Provenance Shift Research Articles

Provenance evolution of Oligocene–Pliocene foreland deposits in the Dezful embayment to constrain Central Zagros exhumation history

This paper presents a detailed provenance analysis of the 6.5 km thick Oligocene–Pliocene foreland succession in the north Dezful embayment in Zagros, Iran. Using petrography, geochemistry and palaeoflow analysis, we determined three provenance shifts during the exhumation of the Zagros orogen. Above the Ahwaz sandstones, sourced from the Arabian craton, a sharp decrease in SiO 2 /Al 2 O 3 , Zr/Sc, Th/Sc, Th/Co and Th/Cr within the Gachsaran Fm. and the appearance of first-cycle sands derived from metamorphic and volcanic rocks at the base of the Aghajari Fm. characterize the onset of exhumation, rising topography and denudation of the Zagros orogenic system during the latest Oligocene and constitute the first shift. The second shift, in the middle Aghajari Fm., is marked by a distinct increase in radiolarian cherts and compatible/incompatible elements, indicating the exhumation of Neotethyan radiolarite–ophiolite allochthonous slices in the High Zagros Zone during the Tortonian ( c . 9 Ma). Large quantities of carbonate clasts derived from the nearby growing Izeh Zone anticlines characterize the Messinian ( c . 7 Ma) Bakhtyari conglomerates marking the third shift. In conclusion, a detailed hands-on provenance analysis of the clastic sedimentary sequences in the north Dezful embayment enabled us to determine catchment areas and shifts hitherto unstudied, thus contributing to the exhumation history of the Central Zagros orogenic system. Supplementary material: Details of the petrography and geochemistry results are available at https://doi.org/10.6084/m9.figshare.c.4905558

Geodynamic evolution of the Minas Basin, southern São Francisco Craton (Brazil), during the early Paleoproterozoic: Climate or tectonic?

Like many other cratons around the world, the São Francisco Craton is characterized by an early Paleoproterozoic (2.5–2.1 Ga) unconformity that is reported worldwide as the result of global glacial events leading to a major sea-level drop. To document the duration and the cause(s) of the stratigraphic hiatus in the São Francisco Craton, this study provides U–Pb dates obtained on detrital zircon grains from the Piracicaba Group, which directly overlies the unconformity. Our results show that this sedimentary unit is younger than 2333 ± 11 Ma and consequently deposited during the late Siderian or the early Rhaycian. This maximum depositional age demonstrates that the early Paleoproterozoic stratigraphic gap lasted for at least 60 Ma. Based on quantitative analyses of the age distribution of the Piracicaba Group, we evidence a major shift in sedimentary provenance between the sedimentary units located below and above the unconformity. This change is interpreted to be directly related to the development of a subduction system along the southern and eastern margins of the São Francisco proto-craton. Our results indicate that regional geodynamic events, and not only global glacial events and their consequences, must be accounted for in Earth system models for the early Paleoproterozoic.

Andean Mountain Building and Foreland Basin Evolution During Thin‐ and Thick‐Skinned Neogene Deformation (32–33°S)

AbstractThe southern Central Andes recorded retroarc shortening, basin evolution, and magmatic arc migration during Neogene changes in subduction. At 31–33°S, above the modern flat‐slab segment, spatial and temporal linkages between thin‐ and thick‐skinned foreland shortening, basement‐involved exhumation of the main Cordillera, and lower‐crustal hinterland thickening remain poorly resolved. We integrate new geochronological and thermochronological data for thrust sheets and Neogene foreland basin fill with structural, sedimentological, and passive seismic results to reconstruct the exhumation history and evaluate potential geometric linkages across structural domains. 40Ar/39Ar ages for volcanic horizons and zircon U‐Pb ages for synorogenic clastic deposits in the Manantiales Basin constrain the minimum duration of synorogenic sedimentation to ~22–14 Ma. Detrital zircon age distributions record sequential unroofing of hinterland thrust sheets until ~15 Ma, followed by eastward (cratonward) advance of the deformation front, shutoff of western sediment sources, and a shift from fluvial to alluvial fan deposition at ~14 Ma. Apatite (U‐Th)/He cooling ages confirm rapid exhumation of basement‐involved structural blocks and basin partitioning by ~14–5 Ma, consistent with the timing of the Manantiales facies and provenance shifts and a coeval (~12–9 Ma) pulse of thin‐skinned shortening and exhumation previously identified in the eastern foreland. Late Miocene–Pliocene (~8–2 Ma) cooling ages along the Chile‐Argentina border point to hinterland uplift during the latest stage of Andean orogenesis. Finally, geophysical constraints on crustal architecture and low‐temperature thermochronometry results are compatible with a hybrid thin‐ and thick‐skinned décollement spanning retroarc domains.

