Constraints on the Timing of Surface Uplift of the Iranian Plateau (Arabia-Eurasian Collision Zone) from Clumped Isotope Thermometry on Pedogenic Carbonates

2020 ◽  
Author(s):  
Paolo Ballato ◽  
Alexis Licht ◽  
Katharine Huntington ◽  
Andrew Schauer ◽  
Andreas Mulch ◽  
...  
Keyword(s):  
Global Climate ◽  
Time Interval ◽  
Plate Boundaries ◽  
Order Problem ◽  
Iranian Plateau ◽  
Surface Uplift ◽  
Pedogenic Carbonates ◽  
Collision Zone ◽  
Clumped Isotope ◽  
Orogenic Plateaus

<p>Orogenic plateaus are extensive, elevated, arid, generally internally drained, morphotectonic provinces of low internal topographic relief that represent a striking and enigmatic feature of Earth’s continental landscapes. They are located along convergent plate boundaries and have a profound impact on regional and global climate, erosional processes, local- to far-field deformation mechanisms and the long-term distribution of biomes and biodiversity. Although the paramount role of large orogenic plateaus in shaping our planet is widely appreciated, the question of why, where, and how some orogenic systems develop large plateaus remains a first-order problem in our understanding of lithospheric evolution and orogenic processes.</p><p>Here, we present a clumped isotope paleoaltimetry study to document the elevation history of the Iranian Plateau, with the goal of understanding the rates and mechanisms of orogenic plateau rise. This plateau is in the Arabia-Eurasia collision zone, has a mean elevation of ~ 1.8 km, steep margins with mountain peaks higher than 4 km, and experienced surface uplift sometime after the middle Miocene as documented by the occurrence of ca. 17-My-old marine deposits in the plateau interior.</p><p>Preliminary results from Early Miocene to Quaternary pedogenic carbonates on the plateau interior and the adjacent, less elevated, intermontane Tarom basin suggest that surface uplift must have occurred sometime between 12-11 and 8 Ma. The lack of significant crustal shortening and thickening during this time interval and the occurrence of a renewed phase of adakitic volcanism by ca. 11 Ma suggests that surface uplift may have been driven by deep-seated processes associated with asthenospheric flow.</p>

scholarly journals Low-latitude arc–continent collision as a driver for global cooling

2020 ◽  
Author(s):  
Oliver Jagoutz ◽  
Leigh Royden ◽  
Francis Macdonald
Keyword(s):  
Chemical Weathering ◽  
Global Climate ◽  
Time Interval ◽  
Plate Boundaries ◽  
Ocean Bottom ◽  
Humid Climate ◽  
Low Latitude ◽  
Early Eocene Climatic Optimum ◽  
Iapetus Ocean ◽  
Global Cooling

<p>New constraints on the tectonic evolution of the Neo-Tethys Ocean indicate that at ∼90–70 Ma and at ∼50–40 Ma, vast quantities of mafic and ultramafic rocks were emplaced at low latitude onto continental crust within the tropical humid belt. These emplacement events correspond temporally with, and are potential agents for, the global climatic cooling events that terminated the Cretaceous Thermal Maximum and the Early Eocene Climatic Optimum. We model the temporal effects of CO2 drawdown from the atmosphere due to chemical weathering of these obducted ophiolites, and of CO2 addition to the atmosphere from arc volcanism in the Neo-Tethys, between 100 and 40 Ma. Modeled variations in net CO2-drawdown rates are in excellent agreement with contemporaneous variation of ocean bottom water temperatures over this time interval, indicating that ophiolite emplacement may have played a major role in changing global climate. We demonstrate that both the lithology of the obducted rocks (mafic/ultramafic) and a tropical humid climate with high precipitation rate are needed to produce significant consumption of CO2. Based on these results, we suggest that the low-latitude closure ofoceanbasins alongeast–west trending plate boundaries may also have initiated other long-term global cooling events, such as Middle to Late Ordovician cooling and glaciation associated with the closure of the Iapetus Ocean.</p>

scholarly journals Low-latitude arc–continent collision as a driver for global cooling

2016 ◽  
Vol 113 (18) ◽  
pp. 4935-4940 ◽  
Author(s):  
Oliver Jagoutz ◽  
Francis A. Macdonald ◽  
Leigh Royden
Keyword(s):  
Chemical Weathering ◽  
Global Climate ◽  
Time Interval ◽  
Plate Boundaries ◽  
Ocean Bottom ◽  
Humid Climate ◽  
Low Latitude ◽  
Early Eocene Climatic Optimum ◽  
Iapetus Ocean ◽  
Global Cooling

New constraints on the tectonic evolution of the Neo-Tethys Ocean indicate that at ∼90–70 Ma and at ∼50–40 Ma, vast quantities of mafic and ultramafic rocks were emplaced at low latitude onto continental crust within the tropical humid belt. These emplacement events correspond temporally with, and are potential agents for, the global climatic cooling events that terminated the Cretaceous Thermal Maximum and the Early Eocene Climatic Optimum. We model the temporal effects of CO2 drawdown from the atmosphere due to chemical weathering of these obducted ophiolites, and of CO2 addition to the atmosphere from arc volcanism in the Neo-Tethys, between 100 and 40 Ma. Modeled variations in net CO2-drawdown rates are in excellent agreement with contemporaneous variation of ocean bottom water temperatures over this time interval, indicating that ophiolite emplacement may have played a major role in changing global climate. We demonstrate that both the lithology of the obducted rocks (mafic/ultramafic) and a tropical humid climate with high precipitation rate are needed to produce significant consumption of CO2. Based on these results, we suggest that the low-latitude closure of ocean basins along east–west trending plate boundaries may also have initiated other long-term global cooling events, such as Middle to Late Ordovician cooling and glaciation associated with the closure of the Iapetus Ocean.

