Asthenosphere viscosity in the Caribbean region constrained by gravity anomalies, seismic structure and regional magmatism

2020 ◽  
Author(s):  
Yi-Wei Chen ◽  
Lorenzo Colli ◽  
Dale E. Bird ◽  
Jonny Wu ◽  
Hejun Zhu
Keyword(s):  
Seismic Refraction ◽  
Gravity Anomalies ◽  
Oceanic Lithosphere ◽  
Caribbean Region ◽  
Seismic Structure ◽  
Dynamic Topography ◽  
Borehole Data ◽  
Pacific Side ◽  
The Caribbean ◽  
Free Air Gravity

<p>The Caribbean region has been proposed as a candidate for outflow of asthenospheric mantle, from a shrinking Pacific region to an expanding Atlantic region. If this flow exists it should be associated to a dynamic topography gradient across the region. Estimating dynamic topography requires constraining the thicknesses and densities of sediment, crust and lithosphere to remove their isostatic response from the total topography. Dynamic topography has been studied globally in areas of ‘normal’ oceanic lithosphere but the Caribbean region, characterized by overthickened oceanic lithosphere, has not been fully analyzed due to the challenges of estimating crustal thicknesses.</p><p>Thanks to the wealth of seismic reflection, as well as borehole data, the basement relief and bulk sediment density in the Caribbean are well constrained. We performed a structural inversion of free air gravity anomalies, constrained by seismic refraction data, to established an improved Moho surface which provides more detail than existing global models such as Crust 1.0. With the improved basement and Moho relief, we computed residual basement depth. We obtained a ~300 m dynamic topography high on the Pacific-side of the Caribbean, gradually decaying to 0 m to the east near the Aves ridge.</p><p>This result supports the hypothesis of Pacific outflow through the Caribbean. Assuming a ~200 km thick asthenosphere and a flow velocity a few to a few tens of cm/yr, as suggested by tomographic imaging and regional magmatism, our results suggest the viscosity is ~5*10<sup>18</sup> Pa s.</p>

Isostatic and dynamic controls on neotectonic differential vertical movements and sediment transport reorganization of the Pannonian Basin, Central Europe

2020 ◽  
Author(s):  
Attila Balázs ◽  
Ádám Kovács ◽  
Orsolya Sztanó ◽  
Liviu Matenco ◽  
László Fodor ◽  
...  
Keyword(s):  
Large Scale ◽  
Pannonian Basin ◽  
Numerical Models ◽  
Gravity Anomalies ◽  
Seismic Structure ◽  
Dynamic Topography ◽  
Mantle Dynamics ◽  
Vertical Movements ◽  
Preliminary Model ◽  
Sedimentary Fill

<p>Extensive geophysical studies on gravity anomalies and seismic structure of the Pannonian Basin have determined that this extensional sedimentary basin is more elevated than predicted by Airy-type isostatic compensation models. European regional models assuming a two-layered lithosphere containing a uniform crust and a lithospheric mantle estimated ca. 750-1000 meters difference between the actual and calculated isostatic topography for the Pannonian region.</p><p>We have revisited this early finding and calculated a refined residual topography map of the Pannonian Basin that also takes into account the low-density sedimentary fill. We show that the actual residual topography of the eastern part of the region is much lower than previously thought and ca. 4-500 meters of positive residual topography characterizes the central and western part of the Pannonian Basin.</p><p>In order to interpret the observed residual topography of the basin we carried out a series of elasto-visco-plastic thermo-mechanical numerical models. Our simulation of the last 9Myr covering the classical  “post-rift” phase of the Pannonian Basin analyzes forcing factors, such as asthenospheric-scale mantle convection, elastic flexure of the lithosphere due to increased external stress and sediment re-distribution, and ductile lower crustal deformation. The large-scale positive residual topography is dominantly controlled by mantle dynamics.</p><p>Finally, 3D stratigraphic numerical forward modelling has been carried out by DionisosFlow, constrained by our previously calculated tectonic scenario. We analyzed the substantial reorganization of the main sedimentary transport routes in the Pannonian Basin mainly controlled by the development of the observed positive dynamic topography of the basin. Our preliminary model results are in good agreement with geological records, such as the ca. 200 km Pliocene eastward migration of the Paleo-Danube drainage network.</p>

