Journal articles: 'Morrison-Formation'

1

Turner, Christine, and Fred Peterson. "Morrison Ecosystem Project." UW National Parks Service Research Station Annual Reports 18 (January 1, 1994): 152–55. http://dx.doi.org/10.13001/uwnpsrc.1994.3219.

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The Late Jurassic Morrison Formation is one of science's best windows into the world of dinosaurs and Mesozoic ecosystems. The Morrison Formation has significant exposures in many units within the Rocky Mountain Region of the National Park Service. These include Arches National Park (ARCH), Bighorn National Recreation Area (BIRO), Black Canyon of the Gunnison National Monument (BLCA), Capitol Reef National Park (CARE), Colorado National Monument (COLO), Curecanti National Recreation Area (CURE), Dinosaur National Monument (DINO), Glacier National Park (GLAC), Glen Canyon National Recreation Area (GLCA), Hovenweep National Monument (HOVE), and Yellowstone National Park (YELL). The Morrison Formation Extinct Ecosystems Project, hereafter called the Morrison Project, began on June 1 of 1994. The project is a multidisciplinary endeavor to determine the nature, distribution, and evolution of the ancient ecosystems that existed in the Western Interior of the United States during the Late Jurassic Epoch when the Morrison Formation and related rocks were deposited. The information obtained from the research can be used to suggest appropriate resource management actions and the project will also provide an improved understanding of the geological and paleontological history of these NPS units and better information for interpretive programs and publications.

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2

Lucas, Spencer. "The Upper Jurassic Morrison Formation in north-central New Mexico–Linking Colorado Plateau stratigraphy to the stratigraphy of the High Plains." Geology of the Intermountain West 5 (June 21, 2018): 117–29. http://dx.doi.org/10.31711/giw.v5.pp117-129.

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Most study of the Upper Jurassic Morrison Formation has focused on its spectacular and extensive outcrops on the southern Colorado Plateau. Nevertheless, outcrops of the Morrison Formation extend far off the Colorado Plateau, onto the southern High Plains as far east as western Oklahoma. Outcrops of the Morrison Formation east of and along the eastern flank of the Rio Grande rift in north-central New Mexico (Sandoval, Bernalillo, and Santa Fe Counties) are geographically intermediate between the Morrison Formation outcrops on the southeastern Colorado Plateau in northwestern New Mexico and on the southern High Plains of eastern New Mexico. Previous lithostratigraphic correlations between the Colorado Plateau and High Plains Morrison Formation outcrops using the north-central New Mexico sections encompassed a geographic gap in outcrop data of about 100 km. New data on previously unstudied Morrison Formation outcrops at Placitas in Sandoval County and south of Lamy in Santa Fe County reduce that gap and significantly add to stratigraphic coverage. At Placitas, the Morrison Formation is about 141 m thick, in the Lamy area it is about 232 m thick, and, at both locations, it consists of the (ascending) sandstone-dominated Salt Wash Member, mudstone-dominated Brushy Basin Member, and sandstone-dominated Jackpile Member. Correlation of Morrison strata across northern New Mexico documents the continuity of the Morrison depositional systems from the Colorado Plateau eastward onto the southern High Plains. Along this transect, there is significant stratigraphic relief on the base of the Salt Wash Member (J-5 unconformity), the base of the Jackpile Member, and the base of the Cretaceous strata that overlie the Morrison Formation (K unconformity). Salt Wash Member deposition was generally by easterly-flowing rivers, and this river system continued well east of the Colorado Plateau. The continuity of the Brushy Basin Member, and its characteristic zeolite-rich clay facies, onto the High Plains suggests that localized depositional models (e.g., “Lake T’oo’dichi’) need to be re-evaluated. Instead, envisioning Brushy Basin Member deposition on a vast muddy floodplain, with some localized lacustrine and palustrine depocenters, better interprets its distribution and facies.

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3

Lucas, Spencer G. "The Upper Jurassic Morrison Formation in north-central New Mexico–Linking Colorado Plateau stratigraphy to the stratigraphy of the High Plains." Geology of the Intermountain West 5 (June 1, 2018): 117–29. http://dx.doi.org/10.31711/giw.v5i0.23.

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Most study of the Upper Jurassic Morrison Formation has focused on its spectacular and extensive outcrops on the southern Colorado Plateau. Nevertheless, outcrops of the Morrison Formation extend far off the Colorado Plateau, onto the southern High Plains as far east as western Oklahoma. Outcrops of the Morrison Formation east of and along the eastern flank of the Rio Grande rift in north-central New Mexico (Sandoval, Bernalillo, and Santa Fe Counties) are geographically intermediate between the Morrison Formation outcrops on the southeastern Colorado Plateau in northwestern New Mexico and on the southern High Plains of eastern New Mexico. Previous lithostratigraphic correlations between the Colorado Plateau and High Plains Morrison Formation outcrops using the north-central New Mexico sections encompassed a geographic gap in outcrop data of about 100 km. New data on previously unstudied Morrison Formation outcrops at Placitas in Sandoval County and south of Lamy in Santa Fe County reduce that gap and significantly add to stratigraphic coverage. At Placitas, the Morrison Formation is about 141 m thick, in the Lamy area it is about 232 m thick, and, at both locations, it consists of the (ascending) sandstone-dominated Salt Wash Member, mudstone-dominated Brushy Basin Member, and sandstone-dominated Jackpile Member. Correlation of Morrison strata across northern New Mexico documents the continuity of the Morrison depositional systems from the Colorado Plateau eastward onto the southern High Plains. Along this transect, there is significant stratigraphic relief on the base of the Salt Wash Member (J-5 unconformity), the base of the Jackpile Member, and the base of the Cretaceous strata that overlie the Morrison Formation (K unconformity). Salt Wash Member deposition was generally by easterly-flowing rivers, and this river system continued well east of the Colorado Plateau. The continuity of the Brushy Basin Member, and its characteristic zeolite-rich clay facies, onto the High Plains suggests that localized depositional models (e.g., “Lake T’oo’dichi’) need to be re-evaluated. Instead, envisioning Brushy Basin Member deposition on a vast muddy floodplain, with some localized lacustrine and palustrine depocenters, better interprets its distribution and facies.

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4

Turner, Christine, Fred Peterson, D. Chure, T. Demko, and G. Engelmann. "The Morrison Formation Extinct Ecosystems Project." UW National Parks Service Research Station Annual Reports 19 (January 1, 1995): 84–91. http://dx.doi.org/10.13001/uwnpsrc.1995.3257.

