scholarly journals Paleoenvironment and taphonomy of the dinosaur-bearing Ischigualasto Formation (Upper Triassic, Argentina)

1992 ◽  
Vol 6 ◽  
pp. 249-249 ◽  
Author(s):  
Raymond R. Rogers ◽  
Catherine A. Forster ◽  
Cathleen L. May ◽  
Alfredo Monetta ◽  
Paul C. Sereno
Keyword(s):  
Large Scale ◽  
Lower Half ◽  
Coarse Grained ◽  
Fine Grained ◽  
Karoo Basin ◽  
Sand Body ◽  
Faunal Succession ◽  
New Material ◽  
Group A ◽  
Depositional Setting

The oldest-known dinosaurs (Herrerasaurus, Pisanosaurus) occur within the Ischigualasto Formation. Recent work in the formation has brought to light significant new material, including the complete skeleton of a new primitive dinosaur. We sketch below the paleoenvironment and faunal succession during the range of these early dinosaurs, and review some of the taphonomic factors that shaped their fossil record.The Ischigualasto Formation (Carnian?) is included within the Agua de la Peña Group, a series of continental Triassic deposits exposed in the Ischigualasto-Ville Union Basin of northwest Argentina. Ischigualasto sediments rest unconformably upon the carbonaceous fluvial/lacustrine Los Rastros Formation; this contact is characterized locally by marked angular discordance. The upper contact is gradational into red-beds of the Los Colorados Formation. Medium- to coarse-grained conglomeratic sandstones, siltstones, and silty mudstones dominate the section. Sand bodies are characterized by medium- to large-scale trough cross-stratification and broad lenticular/narrow sheet geometries, and are interpreted as deposits of shallow, low-sinuosity streams. Siltstones and mudstones show pervasive evidence of soil development, including root traces, nodular caliche horizons, and pedogenic slickensides. Deposits attributable to lacustrine/paludal sedimentation are scarce, and freshwater vertebrates and invertebrates are extremely rare. These data suggest an upland depositional setting on a low-relief alluvial plain with seasonal climate.The Ischigualasto vertebrate fauna includes archosaurs, rhynchosaurs, traversodontid and carnivorous cynodonts, and temnospondyl amphibians. Rhynchosaurs dominate (relative specimen abundance) in the lower half of the section, but are absent from the upper half. Traversodontid cynodonts occur throughout the formation, but are much more abundant up-section. Archosaurs, carnivorous cynodonts, and particularly temnospondyls are rare throughout, with dinosaurs limited to the lower half. No major stratigraphic or sedimentologic changes occur up-section, and there is no evidence for significant shifts in physical or chemical taphonomic processes. Thus, trends in relative taxon abundance likely record a true biotic signal (e.g., local extinction, immigration) rather than a taphonomically-driven preservational bias.Fossils are preserved as isolated carcasses or disarticulated elements, most often in fine-grained overbank facies. Bone beds and microsites are conspicuously absent. Temnospondyl remains were found within a local carbonaceous lens developed upon a sand body, suggesting autochthonous burial in an abandoned-channel setting. Isolated skulls, particularly those of the traversodontid Exaeretodon, are extremely common. Fifteen isolated crania of this cynodont were mapped in a single stratum with limited areal exposure. Abundant preservation of isolated therapsid crania has also been reported in the Beaufort Series (Permo-Triassic) of the Karoo Basin, South Africa (Smith, 1980). Post-disarticulation hydrodynamic sorting (enhanced by scavenging?) of an areally dispersed mass-mortality assemblage may explain this unusual occurrence.

Microstructural Evolution of Synthetic Forsterite Aggregates Deformed to High Strain

2004 ◽  
Vol 467-470 ◽  
pp. 579-584 ◽  
Author(s):  
A. Kellermann Slotemaker ◽  
J.H.P. de Bresser ◽  
C.J. Spiers ◽  
M.R. Drury
Keyword(s):  
Grain Size ◽  
Dynamic Recrystallization ◽  
Grain Growth ◽  
Microstructural Evolution ◽  
Large Scale ◽  
High Strain ◽  
Confining Pressure ◽  
Size Reduction ◽  
Coarse Grained ◽  
Fine Grained

