Hasil untuk "Geology"

W. C. Krumbein

A. Robertson, J. Dixon

E. Hamilton

A. Gentry

The interchange of plant species between North and South America has been a major factor in determining the Neotropical phytogeographical patterns observed today. Although this has long been realized, recent historical geological evidence as well as increasing knowledge of today's distributional patterns now makes possible a more thorough analysis of how these patterns originated. This paper briefly reviews the geological background, summarizes the composition of the extant Neotropical flora, points out the striking ecological consistency of many taxa and life forms, and suggests how some of the present phytogeographical patterns have developed from the interplay of these factors.

G. Boulton, R. Hindmarsh

M. Farabee

P. Marinos, E. Hoek

K. Kashefi, D. Lovley

K. Gallagher, Roderic Brown, Christopher J. Johnson

Haley Svadlenak, Ross Parnell‐Turner, Margaret Morris

Abstract Tectonic subsidence, sea level, and paleoclimate reconstructions using marine records rely on accurate decompaction of the sediment column. Over time, increased overburden pressure from burial decreases sediment porosity with depth. The porosity‐depth relationship is lithology‐dependent and can be represented by an exponential function determined by initial porosity at the seafloor and compaction decay length. While site‐specific compaction parameters are useful for most studies, these are often unrepresentative due to an insufficient number of measurements. Existing, commonly applied parameter estimates are based upon a handful of spatially restricted sites and lack meaningful uncertainty constraints. We compiled a global porosity data set consisting of 31,808 moisture and density measurements from 280 scientific ocean drilling sites visited during 60 Integrated Ocean Drilling Program and International Ocean Discovery Program (IODP) expeditions between 2009 and 2024. Using bootstrapping techniques, we resampled and fit porosity measurements 10,000 times using nonlinear least squares to obtain compaction parameters and uncertainties both globally and independently for sites in the Pacific, Atlantic, Indian, and Southern Oceans. Measurements from samples dominated by a single lithology (>75%) were used to obtain lithology‐dependent parameters. Average compaction behavior for marine sediments can be described with an initial porosity of 66.3±2.0% and a decay length of 1399±120 m. Our results confirm the lithology‐dependence of these parameters and indicate that sediment compaction behavior is consistent across ocean basins. These globally‐applicable parameters and uncertainties are a valuable resource for evaluating sediment decompaction and will enable error quantification in subsequent analyses of basin evolution and sedimentation.

A. Lord, P. Kobos, D. Borns

C. Stern

El arco volcanico andino incluye mas de 200 estratovolcanes y, al menos, 12 sistemas de calderas gigantes potencialmente activos, dispuestos en cuatro segmentos separados de la cadena andina conocidos como Zonas Volcanicas Norte, Central, Sur y Austral, y cuya actividad es producto de la subduccion de las placas oceanicas Nazca y Antartica bajo la placa sudamericana. Los cuatro segmentos con volcanismo activo ocurren en zonas donde el angulo de subduccion es relativamente inclinado (25°), y entre ellos existen regiones donde el angulo de subduccion es relativamente plano (<10°) a profundidades 100 km y el volcanismo esta ausente. Las zonas de bajo angulo de subduccion habrian comenzado a formarse durante el Mioceno debido a la subduccion de plateaus y dorsales oceanicas, indicando que la actual segmentacion de la zona de subduccion y el volcanismo andino es un rasgo transitorio relacionado a la actividad tectonica neogena. La relacion genetica entre subduccion y volcanismo ha sido confirmada por estudios geoquimicos que indican que la actividad magmatica se inicia por la deshidratacion y/o fusion de la litosfera oceanica subductada y la interaccion de los fluidos liberados con el manto astenosferico que la sobreyace. Componentes derivados de la corteza continental son tambien incorporados en los magmas andinos a traves de la erosion por subduccion del margen continental y/o asimilacion de material cortical en los magmas derivados del manto. Las variaciones en la tasa de erosion por subduccion y subduccion de corteza continental afectan en forma significativa no solo la quimica de los magmas andinos, sino tambien el acomplamiento mecanico de intraplaca en la zona de subduccion y la dinamica orogenica a lo largo de los Andes. Componentes corticales son mas significativos en los magmas extruidos en la Zona Volcanica Central donde la corteza es extremadamente gruesa (70 km) y las tasas de erosion por subduccion del margen continental alcanzan, posiblemente, a consumir un volumen de rocas equivalente hasta un 4% del volumen de la corteza oceanica subductada, son tambien muy elevadas debido a las condiciones climaticas hiperaridas y el bajo aporte de sedimentos a la fosa. Lavas, flujos piroclasticos, lahares, flujos de detritos producto de colapso sectorial de estratovolcanes, y la caida de tefra son algunos de los peligros y riesgos mas importantes asociados al volcanismo andino. Desde el ano 1532 mas de 25.000 personas han muerto como consecuencia de 600 erupciones con registro historico. La mayor parte de estas muertes ocurrio en 1985 durante la erupcion de los Nevados del Ruiz en Colombia. A pesar de que mas de 20 millones de personas viven a menos de 100 km de distancia de un volcan activo en los Andes, principalmente en los valles interandinos de Colombia y Ecuador y el Valle Central del centro-sur de Chile, en la actualidad, menos de 25 volcanes estan siendo monitoreados para determinar los riesgos potenciales asociados a la actividad volcanica andina.