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The Morrison Extinct Ecosystem project is generating interesting results that, although preliminary in nature, are starting to converge on an integrated reconstruction of the Late Jurassic habitat in the Western Interior of the United States. A workshop in April, 1996, helped the participants learn where their data are in agreement and where remaining inconsistencies in the data exist. The workshop thus helped focus collective and individual efforts for the remaining field season so that additional field research and sample collection could be directed toward addressing the unresolved questions. A much more complete picture of the Morrison ecosystem is emerging, with such lines of evidence as the isotopic data confirming regional tectonic interpretations, and trace fossils adding subtle but significant clues to the interpretations of the ancient climate and water-table position and fluctuations. A mesic climate interpretation with a moderate amount of available moisture is derived from some of the plant fossils and, at first glance, contrasts with evidence of an arid to semi-arid climate based on the presence of saline, alkaline lake deposits; eolian strata; and evaporite deposits. Thus, the climate may have changed periodically or episodically, leaving evidence in the geologic record of the contrasting climate regimes-not all of which existed at the same time. A possible resolution of these discrepancies is that there was marked seasonality in which part of the year was relatively dry, as reflected by the arid to semiarid environmental indicators, whereas there may have been more precipitation during other parts of the year, as reflected by the more mesic environmental indicators. An additional factor that will need to be evaluated further is the role of the water table. The trace fossils suggest a fairly shallow water table that many of the plants, especially the larger ones, could tap throughout the year and therefore not be unduly affected by seasonal dryness. Also to be evaluated is the possibility that plants grew near stream courses or in overbank ponds in areas having a high water table, and that areas away from the streams were drier. These issues will be the focus of the remaining work, as outlined at the conclusion of the workshop.

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5

Turner, Christine, Fred Peterson, D. Chure, T. Demko, and G. Engelmann. "The Morrison Formation Extinct Ecosystems Project." UW National Parks Service Research Station Annual Reports 20 (January 1, 1996): 20–27. http://dx.doi.org/10.13001/uwnpsrc.1996.3269.

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The Morrison Project is a multidisciplinary effort to interpret the ancient ecosystem that was present in the Western Interior of the United States during deposition of the Upper Jurassic Morrison Formation. The project began in June of 1994 and the first two years of research (1994-95, 1995-96) were devoted primarily to identifying problems and gathering information that would form the basis for later interpretations. Efforts during the final year (1996-97) were directed toward resolving remaining problems or conflicting findings and synthesizing the various research endeavors into a reconstruction of the Late Jurassic ecosystem.

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6

Davis, Brian, Richard Cifelli, and Guillermo Rougier. "A preliminary report of the fossil mammals from a new microvertebrate locality in the Upper Jurassic Morrison Formation, Grand County, Utah." Geology of the Intermountain West 5 (February 7, 2018): 1–8. http://dx.doi.org/10.31711/giw.v5.pp1-8.

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The first Mesozoic mammals in North America were discovered in the Morrison Formation during the closing decades of the 19th century, as by-products of dinosaurs quarried by teams led by O.C. Marsh. These tiny fossils served as foundational specimens for our understanding of Mesozoic mammal evolution. There are now nearly 25 mammal-bearing localities known from the Morrison Formation, distributed across the Western Interior from the Black Hills to southern Colorado and west into Utah; the most historically important of these are in Wyoming (e.g., Como Quarry 9). Most Morrison mammals are known by jaws or jaw fragments, and several important Mesozoic groups (e.g., docodonts, dryolestoids, and to a large extent triconodonts and symmetrodonts) were established based on Morrison material, shaping the perception of mammalian diversity on a global scale. Despite heavy sampling of coeval sites elsewhere, the Morrison remains the most systematically diverse (at high taxonomic levels) assemblage of Jurassic mammals in the world. Here, we describe two mammalian specimens and highlight other remains yet to be fully identified from a new microvertebrate locality in the Morrison Formation of eastern Grand County, Utah. The site is positioned low in the Brushy Basin Member and is similar in lithology and stratigraphic level to the famous small vertebrate localities of the Fruita Paleontological Area, located less than 50 km to the northeast. In addition to small archosaurs and squamates, limited excavation to date has yielded at least 20 mammalian specimens representing a minimum of six taxa, several of which are new and quite different from typical Morrison taxa. Preservation is generally excellent and includes partially articulated cranial and postcranial elements of small vertebrates. This new site has great potential to contribute new taxa and more complete morphological data than typical Morrison localities, underscoring the importance of continued field work in the Morrison.

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7

Davis, Brian M., Richard L. Cifelli, and Guillermo W. Rougier. "A preliminary report of the fossil mammals from a new microvertebrate locality in the Upper Jurassic Morrison Formation, Grand County, Utah." Geology of the Intermountain West 5 (June 1, 2018): 1–8. http://dx.doi.org/10.31711/giw.v5i0.17.

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The first Mesozoic mammals in North America were discovered in the Morrison Formation during the closing decades of the 19th century, as by-products of dinosaurs quarried by teams led by O.C. Marsh. These tiny fossils served as foundational specimens for our understanding of Mesozoic mammal evolution. There are now nearly 25 mammal-bearing localities known from the Morrison Formation, distributed across the Western Interior from the Black Hills to southern Colorado and west into Utah; the most historically important of these are in Wyoming (e.g., Como Quarry 9). Most Morrison mammals are known by jaws or jaw fragments, and several important Mesozoic groups (e.g., docodonts, dryolestoids, and to a large extent triconodonts and symmetrodonts) were established based on Morrison material, shaping the perception of mammalian diversity on a global scale. Despite heavy sampling of coeval sites elsewhere, the Morrison remains the most systematically diverse (at high taxonomic levels) assemblage of Jurassic mammals in the world. Here, we describe two mammalian specimens and highlight other remains yet to be fully identified from a new microvertebrate locality in the Morrison Formation of eastern Grand County, Utah. The site is positioned low in the Brushy Basin Member and is similar in lithology and stratigraphic level to the famous small vertebrate localities of the Fruita Paleontological Area, located less than 50 km to the northeast. In addition to small archosaurs and squamates, limited excavation to date has yielded at least 20 mammalian specimens representing a minimum of six taxa, several of which are new and quite different from typical Morrison taxa. Preservation is generally excellent and includes partially articulated cranial and postcranial elements of small vertebrates. This new site has great potential to contribute new taxa and more complete morphological data than typical Morrison localities, underscoring the importance of continued field work in the Morrison.

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8

Engelmann, George. "Paleontological Survey of the Jurassic Morrison Formation in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 15 (January 1, 1991): 83–84. http://dx.doi.org/10.13001/uwnpsrc.1991.2975.

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This project was undertaken to survey the surface exposures of the Jurassic Morrison Formation within Dinosaur National Monument (DNM) for fossil occurrences of any sort. The primary purpose of this survey is to provide an assessment of the extent and characteristics of the paleontological resource in this geologic formation within DNM. In so doing, the survey may also have the effect of discovering specimens of obvious and immediate scientific importance and providing observations that will contribute to an improved understanding of the stratigraphy of the Morrison Formation. Dinosaur National Monument was originally established for, and takes its name from the unique occurrence of a quarry (the Carnegie Quarry (CQ) that has produced a diverse and abundant dinosaur fauna. The CQ occurs within the Morrison Formation which is known worldwide as one of the most prolific dinosaur-bearing units in the paleontologic record (Colbert. 1968). In addition to the dinosaurs, the Morrison has produced the best represented fauna of early mammals from the Jurassic (Clemens et al. 1979) and fossils of other vertebrates (Chure & Engelmann 1989). This suggests that the area beyond the CQ at DNM may contain important paleontological resources. This project will provide the first systematic survey of the Morrison Formation within DNM. It will provide a basis for management of the paleontologic resource in the future and is likely to yield immediate results in the discovery of specimens that can be important to ongoing research projects.

