Cominco American Well: Implications for the Reconstruction of the Sevier Orogen and Basin and Range Extension in West-Central Utah

Re-evaluation of acoustic, gamma ray and dip meter logs from the Cominco American Federal No. 2 well in the Sevier Desert basin of west-central Utah sheds new light on the interpretation of Neoproterozoic and Cambrian stratigraphy and Mesozoic structure in a region that has been influential in the development of ideas about crustal shortening and extension. The most prominent of several major thrust faults (the Canyon Range and Pavant thrusts) have been interpreted by DeCelles and Coogan (2006) [Regional structure and kinematic history of the Sevier fold-and-thrust belt, central Utah: Geological Society of America Bulletin, v. 118, n. 7-8, p. 841-864, http://dx.doi.org/10.1130/B25759.1] as having been cut and in part re-activated between late Oligocene and Holocene time by as much as 47 km of displacement on the gently west-dipping Sevier Desert detachment. This interpretation, which is based upon a combination of outcrop, seismic reflection and well data, depends critically on the Canyon Range thrust intersecting the Cominco well at a depth of 2,551 to 2,557 m (8,370-8,389 ft.), and terminating downwards against a re-activated Pavant thrust. Our work suggests that the fault at 2,551 m (8,370 ft.) is a strand of the Pavant thrust, and that the Canyon Range thrust cuts the well at a depth of 1,222 m (4,010 ft.). This alternative interpretation depends in turn on identification of the section between the two faults as terminal Neoproterozoic to middle Cambrian Prospect Mountain Quartzite through Chisholm Formation rather than Neoproterozoic "Pocatello Formation," "Blackrock Canyon Limestone" and lower Caddy Canyon Quartzite. To support this interpretation we present evidence for stratigraphic repetition and for deformation at the 1,222 m (4,010 ft.) level. Use of the lithostratigraphic terms "Pocatello" and "Blackrock Canyon" in west-central Utah is shown to be inappropriate, and among the reasons that the critical interval in the Cominco well has been misinterpreted by some authors. If the Canyon Range and Pavant thrusts are both found in the Cominco well, as we suggest, then they cannot be used as a piercing point for the estimation of displacement on the Sevier Desert detachment or as justification for the existence of the detachment. Published estimates of extension across the Sevier Desert basin therefore need to be reduced, potentially to as little as ∼ 10 km

Abyssal Hill Segmentation: Quantitative Analysis of the East Pacific Rise Flanks 7°S-9°S

The recent RN Maurice Ewing EW9105 Hydrosweep survey of the East Pacific Rise (EPR) and adjacent flanks between 7°S and 9°S provides an excellent opportunity to explore the causal relationship between the ridge and the abyssal hills which form on its flanks. These data cover 100% of the flanking abyssal hills to 115 km on either side of the axis. We apply the methodology of Goff and Jordan (1988) for estimating statistical characteristics of abyssal hill morphology (rms height, characteristic lengths and widths, plan view aspect ratio, azimuthal orientation, and fractal dimension). Principal observations include the following: (I) the rms height of abyssal hill morphology is negatively correlated with the width of the 5- to 20-km-wide crestal high, consistent with the observations of Goff (1991) for northern EPR abyssal hill morphology; (2) the characteristic abyssal hill width displays no systematic variation with position relative to ridge segmentation within the EW9105 survey area, in contrast with observations of Goff (1991) for northern EPR abyssal hill morphology in which characteristic widths tend to be smallest al segment ends and largest toward the middle of segments; (3) abyssal hill rms heights and characteristic widths are very large just north of a counterclockwise rotating "nannoplate", suggesting that the overlap region is being pushed northward in response to microplate-style tectonics; and (4) within the 7°12'S-8°38'S segment, abyssal hill lineaments are generally parallel to the ridge axis, while south of this area, abyssal hill lineaments rotate with a larger "radius of curvature" than does the EPR axis approaching the EPR-Wilkes ridge-transform intersection

M-sequence geomagnetic polarity time scale (MHTC12) that steadies global spreading rates and incorporates astrochronology constraints

Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 117 (2012): B06104, doi:10.1029/2012JB009260.Geomagnetic polarity time scales (GPTSs) have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates. A strategy to obtain an optimal GPTS is to minimize spreading rate fluctuations in many ridge systems; however, this has been possible only for a few spreading centers. We describe here a Monte Carlo sampling method that overcomes this limitation and improves GPTS accuracy by incorporating information on polarity chron durations estimated from astrochronology. The sampling generates a large ensemble of GPTSs that simultaneously agree with radiometric age constraints, minimize the global variation in spreading rates, and fit polarity chron durations estimated by astrochronology. A key feature is the inclusion and propagation of data uncertainties, which weigh how each piece of information affects the resulting time scale. The average of the sampled ensemble gives a reference GPTS, and the variance of the ensemble measures the time scale uncertainty. We apply the method to construct MHTC12, an improved version of the M-sequence GPTS (Late Jurassic-Early Cretaceous, ~160–120 Ma). This GPTS minimizes the variation in spreading rates in a global data set of magnetic lineations from the Western Pacific, North Atlantic, and Indian Ocean NW of Australia, and it also accounts for the duration of five polarity chrons established from astrochronology (CM0r through CM3r). This GPTS can be updated by repeating the Monte Carlo sampling with additional data that may become available in the future.A.M. and J.H. were supported by NSF grant OCE 09–26306, M.T. was supported by a Woods Hole Oceanographic Institution postdoctoral scholarship, and J.E.T.C. was supported by NSF grant OCE 09–60999.2012-12-3