Cenozoic growth of the Eastern Kunlun Range (northern Tibetan Plateau): evidence from sedimentary records in the southwest Qaidam Basin

ABSTRACT The Cenozoic sedimentary infill of the Qaidam Basin in the northern Tibetan Plateau provide significant insights into the uplift history and the tectonic evolution of the basin-bounding mountain ranges. Along the SW basin margin, a continuous record is preserved in the ~3000-m-thick Cenozoic succession at the Changweitai area. An up-section switch from marginal and deep lacustrine sedimentation to lacustrine delta-alluvial fan deposition indicates progradation and increasingly basinward advance of sediment transportation systems. Provenance data from sandstone petrology, palaeocurrent analysis and zircon U-Pb geochronology suggest that the Eastern Kunlun Range has been consistently providing material to the SW Qaidam basin since the deposition of the upper Xiaganchaigou Formation, indicating its latest uplift episode prior to the Late Eocene (before 35.5 Ma). However, variation in depositional systems indicates a clear shift in sediment provenance between the deposition of the Xiayoushashan Formation and the Shangyoushashan Formation. We propose that the Cenozoic Eastern Kunlun Range experienced a northward encroachment of shortening into the Qaidam Basin. During the Early Miocene, extensive topographic growth of the Altyn Tagh Range caused by reactivation of the Altyn Tagh strike-slip fault, provided the main source of sediment for the western Qaidam basin. Subsequently, a new source for the basin was provided by the uplifting Qimen Tagh subrange since ~15 Ma.

Distinct petrographic responses to basin reorganization across the Triassic–Jurassic boundary in the southwestern Barents Sea

AbstractA general shift towards higher mineralogical and textural maturity changes the reservoir character across the Triassic–Jurassic transition in the southwestern Barents Sea basin (SWBSB), largely affecting the hydrocarbon prospectivity in the region. Petrographic and geochronological provenance data presented in this paper suggest that the shift from mineralogically immature to mature sandstones initiated during the deposition of the Norian–Rhaetian Fruholmen Formation, and varies with basin location. Strong contrasts between the Fruholmen Formation and underlying formations are associated with proximity to the rejuvenated Caledonian and Fennoscandian hinterlands and are mainly restricted to the southern basin margins. In the basin interior, subtle petrographic variations between the Fruholmen Formation and older Triassic sandstones reflect a distal position relative to the southern hinterland. The long‐lived misconception of a regional compositional contrast in the Arctic at the turn of the Norian can be attributed to higher sampling frequency associated with hydrocarbon exploration activity along the southern basin margins, and masking by increased annual precipitation and subsequent reworking during the Jurassic. Geothermal signatures and rearrangement of ferric clay material across the Carnian–Norian transition support a recycled origin for the Fruholmen Formation in the basin interior. As the closest tectonically active region at the time, the Novaya Zemlya fold‐and‐thrust belt represents the best provenance candidate for polycyclic components in Norian–Rhaetian strata. In addition to recycling in the hinterland during the Late Triassic, local erosion of exposed intrabasinal highs and platforms at the Triassic–Jurassic transition represents a second process where thermodynamically unstable mineral components originally sourced from the Uralides may be removed. Textural and mineralogical modification may also have occurred in marginal‐marine depositional environments during periods with elevated sea level. Mature sediment supply from the rejuvenated hinterland in the south, multiple cycles of reworking and gradual accumulation of polycyclic grains have likely led to the extreme compositional maturity registered in the Tubåen, Nordmela and Stø formations in the SWBSB. It is likely that increased annual precipitation since the latest Carnian had an amplifying effect on sandstone maturation across the Triassic–Jurassic boundary, but we consider the effect to be inferior compared to provenance shifts and reworking. Findings from this study are important for understanding compositional and textural maturity enhancement processes in siliciclastic sedimentary basins.

