Constraining the age of the first pulse of continental rifting associated with the breakup of Pangea in Southwest Iberia

2021 ◽  
Author(s):  
Margarida Vilas-Boas ◽  
Niall W. Paterson ◽  
Zélia Pereira ◽  
Paulo Fernandes ◽  
Simonetta Cirilli
Keyword(s):  
Financial Support ◽  
Depositional Environment ◽  
Late Triassic ◽  
The North ◽  
Low Diversity ◽  
Southern Portugal ◽  
Palynological Study ◽  
Algarve Basin ◽  
Central Atlantic ◽  
Red Bed

<p>The Algarve Basin is a Mesozoic sedimentary basin located in southern Portugal. The basin was initiated by rifting associated with the opening of the North and Central Atlantic Ocean during the initial breakup of Pangea. Sedimentation commenced with continental red beds, which unconformably overlie folded and faulted late Carboniferous strata. The red bed succession (Silves Sandstones) consists mainly of sandstones and conglomerates at the base, overlain by variegated mudstones interbedded with siltstones and dolomites (Silves Mudstones, Siltstones and Dolomites). The sandstones were deposited in alluvial environments, and the mudstones in alluvial to shallow lacustrine environments. Upper Triassic (Carnian to Norian) macrofossils are scarce in the red bed succession, occurring predominantly in the upper beds of the succession above the Silves Sandstones, and do not accurately constrain the age of the beginning of the Algarve Basin.</p><p>A palynological study of a new road cut outcrop of Silves Sandstones, located in central Algarve, was undertaken in order to ascertain its age. A 3 m thick bed of grey siltstones located ca. 2.5 m above the unconformity yielded age-diagnostic palynomorphs, which date the onset of sedimentation in the basin. Samples from the latter bed yielded a moderately well preserved, low diversity palynomorph assemblage, which is dominated by <em>Aulisporites astigmosus, Converrucosisporites</em> sp. and <em>Tulesporites briscoensis</em>. Other taxa present in the assemblage include <em>Alisporites</em> sp., <em>Calamospora</em> sp., <em>Cycadopites</em> sp., <em>Deltoidospora</em> sp., <em>Ovalipollis</em> cf. <em>ovalis</em>, <em>Triadispora</em> sp., and <em>Vallasporites ignacii</em>.</p><p>The dominance of <em>A. astigmosus</em> together with <em>V. ignacii</em> is indicative of an early Carnian age based on comparison with independently dated sections described elsewhere in Europe. This new dating evidence thus constrains the beginning of sedimentation in the Algarve Basin to the earliest Late Triassic. The co-occurrence of <em>T. briscoensis</em> and <em>A. astigmosus</em> suggests a mixing of palynofloral elements typical of North American and central European Carnian assemblages respectively, which is consistent with the intermediate position of Portugal between those regions. The dominance of phytoclasts and the absence of marine palynomorphs confirms a continental depositional environment as also suggested by sedimentary lithofacies.</p><p><strong>Acknowledgements</strong></p><p>The authors would like to acknowledge the financial support of the Portuguese Foundation of Science and Technology (FCT) with the scholarship with the reference SFRH/BD/144125/2019 and would also like to acknowledge the financial support of the FCT to CIMA through UIDP/00350/2020.</p>

Tectonic evolution of the Mediterranean region from a global plate kinematics perspective: insights from a new deformable tectonic model

2020 ◽  
Author(s):  
Simone Agostini ◽  
Simon Otto ◽  
John Watson ◽  
Roy Howgate
Keyword(s):  
Tectonic Evolution ◽  
Late Triassic ◽  
Plate Model ◽  
Geological Time ◽  
Northern Margin ◽  
Tectonic Model ◽  
The North ◽  
The Mediterranean ◽  
Local Impacts ◽  
Central Atlantic

