Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p> Geomechanics has a marked impact on the safe and sustainable use of the subsurface. This Special Publication contains contributions detailing the latest efforts in present-day <jats:italic>in-situ</jats:italic> stress characterization, prediction and modelling from the borehole to plate-tectonic scale. A particular emphasis is on the uncertainties that are often associated with geomechanics. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> The stress field controls patterns of crustal deformation, including which faults are likeliest to cause earthquakes or transmit fluids. Since the 1950s, maps of maximum horizontal stress ( <jats:italic>S</jats:italic> <jats:sub>Hmax</jats:sub> ) orientations have advanced dramatically, and the style of faulting (relative principal stress magnitudes) has recently been mapped in some regions as well. This perspectives paper summarizes developments in characterizing stress orientations and (relative) magnitudes, including new seismic and borehole methods, as well as progress in identifying the causes of stress variations. Despite these advances, adding far more spatiotemporal detail would allow geoscientists to address many of today's key challenges regarding natural hazards, energy development, and geodynamics. In particular, it is critically important to characterize stress heterogeneity at multiple scales while also recognizing the coherent variability of the stress field. The second part of the paper considers how more detailed stress datasets could prove essential to addressing some of the grand questions in geoscience, including deciphering the poorly understood feedbacks between crustal dynamics and surface processes, improving earthquake and eruption forecasts, and determining the origins and shared properties of plate boundaries. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Old-world rainforests of the Palaeotropical kingdom became established at different times in different regions with changing opportunities for plant dispersals in relation to Late Cretaceous and Cenozoic plate movements and climate change. The Palaeotropical and Neotropical kingdoms differentiated in the Late Cretaceous. Maastrichtian records of fossil <jats:italic>Dipterocarpus</jats:italic> pollen from Sudan show that canopy-forming dipterocarp genera evolved in Africa and Dipterocarpoideae and other taxa dispersed to India with the Africa-India floristic interchange. As the Indian Plate drifted towards Asia in the Eocene multiple lineages dispersed to Southeast Asia from about 48 Myr onward, replacing a depauperate flora of East Asian affinity. Tectonic models for Southeast Asia are in conflict, and the different models impact strongly on how to interpret the subsequent evolution of Southeast Asian rainforests. The lowland floras of the islands of Eastern Indonesia and Oceania originated due to dispersals mainly from Southeast Asia and became established after those areas rose above sea level during the Neogene. Palaeotropical rainforests formed in equatorial Africa during the Campanian, India in the late Maastrichtian to Paleocene, Southeast Asia in the middle Eocene and Oceania in the Miocene. The current megadiverse Southeast Asian rainforests are essentially sourced from immigrants. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Nordland area in northern Norway is the seismically most active area on mainland Fennoscandia. It exhibits patterns of coastal extension, which contrasts with the first-order regional stress pattern that reflects compression aligned with the North Atlantic ridge-push. The regional stress field has been considered to emanate from the interaction of ridge push and glacial isostatic adjustment; while the local stress pattern can be additionally influenced by gravitational, topographic stresses, as well as the flexural effects of erosion and sediment deposition.</jats:p> <jats:p>We employ finite element numerical models at a crustal scale to study the 3D stress field, using existing geometric constraints from previous geophysical studies. Internal body forces, induced by variations in density, topography or Moho depth, already yield significant deviatoric stresses. In the models tested, these can strongly influence the near-surface stress regime, in particular for the continental margin setting we are investigating.</jats:p> <jats:p>In addition, redistribution of rock mass, which occurred mainly under Pleistocene glaciation, can modify the stress field significantly on a semi-regional scale. We consider this process to be the main driver for the coastal extension, in particular in areas where erosion has been high.</jats:p> <jats:p>The northern Atlantic coast of Norway is an area of neotectonic activity and anomalous patterns in seismicity and land uplift. This study aims to improve our understanding of the present-day stress regime in this area. In addition, our study sheds light on the importance of stresses due to redistribution of sediments, a stress driver that is often neglected in stress studies. An earlier version of this manuscript was included in a non-peer reviewed project report (Gradmann et al., 2018).</jats:p>

<jats:p>How do tectonics and climate force surface processes and the evolution of biodiversity in Asia? This book examines some of the most biogeographically distinct and tectonically active areas on Earth today that straddle the highest mountains and spread across equatorial islands, offering insights into the complex processes driving their evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Native hydrogen and helium have been considered important resources in assisting the energy transition. Hydrogen and helium seeps have been reported worldwide, which may indicate large reserves within the subsurface. However, generation of hydrogen and helium is complex; poorly understood and constrained for both generation processes and migration. One source of native hydrogen is ultramafic rocks, which have experienced serpentinization together with water radiolysis. In contrast, helium generation occurs as the result of the radioactive decay of uranium and thorium present within radiogenically enriched basement. An exploration tool, dedicated to identifying areas with the geological settings and conditions favourable for native hydrogen and helium generation, has been developed and tested. Several databases have been created and integrated as part of this study (geological and geochemical generation models) to support and focus the search for both hydrogen and helium. Machine learning algorithms which extract value from geospatial data types for detecting various accumulations have been implemented. The first machine learning results demonstrate the significant