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Reconstruction of Gondwana supercontinent in the late Neoproterozoic (A) and the Cambro-Ordovician (B). Sediment transport paths are diagrammatic to illustrate probable sources. Panel A highlights potential drainage systems that may have been sourced from the early Cambrian orogens on the eastern and western edges of India. We argue that the location of the Neoproteozoic–early Cambrian platform deposits in the eastern and western Himalaya are linked to drainage systems that were limited to the eastern and western edges of the Indian continent. Uniformity in the DZ spectra of the outboard GH and TH strata is due to mixing via large margin-parallel transport systems. The Paro and Jaishidanda Formations would restore medially between these two systems. Panel B highlights our hypothesis of how the transport systems changed in the Cambro-Ordovician when the depositional environment switched from open ocean conditions to an active margin. We suggest that the dramatic increase in sedimentation thickness, clast size and input of Ordovician detritus observed in the GH and TH sections require a more proximal source, such as the uplifted Greater Himalayan rocks and Cambrian–Ordovician granites intruding the Greater Himalayan sequence. B, Bhutan section; KT, Krol-Tal section; K, Kathmandu section; S, Spiti section; red line and F-MCT mark the future location of the Main Central Thrust; see text for discussion.
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Detrital zircon (DZ) ages, augmented with εNd(0) and δ13C isotopic values from 18 new and 22 published samples collected from Lesser Himalayan (LH), Greater Himalayan (GH) and Tethyan Himalayan (TH) rocks in Bhutan, support deposition of > 7 km of sedimentary rock in late Cambrian–Ordovician time and provide a stratigraphic framework for the pre-co...
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... Hu et al., 2016). The eastern Himalaya (Bhutan and Arunachal segments) is traditionally divided into three tectonostratigraphic packages; these include, from north to south, the Tethyan Himalayan Sequence, Greater Himalayan Crystalline Complex, and Lesser Himalayan Sequence (Yin et al., 2010a;McQuarrie et al., 2013). South of the eastern Himalaya lie the Assam and Bengal foreland basins, which are separated by the Shillong Plateau and Mikir Hills, two exposed Indian Craton fragments ( Fig. 1b; Biswas et al., 2007;Yin et al., 2010b). ...
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... In the Himalaya, a major stratigraphic break is postulated between the Outer and Inner Lesser Himalayan sedimentary successions in smaller areas, spanning around 1000 to 500 Ma, based on the U-Pb DZ data from the western or the eastern Himalaya (Kohn et al. 2010;McKenzie et al. 2011;Long et al. 2011;McQuarrie et al. 2013;DeCelles et al. 2016;Bhargava 2021). The main objective of this contribution is to apply the available U-Pb zircon ages from the Outer Lesser Himalayan (oLH) and the Inner Lesser Himalayan (iLH) Sedimentary Belts to critically assess this stratigraphic break on the mountain-scale, prior to the Himalayan Orogeny. ...
... Out of these, six samples indicated the Neoproterozoic maximum deposition age, while three samples gave the younger ages. Thus, the maximum deposition age of Jaishidanda Formation appears to be either (i) Ordovician or younger, with DZ spectra resulting from variation in the sediment source rocks, or (ii) Neoproterozoic to Ordovician (Bgure 5i; Tobgay et al. 2010;Long et al. 2011;McQuarrie et al. 2013;DeCelles et al. 2016). ...
... An interesting 5.5 km thick succession of garnet mica schist, calc-silicate, marble, quartzite and orthogneiss is exposed in an almost circular Paro Window in western Bhutan beneath the MCT. The Paro Formation produces highly variable DZ spectra, with peaks at *500, 800, 1200, 1400, 1700, 1800 and 2500 Ma that are identical to the DZ pattern of the Jaishidanda Formation (Bgure 5m; Tobgay et al. 2010;McQuarrie et al. 2013). ...
... 500 Ma and ca. 830 Ma granites (Long et al., 2011;McQuarrie et al., 2013). This rock suite also hosts generations of leucogranites between 23 and 12 Ma (Kellett et al., 2013;Rubatto et al., 2013). ...
