the samples from southwestern South Dakota and Montana in an offshore environment, and the sample from eastern South Dakota in an offshore environment far from shore. These results agree with previous interpretations about the position of the shoreline based on the distribution of litho- and biofacies.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"137-164"},"PeriodicalIF":0.0,"publicationDate":"2011-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.2.137","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-09-01DOI: 10.2113/GSROCKY.46.2.165
H. Buchheim, R. Cushman, R. Biaggi
The Eocene Green River Formation in Fossil Basin, Wyoming provides a detailed record of the paleoecology and depositional history of ancient Fossil Lake. Fossil Lake was one of three Eocene lakes that formed an extensive lake system in Wyoming, Utah, and Colorado. It began as a flood-plain lake in the southern part of Fossil Basin and expanded northward as the lake evolved. Fossil Lake went through the major stages of lake evolution, including the overfilled (Road Hollow Member), balanced-fill (Fossil Butte Member), and underfilled (Angelo Member) stages. These stages are represented in the sedimentary record by a complete suite of lake-margin to lake-center facies. This study establishes the Road Hollow Member of the Green River Formation as representing the earliest stage of lake evolution in Fossil Lake. We also revise the boundaries for the Fossil Butte and Angelo Members of the Green River Formation, which clearly delineate the latest two stages of lake evolution. These revisions not only describe and add a previously unrecognized and thick sequence of lacustrine rocks in Fossil Basin, but help us to better understand the depositional systems that existed during each stage of lake evolution.
{"title":"Stratigraphic revision of the Green River Formation in Fossil Basin, WyomingOverfilled to underfilled lake evolution","authors":"H. Buchheim, R. Cushman, R. Biaggi","doi":"10.2113/GSROCKY.46.2.165","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.2.165","url":null,"abstract":"The Eocene Green River Formation in Fossil Basin, Wyoming provides a detailed record of the paleoecology and depositional history of ancient Fossil Lake. Fossil Lake was one of three Eocene lakes that formed an extensive lake system in Wyoming, Utah, and Colorado. It began as a flood-plain lake in the southern part of Fossil Basin and expanded northward as the lake evolved. Fossil Lake went through the major stages of lake evolution, including the overfilled (Road Hollow Member), balanced-fill (Fossil Butte Member), and underfilled (Angelo Member) stages. These stages are represented in the sedimentary record by a complete suite of lake-margin to lake-center facies. This study establishes the Road Hollow Member of the Green River Formation as representing the earliest stage of lake evolution in Fossil Lake. We also revise the boundaries for the Fossil Butte and Angelo Members of the Green River Formation, which clearly delineate the latest two stages of lake evolution. These revisions not only describe and add a previously unrecognized and thick sequence of lacustrine rocks in Fossil Basin, but help us to better understand the depositional systems that existed during each stage of lake evolution.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"165-181"},"PeriodicalIF":0.0,"publicationDate":"2011-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.2.165","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-09-01DOI: 10.2113/GSROCKY.46.2.183
Daniel Wegert, D. Parker
Lahar deposits within the Late Cretaceous McDermott Formation (Maastrichtian) contain abundant trachyandesite volcanic clasts with a narrow range of whole rock compositions. The outcrop pattern and thickness variations of the McDermott Formation suggest a source located in the general area of the present-day La Plata Mountains. Major and trace element trends indicate a possible petrogenetic relationship between the McDermott trachyandesite and La Plata Mountains intrusive rocks. Incompatible trace element compositions show subduction signatures in the trachyandesite and La Plata intrusive rocks, as well as in lower crustal xenoliths from the nearby Navajo volcanic field. Trace element patterns of Proterozoic units from the adjacent San Juan uplift rule out involvement of these upper crustal units in McDermott petrogenesis. Near zero ∊Nd t (−1.94 and 0.47) values rule out a Precambrian crustal source for these magmas as crustal values typically range from −6 to −18. Ba/La vs. Nb/La plots and ∊Nd t data suggest a subduction-modified continental lithospheric mantle source for these rocks. This lithospheric mantle may have acquired its orogenic trace-element signature during formation of the Proterozoic Yavapai terrane, which underlies the region.
