Weems R.E.,Paleo Quest |
Sanders A.E.,P.O. Box 1318
Journal of Vertebrate Paleontology | Year: 2014
In the Oligocene Ashley and Chandler Bridge formations near Charleston, South Carolina, remains of three species of pancheloniid sea turtle are common. In their relative order of abundance, they are Carolinochelys wilsoni, Ashleychelys palmeri, gen. et sp. nov., and Procolpochelys charlestonensis, sp. nov. Unlike the other two Oligocene South Carolina genera, Procolpochelys persisted into the middle Miocene. An isolated skull, referable to the Miocene species Procolpochelys grandaeva, is described here to supplement description of the poorly known skull of the Oligocene species P. charlestonensis. These turtles, all referable to Pancheloniidae, represent an endemic, moderately advanced sea turtle assemblage that occupied the Oligocene coastal waters of the southeastern United States. This tendency toward endemism also is seen in some parts of the co-occurring cetacean assemblage, which included at least two endemic families. Regionally restricted endemic assemblages appear to have been the norm among pre-Miocene pancheloniid sea turtles. It is not until the Miocene that crown cheloniids appear and begin to achieve very widespread to global distributions. © 2014 by the Society of Vertebrate Paleontology.
Dalman S.G.,Fort Hays State University |
Dalman S.G.,26tional Center |
Weems R.E.,Paleo Quest |
Weems R.E.,26tional Center
Bulletin of the Peabody Museum of Natural History | Year: 2013
Numerous new trackways of the small, ornithischian dinosaurs ichnogenus Anomoepus were discovered in the Lower Jurassic (Hettangian) East Berlin Formation in Holyoke, Massachusetts. This new material consists of 16 trackways, on two bedding surfaces 1.5 cm apart, all in close proximity to each other. The abundant pedal and manual impressions have well-preserved digital pad impressions, and claw marks are often discernible also. An osteometric analysis allows reconstruction of the pedal digits and weight-bearing portions of the metatarsals. On the basis of their small size, as well as distinctive features and proportions of both the manus and pes impressions, these prints are assigned to the ichnospecies Anomoepus lacertoideus (comb. nov.). Three ichnospecies of Anomoepus can be recognized in the Lower Jurassic of the Newark Supergroup: A. lacertoideus, A. scambus and A. crassus. The A. lacertoideus footprints described herein provide evidence that this small, ornithischian track maker engaged in a variety of locomotion related behaviors. Trackways mostly consist of digitigrade pes prints, reflecting bipedal locomotion, but intervals of quadrupedal progression also are documented by metatarsal and manus imprints in seven trackways. The longest trackways, each consisting of 10 to 15 pes impressions, vary in morphology as a result of the presence or absence of an impression of the distal parts of metatarsals II and IV. The manus prints show two distinct digital divarication angles, 120° and 180°, depending on whether the animal was walking normally or stopping. Variations in substrate consistency influenced locomotor behavior, as shown by the variable pattern of body weight distributions on the pedal digits. Such differences are especially apparent in the longest trackways, which vary in stride and pace lengths. The trends of the abundant trackways at this site also suggest group behavior in Anomoepus, something previously unrecorded for this ichnogenus in the Connecticut River Valley. Evidence from the East Berlin Formation suggests that ichnogenus Anomoepus is not monospecific as some authors have suggested. © 2013 Peabody Museum of Natural History, Yale University. All rights reserved.
Weems R.E.,926tional Center |
Edwards L.E.,926tional Center |
Osborne J.E.,Paleo Quest |
Alford A.A.,Paleo Quest
Journal of Paleontology | Year: 2011
Two protocetid whale vertebrae, here referred to "Eocetus" wardii, have been recovered from the riverbed of the Pamunkey River in east-central Virginia. Neither bone was found in situ, but both were found with lumps of lithified matrix cemented to their surfaces. Most of this matrix was removed and processed for microfossils. Specimens of dinoflagellates were successfully recovered and this flora clearly demonstrates that both vertebrae came from the middle Eocene Piney Point Formation, which crops out above and below river level in the area where the bones were discovered. These vertebrae are the oldest whale remains reported from Virginia and are as old as any cetacean remains known from the western hemisphere. © 2011 The Paleontological Society.
