Forced subduction initiation within the Neotethys: An example from the mid-Cretaceous Wuntho-Popa arc in Myanmar

2021 ◽  
Author(s):  
Liyun Zhang ◽  
Weiming Fan ◽  
Lin Ding ◽  
Alex Pullen ◽  
Mihai N. Ducea ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Geochemical Data ◽  
Diverse Range ◽  
Subduction Initiation ◽  
The North ◽  
Oceanic Spreading ◽  
Tectonic Settings ◽  
Volcanic Succession ◽  
Subduction System ◽  
New Evidence

Despite decades of research, the mechanisms and processes of subduction initiation remain obscure, including the tectonic settings where subduction initiation begins and how magmatism responds. The Cretaceous Mawgyi Volcanics represent the earliest volcanic succession in the Wuntho-Popa arc of western Myanmar. This volcanic unit consists of an exceptionally diverse range of contemporaneously magmatic compositions which are spatially juxtaposed. Our new geochemical data show that the Mawgyi Volcanics comprise massive mid-oceanic ridge basalt (MORB)-like lavas and dikes, and subordinate island arc tholeiite and calc-alkaline lavas. The Mawgyi MORB-like rocks exhibit flat rare earth elements (REEs) patterns and are depleted in REEs, high field strength elements (except for Th) and TiO2 concentrations relative to those of MORBs, resembling the Izu-Bonin-Mariana protoarc basalts. Our geochronological results indicate that the Mawgyi Volcanics formed between 105 and 93 Ma, coincident with formation of many Neotethyan supra-subduction zone ophiolites and intraoceanic arcs along orogenic strike in the eastern Mediterranean, Middle East, Pakistan, and Southeast Asia. Combined with its near-equatorial paleo-latitudes constrained by previous paleomagnetic data, the Wuntho-Popa arc is interpreted as a segment of the north-dipping trans-Neotethyan subduction system during the mid-Cretaceous. Importantly, our restoration with available data provides new evidence supporting the hypothesis of a mid-Cretaceous initiation of this >8000-km-long subduction system formed by inversion of the ∼E-W−trending Neotethyan oceanic spreading ridges, and that this was contemporaneous with the final breakup of Gondwana and an abrupt global plate reorganization.

Challenges and opportunities extending the INTIMATE tephra event stratigraphy into the Levant and Arabia.

2020 ◽  
Author(s):  
Simon Blockley ◽  
Dustin White ◽  
Rhys Timms ◽  
Paul Lincoln ◽  
Simon Armitage ◽  
...  
Keyword(s):  
North Atlantic ◽  
Eastern Mediterranean ◽  
Ice Core ◽  
Limited Range ◽  
Geochemical Data ◽  
Interglacial Period ◽  
The North ◽  
Event Stratigraphy ◽  
The North Atlantic ◽  
The Mediterranean

<p>The nature and expression of climate change in the Eastern Mediterranean, the Levant and further into Arabia is of considerable interest across a range of communities. This is in part due to the need to understand the potential for future climate forcing on environments given the complex range of climatic forcing factors that play out in the region. These include the role of prevailing winds across the Mediterranean, Northerly winds pushing down into the region during cold glacial conditions, and the influence of the Afro-Arabian Monsoon. The last glacial to interglacial period is a critical window to examine such processes, as a range of climatic signals are recorded, many of which have been proposed as correlatives of events seen in the North Atlantic. Dating issues are as ever an issue when trying to precisely compare different climate archives. To address such, the INTIMATE event stratigraphy has been developed for the North Atlantic region, with recent extensions into parts of the Mediterranean. This couples the stratigraphic framework of the Greenland Ice core records as a regional stratotype, with  a number of tephra horizons in the North Atlantic and Europe, aiding the process of correlation. The last INTIMATE event stratigraphy coupled the extended GICC05 timescale for Greenland back to 128 b2k (Blockley et al., 2014). This paper reports on attempts to test the potential for tephrochronology to be extended into the Levant and potentially Arabia, through the identification of tephra layers in sediment focussing archives, such as archaeological cave sequences. We have examined tephra presence in archaeological sites, principally in Israel, that record sediment deposition from ~30ka BP through to >100ka BP. Analyses of these records show that tephra is present in almost all of the studied sites (e.g., Kebara, Tabun, Amud, Shovakh). Moreover, tephra in these sequences can be chemically correlated to known volcanic systems, demonstrating the potential going forward to analyse long lake and marine records around the region for cryptotephra. At the same time clear challenges are emerging. Firstly, there is a range of chemistry in many of the layers and careful analyses is needed to pick apart the geochemical signal and to identify reworking, as opposed to chemically heterogeneous ash layers from a single volcano. This process is complicated by the relatively limited range of published geochemical data from some volcanic centres. This presentation will outline the current state of knowledge of key volcanic centres, particularly in the Aegean and Turkey, alongside the new Levantine data, to consider the steps needed to establish a secure extension of the INTIMATE approach into this region.</p><p>Blockley, S., et al., 2014. Quaternary Science Reviews. 106, 88-100. doi:10.1016/j.quascirev.2014.11.002.</p>