晚白垩世麦克德莫特组(Maastrichtian McDermott组)的拉哈尔沉积含有丰富的粗面山岩火山碎屑，整体岩石组成范围窄。麦克德莫特组的露头模式和厚度变化表明，其来源位于现今拉普拉塔山脉的一般地区。主微量元素趋势表明麦克德莫特粗面山岩与拉普拉塔山侵入岩之间可能存在成岩关系。不相容的微量元素组成在拉普拉塔侵入岩和拉普拉塔侵入岩以及附近纳瓦霍火山场的下地壳捕虏体中显示出俯冲特征。来自邻近圣胡安隆起的元古代单元的微量元素模式排除了这些上地壳单元参与麦克德莫特岩石成因。由于这些岩浆的地壳值通常在- 6到- 18之间，因此在接近零的值(- 1.94和0.47)排除了这些岩浆的前寒武纪地壳来源。Ba/La vs. Nb/La图和Nd t数据表明，这些岩石为俯冲修正的大陆岩石圈地幔源。该岩石圈地幔可能在元古代亚瓦派地体形成期间获得了造山带的微量元素特征。
{"title":"Petrogenesis of the McDermott Formation trachyandesite, San Juan basin, Colorado and New Mexico","authors":"Daniel Wegert, D. Parker","doi":"10.2113/GSROCKY.46.2.183","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.2.183","url":null,"abstract":"Lahar deposits within the Late Cretaceous McDermott Formation (Maastrichtian) contain abundant trachyandesite volcanic clasts with a narrow range of whole rock compositions. The outcrop pattern and thickness variations of the McDermott Formation suggest a source located in the general area of the present-day La Plata Mountains. Major and trace element trends indicate a possible petrogenetic relationship between the McDermott trachyandesite and La Plata Mountains intrusive rocks. Incompatible trace element compositions show subduction signatures in the trachyandesite and La Plata intrusive rocks, as well as in lower crustal xenoliths from the nearby Navajo volcanic field. Trace element patterns of Proterozoic units from the adjacent San Juan uplift rule out involvement of these upper crustal units in McDermott petrogenesis. Near zero ∊Nd t (−1.94 and 0.47) values rule out a Precambrian crustal source for these magmas as crustal values typically range from −6 to −18. Ba/La vs. Nb/La plots and ∊Nd t data suggest a subduction-modified continental lithospheric mantle source for these rocks. This lithospheric mantle may have acquired its orogenic trace-element signature during formation of the Proterozoic Yavapai terrane, which underlies the region.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"183-196"},"PeriodicalIF":0.0,"publicationDate":"2011-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.2.183","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report and describe abundant, well-preserved, parallel-sided, U-shaped spreite burrows ( Rhizocorallium ) in the upper part of the latest Cretaceous into early Paleocene Ferris Formation of south-central Wyoming's Hanna Basin. Rhizocorallium typically is a component of the widely represented ‘ Cruziana ichnofacies,’ principally involving benthic marine environments seaward of the intertidal zone in shallow to offshore settings. Traditionally, this Ferris section has been interpreted as coal-bearing, continental deposits formed after full withdrawal of the Western Interior Seaway from eastern Wyoming and adjacent areas. The burrowed strata overlie fossiliferous rocks diagnostic of parts of the Puercan Land Mammal Age, early Paleocene. At time of burrow formation, and for several million years thereafter, the vicinity of the future Hanna Basin remained as an undivided, eastern component of an enormous, greater Green River Basin that encompassed almost all of Wyoming's southern half. The Rhizocorallium -bearing marine strata represent westward expansion of a previously more restricted Western Interior Seaway that persisted through latest Cretaceous time in what is now the western Great Plains. Even though tidal influences may have affected rapidly aggrading fluvial systems far upstream to the west in Montana and Wyoming, we regard actual Paleocene marine inundations to have been uncommon and geologically ephemeral events as far west as the Hanna Basin. Diverse fossil assemblages from strata of the Williston Basin, representing the first five million years of Paleocene time, have led to documentation of fully open, marine conditions as the Cannonball Formation was deposited. Stratigraphic distribution