Some recent (mainly) non-dino papers:
Paolo Citton, Ausonio Ronchi, Umberto Nicosia, Eva Sacchi, Simone Maganuco, Angelo Cipriani, Giulia Innamorati, Costantino Zuccari, Fabio Manucci & Marco Romano (2020)
Tetrapod tracks from the Middle Triassic of NW Sardinia (Nurra region, Italy)
Italian Journal of Geosciences 139 (2): 309-320
doi:
https://doi.org/10.3301/IJG.2020.07https://pubs.geoscienceworld.org/italianjgeo/article-abstract/139/2/309/587016/Tetrapod-tracks-from-the-Middle-Triassic-of-NWWe report here on the first tetrapod tracks from the Triassic of the Nurra region (north-western Sardinia, Italy). The specimens were found on sandstone blocks used to build a fence limiting a seasonal camping, in the coastal area north of Capo Caccia promontory. Lithologic and petrographic features allowed an assignment of the track-bearing blocks to the middle-upper portion of the Anisian (Middle Triassic) Arenarie di Cala Viola ("Buntsandstein"). Footprints are attributed to the ichnotaxa Rhynchosauroides and Rotodactylus, two common ichnotaxa of late Early Triassic and Middle Triassic ichnofaunas of Europe and United States, commonly referred in the literature to neodiapsid and archosaur producers, respectively.
====
Free pdf:
James I. Kirkland, Donald D. DeBlieux, ReBecca K. Hunt-Foster, John R. Foster, Kelli Trujillo & Emily Finzel (2020)
The Morrison Formation and its bounding strata on the western side of the Blanding basin, San Juan County, Utah.
Geology of the Intermountain West 7: 137-195
DOI:
https://doi.org/10.31711/giw.v7.pp137-195https://giw.utahgeology.org/giw/index.php/GIW/article/view/73Free pdf:
https://giw.utahgeology.org/giw/index.php/GIW/article/view/73/96In 2016 and 2017, the Utah Geological Survey partnered with the U.S. Bureau of Land Management to conduct a paleontological inventory of the Morrison Formation south and west of Blanding, Utah, along the eastern margin of the Bears Ears National Monument. The Morrison in this region is critical to understanding Upper Jurassic stratigraphy across the Colorado Plateau because it is the type area for the Bluff Sandstone, Recapture, Westwater Canyon, and Brushy Basin Members of the Morrison Formation, which are the basis for nomenclature in New Mexico and Arizona as well. Researchers have disagreed about nomenclature and correlation of these units, which transition northward in the study area into the Tidwell, Salt Wash, and Brushy Basin Members. Numerous vertebrate localities make inclusion of the Bluff Sandstone and Recapture Members in the Middle Jurassic San Rafael Group, as suggested by some previous workers, unlikely. The Salt Wash Member does not separate the Bluff Sandstone and Recapture Members at Recapture Wash, but sandstone lenses of Salt Wash facies occur higher in northern Recapture exposures. Northward, along the outcrop belt east of Comb Ridge, the Bluff-Recapture interval thins, interlenses, and pinches out into the Tidwell and lower Salt Wash, with the main lower sandstone interval of the Westwater Canyon merging northward into the upper Salt Wash Member.
The partly covered, 1938 type section of the Brushy Basin Member is identified along Elk Mountain Road at the southern end of Brushy Basin. We describe a detailed, accessible Morrison Formation reference section about 11.2 km (7 mi) to the south along Butler Wash. There, 81.68 m (268 ft) of Brushy Basin Member is well exposed along a road between the top of the Westwater Canyon Member and the base of the Lower Cretaceous Burro Canyon Formation. We informally call the upper sandstone bed(s) of the Westwater Canyon Member that cap mesas and benches in the region "No-Mans Island beds." Smectitic mudstones between the No-Mans Island beds and the main sandstone body of the Westwater Canyon suggest that the Salt Wash-Brushy Basin contact to the north may be somewhat older than the base of the Brushy Basin Member as originally defined in its type area. Determining whether the No-Mans Island beds pinch out to the north or are removed by erosion below the regional basal Brushy Basin paleosol requires further research. Several significant fossil vertebrate and plant sites have been documented in the Brushy Basin type area. Newly identified volcanic ashes provided zircons for U-Pb ages of 150.67 Â 0.32 Ma from near the top of the Brushy Basin Member and of 153.7 Â 2.1 Ma and 153.8 Â 2.2 Ma for two zircons in lower part of Recapture Member. At the top of the Brushy Basin Member, ferruginous paleosols commonly overlying conglomeratic sandstone are speculated to be of Early Cretaceous age (detrital zircon age pending) and are assigned herein to the Yellow Cat Member of the Burro Canyon Formation. These iron-rich paleosols suggest wetter climatic conditions during the Jurassic-Cretaceous transition in the Blanding basin.
