Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p> Avalonia, defined by its distinctive uppermost Ediacaran–Ordovician overstep sequence, extends from New England through Atlantic Canada to Wales. It unconformably overlies: (1) parts of one cratonic Neoproterozoic arc that which records several pulses at: 760–730 Ma, 680–600 Ma and 580–540 Ma; (2) an 800–760 Ma passive margin sequence; and (3) <jats:italic>c.</jats:italic> 976 Ma isolated plutons, possibly basement. Comparisons with modern arc dimensions suggest the dip of the Benioff Zone ranged from <jats:italic>c.</jats:italic> 22° W in Newfoundland to <jats:italic>c.</jats:italic> 52–67° elsewhere. A 600–580 Ma hiatus in arc magmatism in Cape Breton Island is attributed to overriding an oceanic plateau, leading to a 15° decrease in the dip of the Benioff Zone. The Collector magnetic anomaly along the Grand Banks and the Minas Fault is inferred to mark the Neoproterozoic southern margin of the Avalon Plate consisting of leaky transform faults and trench segments characterized by magnetite serpentinite mantle wedge beneath forearcs. The Minas Fault/Collector Anomaly connects similar arc units in Cape Breton Island and southern New Brunswick, suggesting that they were already offset by the Minas transform fault in the late Neoproterozoic. Similar tectonic, palaeomagnetic and isotopic data in the Timan Orogen of Baltica suggest that Avalonia may correlate with the Kipchak arc. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Special Publication 542 is a tribute to the remarkable career of J. Brendan Murphy and features 32 articles by 128 authors from 19 different countries; a testament to the high-profile and far-reaching influence of Brendan's work. The topics are wide-ranging in accord with Brendan's diverse research interests, but fall into three broad categories that encompass Brendan's main fields of influence: (i) supercontinents and the supercontinent cycle, including reconstructions and modeling, (ii) orogenesis and terranes, with a focus on the Appalachian-Variscan and Central Asian orogenic belts and the oceans with which they are associated, and (iii) magmatism and magmatic processes, with an emphasis on the geochemistry and isotopic compositions of magmas in arc and rift settings. Like Brendan's own research, the scope of the papers span the globe from Canada to China and range from regional field-based studies to conceptual global analyses. All of the articles, however, are focused on unraveling some critical aspect of geology or aimed at clarifying some crucial geologic process. Hence they also share a theme common to Brendan's many contributions in emphasizing the importance of process-oriented research.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Songpan-Garze terrane is the largest Triassic remnant flysch basin on Earth that formed as the Palaeo-Tethys Ocean closed during the final amalgamation of the Pangaea supercontinent. However, the origin of the Songpan-Garze terrane is highly controversial. A synthesis of the tectonic evolution of the Palaeo-Tethys Ocean and its branches surrounding the Songpan-Garze terrane is presented, which clarifies the nature and relationships among the many Palaeo-Tethys sutures. Provenance analyses suggest that branches of the Palaeo-Tethys near the Songpan-Garze terrane closed before the Early Triassic. In contrast, the main Palaeo-Tethys Ocean (Longmu Co-Shuanghu) did not close until the early Late Triassic. This study argues against the Songpan-Garze terrane being a remnant ocean basin, and proposes that it was a back-arc basin of the main Palaeo-Tethys Ocean. It initially underwent extension by the combined effects of the main Palaeo-Tethys Ocean subduction and the Emeishan mantle plume in the Late Permian, and subsequently developed into a back-arc basin in the Triassic to deposit huge turbidites derived from all surrounding terranes or orogens. The final closure of the main Palaeo-Tethys Ocean in the early Late Triassic and subsequent continent-continent collision led to basin inversion in the Late Triassic.</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.6751582">https://doi.org/10.6084/m9.figshare.c.6751582</jats:ext-link> </jats:p>