of fossils within the Cannonball shows persistence of the Western Interior Seaway in the northern Western Interior through the Cretaceous, followed by expansion (renamed the ‘Cannonball Sea’) during early Paleocene time. Connections of that seaway to the south, however, remain poorly understood because of later Cenozoic massive erosion of any Paleocene rock record that had existed south of the borderland between the Dakotas. No Paleocene localities in southern Wyoming or Colorado have yet yielded assemblages of marine invertebrate body fossils or microfossils as known from the Williston Basin. No verifiable means, therefore, have been recognized to characterize the Paleocene marine record of the Hanna Basin in terms of species uniquely shared with the Cannonball biota. Short-lived, Paleocene seaway excursions into the Hanna Basin may have been: (1) direct and exclusively from the Gulf Coast; (2) solely from the Cannonball Sea, with seaway contiguity east of the emerging Black Hills; or (3) initiated from a more extensive, midcontinental seaway connecting the Arctic Ocean to the Gulf of Mexico. Substantial structural uplift of the Laramie Mountains prior to mid-Paleocene time would have precluded even brief westward pulses of marine inundation into t
{"title":"Persistence of the Western Interior Seaway Historical background and significance of ichnogenus Rhizocorallium in Paleocene strata, south-central Wyoming","authors":"D. W. Boyd, J. Lillegraven","doi":"10.2113/GSROCKY.46.1.43","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.1.43","url":null,"abstract":"We report and describe abundant, well-preserved, parallel-sided, U-shaped spreite burrows ( Rhizocorallium ) in the upper part of the latest Cretaceous into early Paleocene Ferris Formation of south-central Wyoming's Hanna Basin. Rhizocorallium typically is a component of the widely represented ‘ Cruziana ichnofacies,’ principally involving benthic marine environments seaward of the intertidal zone in shallow to offshore settings. Traditionally, this Ferris section has been interpreted as coal-bearing, continental deposits formed after full withdrawal of the Western Interior Seaway from eastern Wyoming and adjacent areas. The burrowed strata overlie fossiliferous rocks diagnostic of parts of the Puercan Land Mammal Age, early Paleocene. At time of burrow formation, and for several million years thereafter, the vicinity of the future Hanna Basin remained as an undivided, eastern component of an enormous, greater Green River Basin that encompassed almost all of Wyoming's southern half. The Rhizocorallium -bearing marine strata represent westward expansion of a previously more restricted Western Interior Seaway that persisted through latest Cretaceous time in what is now the western Great Plains. Even though tidal influences may have affected rapidly aggrading fluvial systems far upstream to the west in Montana and Wyoming, we regard actual Paleocene marine inundations to have been uncommon and geologically ephemeral events as far west as the Hanna Basin.\u0000\u0000Diverse fossil assemblages from strata of the Williston Basin, representing the first five million years of Paleocene time, have led to documentation of fully open, marine conditions as the Cannonball Formation was deposited. Stratigraphic distribution of fossils within the Cannonball shows persistence of the Western Interior Seaway in the northern Western Interior through the Cretaceous, followed by expansion (renamed the ‘Cannonball Sea’) during early Paleocene time. Connections of that seaway to the south, however, remain poorly understood because of later Cenozoic massive erosion of any Paleocene rock record that had existed south of the borderland between the Dakotas. No Paleocene localities in southern Wyoming or Colorado have yet yielded assemblages of marine