This study presents new geochronological constraints for the Niluo Member within the slope-basin facies of the Late Triassic Nanpanjiang Basin, eastern Tethys. The basin underwent a significant marine-to-continental transition during this period. Previous biostratigraphic studies on platform facies were hindered by inconclusive conodont zonation, leaving the chronology of slope-basin deposits poorly resolved. To address this, we identified volcanic ash layers within the Niluo Member in the Wangmo area. Zircon U-Pb dating of these ashes yielded weighted mean ages of 229.9 Ma and 229.0 Ma, establishing a Carnian depositional age. This result is significantly younger than previous estimates and coincides with the CPE. The Niluo Member is interpreted as a period of slow, oxygen-deficient sedimentation, contrasting with the rapid turbidite deposition of the enclosing formations. This depositional hiatus likely facilitated the preservation of the datable ash layers. The Carnian age and unique lithology suggest the Niluo Member may record the CPE in the slope environment, potentially linked to increased terrigenous input that suppressed carbonate production. Concurrent conodont sampling w
Due to spatial scarcity and uncertainties in sediment data, initial and boundary conditions in deep-time climate simulations are not well constrained. On the other hand, the climate is a nonlinear system with a multitude of feedback mechanisms that compete and balance differently depending on the initial and boundary conditions. This opens up the possibility to obtain multiple steady states under the same forcing in numerical experiments. Here, we use the MIT general circulation model with a coupled atmosphere-ocean-thermodynamic sea ice-land configuration to explore the existence of such alternative steady states around the Permian-Triassic Boundary (PTB). We construct the corresponding bifurcation diagram, taking into account processes on a timescale of thousands of years, in order to identify the stability range of the steady states and tipping points as the atmospheric CO$_2$ content is varied. We find three alternative steady states with a difference in global mean surface air temperature of about 10 $^\circ$C. We also examine how these climatic steady states are modified when feedbacks operating on comparable or longer time scales are included, in particular vegetation dynami
Research Article| February 01, 1996 Global coal gap between Permian–Triassic extinction and Middle Triassic recovery of peat-forming plants Gregory J. Retallack; Gregory J. Retallack 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272 Search for other works by this author on: GSW Google Scholar John J. Veevers; John J. Veevers 2School of Earth Sciences, Macquarie University, New South Wales 2109, Australia Search for other works by this author on: GSW Google Scholar Ric Morante Ric Morante 2School of Earth Sciences, Macquarie University, New South Wales 2109, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Gregory J. Retallack 1Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272 John J. Veevers 2School of Earth Sciences, Macquarie University, New South Wales 2109, Australia Ric Morante 2School of Earth Sciences, Macquarie University, New South Wales 2109, Australia Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1996) 108 (2): 195–207. https://doi.org/10.1130/0016-7606(1996)108<0195:GCGBPT>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Gregory J. Retallack, John J. Veevers, Ric Morante; Global coal gap between Permian–Triassic extinction and Middle Triassic recovery of peat-forming plants. GSA Bulletin 1996;; 108 (2): 195–207. doi: https://doi.org/10.1130/0016-7606(1996)108<0195:GCGBPT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Early Triassic coals are unknown, and Middle Triassic coals are rare and thin. The Early Triassic coal gap began with extinction of peat-forming plants at the end of the Permian (ca. 250 Ma), with no coal known anywhere until Middle Triassic (243 Ma). Permian levels of plant diversity and peat thickness were not recovered until Late Triassic (230 Ma). Tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal-bearing sequences are present also in Early Triassic rocks. Nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers, insects or tetrapod herbivores, which became cosmopolitan and much reduced in diversity across the Permian-Triassic boundary. Instead, we favor explanations involving extinction of peat-forming plants at the Permian-Triassic boundary, followed by a hiatus of some 10 m.y. until newly evolved peat-forming plants developed tolerance to the acidic dysaerobic conditions of wetlands. This view is compatible not only with the paleobotanical record of extinction of swamp plants, but also with indications of a terminal Permian productivity crash from δ13Corg and total organic carbon of both nonmarine and shallow marine shales. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
High temperature impact melt breccias from the Rochechouart (France) meteorite crater record magnetization component with antipodal, normal and reverse polarities. The corresponding paleomagnetic pole for this component lies between the 220 Ma and 210 Ma reference poles on the Eurasian apparent polar wander path, consistent with the 214 $\pm$ 8 Ma 40Ar/39Ar age of the crater. Late Triassic tectonic reconstructions of the Eurasian and North American plates place this pole within 95% confidence limits of the paleomagnetic pole from the Manicouagan (Canada) meteorite impact crater, which is dated at 214 $\pm$ 1 Ma. Together, these observations reinforce the hypothesis of a Late Triassic, multiple meteorite impact event on Earth.