===
Free pdf:
Coelacanths are iconic fishes represented today by a single marine genus. The group was a little bit more diversified in the Mesozoic, with representatives in marine and continental environments in the Late Cretaceous. Here we describe isolated skull bones of the last know freshwater coelacanths found in several fossil sites from the Early Campanian to the Early Maastrichtian of Southern France (in the Departments of Aude, Bouches-du-RhÃne, HÃrault, and Var). The sample does not allow distinguishing different species, and all material is referred to Axelrodichthys megadromos Cavin, Valentin, Garcia originally described from the locality of Ventabren in Southern France. A reconstruction of the skull is proposed. Previously unrecognized features are described, including parts of the postparietal portion of the skull, of the suspensorium and of the mandible. The new data confirm the assignation of the species to the mawsoniids, and more specifically to Axelrodichthys. A cladistic analysis scoring new character states provides a similar topology than a previous analysis, i.e. A. megadromos is placed in a polytomy with Axelrodichthys araripensis and Lualabaea lerichei, two species from the Early Cretaceous of Brazil and from the Late Jurassic of the Democratic Republic of the Congo, respectively. A. megadromos appears to have been restricted to freshwater environments, to the contrary of oldest Western Gondwanan representatives of the family that were able to live in brackish and marine waters. A. megadromos is the last representative of the mawsoniids and its occurrence in Europe is probably the result of a dispersal event from Western Gondwana that happened somewhen in the Cretaceous. Based on the available data, the mawsoniids went extinct in the mid-Maastrichthian, i.e. before the end-Cretaceous mass extinction. But it is possible that the fossil record of this family, which has been only recently recognized in Late Cretaceous European deposits, will geographically and stratigraphically widen with further discoveries.
====
High contents of charcoal indicate that wildfire events occurred in the early Middle Jurassic.
The main types of wildfires were surface fires and ground fires, with less crown fires.
The oxygen levels could have reached from 27% to 29% in the Middle Jurassic.
The greenhouse gases released by wildfires in the Middle Jurassic in Northwest China reached at least 2097.6 Gt
Greenhouse gases released by wildfires might have affected the paleoclimate and paleoecosystems.
Abstract
Today wildfire is an important disturbance in many continental ecosystems, and it is assumed that with ongoing climate changes the frequencies and impacts of wildfires will increase in many regions. One way to obtain information about the potential long term influences of wildfires on ecosystems and the climate system itself is to study palaeo-wildfires. A total of 140 Jurassic samples, including 122 coal samples and 18 rock samples from roof and floor of coal seams, were collected from 4 coalfields in Northwestern China. The samples were analyzed by macropetrography, microscopy, scanning electron microscopy, gas chromatography, and gas chromatographyâmass spectrometry to study the evidences of wildfires and their impact on the paleoclimate. High contents of pyrogenic inertinites (charcoal), natural char and natural coke particles observed in the samples which indicate that widespread wildfire events occurred in the early Middle Jurassic in all over Northwestern China. Additionally, high-molecular-weight polycyclic aromatic hydrocarbons were detected in the coal samples. These aromatic compounds were formed under high temperature and provide further evidence of wildfires. According to a carbon emission model for modern forest fires, the total carbon and gas emissions from wildfires in peat swamps of the Middle Jurassic in Northwest China were calculated by the data from 21,575 coal samples of number of 1567 drill core samples. The total carbon released from peat-swamp forest wildfires was at least 1207 Gt, corresponding to emissions of CO2, CO and CH4 of 1926 Gt, 163 Gt, and 8.8 Gt, respectively. The huge amount of CO2 released by forest fires in the peat swamp systems of the Middle Jurassic in Northwestern China alone was equivalent to 64.20% of the total CO2 in the atmosphere at present (3000Gt). The large amounts of greenhouse gases released by wildfires must have led to long-term changes in the atmospheric composition and have caused global warming, which could have the reason of affected the paleoclimate.
