GeoResJ最新文献

Recent studies have revealed that in high-altitude mountain environments the global warming trend over the last few decades tends to be strongly amplified. However, few attempts have been made to monitor the possible effects of such climate changes on high-altitude rock glaciers. In this paper, we provide a geomorphic analysis of the Varas rock glacier, and present the first observations of rock glacier temperature (air and ground) and surface velocities in the Andes of northwestern Argentina. A network of 30 boulders was monitored every year between 2012 and 2016 using a differential Global Positioning System. Over the observational period, the Varas active rock glacier registered velocities between 125 and 5 cm/yr, except for four boulders which did not shift. Over the five years of monitoring, the mean annual air and ground (at 5 and 50 cm depth) temperature remained above 0 °C. A long-term instrumental weather dataset (106 years), located ∼130 km from the Varas rock glacier, at La Quiaca station, reveals a warming trend of 0.8 °C during the last century, with a steep increase during the last two and half decades. The warming trend recorded in the region may have produced or facilitated the inactivity of the more-exposed sectors of the Varas active rock glacier. However, there also may be a delay in the relatively slow and full response of rock glaciers to the last few decades of warming. Finally, the observations allow us to propose a formation sequence in the Varas rock glacier valley, since postglacial time.

Time-series profiles derived from temperature proxies such as tree rings can provide information about past climate. Signal analysis was undertaken of six such datasets, and the resulting component sine waves used as input to an artificial neural network (ANN), a form of machine learning. By optimizing spectral features of the component sine waves, such as periodicity, amplitude and phase, the original temperature profiles were approximately simulated for the late Holocene period to 1830 CE. The ANN models were then used to generate projections of temperatures through the 20th century. The largest deviation between the ANN projections and measured temperatures for six geographically distinct regions was approximately 0.2 °C, and from this an Equilibrium Climate Sensitivity (ECS) of approximately 0.6 °C was estimated. This is considerably less than estimates from the General Circulation Models (GCMs) used by the Intergovernmental Panel on Climate Change (IPCC), and similar to estimates from spectroscopic methods.

The Fusagasuga megafan is located in the Sumapaz River catchment (main tributary of the Magdalena River) which drains into the Sumapaz moorland. The soils show non consistent hydromorphic palaeofeatures that may be related to recent tectonics, therefore a study was conducted to gain insight into the paleoenvironment of the area, in particular the paleohydrology. We studied 6 profiles under 4 different geomorphological positions: structural eroded mountain, axis, length and base of the alluvial megafan (depositional foothills). Medium-textured Lithic Melanudands are located in a steep high mountain (anticline structural slope), Silty loam Ultic Melanudands are developed from volcanic ashes over thick medium-grained sandstones in the transition mountain to alluvial megafan, very fine-textured Typic Paleudalfs with Bt Horizons (42–85% clay) are found around the middle and proximal parts of the megafan, that become Typic Haplustalfs at the distal parts of the megafan. Kaolinite is the dominant clay in all soils, followed by halloisite, goethite and traces of vermiculite and quartz. Quartz and feldspars dominate the sand fraction, together with amphiboles and volcanic glass chemically weathered epidote in small quantities. Soils are mainly acidic, with a high Al saturation and a low base saturation. Clay illuviation is shown by hypocoatings and microlaminated clay coatings. Different degrees of hydromorphism are observed with gleyic to stagnic patterns. Some of the redoximorphic features are related to the current pore system and others to palaeoenvironmental conditions often associated to old clay coatings. The most clayey soils show striated, undifferenciated, speckled b-fabrics and frequent coatings, and some others point to ferrolysis as iron-depleted hypocoatings and low anisotropic clay coatings along pores, an observation supported by mineralogical data. The morphological and micromorphological redoximorphic features allow us to explain the paleoevolution of the alluvial megafan.