invertebrate body fossils or microfossils as known from the Williston Basin. No verifiable means, therefore, have been recognized to characterize the Paleocene marine record of the Hanna Basin in terms of species uniquely shared with the Cannonball biota. Short-lived, Paleocene seaway excursions into the Hanna Basin may have been: (1) direct and exclusively from the Gulf Coast; (2) solely from the Cannonball Sea, with seaway contiguity east of the emerging Black Hills; or (3) initiated from a more extensive, midcontinental seaway connecting the Arctic Ocean to the Gulf of Mexico. Substantial structural uplift of the Laramie Mountains prior to mid-Paleocene time would have precluded even brief westward pulses of marine inundation into t","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"43-69"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.1.43","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68311017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-03-20DOI: 10.2113/GSROCKY.46.1.101
M. Picard
Profiles of Rocky Mountain Geologists – a continuing series The State of Wyoming could do no better service to the youth of the State, no greater honor to itself than by erecting a fitting and lasting memorial at the university where he worked so faithfully, to the memory of Professor Wilbur Clinton Knight, a sincere and a faithful man, and an earnest student. —S. W. Williston, 1904 Wilbur Clinton Knight (Fig. 1), accomplished geologist and teacher, the son of a farmer, was born on 13 December 1858 at Rochelle, Illinois, then near the limit of civilization on the Great Plains (Williston, 1904). By 1859, petroleum production commenced at Titusville, Pennsylvania, in time reducing the demand for whale oil, coal gas, and lard burned in lamps (Trager, 1992, p. 479). Also this year, Charles Darwin's revolutionary research, On the Origin of Species by Means of Natural Selection , appeared, to great public interest and debate. Thus, Knight's birth occurred at the dawn of momentous industrial and intellectual changes. Figure 1. Wilbur Clinton Knight, about 1900, very near the time that his dissertation was published. Wilbur was around 42 years old. Courtesy American Heritage Center, University of Wyoming. While he was still a child, Wilbur Knight's family moved to a farm in Nebraska near Blue Springs, thirty miles south of Lincoln and a few miles north of the Kansas border. This remote hamlet lies between Beatrice to the northwest and Barneston on the southeast. It was a frontier life, hard and challenging. Fittingly, he was an exceptional marksman and greatly skilled with a fishing rod. Like many other village and farm-and-ranch boys, Knight never really left the land, but became one with it, discovering there the allure of geology. He began very early to roam the plains of southeastern Nebraska, picking up a …
怀俄明州政府为该州的年轻人提供最好的服务，最大的荣誉莫过于在他忠心耿耿地工作过的大学里为威尔伯·克林顿·奈特教授建立一座合适而持久的纪念碑。奈特教授是一位真诚而忠诚的人，也是一位认真的学生。- s。威尔伯·克林顿·奈特(Wilbur Clinton Knight，图1)是一位颇有成就的地质学家和教师，父亲是一个农民，1858年12月13日出生在伊利诺斯州的罗谢尔，当时接近大平原文明的极限(威利斯顿，1904年)。到1859年，石油生产在宾夕法尼亚州的Titusville开始，及时减少了对鲸油、煤气和油灯燃烧的猪油的需求(Trager, 1992, p. 479)。同样是在今年，查尔斯·达尔文的革命性研究《物种起源论》问世，引起了公众的极大兴趣和争论。因此，奈特的出生正值重大的工业和知识变革的黎明。图1所示。威尔伯·克林顿·奈特，大约在1900年，就在他的论文发表的时候。威尔伯大约42岁。由怀俄明大学美国遗产中心提供。当他还是个孩子的时候，威尔伯·奈特的家人就搬到了内布拉斯加州靠近蓝泉的一个农场，在林肯以南30英里，堪萨斯州边境以北几英里。这个偏僻的小村庄位于西北部的比阿特丽斯和东南部的巴尼斯顿之间。那是一种艰苦而富有挑战性的边疆生活。正好，他是一名出色的射手，并且非常熟练地使用鱼竿。像许多其他乡村、农场和牧场的男孩一样，奈特从未真正离开过这片土地，而是与它融为一体，在那里发现了地质的魅力。他很早就开始在内布拉斯加州东南部的平原上游荡，捡起一个……