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9

Göhlich, Ursula B., Luis M. Chiappe, James M. Clark, and Hans-Dieter Sues. "The systematic position of the Late Jurassic alleged dinosaur Macelognathus (Crocodylomorpha: Sphenosuchia)." Canadian Journal of Earth Sciences 42, no. 3 (March 1, 2005): 307–21. http://dx.doi.org/10.1139/e05-005.

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Macelognathus vagans was described by O.C. Marsh in 1884, based on a mandibular symphysis from the Upper Jurassic Morrison Formation of Wyoming. Often considered a dinosaur but later tentatively referred to the Crocodylia, its phylogenetic identity has until now been enigmatic. New material of this species from the Morrison Formation of western Colorado demonstrates its affinities with basal crocodylomorphs commonly grouped together as the Sphenosuchia, which are characterized by a gracile postcranial skeleton with erect limb posture. Macelognathus shares features with Kayentasuchus from the Lower Jurassic Kayenta Formation of Arizona and Hallopus, which may be from the Morrison Formation of eastern Colorado. The new material constitutes the youngest definitive occurrence of a sphenosuchian, previously known from the Late Triassic to the Middle or Late? Jurassic.

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10

Woodruff, D. "What factors influence our reconstructions of Morrison Formation sauropod diversity?" Geology of the Intermountain West 6 (December 19, 2019): 93–112. http://dx.doi.org/10.31711/giw.v6.pp93-112.

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The Upper Jurassic Morrison Formation classically represents the “Golden Age” of sauropods, and the Morrison Formation is reported to have yielded 13 genera and 24 species of sauropods. This incredible diversity has produced numerous theories attempting to reconcile the co-occurrence of such large, and similar taxa. Previously, a comparably high diversity has been proposed for the Late Cretaceous Hell Creek Formation of North America – possibly comprising nearly three dozen species from over 20 genera of ankylosaura, caenagnathids, ceratopsians, dromaeosaurids, hadrosaurs, ornithomimids, pachycephalosaurs, thescelosaurs, and tyrannosaurs. However, much of the morphologic variation previously ascribed to taxonomic differences has recently been shown to be a result of stratigraphy and/or ontogeny – resulting in this rich assemblage being downsized to 13 genera and 16 species. Whereas still rich in diversity, such factors have an immediate effect towards our reconstruction of true richness.Following the example of the Hell Creek Formation, we can investigate the ontogenetic and strati-graphic origin of possible diversity inflation in other formations, and within this study, apply it to the Morrison Formation. New dating techniques are resulting in finer temporal resolution, and are changing the temporal position of well-known quarries. Differences in body size and ontogenetic stages can also affect diversity estimates. Plotting body size stratigraphically, it initially appears that larger specimens (interpreted as different species) occur higher in the section. An increase in average body size may be a legitimate trend, but there are several specimens that counter this “rule” for many genera. Likewise, dramatic allometric ontogenetic trajectories have led to the erection of at least three diplodocid genera – Amphicoelias, Seismosaurus, and Suuwassea – and it is suspected that many more Morrison Formation “species” could alternatively be explained as ontogimorphs. We have a long way to go towards revealing the true nature of Morrison Formation sauropod diversity. Although dietary partitioning undoubtedly occurred at the level of both the species (e.g., Brachiosaurus vs. Diplodocus) and between ontogenetic stages, a base of 24 levels of co-occurring divisions seems unlikely. The Morrison Formation may have exhibited a sauropod-rich assemblage unlike any other in North America, and the implications of stratigraphy, ontogeny, and variation may be minor, yet these factors alter perceived “diversity.” True diversity will not be fully understood unless these factors are considered.

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11

Turner, Christine, and Fred Peterson. "Sedimentology and Stratigraphy of the Morrison Formation in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 16 (January 1, 1992): 86–91. http://dx.doi.org/10.13001/uwnpsrc.1992.3079.

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The overall goal of this study is to establish a stratigraphic, sedimentologic, and geochronologic framework for the Upper Jurassic Morrison Formation within Dinosaur National Monument and to tie that framework to the rest of the Colorado Plateau and other important vertebrate fossil-bearing localities in the western United States. The study is also intended to complement ongoing paleontological inventories of the Morrison Formation within Dinosaur National Monument (DNM).

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12

Trujillo, Kelli, and Bart Kowallis. "Recalibrated legacy 40Ar/39Ar ages for the Upper Jurassic Morrison Formation, Western Interior, U.S.A." Geology of the Intermountain West 2 (January 20, 2015): 1–8. http://dx.doi.org/10.31711/giw.v2.pp1-8.

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As a result of recent updating of decay constants and standard ages used for 40Ar/39Ar dating, it is necessary to recalibrate legacy ages obtained with older methods. These recalibrations bring legacy 40Ar/39Ar ages into better agreement with ages obtained using 238U/206Pb dating methods. We present nine recalibrated 40Ar/39Ar ages for the Upper Jurassic Morrison Formation of the Western Interior, U.S.A., along with the individual geographic and stratigraphic locations for each sample. These recalibrated ages will be useful for researchers looking to place better age constraints on the flora and fauna of the Morrison Formation, as well as for those working to understand stratigraphic relationships across the formation. The recalibrated ages also can now be used reliably for comparisons with newer 238U/206Pb ages obtained for the Morrison Formation.

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13

Carpenter, Kenneth, and Eugene Lindsey. "Redefining the Upper Jurassic Morrison Formation in Garden Park National Natural Landmark and vicinity, eastern Colorado: Geology of the Intermountain West." Geology of the Intermountain West 6 (January 31, 2019): 1–30. http://dx.doi.org/10.31711/giw.v6.pp1-30.

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The Garden Park National Natural Landmark (GPNNL) is north of Cañon City, Colorado, and encompasses all of the major historical dinosaur quarries of the Upper Jurassic Morrison Formation in this area. The formation there can be divided into the lower redefined Ralston Creek Member and an upper unnamed member. The Morrison Formation is bracketed below by the J-5 unconformity and above by the K-1 unconformity. The Ralston Creek Member is composed of up to 55 m of arkosic conglomerate, sandstone, siltstone, and gypsum conformably underlying the unnamed member. Fossil fishes previously used to infer a Middle Jurassic age are non-diagnostic. A diplodocid skeleton 4 m above the J-5 unconformity from the west-adjacent Shaws Park, and a radiometric date of 152.99 + 0.10 Ma from the Purgatoire River area demonstrate that the Ralston Creek rightly belongs in the Morrison Formation and correlates with the Tidwell and Salt Wash Members on the Colorado Plateau. The Ralston Creek was deposited in a broad playa complex analogous to those of central Australia and here called the Ralston Creek boinka. Groundwater flux played an important role in gypsum deposition in gypsisols and playa lakes. The overlying unnamed member in the GPNNL can be subdivided on the west side of Fourmile Creek into a lower part composed largely of mudstone with many thin, discontinuous channel sandstone beds, and a thicker upper part containing more persistent tabular sandstone beds; this subdivision does not occur east of Fourmile Creek. Several thin limestone beds occur in the Ralston Creek Member and in the lower part of the unnamed upper member. The limestone contains fresh water ostracods and aquatic mollusks indicating a lacustrine origin. However, these fauna are apparently stunted and the ostracod valves closed indicating periodic hypersaline conditions. All detrital rocks in the Morrison Formation at Garden Park are composed of varying amounts of quartz, potassic feldspar, and the clay minerals illite, smectite, and kaolinite. Mapping of the clay minerals in the unnamed member reflect various paleosols throughout the mudstone interval, including protosols and argillisols. At the top of the formation, a sandstone previously assigned to the Morrison is reassigned to the overlying Cretaceous Lytle Formation based on similar weathering characteristics, mineral content, and fabric. Thus, the K-1 unconformity between the Morrison and overlying Lytle rests on the uppermost occurrence of the Morrison Formation mudstone-sandstone-limestone complex and beneath the blocky, cliff-forming Lytle Formation.