Paleoecologic study of invertebrate faunas from three successive Early Triassic seaways reveals that biotic recovery from the end-Permian mass extinction event was slow, and that full recovery did not occur until after the Early Triassic. Simple, cosmopolitan, opportunistic generalists, and low-diversity, low-complexity paleocommunities were characteristic of the entire Early Triassic in the Western USA. An increase in guild and taxonomic diversity was observed with the addition of several new higher taxa in the late Early Triassic (Spathian) to the almost exclusively molluscan faunas of the earlier Early Triassic (Nammalian). Potential “disaster forms” (the inarticulate brachiopod, Lingula, and the paper pecten, Claraia) dominated the earliest Early Triassic faunas (Griesbachian) and even occurred in the late Early Triassic (normal marine stromatolites). Comparison with data on faunas from the Permian and Triassic suggests that even the most diverse Early Triassic faunas (in the Spathian) were rather low in guild diversity and species richness. These characteristics of genera and paleocommunities in the Early Triassic may be typical of mass extinction aftermaths.
Scientists have discovered Labrujasuchus expectatus, a bizarre crocodile relative that looked more like an ostrich-like dinosaur than anything resembling a modern crocodile。 It walked on two legs, had tiny arms, and sported a toothless beak—an unexpected combination for a member of the crocodile lineage
Research Article| October 01, 1992 Early Triassic stromatolites as post-mass extinction disaster forms Jennifer K. Schubert; Jennifer K. Schubert 1Department of Geological Sciences, University of Southern California, Los Angeles, California 90089-0740 Search for other works by this author on: GSW Google Scholar David J. Bottjer David J. Bottjer 1Department of Geological Sciences, University of Southern California, Los Angeles, California 90089-0740 Search for other works by this author on: GSW Google Scholar Geology (1992) 20 (10): 883–886. https://doi.org/10.1130/0091-7613(1992)020<0883:ETSAPM>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jennifer K. Schubert, David J. Bottjer; Early Triassic stromatolites as post-mass extinction disaster forms. Geology 1992;; 20 (10): 883–886. doi: https://doi.org/10.1130/0091-7613(1992)020<0883:ETSAPM>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Aftermaths of mass extinctions have been thought to be characterized by relaxation of ecological constraints, accompanied by increased prominence of opportunistic generalists. Such taxa, termed "disaster forms," have been shown to increase dramatically in range and abundance after several mass extinction events. The Cambrian-Ordovician stromatolite decline in normal-marine level-bottom environments has been explained as a direct or indirect consequence of increases in ecological constraints, such as greater levels of predation and/or bioturbation of microbial communities, caused by early Paleozoic benthic invertebrate evolution and diversification. Thus, one would predict that in post-Ordovician strata, stromatolites might appear in normal-marine level-bottom environments as disaster forms in the aftermaths of mass extinctions particularly devastating to the benthic biota, such as during Early Triassic time. Mounded stromatolites are present in two beds (up to 1.5 m thick) of the Lower Triassic (Spathian) Virgin Limestone Member (Moenkopi Formation) in the southwestern Spring Mountains of Nevada. Stromatolites from level-bottom normal-marine subtidal environments have also been described from other Lower Triassic strata in North America, Europe, and Asia. These stromatolites, unusual in level-bottom normal-marine settings, may have developed locally during the long aftermath (4-5 m.y.) of the Permian-Triassic mass extinction because of partial relaxation of the ecological constraints that typically restricted them from unstressed subtidal, normal-marine, level-bottom environments. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| March 01, 2012 Climate warming in the latest Permian and the Permian–Triassic mass extinction Michael M. Joachimski; Michael M. Joachimski 1GeoZentrum Nordbayern, University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany Search for other works by this author on: GSW Google Scholar Xulong Lai; Xulong Lai 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China3State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei 430074, China Search for other works by this author on: GSW Google Scholar Shuzhong Shen; Shuzhong Shen 4State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Haishui Jiang; Haishui Jiang 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Search for other works by this author on: GSW Google Scholar Genming Luo; Genming Luo 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Search for other works by this author on: GSW Google Scholar Bo Chen; Bo Chen 1GeoZentrum Nordbayern, University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany Search for other works by this author on: GSW Google Scholar Jun Chen; Jun Chen 4State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China Search for other works by this author on: GSW Google Scholar Yadong Sun Yadong Sun 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Search for other works by this author on: GSW Google Scholar Author and Article Information Michael M. Joachimski 1GeoZentrum Nordbayern, University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany Xulong Lai 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China3State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, Hubei 430074, China Shuzhong Shen 4State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China Haishui Jiang 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Genming Luo 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Bo Chen 1GeoZentrum Nordbayern, University Erlangen-Nuremberg, Schlossgarten 5, 91054 Erlangen, Germany Jun Chen 4State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China Yadong Sun 2Faculty of Earth Sciences, China University of Geosciences, Wuhan, Hubei 430074, China Publisher: Geological Society of America Received: 02 Aug 2011 Revision Received: 23 Sep 2011 Accepted: 27 Sep 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (3): 195–198. https://doi.org/10.1130/G32707.1 Article history Received: 02 Aug 2011 Revision Received: 23 Sep 2011 Accepted: 27 Sep 2011 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michael M. Joachimski, Xulong Lai, Shuzhong Shen, Haishui Jiang, Genming Luo, Bo Chen, Jun Chen, Yadong Sun; Climate warming in the latest Permian and the Permian–Triassic mass extinction. Geology 2012;; 40 (3): 195–198. doi: https://doi.org/10.1130/G32707.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract High-resolution oxygen isotope records document the timing and magnitude of global warming across the Permian-Triassic (P-Tr) boundary. Oxygen isotope ratios measured on phosphate-bound oxygen in conodont apatite from the Meishan and Shangsi sections (South China) decrease by 2‰ in the latest Permian, translating into low-latitude surface water warming of 8 °C. The oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates, suggesting that the addition of isotopically light carbon to the ocean-atmosphere system by Siberian Traps volcanism and related processes resulted in higher greenhouse gas levels and global warming. The major temperature rise started immediately before the main extinction phase, with maximum and harmful temperatures documented in the latest Permian (Meishan: bed 27). The coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems. In addition, very warm climate conditions in the Early Triassic may have played a major role in the delayed recovery in the aftermath of the Permian-Triassic crisis. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Research Article| March 01, 1989 Synchroneity of climatic change and extinctions in the Late Triassic Michael J. Simms; Michael J. Simms 1Department of Earth Sciences, University of Liverpool, P.O. Box 147, Liverpool L69 3BX, England Search for other works by this author on: GSW Google Scholar Alastair H. Ruffell Alastair H. Ruffell 2School of Earth Sciences, University of Birmingham, P.O. Box 363, Birmingham B15 2TT, England Search for other works by this author on: GSW Google Scholar Geology (1989) 17 (3): 265–268. https://doi.org/10.1130/0091-7613(1989)017<0265:SOCCAE>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Michael J. Simms, Alastair H. Ruffell; Synchroneity of climatic change and extinctions in the Late Triassic. Geology 1989;; 17 (3): 265–268. doi: https://doi.org/10.1130/0091-7613(1989)017<0265:SOCCAE>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Although the Late Triassic was a time of widespread aridity, evidence exists for a significant increase in rainfall during the middle to late Carnian. Upper Triassic playa-lake sediments were interrupted by late Carnian fluviatile sandstones with erosive bases and high kao-linite/illite ratios. There was also an increase