Microstructures provide the crucial link between solid state flow of rock materials in the laboratory and large-scale tectonic processes in nature. In this context, microstructural evolution of olivine aggregates is of particular importance, since this material controls the flow of the Earth’s upper mantle and affects the dynamics of the outer Earth. From previous work it has become apparent that if olivine rocks are plastically deformed to high strain, substantial weakening may occur before steady state mechanical behaviour is approached. This weakening appears directly related to progressive modification of the grain size distribution through competing effects of dynamic recrystallization and syn-deformational grain growth. However, most of our understanding of these processes in olivine comes from tests on coarse-grained materials that show grain size reduction through dynamic recrystallization. In the present study we focused on fine-grained (~1 µm) olivine aggregates (i.e., forsterite/Mg2SiO4), containing ~0.5 wt% water and 10 vol% enstatite (MgSiO3), Samples were axially compressed to varying strains up to a maximum of ~45%, at 600 MPa confining pressure and a temperature of 950°C. Microstructures were characterized by analyzing full grain size distributions and textures using SEM/EBSD. We observed syndeformational grain growth rather than grain size reduction, and relate this to strain hardening seen in the stress-strain curves.

scholarly journals Who Likes What? — SplitLBI in Exploring Preferential Diversity of Ratings

2020 ◽  
Vol 34 (01) ◽  
pp. 262-269
Author(s):  
Qianqian Xu ◽  
Jiechao Xiong ◽  
Zhiyong Yang ◽  
Xiaochun Cao ◽  
Qingming Huang ◽  
...  
Keyword(s):  
Large Scale ◽  
Social Preference ◽  
Learning To Rank ◽  
User Preferences ◽  
Coarse Grained ◽  
Fast Analysis ◽  
Fine Grained ◽  
Level Model ◽  
The Common ◽  
Multi Level

In recent years, learning user preferences has received significant attention. A shortcoming of existing learning to rank work lies in that they do not take into account the multi-level hierarchies from social choice to individuals. In this paper, we propose a multi-level model which learns both the common preference or utility function over the population based on features of alternatives to-be-compared, and preferential diversity functions conditioning on user categories. Such a multi-level model, enables us to simultaneously learn a coarse-grained social preference function together with a fine-grained personalized diversity. It provides us prediction power for the choices of new users on new alternatives. The key algorithm in this paper is based on Split Linearized Bregman Iteration (SplitLBI) algorithm which generates a dynamic path from the common utility to personalized preferential diversity, at different levels of sparsity on personalization. A synchronized parallel version of SplitLBI is proposed to meet the needs of fast analysis of large-scale data. The validity of the methodology are supported by experiments with both simulated and real-world datasets such as movie and dining restaurant ratings which provides us a coarse-to-fine grained preference learning.

The Paleoproterozoic Kombolgie Subgroup (1.8 Ga), McArthur Basin, Australia: Sequence stratigraphy, basin evolution, and unconformity-related uranium deposits following the Great Oxidation Event

2021 ◽  
Vol 59 (5) ◽  
pp. 1049-1083
Author(s):  
Eric E. Hiatt ◽  
T. Kurtis Kyser ◽  
Paul A. Polito ◽  
Jim Marlatt ◽  
Peir Pufahl
Keyword(s):  
Large Scale ◽  
Sedimentary Basins ◽  
Uranium Mineralization ◽  
Coarse Grained ◽  
Uranium Deposits ◽  
Burial Diagenesis ◽  
Fine Grained ◽  
Braided Rivers ◽  
Tectonic Events ◽  
Regional Tectonic

ABSTRACT Proterozoic continental sedimentary basins contain a unique record of the evolving Earth in their sedimentology and stratigraphy and in the large-scale, redox-sensitive mineral deposits they host. The Paleoproterozoic (Stratherian) Kombolgie Basin, located on the Arnhem Land Plateau, Northern Territory, is an exceptionally well preserved, early part of the larger McArthur Basin in northern Australia. This intracratonic basin is filled with 1 to 2 km-thick, relatively undeformed, nearly flat-lying, siliciclastic rocks of the Kombolgie Subgroup. Numerous drill cores and outcrop exposures from across the basin allow sedimentary fabrics, structures, and stratigraphic relationships to be studied in great detail, providing an extensive stratigraphic framework and record of basin development and evolution. Tectonic events controlled the internal stratigraphic architecture of the basin and led to the formation of three unconformity-bounded sequences that are punctuated by volcanic events. The first sequence records the onset of basin formation and is comprised of coarse-grained sandstone and polymict lithic conglomerate deposited in proximal braided rivers that transported sediment away from basin margins and intra-basin paleohighs associated with major uranium mineralization. Paleo-currents in the upper half of this lower sequence, as well as those of overlying sequences, are directed southward and indicate that the major intra-basin topographic highs no longer existed. The middle sequence has a similar pattern of coarse-grained fluvial facies, followed by distal fluvial facies, and finally interbedded marine and eolian facies. An interval marked by mud-rich, fine-grained sandstones and mud-cracked siltstones representing tidal deposition tops this sequence. The uppermost sequence is dominated by distal fluvial and marine facies that contain halite casts, gypsum nodules, stromatolites, phosphate, and “glauconite” (a blue-green mica group mineral), indicating a marine transgression. The repeating pattern of stratigraphic sequences initiated by regional tectonic events produced well-defined coarse-grained diagenetic aquifers capped by intensely cemented distal fluvial, shoreface, eolian, and even volcanic units, and led to a well-defined heterogenous hydrostratigraphy. Basinal brines migrated within this hydrostratigraphy and, combined with paleotopography, dolerite intrusion, faulting, and intense burial diagenesis, led to the economically important uranium deposits the Kombolgie Basin hosts. Proterozoic sedimentary basins host many of Earth's largest high-grade iron and uranium deposits that formed in response to the initial oxygenation of the hydrosphere and atmosphere following the Great Oxygenation Event. Unconformity-related uranium mineralization like that found in the Kombolgie Basin highlights the interconnected role that oxygenation of the Earth, sedimentology, stratigraphy, and diagenesis played in creating these deposits.

