—The first radiometric age for the Nacimiento Formation in the San Juan Basin was from an altered volcanic ash bed at Mesa de Cuba, near Cuba, NM. This 40 ar/ 39 ar single-crystal sanidine age of 64.0 ± 0.4 Ma was determined relative to the Fish Canyon Sanidine (FCS) with an age of 28.02 Ma. The age of the FCS has recently been revised to 28.294 Ma which makes the adjusted age for the Nacimiento ash bed 64.63 Ma. Based on this age and a newly reported age for an ash bed in the lower part of the Nacimiento Formation of 65.70 ± 0.03 Ma the base of magnetochron C29n has been moved from within and near the base of the Ojo alamo Sandstone to about the top of the Ojo alamo. The base of chron C29n and the Nacimiento Formation-Ojo alamo Sandstone contact appear to be coeval, with an age of 65.76 Ma. The short normal-polarity interval in the lower part of the Ojo Alamo Sandstone present at multiple localities in the southern San Juan Basin is no longer considered to be part of magnetochron C29n, but rather must be a hitherto unknown short-normal interval within chron C29r. The rate of deposition for the stratigraphic interval between the dated Nacimiento ash bed and the top of the Ojo alamo Sandstone (base of chron C29n) is 57 m/m.y. extrapolation over the 201 m interval, between the Nacimiento ash bed and the base of the overlying eocene San Jose Formation results in an age of 61.1 Ma for the base of the San Jose. The Paleocene-eocene contact is 56.34 Ma, thus a hiatus of at least 4.8 m.y. must be present at the Paleocene-eocene contact at Mesa de Cuba (assuming there are no significant, intervening unconformities). Puercan and Torrejonian mammal fossils have been identified in the Nacimiento Formation at numerous localities in the southern San Juan Basin. The boundary between these land-mammal stages is estimated to be at about the top of magnetochron C29n with an age of 65.06 Ma. This makes the duration of the Puercan Stage in the southern San Juan Basin about 1 m.y. In addition, this study shows that a recently reported U-Pb age of 64.8 Ma for a dinosaur bone from the Ojo alamo Sandstone is too young. However, robust palynologic data still strongly support the Paleocene age of the Ojo Alamo Sandstone and its contained dinosaur fossils throughout the San Juan Basin.
{"title":"Revised geochronology and paleomagnetic interpretations of uppermost Cretaceous and lowermost Paleocene rocks in the southern San Juan Basin","authors":"J. Fassett","doi":"10.56577/ffc-64.215","DOIUrl":"https://doi.org/10.56577/ffc-64.215","url":null,"abstract":"—The first radiometric age for the Nacimiento Formation in the San Juan Basin was from an altered volcanic ash bed at Mesa de Cuba, near Cuba, NM. This 40 ar/ 39 ar single-crystal sanidine age of 64.0 ± 0.4 Ma was determined relative to the Fish Canyon Sanidine (FCS) with an age of 28.02 Ma. The age of the FCS has recently been revised to 28.294 Ma which makes the adjusted age for the Nacimiento ash bed 64.63 Ma. Based on this age and a newly reported age for an ash bed in the lower part of the Nacimiento Formation of 65.70 ± 0.03 Ma the base of magnetochron C29n has been moved from within and near the base of the Ojo alamo Sandstone to about the top of the Ojo alamo. The base of chron C29n and the Nacimiento Formation-Ojo alamo Sandstone contact appear to be coeval, with an age of 65.76 Ma. The short normal-polarity interval in the lower part of the Ojo Alamo Sandstone present at multiple localities in the southern San Juan Basin is no longer considered to be part of magnetochron C29n, but rather must be a hitherto unknown short-normal interval within chron C29r. The rate of deposition for the stratigraphic interval between the dated Nacimiento ash bed and the top of the Ojo alamo Sandstone (base of chron C29n) is 57 m/m.y. extrapolation over the 201 m interval, between the Nacimiento ash bed and the base of the overlying eocene San Jose Formation results in an age of 61.1 Ma for the base of the San Jose. The Paleocene-eocene contact is 56.34 Ma, thus a hiatus of at least 4.8 m.y. must be present at the Paleocene-eocene contact at Mesa de Cuba (assuming there are no significant, intervening unconformities). Puercan and Torrejonian mammal fossils have been identified in the Nacimiento Formation at numerous localities in the southern San Juan Basin. The boundary between these land-mammal stages is estimated to be at about the top of magnetochron C29n with an age of 65.06 Ma. This makes the duration of the Puercan Stage in the southern San Juan Basin about 1 m.y. In addition, this study shows that a recently reported U-Pb age of 64.8 Ma for a dinosaur bone from the Ojo alamo Sandstone is too young. However, robust palynologic data still strongly support the Paleocene age of the Ojo Alamo Sandstone and its contained dinosaur fossils throughout the San Juan Basin.","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"401 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124274419","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}
{"title":"Third-day road log: Trip 1 - A brief tour of Mount Taylor","authors":"L. Crumpler, F. Goff","doi":"10.56577/ffc-64.59","DOIUrl":"https://doi.org/10.56577/ffc-64.59","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126698453","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}
—This paper describes a large-volume travertine deposit that formed at the northeastern end of Mesa del Oro, a basalt mesa located at the southwestern edge of the Colorado Plateau and along the Jemez lineament. The travertine deposit forms two topographically elevated platforms that cover an area of 27 km 2 , are up to 63 m thick, and have a calculated volume of 0.7 km 3 . We report six new dates for the Mesa del Oro accumulation and show that travertine formation occurred in two main intervals, 360-250 ka and 760-560 ka. The intervals overlap with episodes of basaltic volcanism in the area. The northern platform was deposited along a fissure ridge and an associated marsh as shown by both travertine morphology and facies. Large-volume travertine formation requires both high CO 2 influx and significant groundwater discharge. The high CO 2 influx is interpreted to be related to the episodic volcanic activity that produced over-pressuring of the CO 2 /groundwa- ter system with magmatic gasses. Intervals of high groundwater discharge are attributed to high head in a confined aquifer achieved through increased recharge and thus, episodes of travertine formation at Mesa del Oro are interpreted to record wet paleoclimate periods.