Evolution of Orogenic Plateaus at Subduction Zones - Sinking and raising the southern margin of the Central Anatolian Plateau

2018 ◽  
Author(s):  
David Fernández-Blanco
Keyword(s):  
Tectonic Evolution ◽  
Subduction Zones ◽  
Inversion Tectonics ◽  
High Discharge ◽  
Anatolian Plateau ◽  
Surface Uplift ◽  
Southern Margin ◽  
Wide Range ◽  
Forearc Basins ◽  
Orogenic Plateaus

Orogenic plateaus have raised abundant attention amongst geoscientists during the last decades, offering unique opportunities to better understand the relationships between tectonics and climate, and their expression on the Earth’s surface.Orogenic plateau margins are key areas for understanding the mechanisms behind plateau (de)formation. Plateau margins are transitional areas between domains with contrasting relief and characteristics; the roughly flat elevated plateau interior, often with internally drained endorheic basins, and the external steep areas, deeply incised by high-discharge rivers. This thesis uses a wide range of structural and tectonic approaches to investigate the evolution of the southern margin of the Central Anatolian Plateau (CAP), studying an area between the plateau interior and the Cyprus arc. Several findings are presented here that constrain the evolution, timing and possible causes behind the development of this area, and thus that of the CAP. After peneplanation of the regional orogeny, abroad regional subsidence took place in Miocene times in the absence of major extensional faults, which led to the formation of a large basin in the northeast Mediterranean. Late Tortonian and younger contractional structures developed in the interior of the plateau, in its margin and offshore, and forced the inversion tectonics that fragmented the early Miocene basin into the different present-day domains. The tectonic evolution of the southern margin of the CAP can be explained based on the initiation of subduction in south Cyprus and subsequent thermo-mechanical behavior of this subduction zone and the evolving rheology of the Anatolian plate. The Cyprus slab retreat and posterior pull drove subsidence first by relatively minor stretching of the crust and then by its flexure. The growth by accretion and thickening of the upper plate, and that of the associated forearc basins system, caused by accreting sediments, led to rheological changes at the base of the crust that allowed thermal weakening, viscous deformation, driving subsequent surface uplift and raising the modern Taurus Mountains. This mechanism could be responsible for the uplifted plateau-like areas seen in other accretionary margins. ISBN: 978-90-9028673-0

scholarly journals The δ13C, δ18O and Δ47 records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

2021 ◽  
pp. 1-17
Author(s):  
Kazem Zamanian ◽  
Alex R. Lechler ◽  
Andrew J. Schauer ◽  
Yakov Kuzyakov ◽  
Katharine W. Huntington
Keyword(s):  
Land Snail ◽  
Isotopic Signature ◽  
Sediment Layer ◽  
Isotopic Signatures ◽  
Pedogenic Carbonates ◽  
Rhine Valley ◽  
Clumped Isotope ◽  
Time Specific ◽  
Sediment Layers ◽  
Paleoenvironmental Reconstructions

Abstract Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.

scholarly journals Microfossil evidence for trophic changes during the Eocene–Oligocene transition in the South Atlantic (ODP Site 1263, Walvis Ridge)

2015 ◽  
Vol 11 (9) ◽  
pp. 1249-1270 ◽  
Author(s):  
M. Bordiga ◽  
J. Henderiks ◽  
F. Tori ◽  
S. Monechi ◽  
R. Fenero ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Global Climate ◽  
Food Delivery ◽  
Marine Phytoplankton ◽  
Time Interval ◽  
Foraminiferal Assemblage ◽  
Sea Floor ◽  
Walvis Ridge ◽  
Bottom Waters ◽  
Latest Eocene