Ordovician tectonic shift in the western North China Craton constrained by stratigraphic and geochronological analyses

AbstractThe western North China Craton (W‐NCC) comprises the Alxa Terrane in the west and the Ordos Block in the east; they are separated by the Helanshan Tectonic Belt (HTB). There is an extensive debate regarding the significant Ordovician tectonic setting of the W‐NCC. Most paleogeographic reconstructions emphasized the formation and rapid subsidence of an aulacogen along the HTB during the Middle–Late Ordovician, whereas paleomagnetic and geochronologic results suggested that the Alxa Terrane and the Ordos Block were independent blocks separated by the HTB. In this study, stratigraphic and geochronologic methods were used to constrain the Ordovician tectonic processes of the W‐NCC. Stratigraphic correlations show that the Early Ordovician strata comprise ~500‐m‐thick tidal flat and lagoon carbonate successions with a progressive eastward onlap, featuring a west‐deepening shallow‐water carbonate shelf. In contrast, the Late Ordovician strata are composed of ~3,000‐m‐thick abyssal turbidites in the west and ~400‐m‐thick shallow‐water carbonates in the east, defining an eastward‐tapering basin architecture. Early Ordovician detrital zircons with ages of ~2,800–1,700 Ma were derived from the Ordos Block; the Late Ordovician turbidites were sourced from the western Alxa Terrane, based on zircon ages clustered at ~1,000–900 Ma. The petrographic modal composition and zircon age distribution imply a provenance shift from a stable craton to a recycled orogen in the Middle Ordovician. These shifts define a tectonic conversion from a passive continental margin to a foreland basin at ~467 Ma, resulting in the eastward progradation of the turbidite wedge around the HTB, the eastward backstepping of the carbonate platform in the east and the eastward expansion of orogenic thrusting in the western Alxa Terrane. This tectono‐sedimentary shift coincided with the advancing subduction of the southern Paleo‐Asian Ocean beneath the Alxa Terrane, generating the western Alxa continental arc and the paired retro‐arc foredeep in the east under a compressional tectonic regime.

Holocene dynamics of the southern westerly winds over the Indian Ocean inferred from a peat dust deposition record

The southern westerly winds (SWW) play a major role in climate variability in Southern Hemisphere mid- and high-latitudes, regulating rainfall, ocean circulation, and the Southern Ocean carbon sink. Despite their importance, little is known about millennial scale changes in the SWW and how they have influenced the climate system in the past and interacted with the Earth’s surface elements, such as dust, nutrients and carbon. Here we present a dust record from a 6.6 kyr old peat core in Amsterdam Island (AMS) situated at the northern edge of the SWW (37°S) in the Southern Indian Ocean. Mineral dust flux was used to track atmospheric dust production, long-distance transport and subsequent deposition. Dust provenance was determined from rare earth element (REE) and Nd isotopic signatures (εNd) in the peat core, compared with a reference dataset of Southern Hemisphere dust sources. Using a multi-proxy mixing model, the εNd and REE ratios show a relatively uniform mixture of ca. 40% local, 15% Southern African and 45% Southern South American dust sources since 6.6 cal kyr BP. However, from 1910 AD onwards, there is a doubling in the contribution from Southern Africa (32%). Two mineral dust flux minima occur at 6.2–4.9 cal kyr BP and 3.9–2.7 cal kyr BP, interpreted as periods with equatorward-shifted and/or strengthened SWW at the northern edge of the wind belt. Conversely, periods of higher dust flux at 6.6–6.2 cal kyr BP, 4.9–3.9 cal kyr BP, and 1.4 cal kyr BP onwards are interpreted as poleward-shifted and/or weakened SWW. These interpretations are based on the findings that higher (lower) wind speeds lead to enhanced (less) removal of distal dust on the way to AMS, by wet deposition and turbulence. Published Holocene SWW records at the northern edge of the wind belt (33–41°S) covering South-America, Southern-Africa and Australia, show much variability over the last 6.6 kyr. We suggest this reflects complex regional climate variability in the different SH longitudinal sectors, indicating that SWW are not zonally homogeneous at the northern edge of the wind belt. The recent shift in dust provenance is not accompanied by enhanced total dust deposition at AMS. We therefore suggest that human impact (e.g., land use changes) and drier climate conditions in Southern Africa have led to enhanced dust mobilization.