Electrical anisotropy due to gas hydrate-filled fractures

In 2006, the Indian National Gas Hydrate Program Expedition 01, or NGHP-01, discovered gas hydrate as fill in near-vertical fractures in unconsolidated sediments at several drilling sites on the Indian continental margins. These gas hydrate-filled fractures were identified on logging-while-drilling resistivity images. The gas hydrate-filled fracture intervals coincide with high measured resistivity at the NGHP-01 sites. High measured resistivity translates into high hydrate saturations via Archie's equation; however, these high saturations contradict lower gas hydrate saturations determined from pressure core and chlorinity measurements. Also, in intervals with near-vertical gas hydrate-filled fractures, there is considerable separation between phase shift and attenuation resistivity logs, with 2-MHz resistivity measurements being significantly higher than 400-kHz resistivity measurements. We modeled the sensitivity of the propagation resistivity measurements in the gas hydrate-filled fracture intervals at NGHP-01 Sites 5 and 10. Near-vertical hydrate-filled fractures can cause the abnormally high resistivity measurements in vertical holes due to electrical anisotropy. The model suggests the gas hydrate saturations in situ are usually significantly lower than those calculated from Archie's equation. In addition, these modeled gas hydrate saturations generally agree with the lower gas hydrate saturations obtained from pressure core and chlorinity measurements at NGHP-01 Sites 5 and 10

Morphology of a 'Superfast' Mid-Ocean Ridge Crest and Flanks: The East Pacific Rise, 7°- 9° S

Detailed bathymetric data from a Hydrosweep multibeam sonar survey of a 250 km-long portion of the 'superfast'- spreading southern East Pacific Rise crest and flanks show that the along-axis variation in morphology and axial depth differs significantly from that observed at the fast-spreading northern East Pacific Rise. While the deep mantle upwelling pattern is similar under the northern and southern East Pacific Rise, our observations require that the connectivity of the shallow, subcrestal plumbing system be more efficient beneath the 'super-fast' spreading southern East Pacific Rise than beneath the slower spreading northern East Pacific Rise

Systematic along-axis tidal triggering of microearthquakes observed at 9°50′N East Pacific Rise

Hydrothermal fluid circulation at mid-ocean ridges facilitates the exchange of heat and chemicals between the oceans and the solid Earth, and supports chemosynthetic microbial and macro-faunal communities. The structure and evolution of newly formed oceanic crust plays a dominant role in controlling the character and longevity of hydrothermal systems; however, direct measurements of subsurface processes remain technologically challenging to obtain. Previous studies have shown that tidally-induced stresses within the subseafloor modulate both fluid flow and microearthquake origin times. In this study, we observe systematic along-axis variations between peak microearthquake activity and maximum predicted tidal extension beneath the hydrothermal vent site at 9°50′N East Pacific Rise. We interpret this systematic triggering to result from pore-pressure perturbations propagating laterally through the hydrothermal system. Based on our observations and a one-dimensional pore pressure perturbation model, we estimate bulk permeability at ∼10⁻¹³ to 10⁻¹² m² within layer 2B over a calculated diffusive lengthscale of 2.0 km

Looking for the key to preservation of fossil marine vertebrates in the Pisco Formation of Peru: new insights from a small dolphin skeleton

The upper Neogene Pisco Formation of Peru is known worldwide as one of the most significant Cenozoic marine vertebrate Konservatt-Lagerstätten, even featuring cetacean specimens that retain remains of soft tissues or stomach contents. Previous works showed that biomediated precipitation of dolomite concretions around large-sized decaying carcasses was one of the most relevant processes responsible for exceptional fossil preservation. In turn, little is known about the modes of fossilization of well-preserved small-sized vertebrates, which are rather common in the Pisco Formation, but mostly do not exhibit dolomite concretions. We report on a cetacean specimen, identified as belonging to the extinct short-snouted, small dolphin species Brachydelphis mazeasi (Pontoporiidae), preserved within a late Miocene sandy deposit at the site of Pampa Corre Viento. This specimen consists of a moderately disarticulated partial skeleton exhibiting well-mineralized bones; it is not enclosed within a dolomite concretion, being however delimited by an evident dark boundary in the host sediment. Scanning electron microscopy and microanalytical investigations identify Mn-oxides and apatite as early diagenetic minerals around the skeleton. We argue that a rapid burial of the specimen was pivotal for the preservation of the bones, and allowed the early establishment of anoxic processes for degradation of organic matter. Coupled with availability of P in porewater, the reducing conditions and the lowered pH allowed precipitation of Ca-phosphate while increasing Mn solubility close to the pontoporiid carcass. Mn-oxides precipitated at the redox boundary, the latter defining the outer edge of the volume of sediment affected by altered chemical conditions due to the decaying processes. The permeability of the sediment and the small size of the carcass were possible factors unfavorable to extensive sulfate reduction, thus preventing the formation of a dolomite concretion and allowing bone phosphatization. This record emphasizes the role of conditions favorable to bone mineralization in absence of an isolating carbonate concretion, in cases of high quality preservation of small-sized vertebrates observed in the Pisco Formation. The observation of patterns in the distribution of diagenetic minerals in the sediment enclosing vertebrate remains without, or with limited carbonate concretions provides insights into early taphonomic processes