This study recognizes a transition in the modes of ductile deformation across the Himalayan Crystalline Complex (HCC) from field and microstructural evidence. This transition leads to the Main Central Thrust (MCT) zone localization in the Darjeeling-Sikkim Himalaya. In the initial stage of crustal shortening (prior to ~16 Ma), the HCC experienced temporally varying distributed ductile strains that produced regionally occurring planar fabrics and folds of three generations. Thereafter, the tectonic transition (from distributed to localized deformation) at ~16 Ma occurred, forming the MCT zone in the HCC. This MCT zone (~ 4 to 6 km thick) marks a diffuse metamorphic/rheological boundary between the hot HCC and the relatively colder Lesser Himalayan terrane to the south. The field data suggests that the base of compressed reverse paleo-isograds at the bottom of the MCT zone coincides with the transition of quartz creep mechanisms, from sub-grain rotation (SGR) to grain boundary migration (GBM). The present study documents the prograde metamorphic imprints to establish the P-T conditions of these multiple deformation episodes. Finally, this study presents a conceptual tectonic model, based on previous laboratory findings, to propose a two-stage tectono-thermal evolution of the Higher Himalaya.
... The Munsiari Group overrides the iLH along the MT/MCT 1 or lower MCT (in Nepal Himalaya)/MCT [3,9,23,25,43,[61][62][63] and contains mylonitized and imbricated Paleoproterozoic megacryst granite gneiss, fine-grained biotite paragneiss, garnetiferous mica schist, phyllonite and sheared Amphibolite [3]. Based on DOI: http://dx.doi.org/10.5772/intechopen.104259 the geochemistry and geochronological studies, these rocks have been part of the Paleoproterozoic magmatic arc [42], as most of the zircon U-Pb ages of these rocks lie between ~1.97 and 1.75 Ga [55,59,60,[64][65][66][67][68][69], that is, similar to iLH rocks. ...
Understanding the crustal evolution of any orogen is essential in delineating the nomenclature of litho units, stratigraphic growth, tectonic evolution, and, most importantly, deciphering the paleogeography of the Earth. In this context, the Himalayas, one of the youngest continent-continent collisional orogen on the Earth, has played a key role in understanding the past supercontinent cycles, mountain building activities, and tectonic-climate interactions. This chapter presents the journey of Himalayan rocks through Columbian, Rodinia, and Gondwana super-continent cycles to the present, as its litho units consist of the record of magmatism and sedimentation since ~2.0 Ga. The making of the Himalayan orogen started with the rifting of India from the Gondwanaland and its subsequent movement toward the Eurasian Plate, which led to the closure of the Neo-Tethyan ocean in the Late-Cretaceous. India collided with Eurasia between ∼59 Ma and ∼40 Ma. Later, the crustal thickening and shortening led to the metamorphism of the Himalayan crust and the development of the north-dipping south verging fold-and-thrust belt. The main phase of Himalayan uplift took place during the Late-Oligocene-Miocene. This chapter also provides insights into the prevailing kinematic models that govern the deep-seated exhumation of Himalayan rocks to the surface through the interplay of tectonics and climate.
... However, abundant Greenville and Pan-African detrital zircons from the East Gondwana were imported into the early Paleozoic sedimentary rocks in the Yidun-Songpan-Ganze terranes and Yangtze Block (Fig. 10). This shift of sediment provenance indicates significant tectonic and paleogeographic location change of the Yidun-Songpan-Ganze terranes and Yangtze Block, which could be best ascribed to the collision Fig. 12. Relative probability plots of detrital zircon U-Pb age from the lower Paleozoic sedimentary rocks in the (a) Yidun Terrane (this study), (b) South Qiangtang Terrane (Pullen et al., 2008;Dong et al., 2011;Zhu et al., 2011a), (c) Tethyan Himalaya (Myrow et al., 2009(Myrow et al., , 2010Hughes et al., 2011;McQuarrie et al., 2013), (d) Greater Himalaya (Gehrels et al., 2006a(Gehrels et al., , 2006bMcQuarrie et al., 2013), (e) Lesser Himalaya (McQuarrie et al., 2008(McQuarrie et al., , 2013Myrow et al., 2010;Hofmann et al., 2011;Long et al., 2011), (f) northwestern India Craton (Turner et al., 2014;Wang et al., 2019), (g) Lhasa Terrane Dong et al., 2009Dong et al., , 2010, (h) East Antarctica (Goodge et al., 2002(Goodge et al., , 2004a(Goodge et al., , 2004b, (i) western Australia (Cawood and Nemchin, 2000;Markwitz et al., 2017), (j) northeastern Australia (Fergusson et al., 2001(Fergusson et al., , 2007, and (k) southeastern Australia (Ireland et al., 1998;Berry et al., 2001). ...
