The Bengal Fan sediment archive: a record of Himalayan tectonics, climate, and/or drainage routing change between source and sink?

2020 ◽  
Author(s):  
Yani Najman ◽  
Mike Blum ◽  
Jamie Gleason ◽  
Kimberly Rogers ◽  
Devon Orme ◽  
...  
Keyword(s):  
Drainage Basin ◽  
Foreland Basin ◽  
Deep Ocean ◽  
Detrital Zircons ◽  
Bengal Fan ◽  
Zircon Fission Track ◽  
Major Increase ◽  
The Difference ◽  
Hf Isotopic Composition ◽  
Himalayan Tectonics

<p>The Bengal Fan IODP Exp 354 core provides a Neogene re­cord of eastern and central Himalayan exhu­mation. U-Pb analyses of detrital zircons from this sediment archive shows that from ~ 4 Ma, there was a major increase in grains aged <300 Ma, indicating a major increase in contribution from the Trans-Himalaya (Blum et al., Nature SR, 2018). Detrital rutile U-Pb and detrital zircon fission track data from the same archive (Najman et al, GSAB 2019) indicates an approximately coeval increase in exhumation rate from the Eastern Himalayan Syntaxis. Thus an attractive explanation to explain the increase in Transhimalayan input may be that it was caused by initiation of exhumation of the syntaxis from beneath its Transhimalayan cover. However, a similar dataset obtained from the proximal foreland basin Siwalik deposits (Govin et al., in review) indicates an earlier onset to syntaxial exhumation, compared to that recorded in the distal sediment archive. We consider therefore whether climate change may be responsible for the increased Transhimalayan input: onset of Northern Hemisphere glaciation may have increased the proportion of erosion in the higher, glaciated, regions of the Transhimalaya, compared to that part of the orogen south of the suture zone. Analyses of Hf isotopic composition of detrital zircons to assess the possibility that drainage basin changes may explain the increase in material at 4 Ma, are ongoing. The difference in timing of the syntaxial exhumational signal between the proximal and distal archives may be the result of downstream dilution, or may result from sequestration of material on the shelf, with release to the deep ocean during sea level low stands.</p>

scholarly journals Climate Drift in the CMIP5 Models*

2013 ◽  
Vol 26 (21) ◽  
pp. 8597-8615 ◽  
Author(s):  
Alexander Sen Gupta ◽  
Nicolas C. Jourdain ◽  
Jaclyn N. Brown ◽  
Didier Monselesan
Keyword(s):  
Climate Models ◽  
Coupled Model ◽  
Deep Ocean ◽  
Internal Variability ◽  
Correction Method ◽  
Physical Models ◽  
Cmip5 Models ◽  
Steric Sea Level ◽  
Biogeochemical Models ◽  
The Difference

Abstract Climate models often exhibit spurious long-term changes independent of either internal variability or changes to external forcing. Such changes, referred to as model “drift,” may distort the estimate of forced change in transient climate simulations. The importance of drift is examined in comparison to historical trends over recent decades in the Coupled Model Intercomparison Project (CMIP). Comparison based on a selection of metrics suggests a significant overall reduction in the magnitude of drift from phase 3 of CMIP (CMIP3) to phase 5 of CMIP (CMIP5). The direction of both ocean and atmospheric drift is systematically biased in some models introducing statistically significant drift in globally averaged metrics. Nevertheless, for most models globally averaged drift remains weak compared to the associated forced trends and is often smaller than the difference between trends derived from different ensemble members or the error introduced by the aliasing of natural variability. An exception to this is metrics that include the deep ocean (e.g., steric sea level) where drift can dominate in forced simulations. In such circumstances drift must be corrected for using information from concurrent control experiments. Many CMIP5 models now include ocean biogeochemistry. Like physical models, biogeochemical models generally undergo long spinup integrations to minimize drift. Nevertheless, based on a limited subset of models, it is found that drift is an important consideration and must be accounted for. For properties or regions where drift is important, the drift correction method must be carefully considered. The use of a drift estimate based on the full control time series is recommended to minimize the contamination of the drift estimate by internal variability.

