Detrital Apatite Fission-track Thermochronology Research Articles

A re-evaluation of the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan (Tian Shan, NW China) based on new basement and detrital apatite fission track thermochronology

ABSTRACT Bogda Shan is a mountain belt located at the eastern extremity of the Chinese Tianshan and records a complex and debated exhumation history. Previous studies have reported a young Cenozoic thermal history for the exhumation of Bogda Shan, which is in conflict with the observation of preserved Mesozoic erosion surfaces in the area. This study re-evaluates the Meso-Cenozoic thermo-tectonic evolution of Bogda Shan using apatite fission track (AFT) thermochronology. Palaeozoic basement (meta-sandstone) samples collected from the northern and southwestern flanks of the mountain ranges reveal apparent Mesozoic AFT ages ranging from ~202 Ma to ~97 Ma. Inverse thermal history modelling results reveal slow to moderate basement cooling during the early Mesozoic, corresponding to relatively low levels of exhumation. This accounts for the preservation of low-relief Mesozoic peneplanation surfaces recognized at elevations of ~3500–4000 m. None of the presented AFT data and thermal history models show any evidence for significant deep Cenozoic exhumation. In the neighbouring Junggar Basin, a Middle Jurassic sandstone sample records partial resetting of the AFT system during the Cretaceous. This observation conflicts with previous data (from the same Jurassic strata) where complete resetting of the AFT clock during the Cenozoic was suggested. Furthermore, Lower Cretaceous and Palaeogene sediments from the Turpan-Hami Basin show non-reset detrital AFT age populations of ~197, ~135, and ~104 Ma, which are coincident with the main pulses of exhumation recorded in the Chinese North Tianshan. Based on a comprehensive summary of the published data, we argue for a Mesozoic building of the Bogda–Balikun–Harlik mountain chain in the eastern Chinese Tianshan. Subsequent Cenozoic exhumation must have been relatively modest at most (<2 km) as it was not recorded by AFT thermochronology.

New Detrital Apatite Fission Track Thermochronological Constraints on the Meso-Cenozoic Tectono-Thermal Evolution of the Micangshan-Dabashan Tectonic Belt, Central China

The Micangshan-Dabashan tectonic belt, located in the southern Qinling-Dabie Orogen near the northeastern Tibetan Plateau, is a crucial area for understanding the processes and mechanisms of orogenesis. Previous studies have been focused on the cooling process via thermochronology and the mechanism and process of basement uplift have been investigated. However, the coupling process of basement exhumation and sedimentary cap cooling is unclear. The tectono-thermal history constrained by the detrital apatite fission track (AFT) results could provide valuable information for understanding crustal evolution and the coupling process. In this study, we provided new detrital AFT thermochronology results from the Micangshan-Dabashan tectonic belt and obtained nine high-quality tectono-thermal models revealing the Meso-Cenozoic cooling histories. The AFT ages and lengths suggest that the cooling events in the Micangshan area were gradual from north (N) to south (S) and different uplift occurred on both sides of Micangshan massif. The cooling in Dabashan tectonic zone was gradual from northeast (NS) to southwest (SW). The thermal histories show that a relatively rapid cooling since ca. 160 Ma occurred in the Micangshan-Dabashan tectonic belt, which was a response to the event of Qinling orogenic belt entered the intracontinental orogenic deformation. This cooling event may relate to the northeastward dextral compression of the Yangtze Block. The sedimentary cap of Cambriano-Ordovician strata responded positively to this rapid cooling event and entered the PAZ since ca. 63 Ma. The deep buried samples may be limited affected by climate and water erosion and the accelerated cooling was not obvious in the Late Cenozoic. Collectively, the cooling processes of basement and sedimentary cap in Micangshan-Dabashan tectonic belt were inconsistent. The uplift of the sedimentary area is not completely consistent with that of the basement under thrust and nappe action. The rigid basement was not always continuous and rapidly uplifted or mainly showed as lateral migration in a certain stage because of the different intensities and modes of thrust and nappe action, and the plastic sedimentary strata rapidly uplifted due to intense folding deformation.