Seismic refraction survey in the Western Approaches to the English Channel: preliminary results

1975 ◽  
Vol 279 (1288) ◽  
pp. 29-39 ◽  
Keyword(s):  
Seismic Refraction ◽  
Gravity Anomalies ◽  
Seismic Signal ◽  
Sea Floor ◽  
Free Air ◽  
Igneous Intrusions ◽  
Seismic Refraction Survey ◽  
Free Air Gravity ◽  
Seismic Refraction Data ◽  
Refraction Data

A seismic refraction survey of the Western Approaches was completed in the autumn of 1973, totalling 28 stations. In addition to a few sonobuoys, an improved method of detection was used, consisting of geophones or hydrophones positioned on the sea floor. The seismic signal was transmitted by radio to a shipboard receiving and recording apparatus. This new technique considerably improved the signal noise ratio. The major structural trend in the Western Approaches to the Channel is NE—SW. Two large northeast—southwest fault systems border a large, downfaulted, elongated basin, floored by depressions and ridges. The seismic refraction data lead to the recognition of two distinct geological sequences. The first is associated with the tectonized, metamorphic floor with igneous intrusions and conformably layered Palaeozoic series. The second sequence is made up of nearly horizontal layers, consisting mainly of secondary and younger sediments. The two sequences seem to be separated by an unconformity. The relatively light sediments filling depressions of the Palaeozoic floor may partially cause the observed low free-air gravity anomalies. The basement has a block-faulted aspect, the blocks being tilted in a southeast and possibly also in a southwest direction.

Lithospheric flexure and the evolution of sedimentary basins

1982 ◽  
Vol 305 (1489) ◽  
pp. 249-281 ◽  
Keyword(s):  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
Oceanic Lithosphere ◽  
Oceanic Islands ◽  
Geological Time ◽  
Lithospheric Flexure ◽  
Free Air ◽  
Apparent Decrease ◽  
Basin Formation ◽  
Free Air Gravity

The sediments that have accumulated in sedimentary basins during geological time represent a load on the lithosphere that should respond by flexure. Simple elastic and viscoelastic (Maxwell) plate models have been used to examine quantitatively the contribution of flexure to basin formation. The models have been used to predict the stratigraphy and gravity anomalies associated with basins for different thermal and loading histories. The predictions of the models have been compared with observed stratigraphy and free-air gravity anomalies from interior and cratonic basins. The best overall fit to the observations is for an elastic plate model in which the flexural strength of the lithosphere increases with age. A similar model has recently been used successfully to explain observations from continental margin basins, oceanic islands and seamounts, and deep-sea trench - outer rise systems. This model explains the increase in the overall width of basins during their evolution as well as the stratigraphy of the basin edges. The apparent decrease in the widths of some basins through time can be explained by the model if sediment deposition is followed by erosion of the basin and its edges. The models results suggest that the flexural properties of continental and oceanic lithosphere are generally similar and that flexure is an important factor to consider in backstripping studies in which the tectonic subsidence of a basin is isolated and stratigraphic studies in which relative changes of sea level are estimated.

scholarly journals Petrogenesis of the chromitite body from the Cerro Colorado ophiolite, Paraguaná Peninsula, Venezuela

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
David J. Mendi ◽  
José María González-Jiménez ◽  
Joaquín A. Proenza ◽  
Franco Urbani ◽  
Fernando Gervilla
Keyword(s):  
Trace Elements ◽  
Oceanic Lithosphere ◽  
Upper Jurassic ◽  
Ca 125 ◽  
Caribbean Region ◽  
Ultramafic Complex ◽  
Eastern Cuba ◽  
The Caribbean ◽  
Back Arc ◽  
Cerro Colorado

