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Research paper thumbnail of Intensely bioturbated ichnofabric in a Jurassic eolianite, Navajo Sandstone, southern Utah

Research paper thumbnail of Intensely bioturbated ichnofabric in a Jurassic eolianite, Navajo Sandstone, southern Utah

Research paper thumbnail of PRELUDE TO SEVEN SLOTS: FILLING AND SUBSEQUENT MODIFICATION OF SEVEN BROAD CANYONS IN THE NAVAJO SANDSTONE, SOUTH-CENTRAL UTAH

Research paper thumbnail of KANSAS GEOLOGY-AN INTRODUCTION TO LANDSCAPES, ROCKS, MINERALS, AND FOSSILS-BUCHANAN, R

Research paper thumbnail of ROADSIDE GEOLOGY OF TEXAS-SPEARING, D

Research paper thumbnail of Pacific and Atlantic SST influences on Medieval drought in 4 North America simulated by Community Atmospheric Model 5

Research paper thumbnail of Eolianite

Research paper thumbnail of A Jurassic Shock-Aftershock Earthquake Sequence Recorded by Small Clastic Pipes and Dikes within Dune Cross-Strata, Zion National Park, Utah

Research paper thumbnail of MICROBIALLY MEDIATED IRON-OXIDE BANDS AT PETRA (SOUTHERN JORDAN) ARE OXIDATION PRODUCTS OF LATE DIAGENETIC SIDERITE

Research paper thumbnail of PALEOENVIRONMENTAL IMPLICATIONS OF IRON DIAGENSIS IN THE TRIASSIC SHINARUMP MEMBER OF THE CHINLE FORMATION

Research paper thumbnail of CONFUSING SEISMITES IN EOLIAN SANDSTONES WITH TRACE FOSSILS

Research paper thumbnail of IRON ISOTOPE EVIDENCE FOR THE ORIGIN OF IRON OXIDE CONCRETIONS FROM THE NAVAJO SANDSTONE, UTAH (USA)

Research paper thumbnail of WATER TABLE CONTROLS ON THE MORPHOLOGY OF IRON-OXIDE CONCRETIONS IN THE NAVAJO SANDSTONE OF SOUTHERN UTAH

Research paper thumbnail of Temporal and spatial variability in dune reactivation across the Nebraska Sand Hills, USA

ABSTRACT The Nebraska Sand Hills is a stabilized dune field on the Great Plains of North America.... more ABSTRACT The Nebraska Sand Hills is a stabilized dune field on the Great Plains of North America. Although it is well known that this dune field, like several others on the Great Plains, last experienced widespread activity during the Medieval Climatic Anomaly (MCA, ~AD 900-1300), spatial variation in the timing and nature of drought development is poorly constrained. To elucidate spatial trends in dune reactivation, samples potentially representing MCA activity across the Sand Hills were collected and dated using optically stimulated luminescence (OSL). Ages from the older part of the MCA were obtained from eolian sediments in the northwestern Sand Hills, while ages from later in the episode were obtained to the southeast, suggesting a geographic trend in the timing of revegetation of the dunes near the end of the drought. Revegetation likely occurred to the northwest initially as a result of renewed moisture availability from a rising water table in the interdunes, which serve as refugia for vegetation during times of drought. Vegetation then gradually spread to the southeastern Sand Hills. An additional spatial trend in ages is apparent in the chronology of linear dune mobilization across the Sand Hills. Linear dunes in the northwest are superimposed on megadunes and originated during the last reactivation, while linear dunes in the southeast are built around older cores of dunes and formed during several reactivations. Our geochronology reveals three episodes of eolian transport, including the MCA, in the formation of linear dunes in the southeast.

Research paper thumbnail of Jurassic earthquake sequence recorded by multiple generations of sand blows, Zion National Park, Utah

Earthquakes along convergent plate boundaries commonly occur in sequences that are complete withi... more Earthquakes along convergent plate boundaries commonly occur in sequences that are complete within 1 yr, and may include 8-10 events strong enough to generate sand blows. Dune crossbeds within the Jurassic Navajo Sandstone of Utah (western United States) enclose intact and truncated sand blows, and the intrusive structures that fed them. We mapped the distribution of more than 800 soft-sediment dikes and pipes at two small sites. All waterescape structures intersect a single paleo-surface, and are limited to the upper portion of the underlying set of cross-strata and the lower portion of the overlying set. A small portion of one set of crossbeds that represents ~1 yr of dune migration encloses eight generations of eruptive events. We interpret these superimposed depositional and deformational structures as the record of a single shock-aftershock earthquake sequence. The completeness and temporal detail of this paleoseismic record are unique, and were made possible when sand blows repeatedly erupted onto lee slopes of migrating dunes. Similar records should be sought in modern dunefi elds with shallow water tables.