Early Cenozoic exhumation in the Qilian Shan, northeastern margin of the Tibetan Plateau: Insights from detrital apatite fission track thermochronology

AbstractThe Qilian Shan is a reactivated fold‐thrust belt at the northeastern margin of the Tibetan Plateau (TP). The initiated timing of the Qilian Shan's tectonic response to Indian‐Asian plate convergence has significant implications for our understanding of the growth of the TP, yet remains a controversial topic. We conducted apatite fission track analyses of the Cenozoic synorogenic sediments in the Subei Basin on the northwestern flank of the Qilian Shan to investigate the time of initial Qilian Shan deformation during the Cenozoic. An integration of new and existing detrital apatite fission track ages indicates that terranes in the Qilian Shan experienced a prominent tectonic exhumation event at ~60–50 Ma. This result suggests that tectonism initiated on the northeastern margin of the TP nearly simultaneously with the India‐Asia collision.

Detrital Thermochronology Reveals Major Middle Miocene Exhumation of the Eastern Flank ofthe Andes That Predates the PampeanFlat Slab (33°–33.5°S)

AbstractThe Cordón del Plata and Cordón del Portillo (32.6°–33.8°S) are the portions of the Frontal Cordillera that straddle the transition zone between the Pampean flat‐slab subduction segment to the north and the normal subduction segment to the south. A complete understanding of how the Frontal Cordillera developed is necessary in order to evaluate different tectonic models for the Andes along with their relation to subduction dynamics and contractional upper‐crustal deformation. Detrital apatite fission track thermochronology of modern river sediments that drain the eastern and western slopes of the Cordón del Plata and the northern Cordón del Portillo provides constraints on regional exhumation histories. AFT data from each catchment typically contain multiple age peaks, but all have a prominent 15.3–17 Ma age peak. One catchment, the Las Tunas River has a unimodal distribution at 17.0 ± 1.1 Ma, with a confined track length distribution indicative of rapid cooling at that time. These results, combined with provenance analysis in the adjacent Cacheuta Basin, indicate significant early to middle Miocene (~16 Ma) exhumation in the Cordón del Plata and the northern sector of the Cordón del Portillo. Exhumation related to rock uplift occurred prior to the ~11 Ma onset of a flat slab geometry at these latitudes, but immediately after the main east vergent contractional event in the adjacent Principal Cordillera. Such Frontal Cordillera exhumation fits in an eastward, youngest to the foreland sequence of deformation of the different morphostructural Andean units at ~33°–34°S, arguing against the recently proposed west vergent orogenic system at these latitudes.

Cenozoic deformation history of the Qilian Shan (northeastern Tibetan Plateau) constrained by detrital apatite fission-track thermochronology in the northeastern Qaidam Basin

The Cenozoic deformation history of the Qilian Shan, which is a reactivated fold-thrust belt in the northeastern region of the Tibetan Plateau, is poorly understood but features prominently in the geodynamic mechanism of the evolution of the plateau. The northeastern Qaidam Basin, which is located on the south flank of the Qilian Shan, provides a valuable record of the timing and pattern of the Cenozoic deformation of the Qilian Shan in its synorogenic sediments. This study analyzes the apatite fission-track (AFT) thermochronological signatures of the middle Miocene-Quaternary detrital sediments in the northeastern Qaidam Basin and modern stream sands draining the Qilian Shan as a proxy for the timing of tectonic deformation in the Qilian Shan. Our detrital AFT ages indicate that a Cenozoic initial rapid exhumation event occurred in the Qilian Shan in the late Paleocene-early Eocene (~60–54 Ma), followed by another rapid exhumation event during the middle-late Eocene (~42–38 Ma) and some exhumation during the Oligocene-middle Miocene (~33–14 Ma). Distinct changes in detrital AFT ages at depositional ages of ~12 Ma and ~2.1 Ma suggest that further tectonic deformation affected the Qilian Shan at these times. Our results, along with those of previous studies, suggest that tectonic deformation propagated into the northeastern edge of the Tibetan Plateau almost simultaneously with the India-Asia collision. The spatial evolution of Cenozoic deformation in the Qilian Shan is likely based on the distribution of weak structures in the upper crust.

