Geology of Chief Joseph Pass, Wyoming: Crest of Rattlesnake Mountain anticline and escape path of the Eocene Heart Mountain slide

ABSTRACT Rattlesnake Mountain is a Laramide uplift cored by Archean gneiss that formed by offset along two reverse faults with opposing dips, the result being an asymmetric anticline with a drape fold of Cambrian–Cretaceous sediments. Rattlesnake Mountain was uplifted ca. 57 Ma and was a structural buttress that impeded motion of upper-plate blocks of the catastrophic Heart Mountain slide (49.19 Ma). North of Pat O’Hara Mountain anticline, Rattlesnake Mountain anticline has a central graben that formed ca. 52 Ma (U-Pb age on vein calcite in normal faults) into which O- and C-depleted fluids propagated upward with hydrocarbons. The graben is defined by down-dropped Triassic Chugwater shales atop the anticline that facilitated motion of Heart Mountain slide blocks of Paleozoic limestones dolomite (i.e., the Ordovician Bighorn Dolomite and Mississippian Madison Limestone) onto, and over, Rattlesnake Mountain into the Bighorn Basin. Heart Mountain fault gouge was also injected downward into the bounding Rattlesnake Mountain graben normal faults (U-Pb age ca. 48.8 ± 5 Ma), based on O and C isotopes; there is no anisotropy of magnetic susceptibility fabric present. Calcite veins parallel to graben normal faults precipitated from meteoric waters (recorded by O and C isotopes) heated by the uplifting Rattlesnake Mountain anticline and crystallized at 57 °C (fluid inclusions) in the presence of oil. Calcite twinning strain results from graben injectites and calcite veins are different; we also documented a random layer-parallel shortening strain pattern for the Heart Mountain slide blocks in the ramp region (n = 4; west) and on the land surface (n = 5; atop Rattlesnake Mountain). We observed an absence of any twinning strain overprint (low negative expected values) in the allochthonous upper-plate blocks and in autochthonous carbonates directly below the Heart Mountain slide surface, again indicating rapid motion including horizontal rotation about vertical axes of the upper-plate Heart Mountain slide blocks during the Eocene.

Primary versus carbonate production in the Toarcian, a case study from the Llanbedr borehole (Mochras Farm, Wales)

The leading hypothesis for the Toarcian oceanic anoxic event (T-OAE; ∼183Ma) and the associated negative C-isotope excursion is the massive release of 12C favouring greenhouse and continental weathering. The nutrient delivery to shallow-basins supported productivity and, because of O2-consumption by organic-matter respiration, anoxia development. However, several works showed that calcareous nannoplankton experienced a decrease during the T-OAE. Nannofossil fluxes measured in the Llanbedr borehole (Mochras Farm; Wales, UK) were the highest prior to the negative C-isotope excursion, along with high amounts of taxa indicative of nutrient-rich environments (Biscutaceae). Such conditions attest to high productivity. Fluxes show the lowest values in the core of the event, along with a size decrease of Schizosphaerella and a peak in Calyculaceae. The recovery of nannofossil fluxes and Schizosphaerella size occurred concomitant with the return of C-isotopes to more positive values. Concomitantly, deep-dwellers (Crepidolithus crassus) dominated, indicating a recovery of the photic-zone productivity. These observations demonstrate that the cascade of environmental responses to the initial perturbation was more complex than previously considered. In spite of elevated nutrient delivery to epicontinental basins in the early Toarcian, carbonate and primary productions of nannoplankton were depressed in the core the T-OAE likely because of prolonged thermohaline sea-water stratification.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5541440

Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) is essential for growth of the methanotroph Methylococcus capsulatus Bath.

The ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) enzyme found in plants, algae, and an array of autotrophic bacteria is also encoded by a subset of methanotrophs, but its role in these microbes has largely remained elusive. In this study, we identified that CO 2 was requisite for RubisCO-encoding Methylococcus capsulatus Bath growth in a bioreactor with continuous influent and effluent gas flow. RNA sequencing identified active transcription of several carboxylating enzymes, including key enzymes of the Calvin and serine cycles, that could mediate CO 2 assimilation during cultivation with both CH 4 and CO 2 as carbon sources. Marker-exchange mutagenesis of M. capsulatus Bath genes encoding key enzymes of potential CO 2 -assimilating metabolic pathways indicated that a complete serine cycle is not required while RubisCO is essential for growth of this bacterium. 13 CO 2 tracer analysis showed that CH 4 and CO 2 enter overlapping anaplerotic pathways and implicated RubisCO as the primary enzyme mediating CO 2 assimilation in M. capsulatus Bath. Notably, we quantified the relative abundance of 3-phosphoglycerate and ribulose-1,5-bisphosphate 13 C isotopes, which supported that RubisCO-produced 3-phosphoglycerate is primarily converted to ribulose-1-5-bisphosphate via the oxidative pentose phosphate pathway in M. capsulatus Bath. Collectively, our data establish that RubisCO and CO 2 play essential roles in M. capsulatus Bath metabolism. This study expands the known capacity of methanotrophs to fix CO 2 via RubisCO, which may play a more pivotal role in the Earth’s biogeochemical carbon cycling and greenhouse gas regulation than previously recognized. Further, M. capsulatus Bath and other CO 2 -assimilating methanotrophs represent excellent candidates for use in the bioconversion of biogas waste streams that consist of both CH 4 and CO 2 . Importance The importance of RubisCO and CO 2 in M. capsulatus Bath metabolism is unclear. In this study, we demonstrated that both CO 2 and RubisCO are essential for M. capsulatus Bath growth. 13 CO 2 tracing experiments supported that RubisCO mediates CO 2 fixation and a non-canonical Calvin cycle is active in this organism. Our study provides insights into the expanding knowledge of methanotroph metabolism and implicates dual CH 4 /CO 2 -utilizing bacteria as more important players in the biogeochemical carbon cycle than previously appreciated. In addition, M. capsulatus and other methanotrophs with CO 2 assimilation capacity represent candidate organisms for the development of biotechnologies to mitigate the two most abundant greenhouse gases CH 4 and CO 2 .

Quantitively and novelty source fingerprinting N and P pollutants in sediment: Case study in a small catchment, North China

<p>The intensive farmland in north China accounts for more than 17% of China's arable land area and is main producing area of wheat and corn in China. The response of sources and loads of sediment of N and P pollutants to the high-intensity agricultural activities in north China still remains unclear. The study aims to quantify the source and magnitude of N and P pollutants in the sediment from different land use types using a novel application of compound-specific δ<sup>13</sup>C isotopes (CSSI), <sup>137</sup>Cs and <sup>210</sup>Pb<sub>ex</sub> (FRNs), in a representative agricultural catchment (Jiangou). Surface (0-2 cm) soil and sediment samples were collected from different plant species for CSSI and FRNs, while subsurface (5-30 cm) soil samples were collected from channel bank for FRNs. The <sup>137</sup>Cs cores (0-60 cm) collected at the outlet of the catchment and also at reference sites. Sediment sources from surface and subsurface soils were derived by FRNs data which accounted by 83±6% and 17±6%, respectively, while the sediment sources from maize, bean, vegetable farmlands and forestlands on the surface soil areas were identified by CSSI data. Combining FRNs and CSSI fingerprinting techniques, the dominant sediment source was derived from maize farmland which contributed by 60±8%, followed by channel bank, bean farmland and vegetable farmland which accounted for 17±6%, 12±3% and 8±3%, respectively, and the least contribution was from forestland (3±1%). According to the <sup>137</sup>Cs cores (0-60 cm) collected at the outlet of Jiangou catchment, a sedimentation rate of 23.38±0.22 t ha<sup>-1</sup> yr<sup>-1 </sup>of this study catchment was quantified. The <sup>137</sup>Cs inventory of the reference site was 1162±131Bq m<sup>-2</sup>. Based on the measured of N and P concentrations in source samples, and areas of land uses in this catchment, we quantitatively estimated the N pollutant in sediment (t yr<sup>-1</sup>) from maize (2.19), bean (0.42), vegetable farmlands (0.31), forestland (0.49) and channel bank (0.05), while P pollutant (t yr<sup>-1</sup>) were 4.39 for maize, 0.18 for beans, 0.28 for vegetable farmland, 0.37 for forestland and 0.04 for channel bank. This study shows that the novel conjunctive use of FRNs and CSSI techniques could quantify the N and P pollutants in sediment from different land uses in catchment, which is critical to assess and implement effective agricultural and land management practices.</p>