====
Free pdf:
First report of Milankovitch cycles in Middle Permian terrestrial strata
The Lucaogou Formation, in Junggar Basin was deposited at ~270â267 Ma.
The "grand cycle" influenced climate and depositional processes in middle Permian.
Two approaches are used to estimate the Middle Permian astronomical parameters.
Cyclostratigraphic analysis refines the Earth-Moon history in the Paleozoic.
Abstract
Geological records of Milankovitch cycles provide a temporal framework for reconstructing Earth climate evolution and mapping out the history of the ancient Solar System. Understanding the fundamental celestial mechanics driving astronomical rhythms during the Permian Period from stratigraphic record is challenging because of the inherent limitations of astronomical solutions, the chaotic nature of Solar System motion, and the paucity of cyclostratigraphic studies of geological records. The Junggar and adjacent basins of northwestern China constituted a large tectonic lake in the Middle Permian, which deposited one of the thickest and richest petroleum source rock intervals in the world. Constructing an accurate timescale for the Permian Junggar Basin is critical to understand the processes that controlled organic carbon burial as well as paleoclimatic and paleoenvironmental background conditions. In this study, detailed spectral analyses of natural gamma ray (NGR) data were performed on the lacustrine muddy-dominated Lucaogou Formation from five exploitation wells. The results reveal significant meter-scale sedimentary cycles of 37.8 m, 10.7â10 m, 3.85â3.2 m, and 2.0â1.58 m, reflecting oscillations in lithologies (variations in changing clay content within the mudstone, sandstone and dolomite). These cycle wavelength ratios match well with those of the Milankovitch cycles predicted for Middle Permian Period. The depositional duration of the Lucaogou Formation was estimated at ~3 Myr. Correlation of the ~1.2 Myr obliquity modulation cycles among the NGR logs, sedimentation rates, and lake levels of the Junggar Basin, as well as with the Middle Permian global sea level, suggests that long-term astronomical âgrand cyclesâ tightly forced climatic and sedimentary processes throughout the Lucaogou Formation. According to two independent approaches, we reconstruct Middle Permian astronomical parameters (Earth precession constant: k and fundamental frequencies terms: gi, i = 1, 2, 3, 4, 5) and calculate astronomical periods (eccentricity, obliquity and precession). These results document astronomical forcing of Paleozoic lake systems, constrain Earth-Moon orbital evolution, and refine the fundamental astronomical frequencies of the Solar System during the Middle Permian.
=====
Free pdf:
Free pdf:
https://www.nature.com/articles/s41598-020-65974-2.pdfChicxulub impact (66âMa) event resulted in deposition of spheroids and melt glass, followed by deposition of diamectite and carbonate ejecta represented by large polished striated rounded pebbles and cobbles, henceforth, called Albion Formation1 Pook's Pebbles, name given from the first site identified in central Belize, Cayo District. Here we report that magnetic analysis of the Pook's Pebbles samples revealed unique electric discharge signatures. Sectioning of Pook's Pebbles from the Chicxulub ejecta from the Albion Formation at Belize showed that different parts of Pook's Pebbles had not only contrasting magnetization directions, but also sharply different level of magnetizations. Such behavior is indicative of electric discharge taking place sometimes during the formation of the Chicxulub ejecta blanket. In addition, some of the Pook's Pebbles' surface had recrystallized down to 0.2âmm depth. This is evidence of localized extreme pressures and temperatures during the fluidized ejecta formation which was imprinted in the outer layer of Pook's Pebbles. Recrystallization caused formation of nanophase iron along the surface, which was revealed by mapping of both natural remanent magnetization and of saturation remanence magnetization signatures. While the spheroids' magnetization orientation is consistent with reversed magnetic field at the time of impact, the study of the Pook's Pebbles provided, in addition, new evidence of electric charging during the vapor plume cloud processes.