... However, abundant Greenville and Pan-African detrital zircons from the East Gondwana were imported into the early Paleozoic sedimentary rocks in the Yidun-Songpan-Ganze terranes and Yangtze Block (Fig. 10). This shift of sediment provenance indicates significant tectonic and paleogeographic location change of the Yidun-Songpan-Ganze terranes and Yangtze Block, which could be best ascribed to the collision Fig. 12. Relative probability plots of detrital zircon U-Pb age from the lower Paleozoic sedimentary rocks in the (a) Yidun Terrane (this study), (b) South Qiangtang Terrane (Pullen et al., 2008;Dong et al., 2011;Zhu et al., 2011a), (c) Tethyan Himalaya (Myrow et al., 2009(Myrow et al., , 2010Hughes et al., 2011;McQuarrie et al., 2013), (d) Greater Himalaya (Gehrels et al., 2006a(Gehrels et al., , 2006bMcQuarrie et al., 2013), (e) Lesser Himalaya (McQuarrie et al., 2008(McQuarrie et al., , 2013Myrow et al., 2010;Hofmann et al., 2011;Long et al., 2011), (f) northwestern India Craton (Turner et al., 2014;Wang et al., 2019), (g) Lhasa Terrane Dong et al., 2009Dong et al., , 2010, (h) East Antarctica (Goodge et al., 2002(Goodge et al., , 2004a(Goodge et al., , 2004b, (i) western Australia (Cawood and Nemchin, 2000;Markwitz et al., 2017), (j) northeastern Australia (Fergusson et al., 2001(Fergusson et al., , 2007, and (k) southeastern Australia (Ireland et al., 1998;Berry et al., 2001). ...
... However, abundant Greenville and Pan-African detrital zircons from the East Gondwana were imported into the early Paleozoic sedimentary rocks in the Yidun-Songpan-Ganze terranes and Yangtze Block (Fig. 10). This shift of sediment provenance indicates significant tectonic and paleogeographic location change of the Yidun-Songpan-Ganze terranes and Yangtze Block, which could be best ascribed to the collision Fig. 12. Relative probability plots of detrital zircon U-Pb age from the lower Paleozoic sedimentary rocks in the (a) Yidun Terrane (this study), (b) South Qiangtang Terrane (Pullen et al., 2008;Dong et al., 2011;Zhu et al., 2011a), (c) Tethyan Himalaya (Myrow et al., 2009(Myrow et al., , 2010Hughes et al., 2011;McQuarrie et al., 2013), (d) Greater Himalaya (Gehrels et al., 2006a(Gehrels et al., , 2006bMcQuarrie et al., 2013), (e) Lesser Himalaya (McQuarrie et al., 2008(McQuarrie et al., , 2013Myrow et al., 2010;Hofmann et al., 2011;Long et al., 2011), (f) northwestern India Craton (Turner et al., 2014;Wang et al., 2019), (g) Lhasa Terrane Dong et al., 2009Dong et al., , 2010, (h) East Antarctica (Goodge et al., 2002(Goodge et al., , 2004a(Goodge et al., , 2004b, (i) western Australia (Cawood and Nemchin, 2000;Markwitz et al., 2017), (j) northeastern Australia (Fergusson et al., 2001(Fergusson et al., , 2007, and (k) southeastern Australia (Ireland et al., 1998;Berry et al., 2001). ...