Erosional and Tectonic Evolution of a Retroarc Orogenic Wedge as Revealed by Sedimentary Provenance: Case of the Oligocene – Miocene Patagonian Andes

Sedimentary provenance techniques have been widely applied in foreland basin settings to understand tectonic and magmatic processes by tracking the exposure and erosion of distinct sediment source areas through time. We present a case example from the Magallanes-Austral retroarc foreland basin of Chile and Argentina (51°30’S), where modal sandstone and conglomerate compositional data, detrital zircon U-Pb geochronology, and sedimentology data from the Oligocene-Miocene Rio Guillermo Formation document a change in source areas during an important stage of orogenic development. In particular, our results from the ~24.3-21.7 Ma Rio Guillermo Formation record an abrupt shift from transitional to undissected arc provenance that indicate rejuvenated magmatism within the contemporary arc. Minor components of lithic grains suggest a subordinate source of recycled sediments that we interpret may have been derived from the intervening external fold-and-thrust belt, rather than directly from sources in the hinterland thrust domain. Detrital zircon U-Pb geochronology data show mostly Neogene (~20-40 Ma) and Cretaceous (~70-110 Ma) age groups, with minor amounts of Jurassic (~145-155 Ma) and Paleozoic (~260-540 Ma) age groups, which are consistent with a syndepositional arc and recycled external fold-and-thrust belt sources. Stratigraphic data suggest a vegetated, channelized braidplain environment developed above an erosional unconformity with the underlying shallow-marine Rio Turbio Formation. Upsection, the Rio Guillermo Formation locally transitions to a low-energy, organic-rich floodplain setting located within the upper reaches of a fluvial-tidal transition zone of the coastal plain, and the uppermost part of the formation is characterized by a coarse-grained sandy channelized braidplain environment along the foreland basin margin. Moderate sediment accumulation rates and coastal plain progradation during this period is consistent with sustained sediment flux from the Patagonian Andes and tectonic subsidence along the basin margin. Taken collectively, we propose that the abrupt provenance shift dominantly records erosion of the rejuvenated mafic volcanic arc, despite coeval changes in orogenic wedge dynamics brought about by increased plate convergence rates that drove uplift of the intervening external-fold-and-thrust belt along reactivated deep-seated high-angle basin structures.

Sediment provenance of pre- and post-collisional Cretaceous–Paleogene strata from the frontal Himalaya of northwest India