Ultramafic-mafic rocks of ophiolitic affinity crop out along the Venezuelan Caribbean region. They have been interpreted as remnants of the oceanic lithosphere of the Caribbean volcanic arc (135-70 Ma) as well as relicts of proto-Caribbean oceanic lithosphere (Upper Jurassic-Lower Cretaceous) related to Pangea’s break-up. The Cerro Colorado ophiolite, located in the Paraguaná Peninsula, together with the case of the Cordillera de la Costa in north-central Venezuela, are a unique case of these Venezuelan ophiolites containing chromitite bodies. However, the petrogenesis of such a mafic-ultramafic complex and associated chromite ore remains are unknown to date. To advance our understanding of chromite ores in the Caribbean region, the genesis of the Cerro Colorado chromitite body is challenged. The Cerro Colorado chromitite body is characterized by a low-Cr content [Cr# =Cr/ Cr+Al= 0.44-0.60] and a distribution of trace elements in chromite as is typical of high-Al chromitites found in the shallower portions of the petrological Moho Transition Zone of Mesozoic ophiolites. The calculated melts in equilibrium with chromite forming this high-Al chromitite body are back-arc basin basalts. These melts were extracted after ~20 % partial melting of moderately depleted peridotites, which resulted in the precipitation of high-Al chromitite relatively impoverished in PGE (≤ 100 ppb total PGE). A comparison of the geochemical signatures of minor and trace elements in chromite and bulk-PGE contents of the Cerro Colorado chromitite with those of other known chromitites in the peri-Caribbean ophiolites show certain similitude with those high-Al described in the Moa-Baracoa ophiolite in eastern Cuba. The obtained results allow us to suggest that the ultramafic rocks of the Cerro Colorado and the chromitite body associated with it are closely related to the formation of a back-arc basin developed between ca. 125-120 Ma in the rear of the Great Antilles Arc.

African Caribbean Residents of Edinburgh in the Eighteenth and Nineteenth Centuries

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Lisa Williams
Keyword(s):  
Nineteenth Century ◽  
British Empire ◽  
Caribbean Region ◽  
African Caribbean ◽  
The Caribbean ◽  
Eighteenth And Nineteenth Centuries

Scotland is gradually coming to terms with its involvement in slavery and colonialism as part of the British Empire. This article places the spotlight on the lives of African Caribbean people who were residents of Edinburgh during the eighteenth and nineteenth centuries. I discuss their varied experiences and contributions: from runaways and men fighting for their freedom in the Scottish courts to women working as servants in city households or marrying into Edinburgh high society. The nineteenth century saw activism among political radicals from abolitionists to anticolonialists; some of these figures studied and taught at Edinburgh University. Their stories reflect the Scottish capital’s many direct connections with the Caribbean region.

Wind Power Assessment In The Caribbean Region Of Colombia, Using Ten-Minute Wind Observations And Era5 Data

2021 ◽  
Author(s):  
Samuel Andrés Gil Ruiz ◽  
Julio Eduardo Cañón Barriga ◽  
J. Alejandro Martínez
Keyword(s):  
Wind Power ◽  
Caribbean Region ◽  
The Caribbean

Wider Caribbean Region—A Pivotal Time to Strengthen Regional Instruments For Biodiversity Conservation

2008 ◽  
Vol 23 (3) ◽  
pp. 499-530 ◽  
Author(s):  
Barbara Lausche
Keyword(s):  
Biodiversity Conservation ◽  
Sustainable Management ◽  
Marine Ecosystem ◽  
Legal Framework ◽  
Caribbean Region ◽  
International Policy ◽  
Global Environment Facility ◽  
Large Marine Ecosystem ◽  
The Caribbean ◽  
Specially Protected Areas

AbstractThe countries of the Wider Caribbean Region (WCR) are linked economically by their transboundary living marine resources. The region is facing a continued decline of these resources. Science is improving our understanding of the human contributions to this decline, but national policies and programmes have not kept pace with this understanding. The Caribbean Regional Seas Programme and its Cartagena Convention and Protocols provide the regional legal framework for protection and sustainable management of the WCR's living marine and coastal resources. This article focuses on the Cartagena Convention's Protocol for biodiversity conservation, the Protocol Concerning Specially Protected Areas and Wildlife (SPAW), arguing that governments and organizations need to significantly increase participation in this regional treaty regime to effectively address transboundary environmental challenges. A new initiative, the Global Environment Facility-supported Caribbean Large Marine Ecosystem project, will help in this effort. International policy supports strengthened regional seas programmes. It is now imperative for all levels and sectors to assist governments in strengthening this important treaty regime for biodiversity conservation in the Wider Caribbean Region.

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