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14

Carpenter, Kenneth, and Eugene Lindsey. "Redefining the Upper Jurassic Morrison Formation in Garden Park National Natural Landmark and vicinity, eastern Colorado: Geology of the Intermountain West." Geology of the Intermountain West 6 (January 25, 2019): 1–30. http://dx.doi.org/10.31711/giw.v6i0.33.

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The Garden Park National Natural Landmark (GPNNL) is north of Cañon City, Colorado, and encompasses all of the major historical dinosaur quarries of the Upper Jurassic Morrison Formation in this area. The formation there can be divided into the lower redefined Ralston Creek Member and an upper unnamed member. The Morrison Formation is bracketed below by the J-5 unconformity and above by the K-1 unconformity. The Ralston Creek Member is composed of up to 55 m of arkosic conglomerate, sandstone, siltstone, and gypsum conformably underlying the unnamed member. Fossil fishes previously used to infer a Middle Jurassic age are non-diagnostic. A diplodocid skeleton 4 m above the J-5 unconformity from the west-adjacent Shaws Park, and a radiometric date of 152.99 + 0.10 Ma from the Purgatoire River area demonstrate that the Ralston Creek rightly belongs in the Morrison Formation and correlates with the Tidwell and Salt Wash Members on the Colorado Plateau. The Ralston Creek was deposited in a broad playa complex analogous to those of central Australia and here called the Ralston Creek boinka. Groundwater flux played an important role in gypsum deposition in gypsisols and playa lakes. The overlying unnamed member in the GPNNL can be subdivided on the west side of Fourmile Creek into a lower part composed largely of mudstone with many thin, discontinuous channel sandstone beds, and a thicker upper part containing more persistent tabular sandstone beds; this subdivision does not occur east of Fourmile Creek. Several thin limestone beds occur in the Ralston Creek Member and in the lower part of the unnamed upper member. The limestone contains fresh water ostracods and aquatic mollusks indicating a lacustrine origin. However, these fauna are apparently stunted and the ostracod valves closed indicating periodic hypersaline conditions. All detrital rocks in the Morrison Formation at Garden Park are composed of varying amounts of quartz, potassic feldspar, and the clay minerals illite, smectite, and kaolinite. Mapping of the clay minerals in the unnamed member reflect various paleosols throughout the mudstone interval, including protosols and argillisols. At the top of the formation, a sandstone previously assigned to the Morrison is reassigned to the overlying Cretaceous Lytle Formation based on similar weathering characteristics, mineral content, and fabric. Thus, the K-1 unconformity between the Morrison and overlying Lytle rests on the uppermost occurrence of the Morrison Formation mudstone-sandstone-limestone complex and beneath the blocky, cliff-forming Lytle Formation.

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15

Trujillo, Kelli C., and Bart J. Kowallis. "Recalibrated legacy ⁴⁰Ar/³⁹Ar ages for the Upper Jurassic Morrison Formation, Western Interior, U.S.A." Geology of the Intermountain West 2 (May 28, 2015): 1–8. http://dx.doi.org/10.31711/giw.v2i0.3.

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As a result of recent updating of decay constants and standard ages used for 40Ar/39Ar dating, it is necessary to recalibrate legacy ages obtained with older methods. These recalibrations bring legacy 40Ar/39Ar ages into better agreement with ages obtained using 238U/206Pb dating methods. We present nine recalibrated 40Ar/39Ar ages for the Upper Jurassic Morrison Formation of the Western Interior, U.S.A., along with the individual geographic and stratigraphic locations for each sample. These recalibrated ages will be useful for researchers looking to place better age constraints on the flora and fauna of the Morrison Formation, as well as for those working to understand stratigraphic relationships across the formation. The recalibrated ages also can now be used reliably for comparisons with newer 238U/206Pb ages obtained for the Morrison Formation.

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16

Leach, Connor T., Emma Hoffman, and Peter Dodson. "The promise of taphonomy as a nomothetic discipline: taphonomic bias in two dinosaur-bearing faunas in North America1." Canadian Journal of Earth Sciences 58, no. 9 (September 2021): 852–69. http://dx.doi.org/10.1139/cjes-2020-0176.

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The fossil record of dinosaurs is a rich, if biased, one with nearly complete skeletons, partial skeletons, and isolated parts found in diverse, well-studied faunal assemblages around the world. Among the recognized biases are the preferential preservation of large dinosaurs and the systematic underrepresentation of small dinosaurs. Such biases have been quantitatively described in the Upper Cretaceous (Campanian) Dinosaur Park Formation of Alberta, where large, nearly complete dinosaurs were found and described early in collecting history and small, very incomplete dinosaurs were found and described later. This pattern, apparently replicated in the Maastrichtian Hell Creek Formation of Montana, is so striking that it begs the question of whether this is a nomothetic principle for the preservation of dinosaur faunas elsewhere. We tested this hypothesis by analyzing the very well-studied dinosaur fauna of the Upper Jurassic (Kimmeridgian) Morrison Formation of the western United States. The Morrison Formation fails to show any correlation between body size and completeness, order of discovery, or order of description. Both large and small dinosaurs of the Morrison include highly complete as well as highly incomplete taxa, and both large and small dinosaurs were discovered and described early in collecting history as well as more recently. The differences in preservation between the Dinosaur Park Formation and the Morrison Formation are so striking that we posit a Dinosaur Park model of dinosaur fossil preservation and a Morrison model. Future study will show whether either or both represent durable nomothetic models for dinosaur fossil preservation.

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Turner, Christine, and Fred Peterson. "Sedimentology and Stratigraphy of the Morrison Formation in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 15 (January 1, 1991): 91–93. http://dx.doi.org/10.13001/uwnpsrc.1991.2979.

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The objective of this study is to establish a stratigraphic, sedimentologic, and geochronologic framework of the Upper Jurassic Morrison Formation within Dinosaur National Monument (DNM) and to tie this framework to the rest of the Colorado Plateau and other important fossil-bearing localities in the Western Interior of the U.S. The study is also designed to complement ongoing paleontological inventories of the Morrison Formation within the Monument. During the 1990 field season emphasis was placed on the larger aspects of stratigraphic and sedimentologic work and collection of samples for various types of analyses. Work during the 1991 field season was concentrated on detailed stratigraphic and sedimentologic studies of the quarry interval and on the regional studies that will relate the Morrison Formation at DNM and its contained bones to important bone-bearing localities elsewhere in the Western Interior of the U.S.