The Yidun Terrane, sandwiched between the Qiangtang and Songpan-Ganze terranes, hosts important information on the tectonic evolution of the eastern Tibetan Plateau. However, its tectonic link with adjacent terranes and East Gondwana remains equivocal. Here, we present U-Pb-Hf isotopes of detrital zircons from the upper Neoproterozoic-lower Paleozoic clastic rocks in the Yidun Terrane. The results show that detrital zircons from the Neoproterozoic rocks are mainly of ca. 821 – 890 Ma, 1714 – 1977 Ma, and 2317 – 2520 Ma, with εHf(t) values of each group comparable to coeval magmatic rocks in the nearby South China Block. This suggests that the Yidun Terrane and South China were possibly connected in the late Neoproterozoic, with the latter being the main sedimentary provenance. In contrast, the five Paleozoic samples have markedly different detrital zircon age spectra at ca. 2600 – 2300 Ma, 1100 – 900 Ma, 900 – 740 Ma, and 690 – 480 Ma, which were interpreted to have derived from Pan-African and Grenville-age provinces in the East Gondwana, as well as the South China Block and Songpan-Ganze Terrane. Such a major change on provenance suggests that after prolonged isolation in the Proto-Tethys, the Yidun Terrane began to collide with the East Gondwana in late Ediacaran to early Paleozoic. Integrated with published works, we consider that the Yidun Terrane, along with Songpan-Ganze Terrane and Yangtze Block, was located on the northern margin of East Gondwana during the early Paleozoic.
... The THS, which is widely exposed to the north of the STDS, mainly consists of Mesozoic marine clasts and limestones from the passive continental margin of the Indian plate. THS rocks are also minorly exposed as klippen to the south of the main trace of the STDS, which are mainly composed of Ordovician fine-grained muscovite quartzite and are locally termed the Chekha Formation McQuarrie et al., 2013). The GHS mainly consists of gneiss of amphibolite-eclogite facies (Daniel et al., 2003) with wide Miocene leucogranite intrusions possibly formed by decompression melting (Grujic et al., 2002). ...
The Main Himalayan Thrust (MHT), the most prominent tectonic boundary between the subducting Indian crust and the overthrusting Himalaya, occurs as a key structure dominating the active tectonics of the Himalaya. Previous studies indicate that the MHT forms a major buried ramp in the mid-crust, which with varying geometry and kinematics leads to a distinctive pattern of uplift along the Himalaya. However, it is unknown if and how these along-strike variations are correlated with the well-known active N-S-trending normal faults across the Himalaya and Tibetan Plateau. In this study, we report 39 new apatite and zircon fission track ages in the Cona area (~92°E) in the eastern Himalaya, coinciding with the easternmost N-S-trending extensional system in southern Tibet, the Cona Cross Structure (CCS). Spatial patterns of surface cooling ages are consistent with an overthrusting of the Himalayan wedge above a mid-crustal ramp in the MHT. Thermokinematic inverse modeling yields contrasting geometries and kinematics for the mid-crustal ramp on both sides of the CCS. Specifically, to the west of the CCS, the MHT developed a major ramp (with a dip angle of 20.4 ± 2.9°) spanning 50–70 km, which initiated at ~11.7 ± 0.6 Ma. To the east, thermokinematic inversion suggests a much less developed ramp spanning only ~10–15 km, initiated at ~6.8 ± 0.3 Ma. These results imply an ~14-km deeper depth of the MHT to the west of the CCS than to the east. Our modeling also suggests distinctive and evolving ramp-thrusting rates for the MHT on both sides of the CCS. This suggests an independent deformation accommodation by the MHT ramp thrusting in segments divided by the CCS along strike. Our study highlights a genetic correlation between the active orogenic-parallel ramp evolution and the N-S-trending faulting across the Himalaya, which divides the orogenic-parallel tectonics into independent structural segments.