Research paper thumbnail of FOSSIL VERTEBRATE FOOTPRINTS IN THE COCONINO SANDSTONE (PERMIAN) OF NORTHERN ARIZONA-EVIDENCE FOR UNDERWATER ORIGIN-COMMENT

Research paper thumbnail of Geological evidence of microbial dissolution of iron carbonate

Research paper thumbnail of Rinded iron‐oxide concretions: hallmarks of altered siderite masses of both early and late diagenetic origin

Page 1. This is an Accepted Article that has been peer-reviewed and approved for publication in t... more Page 1. This is an Accepted Article that has been peer-reviewed and approved for publication in the Sedimentology, but has yet to undergo copy-editing and proof correction. Please cite this article as an ???Accepted Article???; doi: 10.1111/j.1365-3091.2012.01325.x ...

Research paper thumbnail of Biosignatures within iron-rich concretions originating in a sandstone paleoaquifer: evidence of microbial oxidative dissolution of Fe (II)-carbonates

Research paper thumbnail of Abnormal, multilayered titanosaur (Dinosauria: Sauropoda) eggs from in situ clutches at the Auca Mahuevo locality, Neuquen Province, Argentina

Journal of Vertebrate Paleontology, 2004

Abnormal, multilayered eggshells are frequently reported in fossil specimens. However, previous r... more Abnormal, multilayered eggshells are frequently reported in fossil specimens. However, previous reports of this pathological condition pertain to taxonomically unidentified fossil eggs or eggshell fragments rather than in situ clutches. A survey of 393 in situ clutches, referable to titanosaur sauropod dinosaurs, from Upper Cretaceous rocks in northwestern Patagonia, Argentina, revealed that six of these clutches contain both normal eggs

Research paper thumbnail of Intensely bioturbated ichnofabric in a Jurassic eolianite, Navajo Sandstone, southern Utah

Research paper thumbnail of Intensely bioturbated ichnofabric in a Jurassic eolianite, Navajo Sandstone, southern Utah

Research paper thumbnail of PRELUDE TO SEVEN SLOTS: FILLING AND SUBSEQUENT MODIFICATION OF SEVEN BROAD CANYONS IN THE NAVAJO SANDSTONE, SOUTH-CENTRAL UTAH

Research paper thumbnail of KANSAS GEOLOGY-AN INTRODUCTION TO LANDSCAPES, ROCKS, MINERALS, AND FOSSILS-BUCHANAN, R

Research paper thumbnail of ROADSIDE GEOLOGY OF TEXAS-SPEARING, D

Research paper thumbnail of Pacific and Atlantic SST influences on Medieval drought in 4 North America simulated by Community Atmospheric Model 5

Research paper thumbnail of Eolianite

Research paper thumbnail of A Jurassic Shock-Aftershock Earthquake Sequence Recorded by Small Clastic Pipes and Dikes within Dune Cross-Strata, Zion National Park, Utah

Research paper thumbnail of MICROBIALLY MEDIATED IRON-OXIDE BANDS AT PETRA (SOUTHERN JORDAN) ARE OXIDATION PRODUCTS OF LATE DIAGENETIC SIDERITE

Research paper thumbnail of PALEOENVIRONMENTAL IMPLICATIONS OF IRON DIAGENSIS IN THE TRIASSIC SHINARUMP MEMBER OF THE CHINLE FORMATION

Research paper thumbnail of CONFUSING SEISMITES IN EOLIAN SANDSTONES WITH TRACE FOSSILS

Research paper thumbnail of IRON ISOTOPE EVIDENCE FOR THE ORIGIN OF IRON OXIDE CONCRETIONS FROM THE NAVAJO SANDSTONE, UTAH (USA)

Research paper thumbnail of WATER TABLE CONTROLS ON THE MORPHOLOGY OF IRON-OXIDE CONCRETIONS IN THE NAVAJO SANDSTONE OF SOUTHERN UTAH