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18

Harris, Jerald D., and Kenneth Carpenter. "A large pterodactyloid from the Morrison Formation (Late Jurassic) of Garden Park, Colorado." Neues Jahrbuch für Geologie und Paläontologie - Monatshefte 1996, no. 8 (August 1, 1996): 473–84. http://dx.doi.org/10.1127/njgpm/1996/1996/473.

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19

Turner, Christine, and Fred Peterson. "Sedimentology and Stratigraphy of the Morrison Formation in Dinasuar National Monumant." UW National Parks Service Research Station Annual Reports 14 (January 1, 1990): 43–44. http://dx.doi.org/10.13001/uwnpsrc.1990.2869.

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The objective of this study is to establish a stratigraphic, sedimentologic, and geochronologic framework of the Upper Jurassic Morrison Formation within Dinosaur National Monument, and to tie this framework to the rest of the Colorado Plateau and other important fossil-bearing localities. The study is designed to complement ongoing paleontological inventories of the Morrison Formation within the Monument. During the first field season, emphasis was placed on beginning detailed stratigraphic and sedimentologic work and the collection of samples for various types of analyses.

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20

Engelmann, George. "Paleontological Survey of the Jurassic Morrison Formation in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 14 (January 1, 1990): 37–38. http://dx.doi.org/10.13001/uwnpsrc.1990.2865.

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This project has undertaken to survey the surface exposures of the Jurassic Morrison Formation within Dinosaur National Monument (DINO) for fossil occurrences of any sort. The primary purpose of this survey is to provide an assessment of the extent and characteristics of the paleontological resource in this geologic formation within DINO. In so doing, the survey may also have the effect of discovering specimens of obvious and immediate scientific importance and providing observations that will contribute to an improved understanding of the stratigraphy of the Morrison Fm.

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21

Bennett, S. Christopher. "Reassessment ofUtahdactylusfrom the Jurassic Morrison Formation of Utah." Journal of Vertebrate Paleontology 27, no. 1 (March 12, 2007): 257–60. http://dx.doi.org/10.1671/0272-4634(2007)27[257:rouftj]2.0.co;2.

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Button, David J., Emily J. Rayfield, and Paul M. Barrett. "Cranial biomechanics underpins high sauropod diversity in resource-poor environments." Proceedings of the Royal Society B: Biological Sciences 281, no. 1795 (November 22, 2014): 20142114. http://dx.doi.org/10.1098/rspb.2014.2114.

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High megaherbivore species richness is documented in both fossil and contemporary ecosystems despite their high individual energy requirements. An extreme example of this is the Late Jurassic Morrison Formation, which was dominated by sauropod dinosaurs, the largest known terrestrial vertebrates. High sauropod diversity within the resource-limited Morrison is paradoxical, but might be explicable through sophisticated resource partitioning. This hypothesis was tested through finite-element analysis of the crania of the Morrison taxa Camarasaurus and Diplodocus . Results demonstrate divergent specialization, with Camarasaurus capable of exerting and accommodating greater bite forces than Diplodocus , permitting consumption of harder food items. Analysis of craniodental biomechanical characters taken from 35 sauropod taxa demonstrates a functional dichotomy in terms of bite force, cranial robustness and occlusal relationships yielding two polyphyletic functional ‘grades’. Morrison taxa are widely distributed within and between these two morphotypes, reflecting distinctive foraging specializations that formed a biomechanical basis for niche partitioning between them. This partitioning, coupled with benefits associated with large body size, would have enabled the high sauropod diversities present in the Morrison Formation. Further, this provides insight into the mechanisms responsible for supporting the high diversities of large megaherbivores observed in other Mesozoic and Cenozoic communities, particularly those occurring in resource-limited environments.

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Sprinkel, Douglas, Mary Beth Bennis, Dale Gray, and Carole Gee. "Stratigraphic Setting of Fossil Log Sites in the Morrison Formation (Upper Jurassic) near Dinosaur National Monument, Uintah County, Utah, USA." Geology of the Intermountain West 6 (October 31, 2019): 61–76. http://dx.doi.org/10.31711/giw.v6.pp61-76.

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The outcrop belt of the Upper Jurassic Morrison Formation in the northeastern Uinta Basin and southeastern flank of the Uinta Mountains is particularly rich in dinosaurian and non-dinosaurian faunas, as well as in fossil plants. The discovery of several well-preserved, relatively intact, fossil logs at several locations in Rainbow Draw and one location in Miners Draw, both near Dinosaur National Monument (Utah), has provided an opportunity to study the local paleobotany, stratigraphy, and sedimentology of the Morrison Formation in northeastern Utah.

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Lockley, Martin, R. Fleming, and Kelly Conrad. "Distribution and Significance of Mesozoic Vertebrate Trace Fossils in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 14 (January 1, 1990): 39–41. http://dx.doi.org/10.13001/uwnpsrc.1990.2867.

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Dinosaur National Monument (DINO) encompasses an area that has rocks with a high potential for preservation of vertebrate trace fossils, especially dinosaur tracks. The purpose of this research is to document the presence, type, and distribution of vertebrate trace fossils in Mesozoic rocks exposed in DINO. These rocks include the Moenkopi Formation, Chinle/Popo Agie Formation, Glen Canyon Sandstone, Carmel Formation, Entrada Sandstone, Morrison Formation, Cedar Mountain Formation, Dakota Formation, and Frontier Formation. This study will increase our knowledge of the stratigraphic and geographic distribution of vertebrate tracks as well as provide taxonomic, behavioral, and paleoenvironmental data. During the 1990 field season, reconnaissance of the western part of DINO revealed the presence of vertebrate trace fossils in the Chinle/Popo Agie Formation. In addition, our examination of the Moenkopi Formation suggests that vertebrate tracks are probably present in this unit. Locality information was also obtained for probable track-sites in the Carmel Formation, Entrada Sandstone, and Morrison Formation.

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Engelmann, George. "Paleontological Survey of the Jurassic Morrison Formation in Dinosaur National Monument." UW National Parks Service Research Station Annual Reports 16 (January 1, 1992): 71–73. http://dx.doi.org/10.13001/uwnpsrc.1992.3075.

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The paleontological survey of the Morrison Formation within Dinosaur National Monument (DINO) was planned as a three-year project. The objectives of the project have been to exhaustively search the exposures of the Morrison Fm. within DINO for fossil occurrences of any sort and to document in the files of the monument all known and newly discovered localities. This is the third and final year of the project. The work of the previous two years has been described in semiannual and annual reports and summarized in the 14th and 15th Annual Reports of the Research Center (Engelmann 1991, 1992).

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Whitlock, John, Kelli Trujillo, and Gina Hanik. "Assemblage-level structure in Morrison Formation dinosaurs, Western Interior, USA." Geology of the Intermountain West 5 (March 15, 2018): 9–22. http://dx.doi.org/10.31711/giw.v5.pp9-22.