Whereas the timing for India–Asia collision remains debated, contrasting collisional models provide testable predictions in terms of sediment source contributions during the accumulation of Paleocene to middle Eocene deposits now exposed in the frontal Himalayan system. Within the Lesser Himalaya and frontal thrust system of northwest India, discontinuous exposures of the Cretaceous Singtali Formation and upper Paleocene–middle Eocene Subathu Formation yield a record of these early collisional stages. To test competing collisional models, we analyze the provenance of these deposits with new detrital zircon U-Pb and Hf isotopic data which can distinguish among Indian plate, Asian plate, Kohistan-Ladahk arc, and various Himalayan sources. Detrital zircon age distributions for the Singtali Formation are dominated by Paleoproterozoic zircons with a distinct Cretaceous age component, whereas age data from the Subathu Formation record (1) a marked increase in the relative abundance of Cambrian–Neoproterozoic grains, (2) a decrease in the proportion of Paleoproterozoic grains, and (3) distinct Permian and Late Cretaceous–Paleocene age components. All Cretaceous grains from the Singtali Formation yielded crustal Hf isotopic signatures, indicating a distinctive pre-collisional source of Cretaceous grains of Indian affinity. Zircon Hf isotopic signatures from <320 Ma grains in the Subathu Formation show a significant lower to middle Eocene increase in source diversity, including juvenile grains most likely originating from the Asian plate and Kohistan-Ladakh arc. This requires inception of India-Asia collision by ∼44–50 Ma—the depositional age of the uppermost Subathu Formation. This major provenance shift is similar to that observed for pre- and post-collisional Tethyan Himalayan strata in the north, which is suggestive of a single contiguous basin linking the Lesser Himalaya by ∼44–50 Ma and contests the notion that the Lesser and Tethyan Himalaya were separated by a “Greater India Basin” during the Eocene. When coupled with the well documented Paleocene–early Eocene provenance record of the Tethyan Himalaya, these new data provide support for a collisional model in which Asian detritus reached the northernmost edge of India by ∼59 Ma with terminal closure of both the Shyok and Indus-Yarlung suture zones by ∼54 Ma.

Orogen proximal sedimentation in the Permian foreland basin

AbstractThe sedimentary fill of peripheral foreland basins has the potential to preserve a record of the processes of ocean closure and continental collision, as well as the long-term (i.e., 107–108 yr) sediment-routing evolution associated with these processes; however, the detrital record of these deep-time tectonic processes and the sedimentary response have rarely been documented during the final stages of supercontinent assembly. The stratigraphy within the southern margin of the Delaware Basin and Marathon fold and thrust belt preserves a record of the Carboniferous–Permian Pangean continental assembly, culminating in the formation of the Delaware and Midland foreland basins of North America. Here, we use 1721 new detrital zircon (DZ) U-Pb ages from 13 stratigraphic samples within the Marathon fold and thrust belt and Glass Mountains of West Texas in order to evaluate the provenance and sediment-routing evolution of the southern, orogen-proximal region of this foreland basin system. Among these new DZ data, 85 core-rim age relationships record multi-stage crystallization related to magmatic or metamorphic events in sediment source areas, further constraining source terranes and sediment routing. Within samples, a lack of Neoproterozoic–Cambrian zircon grains in the pre-orogenic Mississippian Tesnus Formation and subsequent appearance of this zircon age group in the syn-orogenic Pennsylvanian Haymond Formation point toward initial basin inversion and the uplift and exhumation of volcanic units related to Rodinian rifting. Moreover, an upsection decrease in Grenvillian (ca. 1300–920 Ma) and an increase in Paleozoic zircons denote a progressive provenance shift from that of dominantly orogenic highland sources to that of sediment sources deeper in the Gondwanan hinterland during tectonic stabilization. Detrital zircon core-rim age relationships of ca. 1770 Ma cores with ca. 600–300 Ma rims indicate Amazonian cores with peri-Gondwanan or Pan-African rims, Grenvillian cores with ca. 580 Ma rims are correlative with Pan-African volcanism or the ca. 780–560 Ma volcanics along the rifted Laurentian margin, and Paleozoic core-rim age relationships are likely indicative of volcanic arc activity within peri-Gondwana, Coahuila, or Oaxaquia. Our results suggest dominant sediment delivery to the Marathon region from the nearby southern orogenic highland; less sediment was delivered from the axial portion of the Ouachita or Appalachian regions suggesting that this area of the basin was not affected by a transcontinental drainage. The provenance evolution of sediment provides insights into how continental collision directs the dispersal and deposition of sediment in the Permian Basin and analogous foreland basins.