The PANG0001 well, situated in the Claromecó Basin, Argentina, involves rocks that belong to the Tunas Formation [29], Permian of Gondwana. It is composed of fine to medium sandstones intercalating with black and green mudrocks and three coal seams up to 3 m thick. In the coals, a petrographic analysis was carried out to analyze the depositional environment and the diagenesis level reached by the Tunas Formation. The coals are composed of mono-maceral bands of Collotelinite and Gelinite, from the Vitrinite Group, or Fusinite, from the Inertinite Group. They were deposited in a wet swampy forest with rises and decreases of the phreatic level. The presence of inertinite or charcoal evidence the occurrence of palaeo-fires during the Permian. The vitrinite reflectance values are between 1.3% and 2.38%. The coals classify as semiantracitic to low volatile bituminous, with 10 to 25% of volatile matter. The vitrinite reflectance values indicate temperatures between 140 °C and 190 °C. The Tunas Formation reaches the oil to methane gas window, into a catagenesis to metagenesis range related to the organic matter diagenesis. Coal petrography is a good method for the environment and diagenesis analyses applied to the Tunas Formation.

Archaeological artifacts are abundant in India to undertake archaeointensity (AI) research. High quality AI data from this region are essential to improve global geomagnetic field (GGF) model secular variation curve for the past few millennia for its applicability to the Indian region. Rock magnetic and AI investigations are carried out on 15 rare Megalithic/Iron Age (300–500 BC) pottery samples from the Sengalur site, Tamilnadu, India. Rock magnetic results indicate that either SD/PSD type of ferrimagnetic mineral (magnetite/titanomagnetite) is responsible for magnetic remanence. Temperature versus susceptibility experiments for most of the samples yield reversible heating and cooling curves with Curie temperatures of 565–585 °C. AI values are determined by the Thellier–Thellier method as modified by Coe 1967 (Zero-field/In-field method). The AI data of the present study meets the reliability and quality criteria adopted for the AI determinations worldwide. The mean AI of 47.48 ± 1.72 µT and a mean Virtual Axial Dipole Moment of 11.7 ± 0.4 × 10²² Am² are estimated. This new AI data are in good agreement with the predictions of ARCH3K.1 GGF model for the period of 300–500 BC for India derived from the GEOMAGIA. V₃ updated database. Other models incorporating sediment data are not consistent with the actual values of direct determination.

The spatial paleoceanography of the entire Western Interior Seaway (WIS) during the Cenomanian-Turonian Oceanic Anoxic Event (OAE2) has been reconstructed quantitatively for the first time using Geographic Information Systems. Models of foraminiferal occurrences—derived from Dempster–Shafer theory and driven by fuzzy sets of stratigraphic and spatial data—reflect water mass distributions during a brief period of rapid biotic turnover and oceanographic changes in a greenhouse world. Locality data for four benthic and one planktic foraminiferal species and lithologic and geochemical data from sites distributed throughout the WIS were compiled from four ammonoid biozones of the upper Cenomanian and lower Turonian stages. Of the 14 environmental parameters included in the dataset, percent silt, percent total carbonate, and depositional environment (essentially water depth) were associated with foraminiferal occurrences. The inductive Dempster–Shafer belief models for foraminiferal occurrences reveal the positions of northern and southern water masses consistent with the oceanographic gyre circulation pattern that dominated in the seaway during the Cenomanian/Turonian Boundary Event. The water-mixing interface in the southwestern part of the WIS was mostly restricted to the Four Corners region of the US, while the zone of overlap of northern and southern waters encompassed a much larger area along the eastern margin, where southern waters occasionally entered from the tropics. In addition to its paleospatial significance, this study introduces a rigorous, quantitative methodology with which to analyze paleontological occurrence data, assess the degree of uncertainty and prioritize regions for additional data collection.

Analog archival data can supplement modern digital research, but only if those data are preserved, described, and migrated to appropriate formats. The National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder (CU) is responsible for managing, archiving, and disseminating cryospheric and polar data. The clear majority of these data are digital, but the NSIDC also houses a collection of historical archival materials that include measurements related to the earth's glaciated regions prior to the development of modern instrumentation. Their formats, however, are not conducive to contemporary analysis, rendering them ostensibly “lost” to research. This paper describes a series of efforts to provide access to these collections that date back to their original acquisition, as long ago as the mid-nineteenth century, with focus primarily on activities over the last 15 years. The most recent effort was funded by the Council on Library & Information Resources and won the 2016 International Data Rescue Award. The intent is to highlight key challenges, and our proposed own solutions to those challenges, in designing a digitization project centered on providing online access to analog data in glaciological, geomorphological, and related research.