Detrital apatite fission track constraints on Cenozoic tectonic evolution of the northeastern Qinghai-Tibet Plateau, China: Evidence from Cenozoic strata in Lulehe section, Northern Qaidam Basin

The Northern Qaidam Basin is located at the northeastern part of the Qinghai-Tibetan Plateau. It contains very thick Cenozoic terrestrial clastic sediments, which records the formation of the northern Qaidam Basin due to compressional deformation during the Indo-Asian collision. In this paper, we used detrital apatite fission-track thermochronology, including 4 sandstones and 2 conglomerates samples from the Lulehe section, to reveal the Cenozoic evolution of the northern Qaidam Basin. Fission-track dating indicated the source region of the Lulehe section has experienced important cooling and uplifting in the Late Cretaceous (at ~85.1 Ma and ~65 Ma) and the Eocene (~52 Ma), respectively. The AFT age distribution on the section suggested that the provenance of Lulehe section sediments were mainly derived from the south Qilian Shan (Qilian Mountains) and Altun Shan (Altun Mountains), and two significantly provenance changes may occur at 43.4-46.1 Ma and ~37.8 Ma, respectively. The results may have strong constrains on the Cenozoic deformation and tectonic evolution of the northern Qaidam Basin and Qinghai-Tibet Plateau.

Retraction: Middle Miocene to Early Pliocene Contraction in the Chos Malal Fold‐and‐Thrust Belt (Neuquén Basin, Argentina): Insights from Structural Analysis and Apatite Fission‐Tracks Thermochronology

In the southern Central Andes at 37-38 °S latitude, the Chos Malal fold-and-thrust belt (FTB), which results from the Late Cretaceous closure of the Neuquen Basin, has generated increasing interest because of its potential for hydrocarbon exploration. Using detailed field mapping, seismic reflection and well data analysis, cross-section balancing, and detrital apatite fission-track thermochronology from 18 samples distributed along the FTB, we bring new quantitative constraints on the chronology of the Neogene structural development of the Chos Malal FTB. Our dataset reveals that extensive tectonically-driven exhumation through basement-involved thrusting, occurred at ~15-7 Ma in both the inner and outer sectors of the FTB. This age range is corroborated by indirect dating of the Chos Malal Formation, a syntectonic unit also deformed after deposition, which we find was deposited after 7.2 Ma ± 1.6 / 2.0 Ma, an age much younger than the Miocene age it was previously assigned. We document for the first time an Early Pliocene rapid cooling stage that was ongoing ~ 5.5 to 5.1 Ma ago in the interior of the orogenic wedge, which we attribute to out-of-sequence thrusting along basement-involved thrust faults bounding the Cordillera del Viento, driving the surface uplift of this prominent topographic feature. Finally, our sequential reconstruction of the thick and thin-skinned structures of the Chos Malal FTB shows that most of the horizontal shortening was accommodated after the Middle Miocene, which we thus consider as being the main phase of orogenic building in this sector of the Andes.

Palaeogene growth of the northeastern Tibetan Plateau: Detrital fission track and sedimentary analysis of the Lanzhou basin, NW China

The Palaeogene evolution of the northeastern Tibetan Plateau remains elusive, because of the paucity of well-dated long-lasting and continuous sedimentary records. In this work, we present a detailed detrital apatite fission track thermochronology and stratigraphic study in the Lanzhou basin, located on the eastern-most margin of northeastern Tibet, where Eocene to middle Miocene sediments are well preserved. Combining the analysis of sedimentology records and synsedimentary tectonic structures, four regional tectonic phases are deciphered (52–47Ma, 40–32Ma, 23–20Ma and <16Ma, respectively). These episodes were spaced out by three periods of tectonic stability or quiescence linked to regional relief-reduction. Our apatite fission-track data suggest that far-field stress due to the India-Asia collision had been propagated to this region since early Eocene, and the modern northeastern portion of the Tibetan Plateau has been buildup since then. Thereafter, the growth of the northeastern Tibetan Plateau was dominated by a tectonic activity/inactivity cycle until late Miocene. Thus, the regional growth history appears to have been episodic in nature during the Cenozoic.

Detrital apatite fission track analyses of the Subei basin: implications for basin-range structure of the northern Tibetan Plateau

ABSTRACTThe northern Tibetan Plateau has evolved a unique basin-range structure characterized by alternating elongated mountain ranges and basins over a history of multiple tectonic and fault activities. The Subei basin recorded evolution of this basin-range structure. In this study, detailed detrital apatite fission track (AFT) thermochronological studies in conjunction with previously documented data reveal provenance of the Subei basin, important information about the Indo-Eurasia collision, and two Miocene uplift and exhumation events of the northern Tibetan Plateau. Detrital AFT analyses combined with sedimentary evidences demonstrate that the Danghenanshan Mountains is the major provenance of the Subei basin. In addition, very old age peaks indicate that part sediments in the Subei basin are recycling sediments. Age peak populations of 70–44 Ma and 61–45 Ma from the lower and upper Baiyanghe formations record the tectono-thermal response to the Indo-Eurasia collision. Combined detrital AFT thermochronology, magnetostratigraphy and petrography results demonstrate the middle Miocene uplift and exhumation event initiated 14–12 Ma in the Subei basin, which may resulted from the Miocene east-west extension of the Tibetan Plateau. Another stronger uplift and exhumation event occurred in the late Miocene resulted from strengthened tectonic movement and climate. A much younger AFT grain age, breccia of diluvial facies and boulders of root fan subfacies record the late Miocene unroofing in the Danghenanshan Mountains.