in the clastic component of marine sequences during this interval. Middle and upper Carnian marine carbonates show an extreme depletion in δ13C values, consistent with increased fresh-water influx. Large-scale karstic phenomena in limestone areas subaerially exposed during the Late Triassic are a further indication of increased rainfall. Important faunal and floral changes occurred during the Carnian-Norian interval; marine invertebrate turnover was greatest at the lower/middle Carnian boundary, and terrestrial extinctions were concentrated at the Carnian/Norian boundary. The cause of this Carnian pluvial episode may have been related to the rifting of Pangea, through disruption of atmospheric and oceanic circulation patterns, eustatic changes, or the effects of volcanism associated with rifting. A change in surface ocean temperature, salinity or pH, or habitat loss may have caused the decline of many shallow-marine invertebrates at the start of the middle Carnian; a return to arid conditions at the Carnian/Norian boundary would account for the turnover among terrestrial vertebrates and plants. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
New high-precision U/Pb geochronology from volcanic ashes shows that the Triassic-Jurassic boundary and end-Triassic biological crisis from two independent marine stratigraphic sections correlate with the onset of terrestrial flood volcanism in the Central Atlantic Magmatic Province to <150 ka. This narrows the correlation between volcanism and mass extinction by an order of magnitude for any such catastrophe in Earth history. We also show that a concomitant drop and rise in sea level and negative delta C-13 spike in the very latest Triassic occurred locally in <290 ka. Such rapid sea-level fluctuations on a global scale require that global cooling and glaciation were closely associated with the end-Triassic extinction and potentially driven by Central Atlantic Magmatic Province volcanism.
The hydro-mechanical behavior of clay-sulfate rocks, especially their swelling properties, poses significant challenges in geotechnical engineering. This study presents a hybrid constrained machine learning (ML) model developed using the categorical boosting algorithm (CatBoost) tuned with a Bayesian optimization algorithm to predict and analyze the swelling behavior of these complex geological materials. Initially, a coupled hydro-mechanical model based on the Richards' equation coupled to a deformation process with linear kinematics implemented within the finite element framework OpenGeoSys was used to simulate the observed ground heave in Staufen, Germany, caused by water inflow into the clay-sulfate bearing Triassic Grabfeld Formation. A systematic parametric analysis using Gaussian distributions of key parameters, including Young's modulus, Poisson's ratio, maximum swelling pressure, permeability, and air entry pressure, was performed to construct a synthetic database. The ML model takes time, spatial coordinates, and these parameter values as inputs, while water saturation, porosity, and vertical displacement are outputs. In addition, penalty terms were incorporated into the
The Carnian Pluvial Episode (CPE) was a major global climate change event in the early Late Triassic that significantly affected marine ecosystems and carbon cycles. One of the most prominent features of the CPE is the coupled multiple negative carbonate-organic carbon isotope excursions. However, at Erguan and Xiashulao from eastern Tethys, a decoupling between carbonate-organic carbon isotope during CPE was observed. At the end of early Carnian (Julian), the carbonate carbon isotope showed a negative excursion of 2-3 per-mille, while the organic carbon isotope exhibited a positive excursion of about 3-4 per-mille. In addition, increased terrestrial inputs is indicated by the rising C/N (3 to 10) and decreasing Y/Ho (42 to 27) that coexist with this decoupling. The coupling of carbon isotope negative excursions is from the shallow shelves and the deep slopes, whereas the decoupling occurs from the deep shelf to the shallow slope. In the deep shelf to the shallow slope, sedimentary organic matter is mainly sourced from pelagic before the CPE as evidenced by low C/N (3) and high Y/Ho (36-42). During the CPE, the increased fresh water flux (Sr/Ba <1) enhanced terrestrial input in