value in integrating data and machine learning for high grading areas more conducive to accumulating hydrogen and helium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This contribution presents a detailed geological study of a well-exposed igneous petroleum system at Sierra de Cara Cura, Neuquén basin, Argentina, which consists of sills, dykes, laccoliths and hybrid intrusion morphologies. The size of the exposed intrusive complex (19 km in N-S direction) is similar to those of sill-clusters hosting producing oil fields of the nearby Río Grande Valley. Most sills (&gt;80%) are preferentially emplaced in the organic-rich rocks such as Vaca Muerta and Agrio Formations. Sills are extensively fractured and represent potentially good fractured hydrocarbon reservoirs. We document several fracturing mechanisms that can lead to heterogeneous fracture distribution. Laccoliths represent very different igneous reservoirs with a typical zonation: the core of the laccoliths are massive and poorly fractured, whereas the rims consist of a breccia formed during laccolith emplacement. The Vaca Muerta and Agrio Formations are thermally altered by the cooling of the sills. The deep parts of the outcropping laccoliths likely altered thermally the shale formations they were emplaced in. Hydrogen Index (HI) and Transformation Ratio (TR) of the organic matter are the best parameters to determine the thickness of the thermal aureole. The Sierra de Cara Cura appears as a world-class field analogue of igneous petroleum systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The Northern Carnarvon Basin (NCB) located on Australia's North West Shelf hosts an extensive (∼40,000 km <jats:sup>2</jats:sup> ) intrusive igneous complex related to Mesozoic rifting and breakup. Using an extensive suite of modern 3D seismic reflection surveys, we have mapped this intrusive system across the NCB. We identify three predominant intrusion morphologies: Stacked sheets of large interconnected sill intrusions (up to ∼170 km long) and smaller (8 to 30 km long) isolated, strata concordant intrusions, which often interact with normal faults emplaced into deltaic sedimentary rocks; and variably sized (10 to 40 km long) saucer-shaped intrusions emplaced into marine shales, spread across seven zones (geographically constrained groups of intrusions of a specific morphology). We consider the zones' margin-parallel orientation, suggesting control by sub-crustal extensional processes during rifting; and, variation in intrusion morphology between these zones, suggesting a dominant control by host rock mechanical properties. We integrate previous work with our observations, constraining emplacement to between the Kimmeridgian and Valanginian, coinciding with key phases of margin evolution. Finally, we assess the impact of this intrusive complex on local petroleum systems. There is likely little to no adverse impact on source rock maturation or reservoir contamination by CO <jats:sub>2</jats:sub> . But, there is a spatial dissociation between the location of groups of intrusions and the gas fields, particularly in the Exmouth Plateau; this suggests that migrating hydrocarbons may be blocked, baffled and/or redirected by emplaced igneous rocks. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Volcaniclastic rocks are commonly overlooked as reservoirs or seals in hydrocarbon plays because their compositions are variably unstable and reactive during burial diagenesis. This study investigated the petrography and petrophysical characteristics of 60 volcaniclastic and 4 siliciclastic samples from three Paleogene volcanic provinces - East Greenland, Faroe Islands, and Ethiopia. The volcaniclastic samples have highly variable helium porosities (average: 25.2%), but negligible total optical porosities (average: 1.9%) implying reduced reservoir potential. The samples have, however, highly variable air permeabilities (average: 11 mD) suggesting they could make tight reservoirs. The permeabilities are related to either early calcite cements or the devitrification of volcanic glass. Mercury Injection Capillary Pressure (MICP) data was collected for a subset of 33 samples that at leakage/breakthrough saturations could, under near-surface conditions, hold oil column heights of between 4 m and 1181 m (average: 240 m). The best seals consistently have zeolite contents of &gt;20 vol.% due to their small pore throat radii. Conversely, the worst seals are dominated by smectite and a conspicuous absence of zeolite minerals. The zeolite-rich volcaniclastic rocks could, therefore, make good shallow seals. These features also apply to CO <jats:sub>2</jats:sub> storage, but questions remain about the reactivity of the volcanic material and secondary minerals with injected CO <jats:sub>2</jats:sub> , but also the adsorbent properties of zeolites, particularly clinoptilolite, in the presence of CO <jats:sub>2</jats:sub> . </jats:p> <jats:p content-type="supplementary-material"> Supplementary material at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" specific-use="dataset is-supplemented-by" xlink:href="https://doi.org/10.6084/m9.figshare.c.6986188">https://doi.org/10.6084/m9.figshare.c.6986188</jats:ext-link> </jats:p>

<jats:title>Abstract</jats:title> <jats:p>We model maximum principal horizontal stress orientations in the Arabian Plate using a 3D finite element approach in conjunction with plate velocities. To capture the impact of geometry and tectonics, the model considers an accurate plate boundary shape and associated deformations. Three primary geological units represent plate architecture: sedimentary cover, crust, and upper mantle. The mesh resolution varies to capture important geometrical features. Subsequently, we calculate the stress field using the force balance equation. Displacement boundary conditions are evaluated as accumulative deformation.</jats:p> <jats:p> NE-SW S <jats:sub>Hmax</jats:sub> azimuths dominate in northeastern Saudi Arabia and Kuwait, whilst NW-SE to NNW-SSE define the Dead Sea area. The Red Sea Basin and Saudi Arabia's interior is characterized by N-S S <jats:sub>Hmax</jats:sub> azimuths. Iraq's western area shows azimuths from NNW-SSE to NW-SE due to the collision at the Zagros Mountain Range but changes to NE-SW in the east at the Zagros fold-and-thrust belt. </jats:p> <jats:p> An extensive literature review reveals publicly S <jats:sub>Hmax</jats:sub> azimuth data that augment the sparse records compiled in the World Stress Map database. Our simulated S <jats:sub>Hmax</jats:sub> azimuths are consistent with these data. The results further corroborate ongoing tectonic processes, deepen our understanding of in-situ stress variation drivers, and inform current elastic deformation mechanisms in the Arabian Plate. </jats:p>