Diachronous exhumation of the Carpathians from low-temperature thermochronology

2021 ◽  
Author(s):  
Marion Roger ◽  
Peter van der Beek ◽  
Arjan de Leeuw ◽  
Laurent Husson
Keyword(s):  
Low Temperature ◽  
Foreland Basin ◽  
The Black Sea ◽  
Oblique Collision ◽  
The Carpathians ◽  
Sediment Routing ◽  
Source To Sink ◽  
Zircon Fission Track ◽  
Eastern Carpathians ◽  
Exhumation Rates

<p>The Carpathians fold-and-thrust belt results from oblique collision of ALCAPA and Tisza-Dacia plates with the eastern European margin. It formed during the Oligocene and Miocene, propagating laterally from NW to SE as clearly demonstrated by balanced-cross sections (Nakapelyukh et al., 2017; Castellucio et al., 2016; Merten et al., 2010). The coeval development of the foreland basin (Roure et al., 1993) is revealed by an axial transport system that prograded from NW to SE, ultimately supplying sediments to the Black Sea (de Leeuw et al., 2020). However, lacking a regional synthesis and integration of thermochronology data, lateral propagation of exhumation in the orogen has not been demonstrated yet.</p><p> We reconstruct the exhumation history of the entire Carpathians from the Oligocene onwards and link it with the development of the Carpathians foreland basin (CFB) using a source-to-sink approach. We compiled more than 500 apatite and zircon fission-track and (U-Th)/He ages from the literature. This comprehensive database was separated by region (Western, Eastern, and South-Eastern Carpathians) and by tectonic domain (as defined in Schmid et al., 2008). This partitioning allows for the inversion of large datasets, reflects the tectonic complexity of the belt, and avoids spurious spatial correlations (Schildgen et al., 2018). The thermochronology data was inverted using Pecube (Braun et al., 2012) to constrain exhumation rates in a Bayesian approach. We thus obtain estimates of exhumation rates through time along the belt (with their uncertainty) and convert these into bulk  sediment fluxes over time, permitting tracking of sediment routing from the eroding belt to the CFB. Ultimately, these data will be used to unravel deeper geodynamics, including the possible effects of slab detachment on the evolution of the belt and its foreland basin.</p><p> </p><p>Key words: Low-temperature thermochronology, Carpathians, exhumation, source to sink, Pecube inversions.</p>

scholarly journals Examining the provenance of branched GDGTs in the Tagus River drainage basin and its outflow into the Atlantic Ocean over the Holocene to determine their usefulness for paleoclimate applications

2016 ◽  
Vol 13 (20) ◽  
pp. 5719-5738 ◽  
Author(s):  
Lisa Warden ◽  
Jung-Hyun Kim ◽  
Claudia Zell ◽  
Geert-Jan Vis ◽  
Henko de Stigter ◽  
...  
Keyword(s):  
Iberian Peninsula ◽  
Marine Sediments ◽  
Arid Regions ◽  
Drainage Basin ◽  
Deep Ocean ◽  
Climate Reconstructions ◽  
Source To Sink ◽  
Tagus River ◽  
Global Soil ◽  
Paleoclimate Reconstructions

Abstract. The distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are transported from the soils where they are predominantly produced to marine sediments via rivers, have been applied in reconstructing mean annual air temperature (MAT) and pH of soils. However, paleoclimate reconstructions using sedimentary brGDGTs have proven difficult in arid regions, including the Iberian Peninsula. Recently, six novel 6-methyl brGDGTs have been described using new analytical methods (in addition to the nine 5-methyl brGDGTs previously used for climate reconstructions), and so new pH and MAT calibrations have been developed that were shown to improve the accuracy of reconstructions in a set of global soil samples, especially in arid regions. Because of this we decided to apply the new method to separate the 5- and 6-methyl isomers along with the novel calibrations to a sample set from the Iberian Peninsula to determine whether it improves paleoclimate reconstructions in this area. This set includes samples that run in a transect from source to sink along the Tagus River and out to the deep ocean off the Portuguese margin spanning the last 6000 years. We found that although pH reconstructions in the soils were improved using the new calibration, MAT reconstructions were not much better even with the separation of the 5- and 6-methyl brGDGTs. This confirmed the conclusion of previous studies that the amount of aquatically produced brGDGTs is overwhelming the soil-derived ones in marine sediments and complicating MAT reconstructions in the region. Additionally, the new separation revealed a strong and until now unseen relationship between the new degree of cyclization (DC') of the brGDGTs and MAT that could be making temperature reconstructions in this and other arid regions difficult.

scholarly journals Parameterization of Mixed Layer and Deep-Ocean Mesoscales including Nonlinearity

2018 ◽  
Vol 48 (3) ◽  
pp. 555-572 ◽  
Author(s):  
V. M. Canuto ◽  
Y. Cheng ◽  
M. S. Dubovikov ◽  
A. M. Howard ◽  
A. Leboissetier
Keyword(s):  
Deep Ocean ◽  
Altimetry Data ◽  
Dynamical Equations ◽  
Mean Velocity ◽  
Ocean Stratification ◽  
Large Heat ◽  
Reference Experiment ◽  
The Mean ◽  
The Difference ◽  
Induced Velocity

