Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In March 1833 Charles Darwin discovered Devonian fossils in the Falkland Islands. He was excited by his find but could have had little premonition of the long-running geological controversy that he was initiating. Darwin's fossils matched a coeval South African fauna and, as further collections were made, the association was apparently strengthened. A particularly important contribution arose around 1910 through collaborations between a local collector, Constance Allardyce, and professional palaeontologists: Ernest Schwarz in South Africa and John Clarke in the USA. The accumulating evidence was seized upon by the early proponents of ‘displacement theory’ – continental drift – notably Alexander Du Toit, who relocated the Falkland Islands northward for his 1927 South Atlantic reconstruction. A more radical, but geologically sounder proposal arose in 1952 when Ray Adie suggested that the Falkland Islands, rotated through 180°, had originated as the eastward culmination of the Cape Fold Belt and Karoo Basin. In effect, Adie had presciently described a rotated microplate, perhaps the first on record. An opposing view saw the Falkland Islands as part of a fixed, South American promontory, and argument around these two contrasting interpretations of South Atlantic geology continues to the present day.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Mass transport deposits have long been known on the Exmouth Plateau, offshore NW Australia, identified in 2D and 3D industry seismic lines. The expedition SO257 in 2017 collected 30 high-resolution, shallow seismic lines along targeted transects on the northern Australian margin. Many of these imaged mass transport deposits, with the top 700–800 m of the section captured in detail not available with industry seismic data. We present nine new high-resolution seismic lines from three separate areas of the North West Shelf. Slides in the Roebuck Basin show complex anastomosing ductile extensional mechanisms, with multiple slip surfaces and no headscarps or adjacent faults. Slides on the Exmouth Plateau have fault control, with surface fault offsets of up to 300 m, indicating seismicity as a likely triggering mechanism. Slumps along the western margin of Western Australia are more limited in extent, associated with surface notches, with indications of previous activity at depth. All areas show a repeated history of mass transport deposits. The area of the active landslide province offshore of NW Australia is far larger than the individual slides recognized on the Exmouth Plateau.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The late Carboniferous (Middle Pennsylvanian, ∼307 mya) <jats:bold>Mazon Creek Lagerstätte</jats:bold> found in Northern Illinois, USA is unique for its exceptional biotic diversity as well as the human endeavors, both professional and avocational, that brought vast numbers of fossils and new species to science. In 1997, the Mazon Creek Fossil Beds, exposed along the Mazon River near Benson Road, Morris Illinois became a National Historic Landmark. </jats:p> <jats:p> The fossils are preserved in siderite (iron carbonate, FeCO <jats:sub>3</jats:sub> ) concretions within the lower 3-8 meters of the Francis Creek Shale Member of the Carbondale Formation, and often retain outlines of original soft tissues. The Mazon Creek biota includes over 465 animal and 350 plant species representing more than 100 orders, which is attributed to the preservation of organisms from multiple habitats and the large number of specimens collected. That phenomenon was made possible by coal extraction bringing concretions to the surface and highly motivated amateur collectors pursuing them. Some of the formerly mined areas continue to draw collectors and are preserved as part of the Mazonia-Braidwood State Fish and Wildlife Area. The fossils, fossil collectors and collection sites are a significant part of our cultural and scientific geoheritage. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Along continental margins with rapid sedimentation, overpressure may build up in porous and compressible sediments. Large-scale release of such overpressure has major implications for fluid migration and slope stability. Here, we study if the widespread crater-mound-shaped structures in the subsurface along the mid-Norwegian continental margin are caused by overpressure that accumulated within high-compressibility oozes sealed by low-permeability glacial muds. We interpret 56 000 km <jats:sup>2</jats:sup> of 3D and 150 000 km <jats:sup>2</jats:sup> of 2D-cubed seismic data in the Norwegian Sea, combining horizon picking, well ties and seismic geomorphological analyses of the crater-mound landforms. Along the mid-Norwegian margin, the base of the glacially influenced sediments abruptly deepens to form 28 craters with typical depths of <jats:italic>c.