Research paper thumbnail of Temporal and spatial variability in dune reactivation across the Nebraska Sand Hills, USA

ABSTRACT The Nebraska Sand Hills is a stabilized dune field on the Great Plains of North America.... more ABSTRACT The Nebraska Sand Hills is a stabilized dune field on the Great Plains of North America. Although it is well known that this dune field, like several others on the Great Plains, last experienced widespread activity during the Medieval Climatic Anomaly (MCA, ~AD 900-1300), spatial variation in the timing and nature of drought development is poorly constrained. To elucidate spatial trends in dune reactivation, samples potentially representing MCA activity across the Sand Hills were collected and dated using optically stimulated luminescence (OSL). Ages from the older part of the MCA were obtained from eolian sediments in the northwestern Sand Hills, while ages from later in the episode were obtained to the southeast, suggesting a geographic trend in the timing of revegetation of the dunes near the end of the drought. Revegetation likely occurred to the northwest initially as a result of renewed moisture availability from a rising water table in the interdunes, which serve as refugia for vegetation during times of drought. Vegetation then gradually spread to the southeastern Sand Hills. An additional spatial trend in ages is apparent in the chronology of linear dune mobilization across the Sand Hills. Linear dunes in the northwest are superimposed on megadunes and originated during the last reactivation, while linear dunes in the southeast are built around older cores of dunes and formed during several reactivations. Our geochronology reveals three episodes of eolian transport, including the MCA, in the formation of linear dunes in the southeast.

Research paper thumbnail of Jurassic earthquake sequence recorded by multiple generations of sand blows, Zion National Park, Utah

Earthquakes along convergent plate boundaries commonly occur in sequences that are complete withi... more Earthquakes along convergent plate boundaries commonly occur in sequences that are complete within 1 yr, and may include 8-10 events strong enough to generate sand blows. Dune crossbeds within the Jurassic Navajo Sandstone of Utah (western United States) enclose intact and truncated sand blows, and the intrusive structures that fed them. We mapped the distribution of more than 800 soft-sediment dikes and pipes at two small sites. All waterescape structures intersect a single paleo-surface, and are limited to the upper portion of the underlying set of cross-strata and the lower portion of the overlying set. A small portion of one set of crossbeds that represents ~1 yr of dune migration encloses eight generations of eruptive events. We interpret these superimposed depositional and deformational structures as the record of a single shock-aftershock earthquake sequence. The completeness and temporal detail of this paleoseismic record are unique, and were made possible when sand blows repeatedly erupted onto lee slopes of migrating dunes. Similar records should be sought in modern dunefi elds with shallow water tables.

Research paper thumbnail of FOSSIL VERTEBRATE FOOTPRINTS IN THE COCONINO SANDSTONE (PERMIAN) OF NORTHERN ARIZONA-EVIDENCE FOR UNDERWATER ORIGIN-COMMENT

Research paper thumbnail of Geological evidence of microbial dissolution of iron carbonate

Research paper thumbnail of Rinded iron‐oxide concretions: hallmarks of altered siderite masses of both early and late diagenetic origin

Page 1. This is an Accepted Article that has been peer-reviewed and approved for publication in t... more Page 1. This is an Accepted Article that has been peer-reviewed and approved for publication in the Sedimentology, but has yet to undergo copy-editing and proof correction. Please cite this article as an ???Accepted Article???; doi: 10.1111/j.1365-3091.2012.01325.x ...

Research paper thumbnail of Biosignatures within iron-rich concretions originating in a sandstone paleoaquifer: evidence of microbial oxidative dissolution of Fe (II)-carbonates

Research paper thumbnail of Abnormal, multilayered titanosaur (Dinosauria: Sauropoda) eggs from in situ clutches at the Auca Mahuevo locality, Neuquen Province, Argentina

Journal of Vertebrate Paleontology, 2004

Abnormal, multilayered eggshells are frequently reported in fossil specimens. However, previous r... more Abnormal, multilayered eggshells are frequently reported in fossil specimens. However, previous reports of this pathological condition pertain to taxonomically unidentified fossil eggs or eggshell fragments rather than in situ clutches. A survey of 393 in situ clutches, referable to titanosaur sauropod dinosaurs, from Upper Cretaceous rocks in northwestern Patagonia, Argentina, revealed that six of these clutches contain both normal eggs

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