Godfrey S.J.,Calvert Marine Museum |
Uhen M.D.,George Mason University |
Osborne J.E.,Paleo Quest |
Edwards L.E.,U.S. Geological Survey
Journal of Paleontology | Year: 2016
The holotype partial skull of Agorophius pygmaeus (the monotypic form for both the genus Agorophius and the Family Agorophiidae) has been missing for approximately 140 years. Since the discovery of Agorophius pygmaeus, many additional taxa and specimens have been placed in the Family Agorophiidae, only to be reclassified and removed later. This has created confusion as to what is and what is not an agorophiid and a lack of clarity as to what characteristics delimit the Agorophiidae. A newly discovered skull of an agorophiid recently collected from an underwater cliff face of the Ashley River, South Carolina, USA, is assigned to Agorophius pygmaeus. It derives from the base of the Ashley Formation (early Oligocene). The new specimen consists of most of the skull and periotics, which are well preserved and described for the first time in an agorophiid. The new specimen provides an opportunity to diagnose the Agorophiidae and place the genus and species within the phylogenetic context of the early odontocete radiation in the Oligocene, along with other taxa such as the Ashleycetidae, Mirocetidae, Patriocetidae, Simocetidae, Waipatiidae, and Xenorophidae. Based on this new understanding, Agorophiidae are known with certainty only from the early Oligocene of South Carolina, with other undescribed, potential agorophiid specimens from the Oligocene of the North Pacific region (Japan, Mexico, and Washington State). © 2016, The Paleontological Society.
Marzoli A.,University of Padua |
Jourdan F.,Curtin University Australia |
Puffer J.H.,Rutgers University |
Cuppone T.,University of Padua |
And 6 more authors.
Lithos | Year: 2011
New major and trace element data and 40Ar/39Ar plateau ages constrain the timing, duration and time-related geochemical evolution of the Central Atlantic magmatic province in the U.S.A. (Newark and Culpeper basins) and refine correlations with basaltic lava flows from other Late Triassic-Early Jurassic circum-Atlantic basins. The precise, statistically robust 40Ar/39Ar plateau ages were obtained on biotite and on fresh plagioclase and calculated using the latest 40K decay constants. These ages are supported by a general consistency of the Ca/K calculated from 37Ar/39Ar of the plateau steps and the Ca/K obtained by detailed electron microprobe analyses on plagioclase phenocrysts. The ages of five analyzed basalt lava flows, from all three lava flow units in the Newark basins, and the ages of two sill samples are indistinguishable, indicating a brief magmatic peak phase at 201.8±0.7Ma. Recalibrated 40Ar/39Ar plateau ages from the entire province indicate a near-synchronous onset and peak volcanic activity at the Triassic-Jurassic boundary within the circum-Atlantic basins from the U.S.A., Canada and Morocco. The early erupted magmas (Moroccan Lower to Upper basalts, the Fundy basin North Mountain Basalt, and Orange Mountain and equivalent U.S.A. flows) yield an enriched geochemical signature (e.g., with relatively high La/Yb), whereas late magmas in the U.S.A. (Hook Mountain and Hampden basalts) and Morocco (Recurrent basalt) yield relatively depleted geochemical compositions (low La/Yb). A slight, but significant age difference for eruption of Hook Mountain and Hampden basalts (200.3±0.9Ma) and Recurrent basalts (198.2±1.1Ma) is interpreted as evidence of a diachronous northward rift-drift transition during break-up of Pangea. Our data indicate also a prolonged intrusive sequence that continued until about 195Ma at the Palisades sill and is consistent with sporadic late CAMP magmatism for dykes from the south-eastern U.S.A. and for intrusions from Guinea. © 2011 Elsevier B.V.
Callegaro S.,University of Padua |
Marzoli A.,University of Padua |
Bertrand H.,Ecole Normale Superieure de Lyon |
Chiaradia M.,University of Geneva |
And 5 more authors.
Earth and Planetary Science Letters | Year: 2013
The densest dykes swarm of the Central Atlantic magmatic province (CAMP) occur in southeastern North America (SENA) and were intruded between 202 and 195 Ma during Pangea break-up. New combined geochemical data (major and trace elements, Sr-Nd-Pb-Os isotopes) constrain the mantle source of these magmatic bodies and their evolution path. While Sr-Nd isotopic compositions for SENA rocks (87Sr/86Sr200Ma 0.70438-0.70880 and 143Nd/144Nd200Ma 0.51251-0.51204) fall within the low-Ti CAMP field, Pb-Pb isotopes (206Pb/204Pb200Ma 17.46-18.85, 207Pb/204Pb200Ma 15.54-15.65, 208Pb/204Pb200Ma 37.47-38.76) are peculiar to this area of the CAMP and cover a considerable span of compositions, especially in 206Pb/204Pb200Ma. Given the generally unradiogenic Os isotopic compositions (187Os/188Os200Ma 0.127-0.144) observed and the lack of correlation between these and other geochemical markers, crustal contamination during the evolution of SENA dykes must have been limited (less than 10%). Thus the isotopic variation is interpreted to reside primarily within the mantle source. These observations, coupled with typical continental signatures in trace elements (positive anomaly in Pb and negative anomalies in Ti and Nb), require another means of conveying a continental flavor to these magmas, which is here hypothesized to be the shallow recycling within the upper mantle of subducted lower and upper crustal materials. Pseudo-ternary mixing models show that a maximum of 10% recycled crust is enough to explain their trace element patterns as well as their isotopic heterogeneity. Looking at the larger picture of the origin of the CAMP, the thermal contribution of a mantle plume cannot be ruled out due to the relatively high mantle potential temperatures (1430-1480 °C) calculated for high-Fo SENA olivines. Nevertheless, our results suggest that the chemical involvement of a mantle plume is negligible (less than 5%) if either a C- or an EM-flavored plume is considered. Rather, the possibility of a PREMA-flavored mantle plume, enriched by 5-20% recycled crustal material, remains a possible, though less plausible, source for these tholeiites. © 2013 Elsevier B.V.