本文描述了形成于Mesa del Oro东北端的一个大体积钙华矿床，Mesa del Oro是一个位于科罗拉多高原西南边缘的玄武岩台地，沿着Jemez线条。石灰华矿床形成两个地形高架平台，覆盖面积27平方公里，厚达63米，计算体积为0.7平方公里。我们报告了Mesa del Oro堆积的六个新日期，并表明石灰华形成于360-250 ka和760-560 ka两个主要层段。这些间隔期与该地区的玄武岩火山活动相重叠。从石灰华的形态和相上看，北台地沿裂缝脊和伴生的沼泽沉积。大体积石灰华的形成既需要大量的CO 2流入，也需要大量的地下水排放。高CO 2流入被解释为与偶发性火山活动有关，火山活动产生了岩浆气体对CO 2 /地下水系统的超压。高地下水流量的间隔归因于通过增加补给而获得的封闭含水层的高水头，因此，Mesa del Oro的石灰华形成事件被解释为记录了潮湿的古气候时期。
{"title":"U-series ages and morphology of a Quaternary large-volume travertine deposit at Mesa del Oro, NM: Implications for paleohydrology, paleoclimate, and neotectonic proceses","authors":"A. Priewisch, L. Crossey, K. Karlstrom","doi":"10.56577/ffc-64.229","DOIUrl":"https://doi.org/10.56577/ffc-64.229","url":null,"abstract":"—This paper describes a large-volume travertine deposit that formed at the northeastern end of Mesa del Oro, a basalt mesa located at the southwestern edge of the Colorado Plateau and along the Jemez lineament. The travertine deposit forms two topographically elevated platforms that cover an area of 27 km 2 , are up to 63 m thick, and have a calculated volume of 0.7 km 3 . We report six new dates for the Mesa del Oro accumulation and show that travertine formation occurred in two main intervals, 360-250 ka and 760-560 ka. The intervals overlap with episodes of basaltic volcanism in the area. The northern platform was deposited along a fissure ridge and an associated marsh as shown by both travertine morphology and facies. Large-volume travertine formation requires both high CO 2 influx and significant groundwater discharge. The high CO 2 influx is interpreted to be related to the episodic volcanic activity that produced over-pressuring of the CO 2 /groundwa- ter system with magmatic gasses. Intervals of high groundwater discharge are attributed to high head in a confined aquifer achieved through increased recharge and thus, episodes of travertine formation at Mesa del Oro are interpreted to record wet paleoclimate periods.","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131078948","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}
—Strawberry Crater is one of several hundred scoria cones in the San Francisco volcanic field of northern arizona. the process of scoria-cone formation and deconstruction are not completely understood despite the fact that they are the most common landform on earth. Strawberry Crater is an unusual cone in that variable magma characteristics caused scoria during late stages of the eruption to become agglutinated upon deposition. this agglutinated scoria broke into large blocks that were displaced as late-stage eruption of lava breached the walls of the cone. Facies analysis shows that many of the blocks represent formerly continuous depositional horizons, which reflect a variance in magma-gas content and magma-rise rate that may have affected the temperature and accumulation rate of pyroclasts, and therefore the degree of agglutination. Faults between blocks are dominantly vertical to subvertical regardless of block size. this suggests that breaching of the cone occurred abruptly as magma pressure exceeded the strength of the cone walls and released the remaining magma trapped in the cone, or that breaching was caused by an increase in magma flux as late-stage lava emanated from the bottom of the cone.