Mid-Atlantic Ridge hydrothermal events recorded by deep-sea corals

1999 ◽  
Vol 36 (4) ◽  
pp. 511-517 ◽  
Author(s):  
Jodie E Smith ◽  
Uwe Brand ◽  
Michael J Risk ◽  
Henry P Schwarcz
Keyword(s):  
North Atlantic ◽  
Discharge Zone ◽  
Coral Skeletons ◽  
The North ◽  
Oceanic Spreading ◽  
History Of ◽  
Mid Atlantic Ridge ◽  
Tectonic Settings ◽  
The North Atlantic ◽  
Isotope Analyses

Trace-element and stable-isotope analyses were performed on azooxanthellate corals from the North Atlantic, at two different tectonic settings. One set was from Orphan Knoll, near Newfoundland (1700 m depth, 50°25.57'N, 46°22.05'W), the other from the Mid-Atlantic Ridge (1200 m depth, 45°14.12'N, 28°34.12'W). The Mid-Atlantic Ridge corals contain significantly greater quantities of Fe, Mn, Cu, Ni, and Zn within their skeletons than the Orphan Knoll corals. The metal concentrations are not homogeneous within the Mid-Atlantic Ridge coral skeletons, but occur as episodic pulses during a decade or two of each coral's lifetime. We believe these metals originated in a hydrothermal discharge zone associated with the Mid-Atlantic spreading centre. If so, it is evidence that the duration of an individual hydrothermal event is from a decade up to 30 years or so. With more specimens of known ages, it may be possible to reconstruct the history of a particular segment of an oceanic spreading centre.

scholarly journals REMOVAL OF CRUSADERS FROM THE EASTERN MEDITERRANEAN IN THE MAMLUK-CRUSADER STRUGGLE

2020 ◽  
pp. 13-44
Author(s):  
Altan Çetin
Keyword(s):  
Eastern Mediterranean ◽  
Main Body ◽  
14Th Century ◽  
The Balkans ◽  
First Crusade ◽  
The North ◽  
The Mediterranean ◽  
Set Up ◽  
New Evidence

One of the most important issues facing the Mamluk State since its establishment was to continue the struggle with the Crusaders who settled in the region. In fact, after the failure of the 3rd Crusade, Egypt became the new strategic target of the Crusaders under the Ayyubid administration. The developments that started during the reign of Sultan Baybars continued in the period of Kalavun and al-Eshref until the conquest of Akka. From this point on, ez-Zâhir Baybars marched at the head of a large army at the beginning of February 1265 and took over the cities of Kaysariyye, Yafa, Aslis, and Arsuf. In the summer of 1266, he tookover Safad and er-Remle. It caused a heavy blow to Armenia Minor. In 1267, Sultan Baybars looted the districts of Taberiyye and Akkâ and invaded the cities of Jaffa, es-Shakif, and Arnun the following year. Finally, he crowned the invasion wars against the Crusaders with the conquest of Antioch (April 1268). Baybars’ conquering of Antioch has been marked by contradictions. However, he will eliminate the crusader presence in Antioch and its surrounding by various methods and occupy the areas in the north of Syria, and finally narrow the area of the Crusader activity. It is an extremely important event that Antioch was conquered by Muslims in 1268. Because Antioch is the second principality established by the Crusaders in the East (1097) after Urfa, and the capture of this place is a piece of new evidence that the great structure that the Crusaders set up in Syria towards the end of the 11th century began to collapse. This eliminated the presence of crusaders on the shores of the eastern Mediterranean, where they could indeed dominate until the First Crusade, and their withdrawal from the eastern Mediterranean is shown here. The struggle that took place in the period after Sultan Baybars and later, resulted in the fact that the defense against the Crusader attacks was first poured into the Mediterranean and then they were completely removed from there. The great Crusader attack in the 14th century spread over a century from different fronts and took place through the Balkans, the Aegean, and the Eastern Mediterranean. After the Crusaders’ main body was removed from Syria, the Armenian and Cypriot structures, which were their deputies, were also eliminated in the following periods. The Mamluks caused great losses to the Crusaders and their allies in the Eastern Mediterranean during the last period of the Crusades. This article examines how the Crusader presence was eliminated by the Mamluks in Antioch, Çukurova, and Cyprus.

scholarly journals Comment on “Emplazamiento del magmatismo Paleoceno-Eoceno bajo un régimen transtensional y su evolución a un equilibrio dinámico en el borde occidental de Colombia” by Grajales et al., Rev. Mex. Cienc. Geol. (2020), 37(3), 250-268