Insights into the diagenetic environment of fossil marine vertebrates of the Pisco Formation (late Miocene, Peru) from mineralogical and Sr-isotope data

The late Miocene Pisco Formation of Peru is an outstanding example of richness and high-quality preservation of fossil marine vertebrates. In order to reconstruct the fossilization path, we present new textural, mineralogical and Sr-isotope data of diagenetic minerals formed in correspondence of fossil specimens such as marine vertebrates and mollusks. These fossil specimens were found at Cerro los Quesos, in the Ica Desert, within the diatomaceous strata of the Pisco Formation. Dolomite, gypsum, anhydrite and Mn minerals are the main phases found, while the calcium carbonate originally forming the mollusk valves is replaced by gypsum. An early formation of dolomite and of Mn minerals, triggered by the modifications of the geochemical environment due to organic matter degradation, is suggested by the textural relationships and is confirmed by the Sr isotopic ratio of dolomite, which agrees with that of seawater at the time of sedimentation. Instead, gypsum Sr isotopic ratios indicate a pre-Miocene seawater-derived brine circulating within the sedimentary sequence as a source for Sr. Oxidation of diagenetic sulfide causing a lowering of the pH of porewater is proposed as an explanation for Cacarbonate dissolution. The diagenetic chemical environment was, nevertheless, favorable to bone preservation

Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems

The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism through which large concentrations of hydrate can preferentially accumulate in coarse-grained sediments over geologic time. Using one-dimensional compositional reservoir simulations, we examine hydrate distribution patterns at the scale of individual sand layers (1-20 m thick) that are deposited between microbially active fine-grained material buried through the gas hydrate stability zone (GHSZ). We then extrapolate to two-dimensional and basin-scale three-dimensional simulations, where we model dipping sands and multilayered systems. We find that properties of a sand layer including pore size distribution, layer thickness, dip, and proximity to other layers in multilayered systems all exert control on diffusive methane fluxes toward and within a sand, which in turn impact the distribution of hydrate throughout a sand unit. In all of these simulations, we incorporate data on physical properties and sand layer geometries from the Terrebonne Basin gas hydrate system in the Gulf of Mexico. We demonstrate that diffusion can generate high hydrate saturations (upward of 90%) at the edges of thin sands at shallow depths within the GHSZ, but that it is ineffective at producing high hydrate saturations throughout thick (greater than 10 m) sands buried deep within the GHSZ. Furthermore, we find that hydrate in fine-grained material can preserve high hydrate saturations in nearby thin sands with burial

Inflammation and neutrophil extracellular traps in cerebral cavernous malformation

Correction: Volume79, Issue7 Article Number: 388 DOI: 10.1007/s00018-022-04418-8Cerebral Cavernous Malformation (CCM) is a brain vascular disease with various neurological symptoms. In this study, we describe the inflammatory profile in CCM and show for the first time the formation of neutrophil extracellular traps (NETs) in rodents and humans with CCM. Through RNA-seq analysis of cerebellum endothelial cells from wild-type mice and mice with an endothelial cell-specific ablation of the Ccm3 gene (Ccm3(iECKO)), we show that endothelial cells from Ccm3(iECKO) mice have an increased expression of inflammation-related genes. These genes encode proinflammatory cytokines and chemokines, as well as adhesion molecules, which promote recruitment of inflammatory and immune cells. Similarly, immunoassays showed elevated levels of these cytokines and chemokines in the cerebellum of the Ccm3(iECKO) mice. Consistently, both flow cytometry and immunofluorescence analysis showed infiltration of different subsets of leukocytes into the CCM lesions. Neutrophils, which are known to fight against infection through different strategies, including the formation of NETs, represented the leukocyte subset within the most pronounced increase in CCM. Here, we detected elevated levels of NETs in the blood and the deposition of NETs in the cerebral cavernomas of Ccm3(iECKO) mice. Degradation of NETs by DNase I treatment improved the vascular barrier. The deposition of NETs in the cavernomas of patients with CCM confirms the clinical relevance of NETs in CCM.Peer reviewe