</jats:italic> 100 m, areal extents of up to 5130 km <jats:sup>2</jats:sup> and volumes of up to 820 km <jats:sup>3</jats:sup> . Mounds are observed in the vicinity of the craters at several stratigraphic levels above the craters. We present a new model for the formation of the craters and mounds where the mounds consist of remobilized oozes evacuated from the craters. In our model, repeated and overpressure-driven sediment failure is interpreted to cause the crater-mound structures, as opposed to erosive megaslides. Seismic geomorphological analyses suggest that ooze remobilization occurred as an abrupt energetic and extrusive process. The results also suggest that rapidly deposited, low-permeability and low-porosity glacial sediments seal overpressure that originated from fluids being expelled from the underlying high-permeability and high-compressibility biosiliceous oozes. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> Wadi Al-Hitan is a UNESCO World Heritage Site in the Western Desert of Egypt famous for the fossils it has produced, including some of the most complete skulls and skeletons of Eocene whales known anywhere in the world. Most are from the early part of the late Eocene epoch of earth history and lived in the Tethys Sea some 38 to 36 million years before present. <jats:italic>Basilosaurus isis</jats:italic> and <jats:italic>Dorudon atrox</jats:italic> are the most abundant and best known of the archaic whales. Sea cow skeletons are present as well, as are bones or teeth of a bird, crocodiles, turtles, bony fishes, and a diversity of sharks and rays. The fossils are preserved in sedimentary strata that accumulated as sea level rose and fell, producing a succession of nearshore marine environments. Rocks exposed at the surface, now dissected by erosion, enable study of stratigraphic sequences and their architecture. Taken together, the fossil-and-strata geoheritage of Wadi Al-Hitan has exceptional value for science and for public education. </jats:p>

<jats:title>Abstract</jats:title> <jats:p> While Olduvai Gorge, Tanzania, is most famous for its impressive and formative record of early human technology, Pleistocene fauna, and hominin fossils, its geological record is equally important. At Olduvai, palaeoanthropologically significant sites are often preserved in primary context (not redeposited), and they can be contextualized within the palaeoenvironments in which the hominins lived. This has provided an exceptional opportunity to assess not only hominin evolutionary changes over time, but also to understand their adaptive behavior including toolmaking, foraging, and sociality. Abundant volcanic material from the nearby Ngorongoro Volcanic Highlands (NVH), interspersed within and between archaeology-bearing deposits, made Olduvai a target for some of the earliest applications of radiometric dating using the K/Ar system. Ultimately, the <jats:sup>40</jats:sup> Ar/ <jats:sup>39</jats:sup> Ar dating system has produced ages with exceptional precision. Early radiometric dating at Olduvai helped establish the antiquity of the hominin lineage, and early palaeomagnetic studies (and the “Olduvai event,” the longest normal subchron within the reversed Matuyama Chron) was critical in establishing the importance of Olduvai in the field of geochronology. More recently, high-resolution palaeoclimate studies of the palaeolake that once occupied the Olduvai basin have helped to reconstruct the palaeoenvironments encountered by hominin species. Over a century of geological research has secured Olduvai's status as an important site for geoheritage. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Geoparks and the valorization of sites with a strong geoheritage component are a new frontier for sustainable tourism. An UNESCO special recognition was established in 2015 and much work has been done for establishing sites in Europe and Asia, but only five localities have been recognized by UNESCO in North America. This paper discusses three sites relevant to geoheritage: Pulpit Rock in Massachusetts, Montmorency Falls in Quebec and Niagara Falls that were visited in 1863, by the newly appointed professor of geology at the Bologna University, Giovanni Capellini, who sailed for a four-month journey across north-eastern North America. Through his travels, he made sketches, took notes, and collected more than 2,000 specimens that together provide a depth of perspective on the importance of the geoheritage of sites he visited. We chose these sites, among the many visited by Capellini, because Niagara Falls is now seeking the UNESCO recognition, and the other two, though no longer fully accessible (Montmorency Falls and Pulpit Rock) remain important tourist sites and areas of geological interest.