... 1250-900 Ma) grains, including the East African Orogen between eastern Africa and Indo-Antarctica (Stern 1994), the Kuunga-Pinjarra Orogen between Australia-Antarctica and Indo-Antarctica (Meert 2003;Collins and Pisarevsky 2005). Age distribution spectra for detrital zircons from Cambrian sandstone from the NCC stand in striking contrast to the existing Cambrian spectra from North Africa and Arabia (Avigad et al. 2005), Tethyan Himalaya (Myrow et al. 2009(Myrow et al. , 2010McQuarrie et al. 2013), West Australia (Markwitz et al. 2017), and many peri-Gondwanan terranes (Zhu et al. 2011;Zoleikhaei et al. 2021), which share a similar age distribution pattern dominated by two prominent population of ca. 650-550 Ma and ca. ...
... 1.85 Ga granitic gneiss in the Maizuru belt (Kimura et al. 2021) provide the supports for the linkage Figure 6. Comparison of distribution patterns of zircon ages from the basement (Nutman et al. 2011;Lv et al. 2012;Bai et al. 2014Bai et al. , 2015Bai et al. , 2019Zhang et al. 2015Sawaki et al. 2016;Li et al. 2016a;Liu et al. 2017b;Duan et al. 2019;Wang et al. 2019Wang et al. , 2019aWang et al. , 2019bZhao et al. 2020a;Dong et al. 2021;Liu and Zhang 2021;Xiao et al. 2021), Paleo-to Mesoproterozoic sediments Ying et al. 2011;Liu et al. 2014Liu et al. , 2017aZhang et al. 2014aZhang et al. , 2016bZhang et al. , 2020Zhong et al. 2015;Wang et al. 2020a), Neoproterozoic sediments Dong et al. 2017;Li et al. 2020;Zhang et al. 201), and the early-middle Cambrian sediments from the NCC (this study; Darby and Gehrels 2006;McKenzie et al. 2011;Hu et al. 2013;Kim et al. 2013bKim et al. , 2017Kim et al. , 2019Lee et al. 2016;Li et al. 2018a;He et al. 2017;Jang et al. 2018;Pang et al. 2018;Sun and Dong 2019;Wan et al. 2019;Zhang et al. 2020;Cho et al. 2021), and the Cambrian strata in the Northern Gondwana (Squire et al. 2006;Myrow et al. 2009Myrow et al. , 2010Wang et al. 2010;Zhu et al. 2011;McQuarrie et al. 2013;Markwitz et al. 2017;He et al. 2020;Zoleikhaei et al. 2021). ...
The basal Cambrian sandstone unit in the North China craton (NCC) is an example of globally widespread siliciclastic succession that resides on the Great Unconformity and deposited on a hypothesized low-lying peneplain during the Cambrian global eustatic sea-level rise. Detrital zircon age signatures from this distinct sequence enable recognition of the ancient drainage system of the NCC in deep time and track its potential linkage with the Gondwana landmass. LA-ICP-MS U-Pb dating of the fossil-calibrated basal Cambrian (Series 2) detrital zircon samples from seven measured sections reveal marked spatial changes in their age signatures that can be divided into three distinct types. The first is generally characterized by the bimodal age populations with broad peaks at ~1.85 Ga and ~2.5 Ga that correlate with the Archean to Paleoproterozoic basement inboard of the NCC. The second is featured by multi-modal distribution with diagnostic Neoproterozoic peaks that correspond to subregional magmatic record. The third also shows multiple-zircon age populations, but yields significant crystallization ages close to the early Cambrian age. Comparing our new data with existing age spectra for the Cambrian strata across the NCC and the northern Gondwana demonstrates that separate drainage systems did exist in the peneplained basement during global Cambrian transgression and the basal Cambrian unit in the NCC was not a part of the far-travelled sand sheet across the northern margin of Gondwana. The most suitable source for Cambrian-aged grains constrained by paleogeographic restoration is the arc terrane developed along the northern margin of the NCC as a result of subduction of the Paleo-Asian oceanic plate. Our new continental-scale detrital zircon provenance signatures in the basal Cambrian unit suggest that the NCC should be considered a discrete continental block separated by the Proto-Tethys Ocean in the Cambrian, rather than an integral part of the northern Gondwana.