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The Upper Jurassic Morrison Formation is both geographically extensive and well-sampled, making it an ideal candidate for biogeographic analysis at both coarse and finer scales. Historically, however, this has not translated into a consensus on patterns of ecological structure and connectivity, particularly with regard to the characteristic dinosaur faunas. Here, we use both traditional (genus richness, alpha and beta diversity) and bipartite network-based (biogeographic connectivity, local endemism, and average occurrence) measures to examine patterns of structure on a per-locality basis. Given the broad geographic range of the formation, we subdivide the Morrison Formation into four discrete regions based roughly on latitude and lithology—north (Montana, South Dakota, and northern Wyoming), west (Utah and western Colorado), east (central and eastern Colorado and southern Wyoming), and south (Arizona, New Mexico and Oklahoma). Further investigation revealed many coeval sites (ca. 152 Ma) in the east and west regions. Presence-absence data were also compared using network analysis to determine the presence and content of discrete subassemblages within the larger region-level assemblages. Based on our results, we favor reconstructions of the Morrison Formation as a ‘mosaic’ type environment over most of its depositional history, with patches of open environments interspersed with more closed, forested regions. is is suggested by relatively low rates of local endemism (patches are consistent in plant and animal structure) and connectivity across the majority of the formation, as well as the recovery of three non-overlapping assemblages dominated by dierent guilds of herbivorous dinosaurs.

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Whitlock, John A., Kelli C. Trujillo, and Gina M. Hanik. "Assemblage-level structure in Morrison Formation dinosaurs, Western Interior, USA." Geology of the Intermountain West 5 (June 1, 2018): 9–22. http://dx.doi.org/10.31711/giw.v5i0.18.

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The Upper Jurassic Morrison Formation is both geographically extensive and well-sampled, making it an ideal candidate for biogeographic analysis at both coarse and ‑ner scales. Historically, however, this has not translated into a consensus on patterns of ecological structure and connectivity, particularly with regard to the characteristic dinosaur faunas. Here, we use both traditional (genus richness, alpha and beta diversity) and bipartite network-based (biogeographic connectivity, local endemism, and average occurrence) measures to examine patterns of structure on a per-locality basis. Given the broad geographic range of the formation, we subdivide the Morrison Formation into four discrete regions based roughly on latitude and lithology—north (Montana, South Dakota, and northern Wyoming), west (Utah and western Colorado), east (central and eastern Colorado and southern Wyoming), and south (Arizona, New Mexico and Oklahoma). Further investigation revealed many coeval sites (ca. 152 Ma) in the east and west regions. Presence-absence data were also compared using network analysis to determine the presence and content of discrete subassemblages within the larger region-level assemblages. Based on our results, we favor reconstructions of the Morrison Formation as a ‘mosaic’ type environment over most of its depositional history, with patches of open environments interspersed with more closed, forested regions. is is suggested by relatively low rates of local endemism (patches are consistent in plant and animal structure) and connectivity across the majority of the formation, as well as the recovery of three non-overlapping assemblages dominated by dierent guilds of herbivorous dinosaurs.

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Dunagan, Stan P. "A North American freshwater sponge (Eospongilla morrisonensis new genus and species) from the Morrison Formation (Upper Jurassic), Colorado." Journal of Paleontology 73, no. 3 (May 1999): 389–93. http://dx.doi.org/10.1017/s0022336000027906.

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Eospongilla morrisonensis n. gen. and sp., the oldest-described freshwater sponge (Demospongea: Spongillidae), is found in the Upper Jurassic (?Oxfordian/Kimmeridgian to Tithonian) Morrison Formation, east-central Colorado, U.S.A. Eospongilla morrisonensis occurs within the well-developed lacustrine carbonate succession of the Morrison Formation, and is represented by two micritic body fossils with calcite-replaced megascleres that range in length from 180 to 300 μm and in diameter from 20 to 35 μm. Megascleres are simple oxeas and strongyles and lack apparent ornamentation, possibly due to the diagenetic replacement. The oxeas are straight but the strongyles display a slight curvature. Microscleres are absent; gemmoscleres were not observed.

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Smith, Dena M., Mark A. Gorman, Jason D. Pardo, and Bryan J. Small. "First fossil orthoptera from the Jurassic of North America." Journal of Paleontology 85, no. 1 (January 2011): 102–5. http://dx.doi.org/10.1666/10-096.1.

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A new species of Orthoptera,Parapleurites morrisonensis, is described from the upper Jurassic Morrison Formation of Colorado, USA. This is the first insect described from the Morrison Formation and the first orthopteran described from the Jurassic of North America. No other members of the family Locustopsidae have been described in North America previously, and the other species ofParapleuritesare only known from Siberia. The lack of Jurassic Orthoptera in North America is likely due to a combination of taphonomic variables and collector bias. The discovery ofParapleurites morrisonensisand the potential for finding other Jurassic Orthoptera are important to understanding the evolution of this diverse and widely distributed group.

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Maidment, Susannah C. R., and Adrian Muxworthy. "A chronostratigraphic framework for the Upper Jurassic Morrison Formation, western U.S.A." Journal of Sedimentary Research 89, no. 10 (October 29, 2019): 1017–38. http://dx.doi.org/10.2110/jsr.2019.54.

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ABSTRACT The fluvial, overbank, and lacustrine deposits of the Upper Jurassic Morrison Formation of the Western Interior, U.S.A. have been intensively studied due to their diverse and well-preserved dinosaurian fauna, and the presence of economic quantities of uranium and vanadium ores. The formation crops out over 12 degrees of latitude and 1.2 million km2, and is an excellent case study for the examination of paleoecology, community structure, and evolutionary dynamics at a time in Earth's history when the climate was significantly warmer than today. However, paleoecological studies have been hampered by lack of correlation across the formation. Assuming a primarily tectonic control on fluvial architecture, we propose the first chronostratigraphic framework of the formation, which is based on sequence stratigraphy, magnetostratigraphy, and radiometric dating. The formation can be divided into three sequences each represented by a period of degradation followed by aggradation. This chronostratigraphic framework indicates that the formation youngs to the north, and was deposited over about 7 million years during the late Kimmeridgian and Tithonian. This framework provides a foundation for future sedimentological, stratigraphic, and paleobiological studies of the iconic dinosaurian fauna known from the Morrison.

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Mannion, Philip D., Emanuel Tschopp, and John A. Whitlock. "Anatomy and systematics of the diplodocoid Amphicoelias altus supports high sauropod dinosaur diversity in the Upper Jurassic Morrison Formation of the USA." Royal Society Open Science 8, no. 6 (June 2021): 210377. http://dx.doi.org/10.1098/rsos.210377.