Climate and tectonic modulation of sand delivery to deep water lakes in rift basins. Late Pliocene, Corinth Rift, Greece

2020 ◽  
Author(s):  
Martin Muravchik ◽  
Gauti T. Eliassen ◽  
Gijs A. Henstra ◽  
Rob L. Gawthorpe ◽  
Gunn Mangerud ◽  
...  
Keyword(s):  
Deep Water ◽  
Large Scale ◽  
Coarse Grained ◽  
Early Pleistocene ◽  
Correct Identification ◽  
Herbaceous Vegetation ◽  
Surface Mapping ◽  
Fine Grained ◽  
Fault Block ◽  
Sedimentary System

<p>The sedimentary record of deep-water lakes is often used to investigate past climate and environmental change. Correct identification however, of the main controls driving the production and transport of sediment to the deepest parts of tectonically active basins is often challenging, especially when trying to differentiate autogenic from allogenic factors. This study focuses on the changes observed in a deep-water sedimentary system that evolved from mudstone-dominated to the development of a lacustrine sand-dominated channel-lobe distributary fan and back to mudstone deposition during the Pliocene climatic optimum in the Corinth Rift, Greece. This is a multidisciplinary study that involves the integration of sedimentology and structural geology with digital outcrop modelling, palynology, palaeomagnetology and geochronology.</p><p>The studied sedimentary system consisted of a coarse-grained delta (Mavro delta) that fed the deep-water Rethi Dendro Formation (RDF) in the Amphithea fault block during the Pliocene and Early Pleistocene. These syn-rift deposits were sourced from a major hinterland catchment, the Olvios catchment, draining the southern, fault-controlled margin of the rift. The depocentre was located at the exit of a structurally controlled sediment fairway, ~15 km from the source of sediment and ~12 km basinwards from the basin margin coastline. The stratigraphy of the RDF in the study area is well constrained due to the combination of detailed surface mapping and logging with LiDAR, photogrammetry and UAV surveys of large-scale exposures in the Sythas river valley. These were integrated with the information obtained from the analysis of rock cores obtained through wells drilled immediately behind the cliffs where the RDF is exposed. The Amphithea fault block has a half-graben configuration and tilting of the hangingwall was one of the main tectonic controls on the evolution of the depocenter fill. The stratigraphic interval considered in this study is ~130 m thick. It was deposited above a ~6° angular unconformity and it is composed predominantly of fine-grained hemipelagic dominated units, interrupted by the development of an ~30 m thick sandstone-dominated channelized lobe unit. Detailed palynological analysis of this interval shows significant changes in pollen and spore assemblages that are used to interpret the palaeoflora developed in the drainage catchments. The palynoflora in fine-grained hemipelagic intervals is dominated by temperate forests mixed with subtropical elements, whereas the channelized lobe unit is dominated by palynofloras typical of open herbaceous vegetation including steppic taxa, suggesting a dryer and cooler climate. The shift from forest- to herbaceous-dominated palynological assemblages is gradual, recorded from 5 m below the facies change marking the base of the channelized lobe unit.  In contrast, the top of the channelized lobe unit coincides with the abrupt change back to the forest-dominated pollen assemblage. The correlation between the establishment of a sand-dominated channel-lobe distributary fan in the basin floor with the predominance of open herbaceous vegetation is interpreted to reflect the highly erodible condition of land covered in this type of vegetation. In contrast, during periods when forests are dominant, erodibility decreases.</p>

scholarly journals Neutron and Photon Research for Texture and Stress Characterisation of Advanced Materials