{"title":"Processes during scoria-cone collapse as recorded by displacement of crater-rim blocks, Strawberry Crater, AZ","authors":"Courtney M. Pulido, N. Riggs","doi":"10.56577/ffc-64.153","DOIUrl":"https://doi.org/10.56577/ffc-64.153","url":null,"abstract":"—Strawberry Crater is one of several hundred scoria cones in the San Francisco volcanic field of northern arizona. the process of scoria-cone formation and deconstruction are not completely understood despite the fact that they are the most common landform on earth. Strawberry Crater is an unusual cone in that variable magma characteristics caused scoria during late stages of the eruption to become agglutinated upon deposition. this agglutinated scoria broke into large blocks that were displaced as late-stage eruption of lava breached the walls of the cone. Facies analysis shows that many of the blocks represent formerly continuous depositional horizons, which reflect a variance in magma-gas content and magma-rise rate that may have affected the temperature and accumulation rate of pyroclasts, and therefore the degree of agglutination. Faults between blocks are dominantly vertical to subvertical regardless of block size. this suggests that breaching of the cone occurred abruptly as magma pressure exceeded the strength of the cone walls and released the remaining magma trapped in the cone, or that breaching was caused by an increase in magma flux as late-stage lava emanated from the bottom of the cone.","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123937511","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}
L. Crumpler, Jane Aubele, J. Zimbelman, Steve Self, J. Bleacher, B. Garry
{"title":"Third-day road log: Trip 3 - McCartys lava flow field, El Malpais and traverse log to Lava Falls","authors":"L. Crumpler, Jane Aubele, J. Zimbelman, Steve Self, J. Bleacher, B. Garry","doi":"10.56577/ffc-64.75","DOIUrl":"https://doi.org/10.56577/ffc-64.75","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127082530","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}
W. Parker, J. Martz, K. Zeigler, S. Semken, J. Timmons
{"title":"Second-day road log: From a corner in Winslow, Arizona, through Petrified Forest National Park, to the El Rancho Hotel in Gallup, New Mexico","authors":"W. Parker, J. Martz, K. Zeigler, S. Semken, J. Timmons","doi":"10.56577/ffc-64.25","DOIUrl":"https://doi.org/10.56577/ffc-64.25","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133898101","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}
{"title":"Uranium mining adjacent to Petrified Forest National Monument, Arizona","authors":"W. L. Chenoweth","doi":"10.56577/ffc-64.127","DOIUrl":"https://doi.org/10.56577/ffc-64.127","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115883357","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}
K. Zeigler, N. Riggs, J. Timmons, M. Ort, S. Semken
{"title":"First-day road log: From Flagstaff to S P and Colton Craters, Wupatki and Sunset Crater National Monuments and Meteor Crater","authors":"K. Zeigler, N. Riggs, J. Timmons, M. Ort, S. Semken","doi":"10.56577/ffc-64.9","DOIUrl":"https://doi.org/10.56577/ffc-64.9","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117011871","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}
{"title":"Third-day road log: Trip 2 -Tuffs of San Mateo Canyon","authors":"S. Kelley, N. Dunbar, W. McIntosh, F. Goff","doi":"10.56577/ffc-64.70","DOIUrl":"https://doi.org/10.56577/ffc-64.70","url":null,"abstract":"","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130166681","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 present data on trends, widths, petrography and chemistry of volcanic dikes in the Mount Taylor vol- cano region, New Mexico. The dikes are subdivided into two distinct groups: 1) Nephelinite to trachybasalt dikes cutting Cretaceous sediments and Pliocene volcanic rocks in canyons and ravines south and west of Mount Taylor, and 2) Trachyandesite to trachydacite dikes cutting volcanic and intrusive rocks in the amphitheater of Mount Taylor. one dike from each group with particularly good exposures (horace Mesa and South Wall dikes) is highlighted to show the differences in each dike type. Lastly, Mount Taylor mafic and silicic dikes are briefly compared to those at Ship Rock, New Mexico, and Summer Coon, Colorado, respectively. Although there are some similarities, there are many more differences primarily in dike configuration, length, and other varying characteristics.
{"title":"Mount Taylor dikes","authors":"F. Goff, J. Wolff, Kamilla Fallah","doi":"10.56577/ffc-64.159","DOIUrl":"https://doi.org/10.56577/ffc-64.159","url":null,"abstract":"—We present data on trends, widths, petrography and chemistry of volcanic dikes in the Mount Taylor vol- cano region, New Mexico. The dikes are subdivided into two distinct groups: 1) Nephelinite to trachybasalt dikes cutting Cretaceous sediments and Pliocene volcanic rocks in canyons and ravines south and west of Mount Taylor, and 2) Trachyandesite to trachydacite dikes cutting volcanic and intrusive rocks in the amphitheater of Mount Taylor. one dike from each group with particularly good exposures (horace Mesa and South Wall dikes) is highlighted to show the differences in each dike type. Lastly, Mount Taylor mafic and silicic dikes are briefly compared to those at Ship Rock, New Mexico, and Summer Coon, Colorado, respectively. Although there are some similarities, there are many more differences primarily in dike configuration, length, and other varying characteristics.","PeriodicalId":367315,"journal":{"name":"Geology of Route 66 Region: Flagstaff to Grants","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125708041","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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