AbstractIn 2011, Chelton et al. carried out a comprehensive census of mesoscales using altimetry data and reached the following conclusions: “essentially all of the observed mesoscale features are nonlinear” and “mesoscales do not move with the mean velocity but with their own drift velocity,” which is “the most germane of all the nonlinear metrics.” Accounting for these results in a mesoscale parameterization presents conceptual and practical challenges since linear analysis is no longer usable and one needs a model of nonlinearity. A mesoscale parameterization is presented that has the following features: 1) it is based on the solutions of the nonlinear mesoscale dynamical equations, 2) it describes arbitrary tracers, 3) it includes adiabatic (A) and diabatic (D) regimes, 4) the eddy-induced velocity is the sum of a Gent and McWilliams (GM) term plus a new term representing the difference between drift and mean velocities, 5) the new term lowers the transfer of mean potential energy to mesoscales, 6) the isopycnal slopes are not as flat as in the GM case, 7) deep-ocean stratification is enhanced compared to previous parameterizations where being more weakly stratified allowed a large heat uptake that is not observed, 8) the strength of the Deacon cell is reduced. The numerical results are from a stand-alone ocean code with Coordinated Ocean-Ice Reference Experiment I (CORE-I) normal-year forcing.

scholarly journals Spatial and temporal trends in exhumation of the Eastern Himalaya and syntaxis as determined from a multitechnique detrital thermochronological study of the Bengal Fan

2019 ◽  
Vol 131 (9-10) ◽  
pp. 1607-1622 ◽  
Author(s):  
Yani Najman ◽  
Chris Mark ◽  
Dan N. Barfod ◽  
Andy Carter ◽  
Randy Parrish ◽  
...  
Keyword(s):  
Fission Track ◽  
Temporal Trends ◽  
White Mica ◽  
Eastern Himalaya ◽  
Bengal Fan ◽  
Zircon Fission Track ◽  
Lag Times ◽  
Depositional Age ◽  
International Ocean Discovery Program ◽  
Greater Himalaya

AbstractThe Bengal Fan provides a Neogene record of Eastern and Central Himalaya exhumation. We provide the first detrital thermochronological study (apatite and rutile U-Pb, mica Ar-Ar, zircon fission track) of sediment samples collected during International Ocean Discovery Program (IODP) Expedition 354 to the mid–Bengal Fan. Our data from rutile and zircon fission-track thermochronometry show a shift in lag times over the interval 5.59–3.47 Ma. The oldest sample with a lag time of <1 m.y. has a depositional age between 3.76 and 3.47 Ma, and these short lag times continue to be recorded upward in the core to the youngest sediments analyzed, deposited at <1 Ma. We interpret the earliest record of short lag times to represent the onset of extremely rapid exhumation of the Eastern Himalayan syntaxial massif, defined as the syntaxial region north of the Nam La Thrust. Below the interval characterized by short lag times, the youngest sample analyzed with long lag times (>6 m.y.) has a depositional age of 5.59–4.50 Ma, and the zircon and rutile populations then show a static peak until >12 Ma. This interval, from 5.59–4.50 Ma to >12 Ma, is most easily interpreted as recording passive erosion of the Greater Himalaya. However, single grains with lag times of <4 m.y., but with high analytical uncertainty, are recorded over this interval. For sediments older than 10 Ma, these grains were derived from the Greater Himalaya, which was exhuming rapidly until ca. 14 Ma. In sediments younger than 10 Ma, these grains could represent slower, yet still rapid, exhumation of the syntaxial antiform to the south of the massif. Lag times <1 m.y. are again recorded from 14.5 Ma to the base of the studied section at 17 Ma, reflecting a period of Greater Himalayan rapid exhumation. Mica 40Ar/39Ar and apatite U-Pb data are not sensitive to syntaxial exhumation: We ascribe this to the paucity of white mica in syntaxial lithologies, and to high levels of common Pb, resulting in U-Pb ages associated with unacceptably high uncertainties, respectively.