2010 ◽  
Vol 146-147 ◽  
pp. 891-894 ◽  
Author(s):  
Heinz Guenter Brokmeier
Keyword(s):  
Synchrotron Radiation ◽  
Large Scale ◽  
Materials Science ◽  
Advanced Materials ◽  
Coarse Grained ◽  
X Rays ◽  
Fine Grained ◽  
High Penetration ◽  
In Situ Experiments ◽  
As Stress

Worldwide materials science diffractometers at large scale facilities were built recently to improve experimental options for the characterization of advanced materials. Thermal neutrons as well as hard X-rays have a relatively high penetration power that non-destructive investigations of stress profiles and texture gradients are possible. Due to the main difference between neutrons and photons, which is the brilliance of the beam, the gage volume of synchrotron experiments is much smaller than with neutrons. That means, according to the material itself local resolution in mm-scale is preferred by neutrons and in μm scale by synchrotron radiation. The microstructure of laser welded Al shows fine grained parts were synchrotron radiation can be used while coarse grained parts need neutrons for better grain statistics. Both radiations can also be used to perform in situ experiments for stress and texture analysis. A combination of neutron and synchrotron measurements was used to explain the texture influence on the activation of twinning during Mg-extrusion. Neutron diffractometers, such as Stress-Spec@FRM II/Garching-Germany, or synchrotron diffractometers, such as Harwi-II@Haslab/Hamburg-Germany, are excellent for materials characterization in combination with electron diffraction and laboratory X-ray diffraction.

A COMPONENT-BASED MODELING AND SIMULATION SUPPORTING ENVIRONMENT

2013 ◽  
Vol 04 (04) ◽  
pp. 1342006 ◽  
Author(s):  
TENG DA ◽  
SONG XIAO
Keyword(s):  
Modeling And Simulation ◽  
Large Scale ◽  
Coarse Grained ◽  
Simulation Environment ◽  
Application Development ◽  
Simulation Tools ◽  
Fine Grained ◽  
Complex Simulation ◽  
Architecture Modeling ◽  
Effective Development

Simulation modelers, engineers and managers are faced with new challenges at large-scale complex simulation application development. To reduce the difficulty of developing such simulation applications, the simulation environment is required to be extensible, reusable and composable. In order to promote the reusability from coarse-grained federate to fine-grained components, this paper proposes a modeling and simulation environment which consists of component-based architecture, modeling methods, and simulation services to support and simplify the process of complex simulation application construction. Moreover, a standard process and simulation tools are developed to ensure the rapid and effective development of simulation applications.

scholarly journals Exploiting Coarse-to-Fine Task Transfer for Aspect-Level Sentiment Classification

2019 ◽  
Vol 33 ◽  
pp. 4253-4260 ◽  
Author(s):  
Zheng Li ◽  
Ying Wei ◽  
Yu Zhang ◽  
Xiang Zhang ◽  
Xin Li
Keyword(s):  
Large Scale ◽  
Specific Aspect ◽  
Sentiment Classification ◽  
Coarse Grained ◽  
Target Domain ◽  
Fine Grained ◽  
Feature Representations ◽  
Task Transfer ◽  
Coarse To Fine ◽  
Feature Alignment

Aspect-level sentiment classification (ASC) aims at identifying sentiment polarities towards aspects in a sentence, where the aspect can behave as a general Aspect Category (AC) or a specific Aspect Term (AT). However, due to the especially expensive and labor-intensive labeling, existing public corpora in AT-level are all relatively small. Meanwhile, most of the previous methods rely on complicated structures with given scarce data, which largely limits the efficacy of the neural models. In this paper, we exploit a new direction named coarse-to-fine task transfer, which aims to leverage knowledge learned from a rich-resource source domain of the coarse-grained AC task, which is more easily accessible, to improve the learning in a low-resource target domain of the fine-grained AT task. To resolve both the aspect granularity inconsistency and feature mismatch between domains, we propose a Multi-Granularity Alignment Network (MGAN). In MGAN, a novel Coarse2Fine attention guided by an auxiliary task can help the AC task modeling at the same finegrained level with the AT task. To alleviate the feature false alignment, a contrastive feature alignment method is adopted to align aspect-specific feature representations semantically. In addition, a large-scale multi-domain dataset for the AC task is provided. Empirically, extensive experiments demonstrate the effectiveness of the MGAN.