2021 ◽  
Vol 38 (2) ◽  
pp. 141-147
Author(s):  
Ángel A. Barbosa-Espitia ◽  
George D. Kamenov ◽  
David A. Foster ◽  
Sergio A. Restrepo-Moreno ◽  
Andrés Pardo-Trujillo ◽  
...  
Keyword(s):  
Alternative Interpretation ◽  
Geochemical Data ◽  
Northern Andes ◽  
The North ◽  
Western Cordillera ◽  
Plausible Model ◽  
The Caribbean ◽  
Subduction System ◽  
Central Cordillera ◽  
North Western

Grajales et al. (2020) reviewed geochronological and geochemical data from Paleogene volcanic and plutonic rocks outcropping in the Panama-Choco Block (north western Cordillera) and southern Western Cordillera, as well as the Central Cordillera of Colombia. These data were used to support a model of continuous Paleogene arc magmatism along the Colombian continental margin, and to propose a paleogeographic model for the arc. The authors did not discuss previously published paleomagnetic, geochemical, geochronological, thermochronological and provenance constraints from Cretaceous to Miocene rocks of western and northern Colombia, Panama, and Ecuador that support a more plausible model of a double subduction system controlled by the convergence of the Caribbean and Farallon plates beneath the north Andean block during Paleogene. In this comment, we discuss shortcomings in the data and model proposed by Grajales et al. (2020) and present an alternative interpretation for contemporaneous arc-like magmatism during the Paleogene in the Northern Andes. We conclude that the double subduction system is the more plausible explanation for the contemporaneous arc-like magmatism during the Paleogene, currently exposed in the northern and southern portions of the Northern Andes.

scholarly journals Rapid conversion of an oceanic spreading center to a subduction zone inferred from high-precision geochronology

2016 ◽  
Vol 113 (47) ◽  
pp. E7359-E7366 ◽  
Author(s):  
Timothy E. Keenan ◽  
John Encarnación ◽  
Robert Buchwaldt ◽  
Dan Fernandez ◽  
James Mattinson ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Subduction Zones ◽  
Plate Motion ◽  
Spreading Center ◽  
Fracture Zones ◽  
Subduction Initiation ◽  
Oceanic Spreading ◽  
Tectonic Settings ◽  
Tectonic System ◽  
Weak Zones

Where and how subduction zones initiate is a fundamental tectonic problem, yet there are few well-constrained geologic tests that address the tectonic settings and dynamics of the process. Numerical modeling has shown that oceanic spreading centers are some of the weakest parts of the plate tectonic system [Gurnis M, Hall C, Lavier L (2004) Geochem Geophys Geosys 5:Q07001], but previous studies have not favored them for subduction initiation because of the positive buoyancy of young lithosphere. Instead, other weak zones, such as fracture zones, have been invoked. Because these models differ in terms of the ages of crust that are juxtaposed at the site of subduction initiation, they can be tested by dating the protoliths of metamorphosed oceanic crust that is formed by underthrusting at the beginning of subduction and comparing that age with the age of the overlying lithosphere and the timing of subduction initiation itself. In the western Philippines, we find that oceanic crust was less than ∼1 My old when it was underthrust and metamorphosed at the onset of subduction in Palawan, Philippines, implying forced subduction initiation at a spreading center. This result shows that young and positively buoyant, but weak, lithosphere was the preferred site for subduction nucleation despite the proximity of other potential weak zones with older, denser lithosphere and that plate motion rapidly changed from divergence to convergence.

Westward Palaearctic range expansion of Papilio demoleus Linnaeus, 1758 (Lepidoptera: Papilionidae) and its arrival at Mediterranean coastal regions of Turkey and Syria

2020 ◽  
Vol 71 (4) ◽  
pp. 257-272
Author(s):  
Onat Başbay ◽  
Mudar Salimeh ◽  
Eddie John
Keyword(s):  
Eastern Mediterranean ◽  
Economic Importance ◽  
Invasive Pest ◽  
Pest Species ◽  
Coastal Regions ◽  
The North ◽  
North Eastern ◽  
The World ◽  
Invasive Pest Species ◽  
Papilio Demoleus

We review the continuing and extensive spread of Papilio demoleus in south-eastern Turkey and in regions of Turkey and Syria adjacent to the north-eastern Mediterranean. Since the authors documented the arrival of this attractive but potentially destructive papilionid species at coastal areas of Syria in 2019, regular monitoring has confirmed successful overwintering there, as well as in Turkey. As previously indicated, P. demoleus is widely recognized as an invasive pest species in Citrus-growing areas of the world and hence its arrival is of potential economic importance to a region in which citrus is widely grown.

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