<p>The tectonic evolution of the Mediterranean is well studied, but the models often cover a limited period of geological time and are not always placed in a wider context. Its evolution is linked to the surrounding African and Eurasian continents and their relative movements.</p><p>A new fully deformable tectonic model of the Mediterranean has been created as part of a proprietary plate model. This work has led to the identification of key global tectonic events influencing the development of the Mediterranean from the Early Permian to the present day. This first fully-deformable plate model of the Mediterranean enables to account for the shortening and extension that occurred in the area at a temporal resolution of 1 Ma. In most available plate models, plates are rigidly rotated back to their paleo-position, meaning they preserve their present-day size and shape. In some recent papers, the extent of deformation has been illustrated for selected time-slices, but these models cannot be considered to be ‘deformable’ because the deformation is not modelled in a continuous manner.</p><p>Following Hercynian orogenesis and until the break-up of Pangea, the Mediterranean was dominated by extensional tectonics along its southern margin, as a series small continental blocks rifted from the northern margin of Gondwana. The opening of the Central Atlantic in the Late Triassic-Early Jurassic led to displacement between Eurasia and Africa south of Iberia and the development of the Alpine Tethys, as the Atlantic initially propagated northwards to the east of Iberia. Rotation of Africa caused by the opening of the South Atlantic in the Late Jurassic-Early Cretaceous led to a ‘jump’ in spreading to the west, at the Iberia-Newfoundland margin. These larger scale plate motions overprinted the more local impacts of continued extension along the northern margin of Africa (e.g. Pindos Ocean). Opening of the North Atlantic once again changed the relative motion of Eurasia and Africa, and initiated a period of oceanic subduction and collision that culminated in the Alpine orogeny. Crucial to this story is the paleo-position of Apulia/Adria, which remained attached to Africa and was able to act as an indenter into Eurasia during the Alpine compression. Evidence for this connection will be presented and discussed.</p><p> </p><p> </p>

Depositional Environment Drive as Overpressure Generation: Study Case in “Gap” Field, North West Java Basin

2020 ◽  
Author(s):  
A., C. Prasetyo
Keyword(s):  
Clay Mineral ◽  
Depositional Environment ◽  
Mineral Content ◽  
Hydrocarbon Generation ◽  
Well Test ◽  
Burial History ◽  
The South ◽  
North West ◽  
The North ◽  
Geological Processes

Overpressure existence represents a geological hazard; therefore, an accurate pore pressure prediction is critical for well planning and drilling procedures, etc. Overpressure is a geological phenomenon usually generated by two mechanisms, loading (disequilibrium compaction) and unloading mechanisms (diagenesis and hydrocarbon generation) and they are all geological processes. This research was conducted based on analytical and descriptive methods integrated with well data including wireline log, laboratory test and well test data. This research was conducted based on quantitative estimate of pore pressures using the Eaton Method. The stages are determining shale intervals with GR logs, calculating vertical stress/overburden stress values, determining normal compaction trends, making cross plots of sonic logs against density logs, calculating geothermal gradients, analyzing hydrocarbon maturity, and calculating sedimentation rates with burial history. The research conducted an analysis method on the distribution of clay mineral composition to determine depositional environment and its relationship to overpressure. The wells include GAP-01, GAP-02, GAP-03, and GAP-04 which has an overpressure zone range at depth 8501-10988 ft. The pressure value within the 4 wells has a range between 4358-7451 Psi. Overpressure mechanism in the GAP field is caused by non-loading mechanism (clay mineral diagenesis and hydrocarbon maturation). Overpressure distribution is controlled by its stratigraphy. Therefore, it is possible overpressure is spread quite broadly, especially in the low morphology of the “GAP” Field. This relates to the delta depositional environment with thick shale. Based on clay minerals distribution, the northern part (GAP 02 & 03) has more clay mineral content compared to the south and this can be interpreted increasingly towards sea (low energy regime) and facies turned into pro-delta. Overpressure might be found shallower in the north than the south due to higher clay mineral content present to the north.

scholarly journals Palynological indications for Silurian – earliest Devonian age strata in the Netherlands

2021 ◽  
Vol 100 ◽  
Author(s):  
Alexander J.P. Houben ◽  
Geert-Jan Vis
Keyword(s):  
The Netherlands ◽  
Core Material ◽  
Late Devonian ◽  
Time Interval ◽  
The South ◽  
Early Devonian ◽  
The North ◽  
Depositional Settings ◽  
Palynological Study ◽  
Devonian Age