<jats:title>Abstract</jats:title> <jats:p>What drives the breakup of a supercontinent remains contentious. Previously proposed mechanisms include mantle plumes, subduction retreat and basal traction from mantle convection. Here we review the geological record of plumes, orogens and subduction zones during the breakup of Pangaea and investigate the potential roles played by these factors through 4D spherical geodynamic modelling. We found that mantle plumes provided the dominant force that drove the breakup of Pangaea, particularly in triggering the initial breakup. Young orogens as continental lithospheric weak zones generally guided the development of continental rifts, consistent with the geological record that rifting within Pangaea commonly developed along pre-existing orogens. However, the marginal drag force produced by subduction retreat, and basal traction associated with subduction-related mantle flow, likely also played a role in the breakup of Pangaea. In addition, the weakening effect of plume-induced melts can sometimes help to break the continental lithosphere away from orogens, as exemplified by the breakup between Antarctica and Australia. Furthermore, geodynamic modelling suggests that subduction is responsible for generating mantle plumes. A particular such example is the formation of the Kerguelen plume, triggered by subduction along the northern margin of Australia, which facilitated the breakup between East Antarctica and Australia.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> The pre-accretionary shapes of cratonic margins form successions of promontories and re-entrants inherited from the rifting of supercontinents. In accretionary orogens, the extent of deformation related to a collision with a continent characterized by an irregular margin is obfuscated through the partitioning of deformation along pre-existing structures. In the Northern Appalachians, the extent of the deformation related to the oblique collision of the Meguma terrane with the composite Laurentian margin is disputed. Herein, we use a framework based on modern collisional settings to investigate the Late Devonian to Mississippian deformation inboard of the Avalonia - Meguma boundary and evaluate the regional tectonic setting. We combine published shear zone kinematic interpretations, deformation ages, and regional <jats:sup>40</jats:sup> Ar/ <jats:sup>39</jats:sup> Ar cooling ages with structural interpretation of aeromagnetic and gravimetric depth slices covering the Northern Appalachians. We find that the deformation related to the collision of the Meguma terrane, attributed to the Neoacadian orogeny, has a larger structural footprint than previously documented. While this deformation is partitioned in multiple structures in the Canadian Appalachians, northern New England is characterized by rapid crustal deformation, high paleo-elevation, and fast erosional exhumation, similar to modern syntaxis structures. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>Collisional orogeny is characterized by deep subduction of continental crust and major crustal thickening, leading to high-pressure/high-temperature metamorphism and anataxis of the subducted continental crust. Since conductive heating of large slabs of cold, subducted continental crust is a slow process, heating up to a temperature that is high enough to generate significant partial melting can take tens of millions of years. Where the spatial and temporal relationships are obscured due to later modification (e.g., post-collisional rifting), the peak metamorphism and magmatism may be interpreted as an orogeny that is separate from the collision, or may be interpreted as an intraplate orogeny as no contemporaneous arcs or ophiolite may be present. We propose here that this is the case for the early Paleozoic orogeny in South China. In our model, the West Cathaysia terrane of South China was part of a continent (possibly Australia) on the lower plate and collided with another continent (possibly India) in Cambrian-Ordovician, at the late stage of Gondwana assembly, and the late Ordovician-Silurian Wuyi-Yunkai orogeny, characterized by amphibolite-granulite facies metamorphism and extensive anataxis, was a continuation of the Cambrian-Ordovician collisional orogeny. In this interpretation, the Wuyi-Yunkai orogen was part of the Kuunga orogen before Gondwana breakup.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The core of the Rodinia supercontinent has long been considered to have consisted of three cratons – Baltica, Laurentia and Amazonia – amalgamated along the late Mesoproterozoic Sveconorwegian, Grenville and Sunsas orogens. In recent years, however, it has become increasingly clear that the metamorphic and magmatic evolution of the Sveconorwegian orogen is inconsistent with a collisional model. Although geological data alone do not rule out proximity to Rodinia, palaeomagnetic data indicate significant latitudinal separation of Baltica and Laurentia during supercontinent assembly. In this contribution, we briefly review two recently proposed and mutually exclusive tectonic models for the Sveconorwegian orogeny and present a compilation of previously published and new chemical and isotopic data. A lack of crustal thickening throughout much of the orogen and few if any changes in lower-crustal sources and melting conditions between 1.3 and 0.9 Ga suggest that the western part of the Sveconorwegian orogeny represents a change from a dominantly extensional to a compressional back-arc regime, but without a significant change in overall tectonic setting. This orogenic evolution is incompatible with amalgamation into Rodinia and suggests that Baltica may have been isolated until the Silurian Caledonian orogeny.