Decoupling of long-term exhumation and short-term erosion rates in the Sikkim Himalaya

Understanding the relative strengths of tectonic and climatic forcing on erosion at different spatial and temporal scales is important to understand the evolution of orogenic topography. To address this question, we quantified exhumation rates at geological timescales and erosion rates at millennial timescales in modern river sands from 10 sub-catchments of the Tista River drainage basin in the Sikkim Himalaya (northeast India) using detrital apatite fission-track thermochronology and cosmogenic 10Be analyses, respectively. We compare these rates to several potential geomorphic or climatic forcing parameters. Our results show that millennial erosion rates are generally higher and spatially more variable than long-term exhumation rates in Sikkim. They also show strongly contrasting spatial patterns, suggesting that the processes controlling these rates are decoupled. At geological timescales, exhumation rates decrease from south to north, with rates up to 1.2±0.6 mm/yr recorded in southwest Sikkim and as low as 0.5±0.2 mm/yr in the northernmost catchment. Long-term exhumation rates do not correlate with any geomorphic or climatic parameter. We suggest they are tectonically controlled: high rates in southwest Sikkim may be linked to the building of the Lesser Himalaya Rangit Duplex, whereas low rates in north Sikkim are consistent with cessation of extensional exhumation along the South Tibetan Detachment after 13 Ma. The highest apparent erosion rates recorded by cosmogenic nuclides (∼5 mm/yr) occur in catchments spanning the Main Central Thrust Zone, but these appear to be strongly influenced by recent landsliding. High millennial erosion rates (1–2 mm/yr) also occur in north Sikkim and may be climatically driven through strong glacial inheritance of the landscape, as attested by high channel-steepness values close to the maximum extent of glaciers during the Last Glacial Maximum. In contrast, variations in rainfall rate do not seem to strongly influence either millennial erosion or long-term exhumation rates in Sikkim.

Magnetostratigraphy and detrital apatite fission track thermochronology in syntectonic conglomerates: constraints on the exhumation of the South-Central Pyrenees

ABSTRACT The syntectonic continental conglomerates of the South‐Central Pyrenees record the late stages of thin‐skinned transport of the South‐Pyrenean Central Units and the onset of exhumation of the Pyrenean Axial Zone (AZ) in the core of the orogen. New magnetostratigraphic data of these syntectonic continental conglomerates have established their age as Late Lutetian to Late Oligocene. The data reveal that these materials were deposited during intense periods of tectonic activity of the Pyrenean chain and not during the cessation of the deformation as considered previously. The magnetostratigraphic ages have been combined with new detrital apatite fission track (AFT) thermochronology from AZ‐derived granite cobbles within the syntectonic conglomerates. Distribution of the granitic cobbles with different AFT ages and track lengths combined with their depositional ages reveal information on the timing and rate of episodes of exhumation in the orogen. Some AFT ages are considerably older than the AFT ages of the outcropping AZ granitic massifs, indicating erosion from higher crustal levels within the massifs than presently exposed or from completely eroded plutons. Inverse thermal modelling reveals two well‐defined periods of rapid cooling in the hinterland at ca. 50–40 and ca. 30–25 Ma, with another poorly defined cooling episode at ca. 70–60 Ma. The lowest stratigraphic samples experienced postburial annealing caused by the deposition of younger syntectonic sediments during progressive burial of the south Pyrenean thrust and fold belt. Moreover, samples from the deeper stratigraphic levels also reveal postorogenic cooling during the Late Miocene as a response to the excavation of the Ebro River towards the Mediterranean Sea. Our data strongly support previous ideas about the burial of the South Pyrenean fold and thrust belt by Late Palaeogene syntectonic conglomerates and their subsequent re‐excavation and are consistent with other thermochronological data and thermal modelling from the interior part of the orogen.