{"title":"Wilbur Clinton Knight: Portrait of a pioneer geologist in Wyoming","authors":"M. Picard","doi":"10.2113/GSROCKY.46.1.101","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.1.101","url":null,"abstract":"Profiles of Rocky Mountain Geologists – a continuing series The State of Wyoming could do no better service to the youth of the State, no greater honor to itself than by erecting a fitting and lasting memorial at the university where he worked so faithfully, to the memory of Professor Wilbur Clinton Knight, a sincere and a faithful man, and an earnest student. —S. W. Williston, 1904 \u0000\u0000Wilbur Clinton Knight (Fig. 1), accomplished geologist and teacher, the son of a farmer, was born on 13 December 1858 at Rochelle, Illinois, then near the limit of civilization on the Great Plains (Williston, 1904). By 1859, petroleum production commenced at Titusville, Pennsylvania, in time reducing the demand for whale oil, coal gas, and lard burned in lamps (Trager, 1992, p. 479). Also this year, Charles Darwin's revolutionary research, On the Origin of Species by Means of Natural Selection , appeared, to great public interest and debate. Thus, Knight's birth occurred at the dawn of momentous industrial and intellectual changes. \u0000\u0000\u0000\u0000Figure 1. \u0000Wilbur Clinton Knight, about 1900, very near the time that his dissertation was published. Wilbur was around 42 years old. Courtesy American Heritage Center, University of Wyoming.\u0000\u0000\u0000\u0000While he was still a child, Wilbur Knight's family moved to a farm in Nebraska near Blue Springs, thirty miles south of Lincoln and a few miles north of the Kansas border. This remote hamlet lies between Beatrice to the northwest and Barneston on the southeast. It was a frontier life, hard and challenging. Fittingly, he was an exceptional marksman and greatly skilled with a fishing rod. Like many other village and farm-and-ranch boys, Knight never really left the land, but became one with it, discovering there the allure of geology.\u0000\u0000He began very early to roam the plains of southeastern Nebraska, picking up a …","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"101-109"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.1.101","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68310869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Basaltic lavas form part of the Miocene (∼20.5 to 18 Ma) Goldfield-Superstition silicic large igneous province in central Arizona. Most of the basalt erupted early in the development of this southern Basin and Range volcanic province, and only small amounts of basalt co-erupted with the silicic volcanism. We examined 50 samples of basalt from lower, middle, and upper stratigraphic positions of the province to establish basalt petrogeneses, the characteristics of basalt sources, relationships among compositionally different lavas, and the igneous processes that relate various basalt types. We base our study largely on major and trace elements, mineral compositions, and a small data set for Sr, Nd, and Hf isotopes. Lower-section basalts include the Weekes Wash basalts, which are transitional between alkalic and tholeiitic (SiO2 49–51 wt. %) and with MgO 8.1–10.2 wt. %. They are associated with lavas that are andesitic (SiO2 ∼59–62 wt. %; MgO 8–2.5 wt. %) or are seemingly andesitic due to alteration and felsic xenocrysts. Weekes Wash basalts have incompatible-element abundances that correlate positively with MgO. Their87Sr/86Sr ratios are ∼0.705. Olivines, rarely fresh, have Fo86–89 cores, and clinopyroxenes have Mg#s 86–89. Overlying the Weekes Wash are the Cottonwood Spring basalts, which are alkalic (SiO2 ∼45.5–47.5 wt. %), and can be categorized into subgroups defined by lower and higher incompatible-element abundances, or low Ti-P and high Ti-P (e.g., Ba ∼1100 versus 1800 ppm; La ∼75 versus 110 ppm). The Cottonwood Spring basalts are the closest to primary lavas we observed (MgO 10.1–11.8 wt. %), and their87Sr/86Sr ratios are ∼0.705–0.706. Their olivines are Fo86–89, and their clinopyroxenes have Mg#s 86–90. Overlying the Cottonwood Spring basalts is the Apache Gap Fe-Ti-enriched basalt (TiO2 ∼2.6 wt. %), which