... These observations can be integrated into a pre-Himalayan deformation model that appears valid for the western and central Himalaya (the eastern Himalaya is somewhat dissimilar, see McQuarrie et al., 2008 andYin et al., 2010): progressively younger layers occurred at the surface to the north within a gently north-dipping pattern, and Mesoproterozoic and upper Paleoproterozoic layers pinch out at depth to the north ( Fig. 2) (Webb et al., 2011b;Webb, 2013). Older models involving deposition of the Greater Himalayan Crystalline complex as an accreted terrane (e.g., DeCelles et al., 2000) have been largely abandoned as detrital zircon geochronology has indicated continuity of Neoproterozoic protoliths extending from the Indian craton through all of the Lesser Himalayan Sequence, Greater Himalayan Crystalline complex, and Tethyan Himalayan Sequence (e.g., Myrow et al., 2003;McKenzie et al., 2011;Webb et al., 2011b;McQuarrie et al., 2013;Hughes et al., 2019;cf. Martin 2017). ...
Eclogites represent the highest pressure conditions yet observed from rocks thrust to the surface in the central Himalaya. A detailed investigation of the protolith nature of these eclogites is needed to better understand pre-Himalayan geological history. Retrogressed eclogites were collected from Thongmön (Dingri County) and Riwu (Dinggye County), central Himalaya, China. We investigated the bulk rock major and trace elements, Sr-Nd isotopes, zircon geochronology, and Hf-O isotopes. These retrogressed eclogites experienced five stages of metamorphic evolution from prograde amphibolite-facies to peak eclogite-facies, and high pressure granulites-facies, granulites-facies then final amphibolite-facies overprinting during exhumation. Geochemically, they are subalkaline basalts with high FeO contents and a tholeiitic affinity; trace elements show similarities with enriched mid-ocean ridge basalts. Bulk rocks have a wide range of εNd(t) values from −0.24 to +7.08, and an unusually wide range of initial 87Sr/86Sr ratios of 0.705961−0.821182. Zircon relict magmatic cores from both Thongmön and Riwu eclogites yield a consistent protolith age of ca. 1850 Ma, with enriched heavy rare earth element patterns and significant negative Eu anomalies. These relict cores have oxygen isotopes signatures of δ18O = 5.8−8.1‰, εHf(t) values of −4.85 to +9.59, and two-stage model ages (TDM2) of 1.91−2.81 Ga. Metamorphic overgrowth zircons yield much younger ages of ca. 14 Ma. Integration of all of the above data suggests that the protolith of these central Himalayan retrogressed eclogites might be Proterozoic continental flood basalts of the North Indian Plate, generated under a post-collisional extension setting during the assembly of the Columbia Supercontinent. Occurrence of both Neoproterozoic−early Paleozoic rocks and ca. 1.85 Ga rocks in the regional crystalline rocks may reflect either unrecognized sub-horizontal Main Central Thrust exposure(s) or exhumation of a deeply cut part of the Greater Himalayan Crystalline complex. In combination with previous reports of Late Cretaceous, Neoproterozoic, and similar but younger Paleoproterozoic protolith, it is clear that the central Himalayan eclogites originate from multiple sources of protolith.
... Paleoproterozoic to Cambrian units of the LH zone are exposed north of the Bome thrust ( Figure 1) and include the Paleoproterozoic Shumar and Daling Formations, the Neoproterozoic to Ordovician Jaishidanda Formation, and the Cambrian Rupa Group (DeCelles et al., 2016;Long et al., 2011;McQuarrie et al., 2013;Tobgay et al., 2010). The Daling Fm. is extensively intruded by the Bomdila Gneiss (DeCelles et al., 2016;Kumar, 1997;Sarma et al., 2014;Yin et al., 2006Yin et al., , 2010. ...
The exhumation record of a fold-thrust belt is preserved by thermochronologic minerals, such as zircon and apatite, both in exposed bedrock and in synorogenic sedimentary rocks in the foreland basin. Treating these as separate records can lead to potentially contrasting interpretations of a single exhumation history. Integrating the bedrock and detrital records with thermokinematic models of sequential deformation of a fold-thrust belt can identify viable exhumation pathways of the bedrock and elucidate both how bedrock exhumation varies in space and time and how accurately the basin records exhumation changes in the source region.