scholarly journals Large-Scale Coarse-to-Fine Object Retrieval Ontology and Deep Local Multitask Learning

2019 ◽  
Vol 2019 ◽  
pp. 1-40
Author(s):  
Ngoc Q. Ly ◽  
Tuong K. Do ◽  
Binh X. Nguyen
Keyword(s):  
Network Architecture ◽  
Large Scale ◽  
Data Augmentation ◽  
Imbalanced Data ◽  
Recall Rate ◽  
Coarse Grained ◽  
Object Retrieval ◽  
Fine Grained ◽  
Object Ontology ◽  
Coarse To Fine

Object retrieval plays an increasingly important role in video surveillance, digital marketing, e-commerce, etc. It is facing challenges such as large-scale datasets, imbalanced data, viewpoint, cluster background, and fine-grained details (attributes). This paper has proposed a model to integrate object ontology, a local multitask deep neural network (local MDNN), and an imbalanced data solver to take advantages and overcome the shortcomings of deep learning network models to improve the performance of the large-scale object retrieval system from the coarse-grained level (categories) to the fine-grained level (attributes). Our proposed coarse-to-fine object retrieval (CFOR) system can be robust and resistant to the challenges listed above. To the best of our knowledge, the new main point of our CFOR system is the power of mutual support of object ontology, a local MDNN, and an imbalanced data solver in a unified system. Object ontology supports the exploitation of the inner-group correlations to improve the system performance in category classification, attribute classification, and conducting training flow and retrieval flow to save computational costs in the training stage and retrieval stage on large-scale datasets, respectively. A local MDNN supports linking object ontology to the raw data, and an imbalanced data solver based on Matthews’ correlation coefficient (MCC) addresses that the imbalance of data has contributed effectively to increasing the quality of object ontology realization without adjusting network architecture and data augmentation. In order to evaluate the performance of the CFOR system, we experimented on the DeepFashion dataset. This paper has shown that our local MDNN framework based on the pretrained NASNet architecture has achieved better performance (14.2% higher in recall rate) compared to single-task learning (STL) in the attribute learning task; it has also shown that our model with an imbalanced data solver has achieved better performance (5.14% higher in recall rate for fewer data attributes) compared to models that do not take this into account. Moreover, MAP@30 hovers 0.815 in retrieval on an average of 35 imbalanced fashion attributes.

scholarly journals Conifer regeneration in stand-replacement portions of a large mixed-severity wildfire in the Klamath–Siskiyou Mountains

2009 ◽  
Vol 39 (4) ◽  
pp. 823-838 ◽  
Author(s):  
Daniel C. Donato ◽  
Joseph B. Fontaine ◽  
John L. Campbell ◽  
W. Douglas Robinson ◽  
J. Boone Kauffman ◽  
...  
Keyword(s):  
Large Scale ◽  
Parent Material ◽  
Coarse Grained ◽  
Site Factors ◽  
Fine Grained ◽  
Seed Sources ◽  
Soil Parent Material ◽  
Tree Edge ◽  
Conifer Regeneration ◽  
Live Tree

Large-scale wildfires (∼104–106 ha) have the potential to eliminate seed sources over broad areas and thus may lead to qualitatively different regeneration dynamics than in small burns; however, regeneration after such events has received little study in temperate forests. Following a 200 000 ha mixed-severity wildfire in Oregon, USA, we quantified (1) conifer and broadleaf regeneration in stand-replacement patches 2 and 4 years postfire; and (2) the relative importance of isolation from seed sources (live trees) versus local site conditions in controlling regeneration. Patch-scale conifer regeneration density (72%–80% Douglas-fir ( Pseudotsuga menziesii (Mirb). Franco)) varied widely, from 127 to 6494 stems·ha–1. Median densities were 1721 and 1603 stems·ha–1 2 and 4 years postfire, respectively, i.e., ∼12 times prefire overstory densities (134 stems·ha–1). Because of the complex burn mosaic, ∼58% of stand-replacement area was ≤200 m from a live-tree edge (seed source), and ∼81% was ≤400 m. Median conifer density exceeded 1000 stems·ha–1 out to a distance of 400 m from an edge before declining farther away. The strongest controls on regeneration were distance to live trees and soil parent material, with skeletal coarse-grained soils supporting lower densities (133 stems·ha–1) than fine-grained soils (729–1492 stems·ha–1). Other site factors (e.g., topography, broadleaf cover) had little association with conifer regeneration. The mixed-severity fire pattern strongly influenced the regeneration process by providing seed sources throughout much of the burned landscape.

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