has the lowest MgO (∼5.6–7.5 wt. %) and incompatible-element abundances observed for any basalts in the province (e.g., Ba ∼400 ppm; La ∼25 ppm). All lower-section basalts have primitive-mantle normalizations showing Nb-Ta negative anomalies. Middle-section basalts erupted among silicic lava and pyroclastic flows from ∼19 to 18.5 Ma, and they compositionally resemble Weekes Wash basalts. Upper-section (post-18.5 Ma) lavas are the Willow Springs hawaiite (∼9.5 wt. % MgO;87Sr/86Sr ∼0.705) and Black Mesa basanite (SiO2 ∼44 wt. %; MgO ∼8 wt. %; CaO 14.7 wt. %;87Sr/86Sr ∼0.706). A Nb-Ta anomaly is clear in the hawaiite but weak in the basanite, as the basanite has the highest Nb and Ta observed (∼60 and ∼3 ppm; lowest Zr/Nb, ∼4 versus all others >7). Relevant interpretations are the following. Absence of ultramafic mantle xenoliths in Goldfield-Superstition basalts suggests that magmas occupied crustal reservoirs. The two subgroups of the Cottonwood Spring basalts attest to small-scale trace element and isotopic heterogeneities in lithospheric mantle sources that, based on Nb-Ta and Ce versus Ce/Yb modeling, had subduction zone characteris
{"title":"Miocene basaltic magmatism in the Goldfield-Superstition volcanic province, central Arizona Geochemistry, mineralogy, and petrology","authors":"R. V. Fodor, S. Vetter","doi":"10.2113/GSROCKY.46.1.1","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.1.1","url":null,"abstract":"Basaltic lavas form part of the Miocene (∼20.5 to 18 Ma) Goldfield-Superstition silicic large igneous province in central Arizona. Most of the basalt erupted early in the development of this southern Basin and Range volcanic province, and only small amounts of basalt co-erupted with the silicic volcanism. We examined 50 samples of basalt from lower, middle, and upper stratigraphic positions of the province to establish basalt petrogeneses, the characteristics of basalt sources, relationships among compositionally different lavas, and the igneous processes that relate various basalt types. We base our study largely on major and trace elements, mineral compositions, and a small data set for Sr, Nd, and Hf isotopes.\u0000\u0000Lower-section basalts include the Weekes Wash basalts, which are transitional between alkalic and tholeiitic (SiO2 49–51 wt. %) and with MgO 8.1–10.2 wt. %. They are associated with lavas that are andesitic (SiO2 ∼59–62 wt. %; MgO 8–2.5 wt. %) or are seemingly andesitic due to alteration and felsic xenocrysts. Weekes Wash basalts have incompatible-element abundances that correlate positively with MgO. Their87Sr/86Sr ratios are ∼0.705. Olivines, rarely fresh, have Fo86–89 cores, and clinopyroxenes have Mg#s 86–89. Overlying the Weekes Wash are the Cottonwood Spring basalts, which are alkalic (SiO2 ∼45.5–47.5 wt. %), and can be categorized into subgroups defined by lower and higher incompatible-element abundances, or low Ti-P and high Ti-P (e.g., Ba ∼1100 versus 1800 ppm; La ∼75 versus 110 ppm). The Cottonwood Spring basalts are the closest to primary lavas we observed (MgO 10.1–11.8 wt. %), and their87Sr/86Sr ratios are ∼0.705–0.706. Their olivines are Fo86–89, and their clinopyroxenes have Mg#s 86–90. Overlying the Cottonwood Spring basalts is the Apache Gap Fe-Ti-enriched basalt (TiO2 ∼2.6 wt. %), which has the lowest MgO (∼5.6–7.5 wt. %) and incompatible-element abundances observed for any basalts in the province (e.g., Ba ∼400 ppm; La ∼25 ppm). All lower-section basalts have primitive-mantle normalizations showing Nb-Ta negative anomalies.\u0000\u0000Middle-section basalts erupted among silicic lava and pyroclastic flows from ∼19 to 18.5 Ma, and they compositionally resemble Weekes Wash basalts. Upper-section (post-18.5 Ma) lavas are the Willow Springs hawaiite (∼9.5 wt. % MgO;87Sr/86Sr ∼0.705) and Black Mesa basanite (SiO2 ∼44 wt. %; MgO ∼8 wt. %; CaO 14.7 wt. %;87Sr/86Sr ∼0.706). A Nb-Ta anomaly is clear in the hawaiite but weak in the basanite, as the basanite has the highest Nb and Ta observed (∼60 and ∼3 ppm; lowest Zr/Nb, ∼4 versus all others >7).