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Sauropod dinosaurs were an abundant and diverse component of the Upper Jurassic Morrison Formation of the USA, with 24 currently recognized species. However, some authors consider this high diversity to have been ecologically unviable and the validity of some species has been questioned, with suggestions that they represent growth series (ontogimorphs) of other species. Under this scenario, high sauropod diversity in the Late Jurassic of North America is greatly overestimated. One putative ontogimorph is the enigmatic diplodocoid Amphicoelias altus , which has been suggested to be synonymous with Diplodocus . Given that Amphicoelias was named first, it has priority and thus Diplodocus would become its junior synonym. Here, we provide a detailed re-description of A. altus in which we restrict it to the holotype individual and support its validity, based on three autapomorphies. Constraint analyses demonstrate that its phylogenetic position within Diplodocoidea is labile, but it seems unlikely that Amphicoelias is synonymous with Diplodocus . As such, our re-evaluation also leads us to retain Diplodocus as a distinct genus. There is no evidence to support the view that any of the currently recognized Morrison sauropod species are ontogimorphs. Available data indicate that sauropod anatomy did not dramatically alter once individuals approached maturity. Furthermore, subadult sauropod individuals are not prone to stemward slippage in phylogenetic analyses, casting doubt on the possibility that their taxonomic affinities are substantially misinterpreted. An anatomical feature can have both an ontogenetic and phylogenetic signature, but the former does not outweigh the latter when other characters overwhelmingly support the affinities of a taxon. Many Morrison Formation sauropods were spatio-temporally and/or ecologically separated from one another. Combined with the biases that cloud our reading of the fossil record, we contend that the number of sauropod dinosaur species in the Morrison Formation is currently likely to be underestimated, not overestimated.

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Storrs, Glenn W., Sara E. Oser, and Mark Aull. "Further analysis of a Late Jurassic dinosaur bone-bed from the Morrison Formation of Montana, USA, with a computed three-dimensional reconstruction." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 103, no. 3-4 (September 2012): 443–58. http://dx.doi.org/10.1017/s1755691013000248.

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ABSTRACTA Late Jurassic sauropod bone-bed comprising thousands of individual skeletal elements in the Morrison Formation of Montana, USA, is re-analysed to further elucidate its taphonomic history. New data gained from detailed contextual sampling is assembled and presented to test the hypothesis of a drought-induced, mass-mortality assemblage, and its subsequent depositional emplacement by a debris flow. Large dinosaur bone-beds are well-known in the Morrison, yet the Mother's Day Quarry site is unique for the formation in depicting an apparent debris flow deposit. Use of a computer program tailored to the data allows three-dimensional reconstruction of the bone-bed and recreates the palaeoslope of the deposit, adding support to the debris flow hypothesis. Such digital manipulation of field data may allow a deeper understanding of other bone-bed origination events.

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Hughes, Elijah M., John R. Wible, Michelle Spaulding, and Zhe-Xi Luo. "Mammalian Petrosal from the Upper Jurassic Morrison Formation of Fruita, Colorado." Annals of Carnegie Museum 83, no. 1 (May 15, 2015): 1–17. http://dx.doi.org/10.2992/007.083.0101.

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Kjemperud, Audun V., Edwin R. Schomacker, and Timothy A. Cross. "Architecture and stratigraphy of alluvial deposits, Morrison Formation (Upper Jurassic), Utah." AAPG Bulletin 92, no. 8 (August 2008): 1055–76. http://dx.doi.org/10.1306/03250807115.

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Turner, Christine E., and Fred Peterson. "Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis." Sedimentary Geology 167, no. 3-4 (May 2004): 309–55. http://dx.doi.org/10.1016/j.sedgeo.2004.01.009.

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Turner, Christine E., Fred Peterson, and Stan P. Dunagan. "Reconstruction of the Extinct Ecosystem of the Upper Jurassic Morrison Formation." Sedimentary Geology 167, no. 3-4 (May 2004): 111–13. http://dx.doi.org/10.1016/j.sedgeo.2004.04.005.

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LOCKLEY, MARTIN G., KAREN J. HOUCK, and NANCY K. PRINCE. "North America's largest dinosaur trackway site: Implications for Morrison Formation paleoecology." Geological Society of America Bulletin 97, no. 10 (1986): 1163. http://dx.doi.org/10.1130/0016-7606(1986)97<1163:naldts>2.0.co;2.

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Dayvault, Richard D., and H. Steven Hatch. "Short Shoots from the Late Jurassic Morrison Formation of Southeastern Utah." Rocks & Minerals 78, no. 4 (August 2003): 232–47. http://dx.doi.org/10.1080/00357529.2003.9926728.

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Stoker, Carol R., Jonathan Clarke, Susana O. L. Direito, David Blake, Kevin R. Martin, Jhony Zavaleta, and Bernard Foing. "Mineralogical, chemical, organic and microbial properties of subsurface soil cores from Mars Desert Research Station (Utah, USA): Phyllosilicate and sulfate analogues to Mars mission landing sites." International Journal of Astrobiology 10, no. 3 (April 8, 2011): 269–89. http://dx.doi.org/10.1017/s1473550411000115.

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AbstractWe collected and analysed soil cores from four geologic units surrounding Mars Desert Research Station (MDRS) Utah, USA, including Mancos Shale, Dakota Sandstone, Morrison formation (Brushy Basin member) and Summerville formation. The area is an important geochemical and morphological analogue to terrains on Mars. Soils were analysed for mineralogy by a Terra X-ray diffractometer (XRD), a field version of the CheMin instrument on the Mars Science Laboratory (MSL) mission (2012 landing). Soluble ion chemistry, total organic content and identity and distribution of microbial populations were also determined. The Terra data reveal that Mancos and Morrison soils are rich in phyllosilicates similar to those observed on Mars from orbital measurements (montmorillonite, nontronite and illite). Evaporite minerals observed include gypsum, thenardite, polyhalite and calcite. Soil chemical analysis shows sulfate the dominant anion in all soils and SO4>>CO3, as on Mars. The cation pattern Na>Ca>Mg is seen in all soils except for the Summerville where Ca>Na. In all soils, SO4correlates with Na, suggesting sodium sulfates are the dominant phase. Oxidizable organics are low in all soils and range from a high of 0.7% in the Mancos samples to undetectable at a detection limit of 0.1% in the Morrison soils. Minerals rich in chromium and vanadium were identified in Morrison soils that result from diagenetic replacement of organic compounds. Depositional environment, geologic history and mineralogy all affect the ability to preserve and detect organic compounds. Subsurface biosphere populations were revealed to contain organisms from all three domains (Archaea, Bacteria and Eukarya) with cell density between 3.0×106and 1.8×107cells ml−1at the deepest depth. These measurements are analogous to data that could be obtained on future robotic or human Mars missions and results are relevant to the MSL mission that will investigate phyllosilicates on Mars.

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Gallego, Mar. "Race, Interdependence and Healing in Toni Morrison’s God Help the Child." Contemporary Women's Writing 13, no. 3 (November 2019): 307–20. http://dx.doi.org/10.1093/cww/vpaa006.

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Abstract In Toni Morrison’s works, traumatized characters are victimized by the damaging, racist dominant ideology that still codifies black bodies as the non-human “Other” due to the long-lasting effects of slavery and diasporic dispersal. These individual and collective traumas seemingly hinder their articulation of healthy forms of subject formation and community-building efforts. My contention is that in God Help the Child (2015) Morrison explores the ramifications of early trauma in her characters’ lives but also, more importantly, an array of resistance strategies, which facilitate healing, within an ethics of interdependence. Hence, Morrison critiques fundamental inequities in American society and around the world, by paying attention to the intersections of race, gender, and age discourses.