Tracing volcanic emissions from the CAMP volcanism in the sedimentary and biotic record

<p>The end-Triassic mass extinction (ETME) is thought to have been caused by voluminous, pulsed volcanic activity of the Central Atlantic Magmatic Province (CAMP). Over the last decades, various geochemical signals and proxy records, including δ<sup>13</sup>C, pCO<sub>2</sub>, iridium and other platinum-group elements, mercury, polycyclic aromatic hydrocarbons (PAH), charcoal and SO<sub>2</sub>, have been directly or indirectly attributed to CAMP magmatism. Here, we compile and discuss these various records in a stratigraphic framework to present a cohesive chain of events for the CAMP and the end-Triassic mass extinction. Mercury and iridium anomalies  indicate that CAMP activity commenced prior to the onset of the marine extinctions (as marked by the last occurrence of the Triassic ammonoid <em>Choristoceras marshi</em> or closely related species), and a negative δ<sup>13</sup>C excursion in organic matter (the Marshi CIE). This CIE may be explained by input of light carbon to the atmosphere from CAMP lavas of the Tiourjdal and Prevalent groups. Pedogenic carbonate below and above the Prevalent group in North America indicates a more than twofold increase in atmospheric pCO<sub>2</sub>. Subsequent n-alkane C-isotopes, and stomatal pCO<sub>2</sub> data seem to indicate a temporary cooling after the Marshi CIE, which is consistent with climate models incorporating volcanic emissions of both CO<sub>2 </sub>and SO<sub>2</sub>. Records of excess iridium and Hg/TOC indicate intensified magmatism during the extinction interval. Tectonic and perhaps epeirogenic (i.e. doming due to rise of magma) activity is suggested by the occurrence of multiple and widespread seismites in Europe. Atmospheric <em>p</em>CO<sub>2</sub> proxies indicate global warming, which culminated contemporaneously with a second negative CIE (the Spelae CIE) at the level of the first occurrence of the ammonoid <em>Psiloceras spelae</em>, the index taxon fot the Triassic−Jurassic boundary (TJB). Global warming at this level is corroborated by increased wildfire activity testified by charcoal and pyrolytic PAH records. Just prior to the increase in <em>p</em>CO<sub>2</sub> from stomatal proxy data, fossil plants exhibit SO<sub>2</sub>-induced damage indicating excess sulfur dioxide deposition priot to and across the TJB. This coincides with increased ratios of heavy molecular PAHs (coronene/benzo(a)pyrene) in sediments, which may suggest metamorphism of organic sediments also occurred across the TJB. This suggests that thermogenic release of light carbon and sulfur from sill intrusions in the Trans-Amazonian basins, where both evaporate- and organic-rich sediments are known to have been intruded, may have played an important role during the course of the ETME. Geochemical traces of magmatism, i.e. Ir and Hg, appear to have gradually disappeared during the Hettangian, suggesting that later phases of CAMP were less voluminous. Stomatal proxy data from Greenland and n-alkane C-isotope data from the UK, together with oxygen isotope data from carbonate fossils in the UK, may indicate that the global warming at the Spelae CIE was succeeded by another short-term cooling event. A gradual decrease in δ<sup>13</sup>C culminated at the top-Tilmanni CIE, marking the beginning of a long-term steady state with more negative C-isotope values than prior to the ETME. At this time, terrestrial ecosystems appear to have stabilized globally and ammonoids had begun to rediversify.</p>