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> Oblique accretion zones often display transpressive, strike-slip, and transtensive structures of different orientations with respect to the convergence axis. The Late Devonian oblique collision of Meguma within the Canadian Appalachian orogen is often characterized as transpressive. However, the simultaneous opening of the Maritimes basin indicates that the orogenesis also partitioned into an extensional component. In this context, few of the shear zones reactivated during this time period have been characterized while accounting for the possibility of strain partitioning. To do so, we characterize the kinematics and timing of deformation of the Eastern Highlands shear zone (EHSZ) and the Coinneach Brook shear zone on Cape Breton Island, Nova Scotia, using a combination of U/Pb geochronology (zircon, monazite, xenotime, and apatite) and <jats:sup>40</jats:sup> Ar/ <jats:sup>39</jats:sup> Ar geochronology in situ and step heating experiments (amphibole, muscovite, and biotite). Results show that the Silurian EHSZ was reactivated ca. 385 to 367 Ma and the Coinneach Brook shear zone was formed ca. 395 to 369 Ma both yielding oblique kinematics. Together, these structures accommodated the rapid exhumation of the Cape Breton highlands during the docking of the Meguma terrane. This study thus highlights the heterogenous distribution of transtensive and transpressive deformation during the Neoacadian Orogeny. </jats:p>

<jats:title>Abstract</jats:title> <jats:p>In Mississippi, USA, exposures of fossiliferous Cretaceous and Paleogene strata contributed to geological investigations for more than 200 years. Since 2012, four Mississippi fossiliferous field sites were regularly integrated within university paleontology classrooms, with community engaged learning (CEL) introduced in 2018. Through CEL projects, the students assisted local organizations with optimizing and/or protecting local fossiliferous sites. Analysis of student surveys demonstrated that students were overwhelmingly positive toward local field sites and CEL inclusion in the paleontology courses. Students acknowledged ‘real-world’ interdisciplinary CEL experiences moved them beyond the paleontology content and made them stakeholders in modern issues. While these four sites contain landscapes that qualify as local geoheritage sites because of their educational and potential geotourism value, only one site, W.M. Browning Cretaceous Fossil Park, is preserved for future generations. The other sites (Blue Springs, Osborn Prairie, Smith County) face challenges in their long-term sustainability.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Milwaukee Formation, a sequence of Givetian (Middle Devonian) marine strata deposited in what is now southeastern Wisconsin, USA, was recognized as preserving an exceptionally diverse biota of invertebrates, placoderms, and plants, when local cement companies mined the rock for the manufacture of hydraulic cement from 1876 to 1911. It is now recognized as containing one of North America's most diverse biotas of its age coming from a single formation, having roughly 250 species, 100 families, 16 phyla, and four kingdoms. Intense collecting has revealed the rich biodiversity that prevailed during the Devonian Period in what is now the Milwaukee area. When the cement mines shut down, the quarries were filled and what was already regarded as a localized series of outcrops became even more restricted. Today the formation is known almost exclusively from limited exposures in Estabrook Park and the adjoining Lincoln Park, in Milwaukee County, in the area once occupied by the cement quarries. These outcrops (the type locality) are protected by a Milwaukee County Park Ordinance that prohibits removing materials from the parks, thus enabling the type locality to remain intact for educational and non-destructive research purposes, while largely unstudied museum collections remain available for ongoing research.</jats:p>