Radiolarians are significant contributors to the oceanic primary productivity and the global silica cycle in the last 500 Myr. Their diversity throughout the Phanerozoic shows periodic fluctuations. We identify a possible abiotic candidate for driving these patterns which seems to potentially influence radiolarian diversity changes during this period at a significance level of $\sim 2.2 σ$. Our finding suggests a significant correlation between the origination of new radiolaria species and maximum excursions of the Solar system from the Galactic plane, where the magnetic shielding of cosmic rays is expected to be weaker. We connect the particularly strong radiolaria blooming during the Middle Triassic to the so-called Mesozoic dipole-low of the geomagnetic field, which was in its deepest state when radiolarias were blooming. According to the scenario, high-energy cosmic rays presumably implied particular damage to the DNA during the maximum excursions which may trigger large chromosomal abnormalities leading to the appearance of a large number of new genera and species during these periods.
The Chang 2 bottom water reservoir area in the western part of northern Shaanxi is one of the core oil-producing areas in the Ordos Basin.One of the main reservoirs is the Chang 2 reservoir of the Triassic Yanchang Formation, which has good physical conditions, active edge and bottom water, and high geothermal gradient. In this paper, the reservoir numerical simulation software CMG is used to simulate the water intake and heat recovery in the target study area, and the heat recovery rate and heat recovery of the three water production methods of direct water production, four injection and one production and one injection and four production under different injection pressures are analyzed. The results show that it is difficult to realize the direct water extraction from the bottom water reservoir. The annual heat recovery of single well of four injection and one production and one injection and four production is converted to the standard coal production between 190 ~ 420 t, so the Chang 2 reservoir in the western part of northern Shaanxi has the potential of water injection and heat recovery.
Understanding the co-evolution of complex life with Earth's geology is an enduring challenge. The rock record evidences remarkable correlations between changes in biology and the wider Earth system, yet cause and effect remain unclear. Here, we link the evolutionary history of eukaryotes with the rise and fall of carbonate rock fraction within continental crust - a key variable in controlling the efficiency of carbon drawdown during weathering, solid Earth degassing rates, and ultimately nutrient supply to life. We use geospatial database analyses to demonstrate a strongly non-linear growth and then collapse in Earth's continental crust carbonate reservoir. Biomineralisers reshaped Earth's surface in their image; armouring continental margins with carbonate platforms, such that the continental carbonate reservoir increased in size by 5-fold in under 100 Myr after the Cambrian Radiation of animal life. This Paleozoic carbonate revolution represents among the most dramatic crustal evolutionary events in Earth's history. The Permo-Triassic extinction event coupled to the rise of open ocean calcifiers initiated a steady decline in continental crustal carbonate content; one that still c
Many fundamental parameters of biological systems -- eg. productivity, population sizes and biomass -- are most effectively expressed in absolute terms. In contrast to proportional data (eg. percentages), absolute values provide standardised metrics on the functioning of biological entities (eg. organisism, species, ecosystems). These are particularly valuable when comparing assemblages across time and space. Since it is almost always impractical to count entire populations, estimates of population abundances require a sampling method that is both accurate and precise. Such absolute abundance estimates typically entail more "sampling effort" (data collection time) than proportional data. Here we refined a method of absolute abundance estimates -- the "exotic marker technique" -- by producing a variant that is more efficient without losing accuracy. This new method, the "field-of-view subsampling method" (FOVS method) is based on area subsampling, from which large samples can be quickly extrapolated. Two case studies of the exotic marker technique were employed: 1, computer simulations; and 2, an observational "real world" data set of terrestrial organic microfossils from the Permia