Provenance analysis of Cretaceous peripheral foreland basin in central Tibet: Implications to precise timing on the initial Lhasa-Qiangtang collision

Mesozoic strata along northern margin of the Lhasa terrane near Dingqing, Tibet provide a semi-continuous record of the Bangong-Nujiang Ocean closure and the subsequent Lhasa-Qiangtang collision. In this study, we present results of sandstone petrographic, detrital zircon UPb, and Cr-spinel geochemical data to determine the provenance of the Mesozoic strata (from the Triassic Quehala Group and the Mid-Jurassic to Lower Cretaceous Xihu, Lagongtang, and Duoni Formations, which are young from ~220 Ma to ~100 Ma) in this region, thereby allowing for interpretation of their tectonic setting. The similar 1200–900 age cluster from the lower Xihu Formation to that of the Triassic Quehala Group and the distinct age peaks at ~200 Ma and ~146 Ma from the upper Xihu Formation suggest a Lhasa terrane provenance to the south. Distinctive age clusters of 300–210 Ma and ~1800 Ma and Cr-spinel composition analysis of the Lagongtang Formation indicate a provenance shift from the Lhasa terrane to the Qiangtang terrane and the Bangong-Nujiang suture zone to the north. The Lagongtang Formation was deposited in a bathyal-abyssal to shallow-slope environment from north to south, that we interpret as the foredeep depozone and distal foredeep of a peripheral foreland basin system that developed due to flexural subsidence related to the Lhasa-Qiangtang collision and terrane accretion. The age of the Lhasa-Qiangtang collision is constrained by a ~140 Ma tuffite UPb age at the base of the foreland basin strata. An angular unconformity between the Xihu and Lagongtang Formation, which we interpret as the result of the Lhasa-Qiangtang collision. Our results indicate that the Lhasa-Qiangtang collision initiated around ~140 Ma in the Dingqing region, simultaneously with previous determinations 1200 km to the west near Gaize area. Therefore, we prefer quasi-simultaneous onset of collision along-strike to zippering collision models wherein the east collision age is older than the west.

The Mesoproterozoic Baoban Complex, South China: A missing fragment of western Laurentian lithosphere

Abstract New age data for the Baoban Complex, South China establishes that it lay outboard of western Laurentia in the early Mesoproterozoic but was not part of the Cathaysia Block, with which it is traditional linked, until the mid-Paleozoic. Our geochronology data for detrital zircon and authigenic monazite grains from metasedimentary rocks indicate accumulation between ca. 1.55 Ga and 1.45 Ga for the Gezhencun succession of the Baoban Complex and ca. 1.45 Ga and 1.30 Ga for the Ewenling succession. The former unit is dominated by detrital zircon populations between 1900 Ma and 1500 Ma with two peaks at 1780 Ma and 1580 Ma. The Ewenling succession has detrital zircon peaks at 1720 Ma and 1450 Ma. Newly discovered gneissic granites were emplaced at 1550 Ma and intruded by 1450 Ma leucogranite dykes that are coeval with 1460–1430 Ma bimodal magmatism. The whole Baoban Complex was metamorphosed over the range of 1.3–0.9 Ga based on ages of authigenic zircon and monazite. Depositional ages of metasedimentary rocks are coeval with successions of the Belt-Purcell Basin, western Laurentia. Detrital zircon from the two regions have similar age populations and Lu-Hf compositions, and display a synchronous provenance shift at ca. 1.45 Ga. Basement lithologies on Hainan Island range in age from ca. 1.55–1.43 Ga and underwent metamorphism during 1.3–0.9 Ga. This is younger than basement rocks on the mainland of the Cathaysia Block in South China, suggesting the two regions are spatially unrelated at this time and hence the Mesoproterozoic record of the island cannot constrain the location of the Cathaysia Block in the Nuna and Rodinia supercontinents.

Reconstruction on regional paleo-drainage evolution in the northern Junggar Basin, China during the last ~27 myr from provenance analyses and its implications for uplift of the Altai Mountains