Abstract Knowledge of the stratigraphic development of pre-Carboniferous strata in the subsurface of the Netherlands is very limited, leaving the lithostratigraphic nomenclature for this time interval informal. In two wells from the southwestern Netherlands, Silurian strata have repeatedly been reported, suggesting that these are the oldest ever recovered in the Netherlands. The hypothesised presence of Silurian-aged strata has not been tested by biostratigraphic analysis. A similar lack of biostratigraphic control applies to the overlying Devonian succession. We present the results of a palynological study of core material from wells KTG-01 and S05-01. Relatively low-diversity and poorly preserved miospore associations were recorded. These, nonetheless, provide new insights into the regional stratigraphic development of the pre-Carboniferous of the SW Netherlands. The lower two cores from well KTG-01 are of a late Silurian (Ludlow–Pridoli Epoch) to earliest Devonian (Lochkovian) age, confirming that these are the oldest sedimentary strata ever recovered in the Netherlands. The results from the upper cored section from the pre-Carboniferous succession in well KTG-01 and the cored sections from the pre-Carboniferous succession in well S05-01 are more ambiguous. This inferred Devonian succession is, in the current informal lithostratigraphy of the Netherlands, assigned to the Banjaard group and its subordinate Bollen Claystone formation, of presumed Frasnian (i.e. early Late Devonian) age. Age-indicative Middle to Late Devonian palynomorphs were, however, not recorded, and the overall character of the poorly preserved palynological associations in wells KTG-01 and S05-01 may also suggest an Early Devonian age. In terms of lithofacies, however, the cores in well S05-01 can be correlated to the upper Frasnian – lower Famennian Falisolle Formation in the Campine Basin in Belgium. Hence, it remains plausible that an unconformity separates Silurian to Lower Devonian strata from Upper Devonian (Frasnian–Famennian) strata in the SW Netherlands. In general, the abundance of miospore associations points to the presence of a vegetated hinterland and a relatively proximal yet relatively deep marine setting during late Silurian and Early Devonian times. This differs markedly from the open marine depositional settings reported from the Brabant Massif area to the south in present-day Belgium, suggesting a sediment source to the north. The episodic presence of reworked (marine) acritarchs of Ordovician age suggests the influx of sedimentary material from uplifted elements on the present-day Brabant Massif to the south, possibly in relation to the activation of a Brabant Arch system.

Lithospheric modification at the onset of the destruction of the North China Craton: Evidence from Late Triassic mafic dykes

2021 ◽  
Vol 566 ◽  
pp. 120105
Author(s):  
Chao Wang ◽  
Shuguang Song ◽  
Li Su ◽  
Mark B. Allen ◽  
Jinlong Dong
Keyword(s):  
North China Craton ◽  
North China ◽  
Late Triassic ◽  
Mafic Dykes ◽  
The North

scholarly journals Detrital zircon provenance of the Late Triassic Songpan-Ganzi complex: Sedimentary record of collision of the North and South China blocks: Comment and Reply: REPLY

Geology ◽  
2006 ◽  
Vol 34 (1) ◽  
pp. e107-e108
Author(s):  
A. L. Weislogel ◽  
S. A. Graham ◽  
E. Z. Chang ◽  
J. L. Wooden ◽  
G. E. Gehrels ◽  
...  
Keyword(s):  
South China ◽  
Detrital Zircon ◽  
Late Triassic ◽  
Sedimentary Record ◽  
The North ◽  
North And South

scholarly journals New insights on the early Mesozoic evolution of multiple tectonic regimes in the northeastern North China Craton from the detrital zircon provenance of sedimentary strata

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1375-1397 ◽  
Author(s):  
Yi Ni Wang ◽  
Wen Liang Xu ◽  
Feng Wang ◽  
Xiao Bo Li
Keyword(s):  
North China Craton ◽  
North China ◽  
Early Jurassic ◽  
Orogenic Belt ◽  
Detrital Zircons ◽  
Late Triassic ◽  
Early Triassic ◽  
The South ◽  
The North ◽  
Early Mesozoic

Abstract. To investigate the timing of deposition and provenance of early Mesozoic strata in the northeastern North China Craton (NCC) and to understand the early Mesozoic paleotectonic evolution of the region, we combine stratigraphy, U–Pb zircon geochronology, and Hf isotopic analyses. Early Mesozoic strata include the Early Triassic Heisonggou, Late Triassic Changbai and Xiaoyingzi, and Early Jurassic Yihe formations. Detrital zircons in the Heisonggou Formation yield  ∼ 58 % Neoarchean to Paleoproterozoic ages and  ∼ 42 % Phanerozoic ages and were sourced from areas to the south and north of the basins within the NCC, respectively. This indicates that Early Triassic deposition was controlled primarily by the southward subduction of the Paleo-Asian oceanic plate beneath the NCC and collision between the NCC and the Yangtze Craton (YC). Approximately 88 % of the sediments within the Late Triassic Xiaoyingzi Formation were sourced from the NCC to the south, with the remaining  ∼ 12 % from the Xing'an–Mongolia Orogenic Belt (XMOB) to the north. This implies that Late Triassic deposition was related to the final closure of the Paleo-Asian Ocean during the Middle Triassic and the rapid exhumation of the Su–Lu Orogenic Belt between the NCC and YC. In contrast,  ∼ 88 % of sediments within the Early Jurassic Yihe Formation were sourced from the XMOB to the north, with the remaining  ∼ 12 % from the NCC to the south. We therefore infer that rapid uplift of the XMOB and the onset of the subduction of the Paleo-Pacific Plate beneath Eurasia occurred in the Early Jurassic.