Recent documentation of extreme atmospheric sulfur and methane contents at the time of the vast Permo-Triassic (P-T) extinction makes it possible to interpret an observation that has lain unnoticed in the geological literature for 40 years. This is the finding of microscopic metallic lead tear drops in the fluvial strata of the early Triassic sandstones that overlie Permian coal beds and other sedimentary deposits in the Sydney basin of Australia. Elemental lead is almost unknown in nature, so its occurrence in these graphite-loaded sandstones is a provocative finding. While climate change and vulcanism could explain the carbon and sulfur anomalies, the only way to account for metallic lead aerodynamic droplets is by massive impact and vaporization of lead mineral-containing formations. Since lead occurs geologically as the sulfide and since lead is an easily reduced element, its occurrence in conjunction with sulfur and carbon count anomalies suggests a bolide impact on carbon-loaded strata in a sulfide mineral-rich region. From these clues, and from stream cross-bedding data, we identify a probable site for the impact, in Bass Strait between Tasmania and Victoria. A gravitational
In the solar system, oldhamite (CaS) is generally considered to be formed by the condensation of solar nebula gas. Enstatite chondrites, one of the most important repositories of oldhamite, are believed to be the representative of the material which formed Earth. Thus, the formation mechanism and the evolution process of oldhamite are of great significance to the deeply understanding about the solar nebula, meteorites, the origin of Earth, and the C-O-S-Ca cycles of Earth. To date, no report about the oldhamite in the mantle exists. However, here we show the formation of oldhamite through the reaction between sulfide-bearing orthopyroxenite and molten calcite at 1.5 GPa/1510 K and 0.5 GPa/1320 K. Surprisingly the oxygen fugacities in our experiments are within the range of mantle conditions, which is 6 orders of magnitude higher than that of the solar nebula mechanism. Oldhamite is easily oxidized to calcium sulfate. Both low oxygen fugacity of magma and extreme low oxygen content of atmosphere are necessary for existence of oldhamite on the surface of a planet; otherwise, anhydrite or gypsum will exist in large quantities. The widespread existence of oldhamite on the planet surfac
By utilizing satellite-based estimations of the distribution of clouds, we have studied the Earth's large-scale cloudiness behavior according to latitude and surface types (ice, water, vegetation and desert). These empirical relationships are used here to reconstruct the possible cloud distribution of historical epochs of the Earth's history such as the Late Cretaceous (90 Ma ago), the Late Triassic (230 Ma ago), the Mississippian (340 Ma ago), and the Late Cambrian (500 Ma ago), when the landmass distributions were different from today's. With this information, we have been able to simulate the globally-integrated photometric variability of the planet at these epochs. We find that our simple model reproduces well the observed cloud distribution and albedo variability of the modern Earth. Moreover, the model suggests that the photometric variability of the Earth was probably much larger in past epochs. This enhanced photometric variability could improve the chances for the difficult determination of the rotational period and the identification of continental landmasses for a distant planets.
Natural selection explains how life has evolved over millions of years from more primitive forms. The speed at which this happens, however, has sometimes defied formal explanations when based on random (uniformly distributed) mutations. Here we investigate the application of a simplicity bias based on a natural but algorithmic distribution of mutations (no recombination) in various examples, particularly binary matrices in order to compare evolutionary convergence rates. Results both on synthetic and on small biological examples indicate an accelerated rate when mutations are not statistical uniform but \textit{algorithmic uniform}. We show that algorithmic distributions can evolve modularity and genetic memory by preservation of structures when they first occur sometimes leading to an accelerated production of diversity but also population extinctions, possibly explaining naturally occurring phenomena such as diversity explosions (e.g. the Cambrian) and massive extinctions (e.g. the End Triassic) whose causes are currently a cause for debate. The natural approach introduced here appears to be a better approximation to biological evolution than models based exclusively upon random