Tectonic activity and climate change are regarded as two important driving forces on the evolution of large-scale drainage. The evolution of the Irtysh River and Ulungu River, two large-scale drainage systems in the northern Junggar Basin, can provide a key constraint on the uplift of the Altai Mountains and Central Asian aridification. However, we know little about the evolution of these two large-scale rivers. This study presents new detrital zircon U–Pb data from the late Oligocene to late Miocene sedimentary sequences and modern river sediments to reconstruct Cenozoic paleo-drainage evolution in the northern Junggar Basin. The detrital zircon U–Pb results show a single major population at 460-360 Ma, which is mainly derived from the Altai Mountains, for late Oligocene and early Miocene sequences, but two populations at 460-360 Ma and 340-200 Ma, which are mainly from the Altai Mountains and East Junggar terrane, for middle and late Miocene sequences. Our provenance study argues that the Irtysh River and Ulungu River in their modern extent did not exist prior ~18 Ma when the Altai Mountains allowed southward-flowing rivers to transport sediments into the inner Junggar Basin directly. The provenance shift in northern Junggar Basin at 17–18 Ma represents the progressive drainage expansion of the Ulungu River, evolving from relatively small rivers confined to the eastern Junggar Basin to a near-modern large-scale drainage system, due to the rapid uplift in the East Junggar terrane and eastern Altai Mountains in early Miocene. After ~6 Ma, the Irtysh River experienced a progressive drainage expansion, captured the southward-flowing tributaries of the Ulungu River and formed modern drainage pattern. Our study supports the initiation of exhumation before late Oligocene and a local tectonic uplift in early Miocene in Altai Mountains, which imply a complex deformation process in the Central Asia.

Provenance Control on Chemical Weathering Index of Fluvio‐Lacustrine Sediments: Evidence From the Qaidam Basin, NE Tibetan Plateau

AbstractCarbon dioxide drawdown resulting from enhanced chemical weathering during orogenesis has been invoked to explain late Cenozoic global cooling. Establishing chemical weathering records from the India–Asia collision zone is important to test this hypothesis because uplift of the Tibetan Plateau is thought to be responsible for Cenozoic cooling. However, proxies for the intensity of chemical weathering can be affected by additional factors, such as sediment grain size and provenance. Here we report major element compositions and calculated chemical weathering intensity records of three size fractions (0–5, 5–20, 20–63 μm) from the Dahonggou section of the Qaidam Basin in the northeastern Tibetan Plateau, and compare those records with published provenance data from the same section. Results show that the indices of the fine (0–5 μm) fraction vary in coordination with provenance shifts, but variations of the 5–20 and 20–63 μm fractions are less affected by provenance variations. Comparison with Upper Continental Crust reveals that some labile elements are not leached but instead are enriched in the fine fraction, indicating that it does not faithfully record chemical weathering intensity. In addition, weathering can result in clay mineral transformation instead of elemental variations, complicating the relationship between element‐based parameters and weathering intensity. This work suggests that changes in sediment provenance must be accounted for when inferring variations in chemical weathering intensity on the basis of element‐based weathering intensity indices of the clay fraction.

New insights into the provenance of Cenozoic strata in the Qaidam Basin, northern Tibet: Constraints from combined U-Pb dating of detrital zircons in recent and ancient fluvial sediments

Determining the provenance of Cenozoic strata in the Qaidam Basin is key to understanding the basin-mountain coupling history in the northern Tibetan Plateau (TP). However, the specific source areas of Cenozoic strata in the northern Qaidam Basin remain highly debated. Here, we combine analyses of detrital zircons UPb geochronology for recent and ancient fluvial sediments from the northern Qaidam Basin to trace source areas of Cenozoic strata and reconstruct related mountain-building processes. The results indicate that the diagnostic 270–240 Ma zircon UPb peak, which was previously recognized as the unique input of a southern source area, is widespread in the recent fluvial sediments of the northern Qaidam Basin. Given our new zircon UPb data, the source-to-sink transport processes of Cenozoic sediments in the northern Qaidam Basin can be summarized as follows. (1) The northern Qaidam Basin has received the eroded detrital material from a dominantly northern source throughout the Cenozoic. (2) The Qaidam BeiShan was uplifted already at least by the early Eocene and served as the single contributor of detritus to the Dahonggou (DHG) region, suggesting that far-field stress due to the India-Asia collision had been propagated to this region as early as the early Eocene. (3) An abrupt change in provenance is observed in the DHG region during 46.5–43.7 Ma. We interpret this middle Eocene source change as reflecting the onset of growth of the North Altyn Tagh Range, implying that the North Altyn Tagh Range was already serving as an important source area for the DHG region by the middle Eocene. (4) The South Qilian Range served again as the dominant source area for the DHG region after 24.6 Ma. The shift in provenance from the North Altyn Tagh Range to the South Qilian Range can be attributed to the uplift of the Saishiteng Shan.