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Chure, Daniel, and John McIntosh. "Stranger in a Strange Land: A Brief History of the Paleontological Operations at Dinosaur National Monument." Earth Sciences History 9, no. 1 (January 1, 1990): 34–40. http://dx.doi.org/10.17704/eshi.9.1.x8l67355k7745582.

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Discovered in 1909 by Earl Douglass of the Carnegie Museum, the Dinosaur Quarry (DQ) at Dinosaur National Monument has proven to be one of our best windows into the large vertebrate community of the Morrison Formation (Upper Jurassic). To date, the remains of several hundred individuals belonging to sixteen species of dinosaurs and other vertebrates have been found. The DQ has produced more species, skulls, juveniles, and complete skeletons than any other Morrison Formation quarry. Between 1909 and 1924, the DQ was actively quarried and over 700,000 lbs. of fossils were collected. In 1958 the National Park Service enclosed the unexcavated area of the DQ within a building with both exhibits and research facilities. Since that time over 2,000 bones have been uncovered and left in situ, just as they were deposited. The concept of an enclosed quarry with an in situ exhibit of fossils has been successfully followed at a number of parks both within the U.S. and abroad.

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Armour Smith, Elliott, Mark A. Loewen, and James I. Kirkland. "New social insect nests from the Upper Jurassic Morrison Formation of Utah." Geology of the Intermountain West 7 (August 29, 2020): 281–99. http://dx.doi.org/10.31711/giw.v7.pp281-299.

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This paper reports a new assemblage of social insect ichnofossils from the Brushy Basin Member of the Upper Jurassic Morrison Formation near Green River, Utah. At least seven distinct nests are visible in the locality horizon, identifiable at the outcrop scale by loci of anastomosing, and orthogonally connected hor-izontal burrows and vertical shafts. A boulder-sized block from the in situ horizon has eroded and rolled downhill, revealing the ventral aspect of the nest, showing a view of the overall nest architecture. Burrow and shaft clusters are organized into mega-galleries which have branching arms and ovate, bulbous cham-bers. The organization of distinct trace morphologies is consistent with ethological complexity of the social insects. A small sample was collected and analyzed by serial sectioning and petrographic thin sectioning to observe small-scale morphological features. Centimeter-scale analysis shows chamber, gallery, and burrow walls have complex topography. Pebble-sized, hollow, ellipsoid features are distributed throughout the up-permost facies of the nest and have undergone complete silicification of their outer surfaces. The ellipsoids share similarity with pellet structures made of mud or carton produced by modern termites. This trace fossil assemblage suggests it is possible that termites had acquired subterranean nesting behavior, and mud or carton utilization in nest construction in seasonally arid habitats by the Late Jurassic.

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Foster, John R. "Theropod Dinosaur IchnogenusHispanosauropusIdentified from the Morrison Formation (Upper Jurassic), Western North America." Ichnos 22, no. 3-4 (September 11, 2015): 183–91. http://dx.doi.org/10.1080/10420940.2015.1059335.

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Foster, John R., and Martin G. Lockley. "Tridactyl dinosaur footprints from the Morrison Formation (Upper Jurassic) of northeast Wyoming." Ichnos 4, no. 1 (April 1995): 35–41. http://dx.doi.org/10.1080/10420949509380112.

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Makovicky, Peter J. "A new small theropod from the Morrison Formation of Como Bluff, Wyoming." Journal of Vertebrate Paleontology 17, no. 4 (December 15, 1997): 755–57. http://dx.doi.org/10.1080/02724634.1997.10011024.

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Christiansen, Nicolai A., and Emanuel Tschopp. "Exceptional stegosaur integument impressions from the Upper Jurassic Morrison Formation of Wyoming." Swiss Journal of Geosciences 103, no. 2 (September 2010): 163–71. http://dx.doi.org/10.1007/s00015-010-0026-0.

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Maltese, Anthony, Emanuel Tschopp, Femke Holwerda, and David Burnham. "The real Bigfoot: a pes from Wyoming, USA is the largest sauropod pes ever reported and the northern-most occurrence of brachiosaurids in the Upper Jurassic Morrison Formation." PeerJ 6 (July 24, 2018): e5250. http://dx.doi.org/10.7717/peerj.5250.

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A set of associated left pedal elements of a sauropod dinosaur from the Upper Jurassic Morrison Formation in Weston County, Wyoming, is described here. Several camarasaurids, a nearly complete small brachiosaur, and a small diplodocid have been found at this locality, but none match the exceptionally large size of the pedal elements. Next to the associated pedal elements, an isolated astragalus, phalanx and ungual were found, which match the large metatarsals in size. The elements cannot be ascribed to diplodocids due to the lack of a ventral process of metatarsal I. Moreover, the morphology of metatarsal V has a broad proximal end, with a long and narrow distal shaft, which differs fromCamarasaurus. The size of the material and a medially beveled distal articular surface of metatarsal IV imply an identification as a brachiosaurid. This is the largest pes ever reported from a sauropod dinosaur and represents the first confirmed pedal brachiosaur elements from the Late Jurassic of North America. Furthermore, this brachiosaur material (the pes and the small nearly complete specimen) is the northernmost occurrence of brachiosaurids in the Morrison Formation.

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Foster, John. "A new atoposaurid crocodylomorph from the Morrison Formation (Upper Jurassic) of Wyoming, USA." Geology of the Intermountain West 5 (December 21, 2018): 287–95. http://dx.doi.org/10.31711/giw.v5.pp287-295.

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A left mandible of a small crocodyliform found in the Upper Jurassic Morrsion Formation of northeastern Wyoming represents the first occurrence of the atoposaurid Theriosuchus in North America. The specimen demonstrates lower jaw morphology, including heterodonty (as indicated by alveolus shape), similar to Theriosuchus and Knoetschkesuchus, but autapomorphies and a unique combination of characters among these taxa indicate that it is a distinct, new species of Theriosuchus.

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Foster, John R. "A new atoposaurid crocodylomorph from the Morrison Formation (Upper Jurassic) of Wyoming, USA." Geology of the Intermountain West 5 (December 21, 2018): 287–95. http://dx.doi.org/10.31711/giw.v5i0.32.

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A left mandible of a small crocodyliform found in the Upper Jurassic Morrsion Formation of northeastern Wyoming represents the first occurrence of the atoposaurid Theriosuchus in North America. The specimen demonstrates lower jaw morphology, including heterodonty (as indicated by alveolus shape), similar to Theriosuchus and Knoetschkesuchus, but autapomorphies and a unique combination of characters among these taxa indicate that it is a distinct, new species of Theriosuchus.

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EVANS, S. E., C. LALLY, D. C. CHURE, A. ELDER, and J. A. MAISANO. "A Late Jurassic salamander (Amphibia: Caudata) from the Morrison Formation of North America." Zoological Journal of the Linnean Society 143, no. 4 (April 2005): 599–616. http://dx.doi.org/10.1111/j.1096-3642.2005.00159.x.

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Journal articles on the topic 'Morrison-Formation'

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