L. Nyquist, D. Bogard, C. Shih et al.

Elnur Baloglanov, Ulviyya Yolchuyeva, Ruslan Akhundov et al.

Problem statement. This study explores unconventional hydrocarbon resources in East Azerbaijan, focusing on oil-bearing rocks in the Cheyildere and Gyrgyshlag-Girdagh areas. It examines the spatial and temporal distribution of minerals and chemical compositions in Miocene formations. Terrigenous quartz types identified in the Maikop (Lower Miocene), Chokrak (Lower Miocene), and Diatom (Middle to Upper Miocene) formations provide insights into sedimentological maturity. Geochemical classification and tectonic discriminant diagrams help interpret the protoliths of these sediments. The study also evaluates how mineralogy and moisture affect oil-bearing potential, offering useful data for future exploration and resource management. Purpose. This study aims to explore the genesis and potential of oil-bearing deposits of the Miocene age in East Azerbaijan by characterizing the geological, mineralogical, and geochemical proxies of samples collected from outcrops across various regions. Methods. The mineralogical composition of samples was analyzed using a MiniFlex 600 diffractometer. Chemical composition was determined using S8 TIGER Series 2 and Agilent 7700 Series ICP-MS spectrometers. Results. The geological characteristics of oil-bearing deposits from the Miocene stratigraphic unit were thoroughly analyzed, providing new insights into the distribution patterns of oil-bearing formations and strata within the studied areas. The mineralogical composition was examined in detail, focusing on the spatial and temporal variations in mineral distribution across different formations of Miocene. The chemical composition reveals significant differences between formations in terms of elemental signatures. The study of the chemical proxies enabled the identification of specific terrigenous quartz types. Additionally, the research assessed the influence of mineralogical composition, moisture and oil content on the oil-bearing capacity. The results demonstrated a clear relationship between the mineralogical characteristics and the oil-bearing potential of the rocks. Conclusions. The Chokrak Formation is of particular interest due to its significant oil-bearing potential, with total thicknesses of up to 40 meters in Miocene outcrops studied in the areas of Cheyildere and Gyrgyshlag-Girdagh. Compared to other areas, the Chokrak Formation is dominated by quartz minerals (>70%), while the oil-bearing rocks of this formation contain fewer clay minerals and no carbonate minerals. The Upper Maikop deposits are characterized by calcite, and the Diatom deposits by dolomite. Most oil-bearing rocks of Maikop and Diatom age correlate with greywacke and litharenite, while Chokrak rocks with higher silicon content show a connection with subarkose and sublitharenites. For Diatom oil-bearing rocks, in addition to quartzitic sedimentary sources, some moderate and acidic magmatic rocks can also be considered. Chokrak horizon deposits, rich in quartz, have a more mature mineralogical nature. These deposits, associated with passive continental margins, are typically linked to the interior of cratons or recycled orogenic regions, suggesting long-distance transport. Relatively moist samples containing clay and carbonate minerals exhibit a significantly higher oil accumulation potential than samples with high quartz content. From this perspective, the marly rocks of the Meotis are of particular interest.

M. Lombardo, A. Fees, A. Kaestner et al.

<p>Liquid water flow in snow is important for snow hydrology, remote sensing, and avalanche formation. Water flow in snow is often dominated by capillary effects, which are responsible for the formation of capillary barriers, capillary flow paths, and capillary rise. Unfortunately, there is little quantitative data on the capillary forces of snow, particularly with respect to capillary rise dynamics. Here, we present the results of 4 capillary rise experiments using neutron radiography. The experiments were performed in <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">13</mn><mo>×</mo><mn mathvariant="normal">13</mn><mo>×</mo><mn mathvariant="normal">1</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="55pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="f4ac5dd9c61a1e24aaa7701241619530"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-19-4437-2025-ie00001.svg" width="55pt" height="10pt" src="tc-19-4437-2025-ie00001.png"/></svg:svg></span></span> cm<span class="inline-formula">³</span> glass columns with sand-snow and sand-gravel-snow layering mimicking the capillary forces at the soil-snow interface. Images were taken at 10 to 15 s intervals with a pixel size of 92 <span class="inline-formula">µm</span>. The experiments provided quantitative results of high resolution liquid water profiles, wetting front progression, flow rates, and parameterization of snow hydraulic properties. The experiments showed that the snow properties influenced the capillary rise height while the hydraulic properties of the transitional layer below the snow influenced the flow rates. The saturated hydraulic conductivity values obtained from the experiments were below the expected values from the literature.</p>

Kazuyoshi Z. Nanjo, Takao Kumazawa, Jun Izutsu et al.