Abstract. The biotic response of calcareous nannoplankton to environmental and climatic changes during the Eocene–Oligocene transition was investigated at a high resolution at Ocean Drilling Program (ODP) Site 1263 (Walvis Ridge, southeast Atlantic Ocean) and compared with a lower-resolution benthic foraminiferal record. During this time interval, global climate, which had been warm under high levels of atmospheric CO2 (pCO2) during the Eocene, transitioned into the cooler climate of the Oligocene, at overall lower pCO2. At Site 1263, the absolute nannofossil abundance (coccoliths per gram of sediment; N g−1) and the mean coccolith size decreased distinctly after the E–O boundary (EOB; 33.89 Ma), mainly due to a sharp decline in abundance of large-sized Reticulofenestra and Dictyococcites, occurring within a time span of ~ 47 kyr. Carbonate dissolution did not vary much across the EOB; thus, the decrease in abundance and size of nannofossils may reflect an overall decrease in their export production, which could have led to variations in the food availability for benthic foraminifers. The benthic foraminiferal assemblage data are consistent with a global decline in abundance of rectilinear species with complex apertures in the latest Eocene (~ 34.5 Ma), potentially reflecting changes in the food source, i.e., phytoplankton. This was followed by a transient increased abundance of species indicative of seasonal delivery of food to the sea floor (Epistominella spp.; ~ 33.9–33.4 Ma), with a short peak in overall food delivery at the EOB (buliminid taxa; ~ 33.8 Ma). Increased abundance of Nuttallides umbonifera (at ~ 33.3 Ma) indicates the presence of more corrosive bottom waters and possibly the combined arrival of less food at the sea floor after the second step of cooling (Step 2). The most important changes in the calcareous nannofossil and benthic communities occurred ~ 120 kyr after the EOB. There was no major change in nannofossil abundance or assemblage composition at Site 1263 after Step 2 although benthic foraminifera indicate more corrosive bottom waters during this time. During the onset of latest-Eocene–earliest-Oligocene climate change, marine phytoplankton thus showed high sensitivity to fast-changing conditions as well as to a possibly enhanced, pulsed nutrient supply and to the crossing of a climatic threshold (e.g., pCO2 decline, high-latitude cooling and changes in ocean circulation).

scholarly journals Insight into collision zone dynamics from topography: numerical modelling results and observations

2012 ◽  
Vol 4 (2) ◽  
pp. 889-917 ◽  
Author(s):  
A. D. Bottrill ◽  
J. van Hunen ◽  
M. B. Allen
Keyword(s):  
Sea Level ◽  
Dynamic Models ◽  
Continental Collision ◽  
Dynamic Topography ◽  
Surface Uplift ◽  
Collision Zone ◽  
Phase Surface ◽  
Clastic Sedimentary ◽  
Back Arc ◽  
Topographic Evolution

Abstract. Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away from the base of the overriding plate. Also during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate causes the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. This uplift and subsidence pattern correlates well with our modelled topography changes.

scholarly journals Insight into collision zone dynamics from topography: numerical modelling results and observations

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 387-399 ◽  
Author(s):  
A. D. Bottrill ◽  
J. van Hunen ◽  
M. B. Allen
Keyword(s):  
Sea Level ◽  
Dynamic Models ◽  
Continental Collision ◽  
Dynamic Topography ◽  
Surface Uplift ◽  
Collision Zone ◽  
Phase Surface ◽  
Clastic Sedimentary ◽  
Topographic Evolution ◽  
Insight Into

Abstract. Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene–Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.

The Monte Carlo Independent Column Approximation’s Conditional Random Noise: Impact on Simulated Climate

2005 ◽  
Vol 18 (22) ◽  
pp. 4715-4730 ◽  
Author(s):  
P. Räisänen ◽  
H. W. Barker ◽  
J. N. S. Cole
Keyword(s):  
Monte Carlo ◽  
Global Climate ◽  
Random Noise ◽  
Radiative Heating ◽  
Time Interval ◽  
Additional Time ◽  
Time Step ◽  
Order Of Magnitude ◽  
Independent Column ◽  
The Impact

Abstract The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Results for five experiments are used to assess the impact of McICA-related noise on simulations of global climate made by the NCAR Community Atmosphere Model (CAM). The experiment with the least noise (an order of magnitude below that of basic McICA) is taken as the reference. Two additional experiments help demonstrate how the impact of noise depends on the time interval between calls to the radiation code. Each experiment is an ensemble of seven 15-month simulations. Experiments with very high noise levels feature significant reductions to cloudiness in the lowermost model layer over tropical oceans as well as changes in highly related quantities. This bias appears immediately, stabilizes after a couple of model days, and appears to stem from nonlinear interactions between clouds and radiative heating. Outside the Tropics, insignificant differences prevail. When McICA sampling is confined to cloudy subcolumns and when, on average, 50% more samples, relative to basic McICA, are drawn for selected spectral intervals, McICA noise is much reduced and the results of the simulation are almost statistically indistinguishable from the reference. This is true both for mean fields and for the nature of fluctuations on scales ranging from 1 day to at least 30 days. While calling the radiation code once every 3 h instead of every hour allows the CAM additional time to incorporate McICA-related noise, the impact of noise is enhanced only slightly. In contrast, changing the radiative time step by itself produces effects that generally exceed the impact of McICA’s noise.

Clumped isotope evidence for diachronous surface cooling of the Altiplano and pulsed surface uplift of the Central Andes

2014 ◽  
Vol 393 ◽  
pp. 173-181 ◽  
Author(s):  
Carmala N. Garzione ◽  
David J. Auerbach ◽  
Johanna Jin-Sook Smith ◽  
Jose J. Rosario ◽  
Benjamin H. Passey ◽  
...  
Keyword(s):  
Central Andes ◽  
Surface Cooling ◽  
Surface Uplift ◽  
Isotope Evidence ◽  
Clumped Isotope
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