Lucas S.G.,New Mexico Museum of Natural History |
Tanner L.H.,Le Moyne College |
Kozur H.W.,Rezsu u. 83 |
Weems R.E.,Paleo Quest |
Heckert A.B.,Appalachian State University
Earth-Science Reviews | Year: 2012
The Late Triassic timescale is poorly constrained due largely to the dearth of reliable radioisotopic ages that can be related precisely to biostratigraphy combined with evident contradictions between biostratigraphic and magnetostratigraphic correlations. These problems are most apparent with regard to the age and correlation of the Carnian-Norian boundary (base of the Norian Stage). We review the available age data pertaining to the Carnian-Norian boundary and conclude that the "long Norian" in current use by many workers, which places the Carnian-Norian boundary at ~. 228. Ma, is incorrect. The evidence supports a Norian stage that is much shorter than proposed by these workers, so the Carnian-Norian boundary is considerably younger than this, close to 220. Ma in age. Critical to this conclusion is the correlation of the Carnian-Norian boundary in nonmarine strata of Europe and North America, and its integration with existing radioisotopic ages and magnetostratigraphy. Three biostratigraphic datasets (palynomorphs, conchostracans and tetrapods) reliably identify the same position for the Carnian-Norian boundary (within normal limits of biostratigraphic resolution) in nonmarine strata of the Chinle Group (American Southwest), Newark Supergroup (eastern USA-Canada) and the German Keuper. These biostratigraphic datasets place the Carnian-Norian boundary at the base of the Warford Member of the lower Passaic Formation in the Newark Basin, and, as was widely accepted prior to 2002, this correlates the base of the Norian to a horizon within Newark magnetozone E13n. In recent years a correlation based solely on magnetostratigraphy has been proposed between the Pizzo Mondello section in Sicily and the Newark section. This correlation, which ignores robust biostratigraphic data, places the Norian base much too low in the Newark Basin section (~. at the base of the Lockatong Formation), correlative to a horizon near the base of Newark magnetozone E8. Despite the fact that this correlation is falsifiable on the basis of the biostratigraphic data, it still became the primary justification for placing the Carnian-Norian boundary at ~. 228. Ma (based on Newark cyclostratigraphy). The "long Norian" created thereby is unsupported by either biostratigraphic or reliable radioisotopic data and therefore must be abandoned. While few data can be presented to support a Carnian-Norian boundary as old as 228. Ma, existing radioisotopic age data are consistent with a Norian base at ~. 220. Ma. Although this date is approximately correct, more reliable and precise radioisotopic ages still are needed to firmly assign a precise age to the Carnian-Norian boundary. © 2012 Elsevier B.V.
Kozur H.W.,Rezsu u. 83 |
Weems R.E.,Paleo Quest
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011
Conchostracan-rich beds between the Siberian Trap flood basalts and within the thick underlying Hungtukun tuffs of the Tunguska Basin can be closely correlated with conchostracan faunas of Dalongkou (NW China) and the Germanic Basin. The Germanic Basin faunas in turn can be closely correlated with the marine international stratigraphic time scale, and the accuracy of the biostratigraphic correlation of the Permian-Triassic boundary (PTB) is confirmed by a minimum in δ13Ccarb values at this level. These high-resolution correlations demonstrate conclusively that the PTB is located within the temporally brief but thick Siberian Trap flood basalt sequence. The PTB lies slightly above the level of the main Permo-Triassic extinction event in low latitude marine beds, which occurred at the base of the C. meishanensis-H. praeparvus conodont zone and correlates with the beginning of the Siberian Trap flood basalt event. The main end-Permian continental extinction event was somewhat earlier, within the middle of the C. changxingensis-C. deflecta conodont zone. This horizon marks a mass extinction that devastated a diverse conchostracan fauna and left only low diversity faunas at low and high latitudes. This continental extinction event horizon lies within the middle of the Hungtukun tuffs of the Tunguska Basin and 107m above the base of the Guodikeng Formation at Dalongkou (NW China). A "Triassic type" pioneer flora with numerous lycopod spores appears immediately above this level. Severe high northern and southern latitude marine extinctions occurred concurrently with this continental event, but low latitude marine biota was not then affected. This earlier event is best explained by global warming. The main low latitude extinction event in marine warm water faunas occurred somewhat later and left no signature in high latitude marine faunas or in continental faunas, but it does coincide with a rapid collapse of tropical rain forest environments (disappearance of the highly diverse Gigantopteris flora). This collapse likely was caused by global cooling due to a volcanic winter event. © 2011.