Predicted bedrock cooling ages and modeled basin thickness are used to estimate the amount and source of sediments supplied to the foreland basin during each increment of deformation to predict the detrital cooling signal over time. Applying this integrated bedrock-detrital model to a cross-section in Arunachal Pradesh, NE India demonstrates spatial and temporal variability in exhumation, with a background exhumation rate of <2 mm/yr, periods of rapid exhumation at rates of 3-7 mm/yr, and short pulses of 10-12 mm/yr rates during out-of-sequence thrusting. Our results predict that the detrital apatite fission track (DAFT) system records a constant lag time of 0.5-1 Myr. Although the response of the detrital zircon fission track (DZFT) system is more complex, the system records changes in lag time (1-5 Myr) as a function of the kinematics, deformation rates, and thermal profile of the crust in the hinterland. However, the DZFT cooling signal is delayed by 1-2 Myr relative to the age of marked shifts in location, magnitude, and rate of exhumation in the source region. Our models also highlight the importance of recycled foreland deposits in matching the ~20 Ma static peak in the DZFT record and ~14 Ma static peak in the DAFT record.
... The Jaishidanda Fm. is comprised of garnet-and staurolite-bearing schist, quartzite and intervals of marble (DeCelles et al., 2016). In eastern Bhutan, the Bomdila Gneiss-Daling Fm. is unconformably overlain by a ca. 1 km thick Jaishidanda Fm. north of the Shumar thrust McQuarrie et al., 2013McQuarrie et al., , 2019. In contrast, in western Bhutan, the corelative ca. 5 km thick Paro Formation (Tobgay et al., 2010) is interpreted to be in fault contact with the structurally underlying Daling Fm. (McQuarrie et al., 2013(McQuarrie et al., , 2014. ...
... In eastern Bhutan, the Bomdila Gneiss-Daling Fm. is unconformably overlain by a ca. 1 km thick Jaishidanda Fm. north of the Shumar thrust McQuarrie et al., 2013McQuarrie et al., , 2019. In contrast, in western Bhutan, the corelative ca. 5 km thick Paro Formation (Tobgay et al., 2010) is interpreted to be in fault contact with the structurally underlying Daling Fm. (McQuarrie et al., 2013(McQuarrie et al., , 2014. Similar to western Bhutan, in Arunachal Pradesh the mapped extent of the Jaishidanda Fm. is ca. ...
Quantitative integration of cross-section geometry, kinematics and cooling ages requires notably more complicated kinematic and exhumation pathways than are typically assumed with a simple in-sequence model of cross-section deformation. Incorporating measured basin thickness and depositional ages, determined from magnetostratigraphy or young detrital zircon fission track cooling ages, provide further constraints on the timing of fault motion, as changes in shortening rate that may not alter bedrock cooling ages can affect the depositional age of foreland basin strata. Thermokinematic models of balanced cross-sections in Arunachal Pradesh, NE India demonstrate that the kinematic sequence and shortening rate exert the largest control over the pattern of predicted cooling ages for the region, by dictating the location and timing of rock uplift and exhumation (cooling) over ramps. The best fit to the measured bedrock cooling ages and basin constraints is achieved with a kinematic sequence involving early foreland propagation of four Lesser Himalayan faults combined with variable shortening rates. Fast rates (25-30 mm/yr) are required to accompany early foreland propagation at ~14-13 Ma followed by slower rates (18-20 mm/yr) until 10 Ma. Shortening rates increase to ~25-35 mm/yr at ~10 Ma until ~5-7 Ma. A decrease in shortening rate occurs between 7 Ma and 5 Ma, with rates of 9-15 mm/yr until the present. Although non-unique, the updated cross-section geometry and kinematics highlight components of geometry, deformation and exhumation that must be included in any valid cross-section model for this portion of the eastern Himalaya such as the location of active ramps, and location and age of two key fault systems, the Bomdila imbricate zone and the thrust faults that form the Lumla duplex. Less unique are the specific geometries of faults, thickness of strata they carry, shortening rates, particularly between 14-8 Ma, and model parameters such as topography, heat production and flexure.