\u0000\u0000Relevant interpretations are the following. Absence of ultramafic mantle xenoliths in Goldfield-Superstition basalts suggests that magmas occupied crustal reservoirs. The two subgroups of the Cottonwood Spring basalts attest to small-scale trace element and isotopic heterogeneities in lithospheric mantle sources that, based on Nb-Ta and Ce versus Ce/Yb modeling, had subduction zone characteris","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"1-41"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.1.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68310695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The first International Geological Congress (IGC) ever to be convened in North America (5 th IGC, Washington, D.C., 1891) allowed American geologists to present results of pioneering mapping in the American West to an international community in a field setting. A 25-day “grand excursion” by rail and stagecoach across the Great Plains and Rocky Mountains to Yellowstone and the Grand Canyon for some 90 participants was organized by Samuel F. Emmons who had earlier served with the Fortieth Parallel Survey. Other trip leaders were G. H. Williams and I. C. White (Appalachian geology), J. P. Iddings (Montana geology), Arnold Hague (Yellowstone National Park), G. K. Gilbert (Basin and Range faulting, history of pluvial Lake Bonneville, and Niagara Falls region), J. W. Powell (Grand Canyon region), and C. W. Cross (Colorado geology). The stature of the U.S. Geological Survey in this golden age of geology was reflected in the large proportion of its members among IGC field-trip leaders and/or guidebook contributors.
在北美召开的第一届国际地质大会(IGC)(第5届IGC, 1891年，华盛顿特区)允许美国地质学家在野外环境中向国际社会展示美国西部开创性测绘的成果。塞缪尔·f·埃蒙斯(Samuel F. Emmons)组织了一次为期25天的“大旅行”，乘坐火车和公共马车穿越大平原和落基山脉，到达黄石公园和大峡谷。埃蒙斯曾在第40次平行调查中任职。其他的领队有g·h·威廉姆斯和i·c·怀特(阿巴拉契亚地质学)、j·p·艾丁斯(蒙大拿州地质学)、阿诺德·黑格(黄石国家公园)、g·k·吉尔伯特(盆地和山脉断裂、博纳维尔湖和尼亚加拉大瀑布地区的历史)、j·w·鲍威尔(大峡谷地区)和c·w·克罗斯(科罗拉多州地质学)。在这个地质学的黄金时代，美国地质调查局的地位反映在其成员中IGC实地考察领导和/或指南贡献者的很大比例上。
{"title":"The “grand excursion” of the Fifth International Geological Congress (1891) Celebrating geological exploration of the American West","authors":"K. Aalto","doi":"10.2113/GSROCKY.46.1.85","DOIUrl":"https://doi.org/10.2113/GSROCKY.46.1.85","url":null,"abstract":"The first International Geological Congress (IGC) ever to be convened in North America (5 th IGC, Washington, D.C., 1891) allowed American geologists to present results of pioneering mapping in the American West to an international community in a field setting. A 25-day “grand excursion” by rail and stagecoach across the Great Plains and Rocky Mountains to Yellowstone and the Grand Canyon for some 90 participants was organized by Samuel F. Emmons who had earlier served with the Fortieth Parallel Survey. Other trip leaders were G. H. Williams and I. C. White (Appalachian geology), J. P. Iddings (Montana geology), Arnold Hague (Yellowstone National Park), G. K. Gilbert (Basin and Range faulting, history of pluvial Lake Bonneville, and Niagara Falls region), J. W. Powell (Grand Canyon region), and C. W. Cross (Colorado geology). The stature of the U.S. Geological Survey in this golden age of geology was reflected in the large proportion of its members among IGC field-trip leaders and/or guidebook contributors.","PeriodicalId":34958,"journal":{"name":"Rocky Mountain Geology","volume":"46 1","pages":"85-100"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSROCKY.46.1.85","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68310793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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