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The Cretaceous Period was marked by the formation of numerous Large Igneous Provinces (LIPs), several of which were associated with geologically rapid climate, environmental, and biosphere perturbations, including the early Aptian and latest Cenomanian Oceanic Anoxic Events (OAEs 1a and 2, respectively). In most cases, magmatic CO <jats:sub>2</jats:sub> emissions are thought to have been the major driver of climate and biosphere degradation. This work summarises the relationships between Cretaceous LIPs and environmental perturbations, focussing on how volcanism caused climate warming during OAE 1a using osmium-isotope and mercury concentration data. The new results support magmatic CO <jats:sub>2</jats:sub> output from submarine LIP activity as the primary trigger of climate warming and biosphere stress before/during OAE 1a. This submarine volcanic trigger of OAE 1a (and OAE 2), two of the most climatically/biotically severe Cretaceous events, highlights the capacity of oceanic LIPs to impact Earth's environment as profoundly as many continental provinces. Cretaceous magmatism (and likely output of CO <jats:sub>2</jats:sub> and trace-metal micronutrients) was apparently most intense during those OAEs; further studies are needed to better constrain eruption histories of those oceanic plateaus. Another open question is why the Cretaceous Period overall featured a higher rate of magmatic activity and LIP formation compared to before and afterwards. </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.7026011">https://doi.org/10.6084/m9.figshare.c.7026011</jats:ext-link> </jats:p>

<jats:title>Abstract</jats:title> <jats:p>The explosive radiation of early birds has been well documented by the extraordinary discoveries of the Early Cretaceous fossil birds from China in the past three decades. They have greatly expanded the diversity, disparity, and temporal distribution of Mesozoic birds, refining our knowledge of the evolutionary path leading to the characteristic avian body plan, such as feathers and powered flight, locomotion and habitat differentiation, diet and digestion, reproduction and development, feather colors and display. In addition, studies on the geological background of the Jehol Biota that produced the majority of the Chinese Cretaceous birds have provided important clues to our understanding of the taphonomy as well as the interaction between deep geology process and biological evolution in northeastern China and East Asia during the Early Cretaceous. Future multidisciplinary studies are expected to advance our knowledge of how the paleogeography of Early Cretaceous birds was formed, what had impacted the changes of the diversity of early birds in China, and the roles of early birds had played in the Early Cretaceous terrestrial ecosystem.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Volcanogenic-sedimentary and coal-bearing deposits, which contain abundant fossils of a lacustrine fauna and terrestrial flora, are widespread in the territory of Transbaikalia (Russia), Mongolia, and Northeastern China. These ecosystems are known under the name of ‘Jehol Biota’, which occurs in the Yixian and Jiufotang formations. The discovery of ‘feathered’ dinosaurs and of the earliest angiosperms in western Liaoning Province (China) made them world famous. The history of this biota began in the nineteenth century, when the discoveries in Transbaikalia of the remains of conchostracans, ostracods, insects, fish, and plants collected during the expedition of A.F. Middendorf were described. The Barremian–Aptian sedimentary sequences of Transbaikalia (Russia), Mongolia, and Northeastern China are very similar. The appearance and evolution of the Jehol Biota occurred against the background of extensive volcanism and tectonic revival, after which normal sedimentary rocks were deposited, culminating in relief peneplanation, swamp development and peat formation. The northern limit of the distribution of this biota is determined as up to about 54° modern north latitude. The existence of the Siberian Jehol Biota in extreme climatic conditions is confirmed, as was indicated for the Jehol Biota from Northeast China.</jats:p>