A magnitude (<i>M</i>) 7.7 quake struck on 6 February 2023 in Turkey. Nine hours later, a <i>M</i>7.5 quake occurred near the initial <i>M</i>7.7 quake. We studied seismicity before and after these doublet quakes, integrating physics-based and statistical approaches. We first used the statistical Epidemic-Type Aftershock Sequence (ETAS) and the Bayesian Gutenberg–Richter <i>b</i>-value models to confirm previously reported seismicity transients (seismic activation and low <i>b</i> values) prior to the future <i>M</i>7.7 quake. We then showed that the low <i>b</i>-value area coincided with a high-slip area on the strand segment from which the <i>M</i>7.7 rupture started, a similar result to that obtained for the 2011 Tohoku megaquake case in Japan. We next used the physics-based Coulomb and statistical <i>b</i>-value models to find that the locations of the largest and second-largest events in the post-doublet-quake sequence were in relatively high-stress regions and became closer to failure as a result of the doublet quakes. We further used the ETAS model to show that this sequence is currently active but is decaying with time. The duration of the sequence was estimated at 2.7–5.5 years, which is longer than previously proposed (1–2.5 years). Our result was stable because it was based on quake data from about 600 days, six times longer than the study period used in a previous study.

Lei Xue, Fengchang Bu, Hongran Chen et al.

Abstract Rock bridges have long been recognised to provide crucial resistance against rock mass failure. Multiple rock bridges with diverse scales are widespread in natural rock masses. Despite prior positive contributions to a single rock bridge, mechanical behaviours of diverse-scale rock bridges remain elusive. In particular, whether rock bridges interact and how their failure processes evolve are still open questions. To fill in this gap, a block-based discrete element method, specifically the Universal Distinct Element Code, was employed to simulate diverse-scale rock bridges in granite subjected to direct shear to investigate their mechanical properties, stress and displacement fields, cracking processes, and acoustic emission characteristics. Results reveal a fundamental linear correlation between peak shear resistance and the proportion of rock bridges. As failure progresses, shear stress tends to concentrate at rock bridge tips, more prominently for the one farther from the shear loading end, attributed to the rotation of confining pressure plates. In addition, the irregularity of displacement distribution follows an arc-shaped configuration near rock bridges, and larger rock bridges display lower gradients in nearby displacement fields. Furthermore, wing cracks initiate from rock bridge tips in a tensile stress environment, with a greater length for rock bridges closer to the shear loading end. It is also found that rock bridges rupture in tension near the shear loading end and in shear further away. Expanding upon these findings and considering stress thresholds, we acquire new insights into the interaction patterns between diverse-scale rock bridges: when their sizes are similar, the rupture of the rock bridge closer to the shear loading end will expedite damage in the one farther away from the shear loading end towards its volume-expansion point; conversely, the rupture of a significantly larger rock bridge will overwhelmingly affect the smaller one. The identified interaction patterns provide significant proof of physical precursor patterns for reliably predicting the progressive failure of multiple rock bridges.

Trias Aditya, Adrian N. Pamungkas, Faishal Ashaari et al.

Synchronous interactions from different locations have become a globally accepted modus of interaction since the COVID-19 outbreak. For centuries, professional cadastral survey activities always required an interaction modus whereby surveyors, neighboring landowners, and local officers were present simultaneously. During the systematic adjudication and land registration project in Indonesia, multiple problems in the land information systems emerged, which, up to date, remain unsolved. These include the presence of plots of land without a related title, incorrect demarcations in the field, and the listing of titles without a connection to a land plot. We argue that these problems emerged due to ineffective survey workflows, which draw on inflexible process steps. This research assesses how and how much the use of augmented and virtual reality (AR/VR) technologies can make land registration services more effective and expand collaboration in a synchronous and at distant manner (the so-called same time, different place principle). The tested cadastral survey workflows include the procedure for a first land titling, the one for land subdivision, and the updating and maintenance of the cadastral database. These are common cases that could potentially benefit from integrated uses of augmented and virtual reality applications. Mixed reality technologies using VR glasses are also tested as tools, allowing individuals, surveyors, and government officers to work together synchronously from different places via a web mediation dashboard. The work aims at providing alternatives for safe interactions of field surveyors with decision-making groups in their endeavors to reach fast and effective collaborative decisions on boundaries.

E. T. Gray

C. Kreemer, W. Holt, A. Haines