Dating lacustrine carbonate strata with detrital zircon U-Pb geochronology

Geology ◽  
2020 ◽  
Author(s):  
Emily S. Finzel ◽  
Justin A. Rosenblume
Keyword(s):  
Detrital Zircon ◽  
Relative Proportion ◽  
Foreland Basin ◽  
Depositional Environments ◽  
Detrital Zircons ◽  
Sediment Flux ◽  
Coarse Grained ◽  
Southwestern Montana ◽  
Tectonically Active ◽  
Lacustrine Carbonate

Carbonate lacustrine strata in nonmarine systems hold great potential for refining depositional ages through U-Pb dating of detrital zircons. The low clastic sediment flux in carbonate depositional environments may increase the relative proportion of zircons deposited by volcanic air fall, potentially increasing the chances of observing detrital ages near the true depositional age. We present U-Pb geochronology of detrital zircons from lacustrine carbonate strata that provides proof of concept for the effectiveness of both acid-digestion recovery and resolving depositional ages of nonmarine strata. Samples were collected from Early Cretaceous foreland basin fluvial sandstone and lacustrine carbonate in southwestern Montana (USA). Late Aptian–early Albian (ca. 115–110 Ma) maximum depositional ages young upsection and agree with biostratigraphic ages. Lacustrine carbonate is an important component in many types of tectonic basins, and application of detrital zircon U-Pb geochronology holds considerable potential for dating critical chemical and climatic events recorded in their stratigraphy. It could also reveal new information for the persistent question about whether the stratigraphic record is dominated by longer periods of background fine-grained sedimentation versus short-duration coarse-grained events. In tectonically active basins, lacustrine carbonates may be valuable for dating the beginning of tectonic subsidence, especially during periods of finer-grained deposition dominated by mudrocks and carbonates.

The erosion history of the Central Alps: evidence from zircon fission track data of the foreland basin sediments

Terra Nova ◽  
2000 ◽  
Vol 12 (4) ◽  
pp. 163-170 ◽  
Author(s):  
C. Spiegel ◽  
J. Kuhlemann ◽  
I. Dunkl ◽  
W. Frisch ◽  
H. von Eynatten ◽  
...  
Keyword(s):  
Fission Track ◽  
Foreland Basin ◽  
Central Alps ◽  
Zircon Fission Track ◽  
Erosion History ◽  
History Of

scholarly journals Post-glacial acidification of two alpine lakes (Sudetes Mts., SW Poland), as inferred from diatom analyses

2016 ◽  
Vol 56 (1) ◽  
pp. 65-77
Author(s):  
Elwira Sienkiewicz
Keyword(s):  
Environmental Changes ◽  
Drainage Basin ◽  
Anthropogenic Pollution ◽  
Mountain Lakes ◽  
Glacial Sediments ◽  
Arctic Regions ◽  
Water Ph ◽  
History Of ◽  
The Difference

Abstract Past environmental changes in mountain lakes can be reconstructed with the use of subfossil diatoms from post-glacial sediments. This study applied such an analysis to two mountain lakes in the Sudetes Mts. in Poland: Mały Staw (MS) and Wielki Staw (WS). Cores 882 cm long (MS) and 1100 cm long (WS) taken from the centre of each lake in 1982 were used to study the long-term acidification history of these lakes. Changes in vegetation indicate that the initial phase of MS started at the end of the Pleistocene. WS sediments began to accumulate shortly after that, at the beginning of the Holocene. The majority of the diatom assemblages are typical of oligotrophic acidic lakes located in alpine and arctic regions. A pH reconstruction based on diatoms (DI-pH) showed long-term acidification dating to almost the beginning of the lakes’ existence. Natural acidification began after the deglaciation, and the most intensive acidification continued to the end of the mid-Holocene. Through the whole period studied, pH decreased by 1.4 in MS and 0.9 in WS. After a period of relatively stable lake water pH, it decreased rapidly during the last few decades of the 20th century, due to anthropogenic pollution: pH declined by 0.7 in MS and 0.3 in WS. Mały Staw, being shallower, smaller, and with a larger drainage basin than Wielki Staw, is more sensitive to acid deposition; this accounts for the difference in pH.

An investigation of storm waves in the North Atlantic Ocean

1955 ◽  
Vol 230 (1183) ◽  
pp. 560-569 ◽  
Keyword(s):  
Wind Speed ◽  
Shallow Water ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Deep Ocean ◽  
The North ◽  
Storm Waves ◽  
The Difference ◽  
Tidal Streams ◽  
Wave Recorder

Since February 1953 the Ocean Weather Ship Weather Explorer , using a shipborne wave recorder, has taken records of waves at the positions ‘India’ (61° 00' N, 15° 20' W) and ‘Juliet’ (52° 20' N, 20° 00'W). An investigation of the records shows that conditions of wave generation in the deep ocean are different from those on the continental shelf. In both deep and shallow water, the steepness of the highest waves decreases as the fetch increases until an equilibrium value is reached after about 100 miles. In deep water this equilibrium value increases with the wind speed, whereas in shallow water it tends to decrease with wind speed. Different empirical rules are required for wave prediction in the deep ocean and the shallow sea. The difference can probably be attributed to a greater effect of turbulence near the coast, where the depth is of the same order as the wavelength and there are active tidal streams.

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