Biodiversity and the biogeographic relationships of the Amphipoda: Gammaridea on the French coastline

2004 ◽  
Vol 84 (3) ◽  
pp. 621-628 ◽  
Author(s):  
Jean-Claude Dauvin ◽  
Denise Bellan-Santini
Keyword(s):  
Latitudinal Gradient ◽  
Marine Invertebrate ◽  
English Channel ◽  
Latitude Range ◽  
The North ◽  
North Eastern ◽  
Cool Temperate ◽  
Amphipoda Species ◽  
Central Atlantic ◽  
Warm Temperate

A recent inventory of the benthic Gammaridea: Amphipoda species on the French continental coastline catalogued 495 species. An analysis of the biodiversity and the biogeographic relationships that exist between the French Amphipoda: Gammaridea, living on the coastline that extends along 10° latitude range in the temperate region between 41° and 51° North and the other gammaridean faunas living in the north-eastern Atlantic has drawn the pattern of diversity in this marine invertebrate group on a large biogeographical scale. Gammaridean amphipods exhibit a latitudinal gradient over the total number of species, including the continental shelf species and the bathyal species. There are four main fauna groups, which correspond to the biogeographical zones of the north-eastern Atlantic: (1) a cold arctic and cool-temperate Svalbard and Norwegian coastal fauna; (2) a cool-temperate boreal and Boreal–Lusitanian United Kingdom, Irish and English Channel shallow fauna; (3) a warm-temperate Lusitanian Bay of Biscay and subtropical central Atlantic fauna; and (4) a subtropical Mediterranean fauna. The French fauna appears particularly rich, presenting 44% of the 1119 species recorded in the north-eastern Atlantic along the 50° latitude range (30°N–80°N).  This is obviously due to France's intermediate latitudinal location within the Lusitanian temperate biogeographical zone, which produces a biogeographical cross between the boreal fauna in the north and the warm temperate and sub-tropical fauna in the south.

scholarly journals Modeling the consequences on late Triassic environment of intense pulse-like degassing during the Central Atlantic Magmatic Province using the GEOCLIM model

2012 ◽  
Vol 8 (3) ◽  
pp. 2075-2110 ◽  
Author(s):  
G. Paris ◽  
Y. Donnadieu ◽  
V. Beaumont ◽  
F. Fluteau ◽  
Y. Goddéris
Keyword(s):  
Carbon Cycle ◽  
Carbon Isotope ◽  
Carbon Isotopic Composition ◽  
Late Triassic ◽  
Carbonate Production ◽  
Carbon Isotopic ◽  
Central Atlantic Magmatic Province ◽  
Igneous Provinces ◽  
Central Atlantic ◽  
Sedimentary Carbon

Abstract. The Triassic-Jurassic boundary (TJB) is associated with one of the five largest mass extinctions of the Phanerozoic. A deep carbon cycle perturbation and a carbonate production crisis are observed during the late Triassic. The Central Atlantic Magmatic Province (CAMP), one of the most important large igneous provinces of the Phanerozoic, emplaced at the TJB. To understand the carbon cycle perturbations observed at the TJB, we investigate the consequences of CO2 degassing associated to the CAMP emplacement on atmospheric and oceanic carbon cycle. The CO2 input within the atmosphere due to volcanism has been modeled using a global biogeochemical cycle box model (COMBINE) coupled with a climate model (FOAM). Weathering fluxes and CO2 equilibrium are constrained by the Rhaetian paleogeography and different scenarios of the CAMP emplacement are modeled. The study focuses (1) on the geological record and the carbonate productions crisis and (2) on the sedimentary carbon isotope record. For point (1), comparison of different modeling scenarios shows that a Gaussian CO2 emission distribution over the duration of the main activity phase of the CAMP fails in reproducing any of the geological observations, mainly the carbonate production crisis observed in the late Rhaetian sediments. Contrastingly, intense degassing peaks lead to successive decrease in carbonate production as observed in the geological record. For point (2), the perturbations of carbon cycle due to the degassing of CO2 with a mantellic carbon isotopic composition of −5‰ do not reproduce the intensity of the observed carbon isotope excursions. This was achieved in our model by assuming a mantellic carbon isotopic composition of −20‰. Even if this hypothesis requires further investigations, such low values may be associated to degassing of carbon from pools of light isotopic carbon located at the transition zone (Cartigny, 2010), possibly linked to setting of large igneous provinces (LIP's). Breakdown of biological primary productivity can also partially account for the sedimentary carbon isotope excursions and for the observed increase of atmospheric pCO2.

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