A new integrated and generic Spatial Decision Support System (SDSS) is presented based on a combination of Artificial Intelligence and Multicriteria Decision Analysis techniques. The approach proposed is developed to address commonly faced spatial decision problems of site selection, site ranking, impact assessment and spatial knowledge discovery under one system. The site selection module utilises a theme-based Analytical Hierarchy Process. Two novel site ranking techniques are introduced. The first is based on a systematic neighbourhood comparison of sites with respect to key datasets (criterions). The second utilises multivariate ordering capability of one-dimensional Self-Organizing Maps. The site impact assessment module utilises a new spatially enabled Rapid Impact Assessment Matrix. A spatial variant of General Regression Neural Networks is developed for Geographically Weighted Regression (GWR) and prediction analysis. The developed system is proposed as a useful modern tool that facilitates quantitative and evidence based decision making in multicriteria decision environment. The intended users of the system are decision makers in government organisations, in particular those involved in planning and development when taking into account socio-economic, environmental and public health related issues.

A sediment core aged up to ∼300 kyr from the Equatorial Indian Ocean (EIO) was examined for its inorganic and organic geochemistry, the objective being to identify coherent markers of glacial–interglacial changes and hydrocarbons as biomarkers with additional unique abilities in the deciphering of the oceanic environment. CaCO₃ and biogenic silica (BSi) were dominant constituents of sediments but with no clear glacial–interglacial pattern. The Al:Ti ratio was lowest during the second half of marine isotope stage (MIS) 7 and at the MIS 3/2 transition attributed to higher energy terrestrial (river) input during these interglacials. Concurrently total alkanes (T_alk, the sum of C₈C₃₈ normal alkanes) were high (761 and 446 ppb respectively), and they were dominated by the longer chain (C₂₃C₃₄) alkanes (LCA). Coccoliths were a major contributor to phytoplankton then as indicated by their proxy the C₃₇:C₃₈ alkane ratio. The carbon preference index of LCA (CPI_23–34, 2.39 ± 1.01), its linear increase against T_alk, and the predominance of C₂₉ and C₃₁ alkanes indicated that terrestrial source was a dominant input throughout the core. At the same time, the CPI of shorter chain alkanes CPI_15–22 of the core sediments was low (0.40 ± 0.22) and indicated significant microbial reworking on (phytoplankton originated) organic matter. Newly parameterized as even-over-odd preference (EOP_15–22 = 1/CPI_15–22), this bacterial re-working was linearly related to terrestrial organic matter (T_alk) and inferred that either interglacial epochs were more productive or during glacial epochs the bacterial re-working was limited by bottom water sub-oxicity. The latter was supported by a new phytane–T_alk linear relationship. In glacial sediments, T_alk was lower and phytane increased more steeply against it than in the interglacial sediments. This relationship supports higher terrestrial flux during the interglacials, and indicated that during glacial epochs, suboxic condition prevailed at sediment–water interface agreeing with the established sluggishness of the Antarctic Bottom Water flow.

Legacy soil data have been produced over 70 years in nearly all countries of the world. Unfortunately, data, information and knowledge are still currently fragmented and at risk of getting lost if they remain in a paper format. To process this legacy data into consistent, spatially explicit and continuous global soil information, data are being rescued and compiled into databases. Thousands of soil survey reports and maps have been scanned and made available online. The soil profile data reported by these data sources have been captured and compiled into databases. The total number of soil profiles rescued in the selected countries is about 800,000. Currently, data for 117, 000 profiles are compiled and harmonized according to GlobalSoilMap specifications in a world level database (WoSIS). The results presented at the country level are likely to be an underestimate. The majority of soil data is still not rescued and this effort should be pursued. The data have been used to produce soil property maps. We discuss the pro and cons of top-down and bottom-up approaches to produce such maps and we stress their complementarity. We give examples of success stories. The first global soil property maps using rescued data were produced by a top-down approach and were released at a limited resolution of 1 km in 2014, followed by an update at a resolution of 250 m in 2017. By the end of 2020, we aim to deliver the first worldwide product that fully meets the GlobalSoilMap specifications.