Sediment provenance and routing evolution in the Late Cretaceous–Eocene Ager Basin, south‐central Pyrenees, Spain

AbstractThis study constrains the sediment provenance for the Late Cretaceous–Eocene strata of the Ager Basin, Spain, and reconstructs the interplay between foreland basin subsidence and sediment routing within the south‐central Pyrenean foreland basin during the early phases of crustal shortening using detrital zircon (DZ) U‐Pb‐He double dating. Here we present and interpret 837 new DZ U‐Pb ages, 113 of which are new DZ (U‐Th)/He double‐dated zircons. U‐Pb‐He double dating results allow for a clear differentiation between different foreland and hinterland sources of Variscan zircons (280–350 Ma) by leveraging the contrasting thermal histories of the Ebro Massif and Pyrenean orogen, recorded by the zircon (U‐Th)/He (ZHe) ages, despite their indistinguishable U‐Pb age signatures. Cretaceous–Paleocene sedimentary rocks, dominated by Variscan DZ U‐Pb age components with Permian–Triassic (200–300 Ma) ZHe cooling ages, were sourced from the Ebro Massif south of the Ager Basin. A provenance shift occurred at the base of the Early Eocene Baronia Formation (ca. 53 Ma) to an eastern Pyrenean source (north‐east of the Ager Basin) as evidenced by an abrupt change in paleocurrents, a change in DZ U‐Pb signatures to age distributions dominated by Cambro‐Silurian (420–520 Ma), Cadomian (520–700 Ma), and Proterozoic–Archean (&gt;700 Ma) age components, and the prominent emergence of Cretaceous–Paleogene (&lt;90 Ma) ZHe cooling ages. The Eocene Corçà Formation (ca. 50 Ma), characterized by the arrival of fully reset ZHe ages with very short lag times, signals the accumulation of sediment derived from the rapidly exhuming Pyrenean thrust sheets. While ZHe ages from the Corçà Formation are fully reset, zircon fission track (ZFT) ages preserve older inherited cooling ages, bracketing the exhumation level within the thrust sheets to ca. 6–8 km in the Early Eocene. These DZ ZHe ages yield exhumation rate estimates of ca. 0.03 km/Myr during the Late Cretaceous–Paleocene for the Ebro Massif and ca. 0.2–0.4 km/Myr during the Eocene for the eastern Pyrenees.

Magnetic polarity stratigraphy, provenance, and paleoclimate analysis of Cenozoic strata in the Qaidam Basin, NE Tibetan Plateau

AbstractThe growth and deformation history of the Qilian-Nan Shan thrust belt bounding the NE Qaidam Basin figures importantly in testing models of Tibetan Plateau uplift during the India-Asia collision. However, debate exists about the onset of uplift and exhumation of the Qilian-Nan Shan, with timing estimates ranging from early Paleocene to late Miocene. Here we report integrated analyses of magnetostratigraphy, anisotropy of magnetic susceptibility, sediment provenance, and paleoclimate (using environmental magnetic parameters) for Cenozoic fluvio-lacustrine strata from the Dahonggou section south of the Qilian-Nan Shan. The results are interpreted to demonstrate an early Miocene (ca. 20 Ma) onset of sediment accumulation in this location, with clastic sediment derived initially from the southern Qimen Tagh highland. The sediment source then switched to the northern part of the Qilian Shan region after ca. 18.5 Ma, consistent with initial uplift and exhumation of the Qilian Shan. Thereafter, two additional provenance shifts reveal progressive southward propagation of deformation in the Qilian-Nan Shan. As a result of this southward growth of Qilian-Nan Shan topography, precipitation increased after ca. 11 Ma at the study site due to orographic interception of moisture from the south. This work improves our understanding of the depositional age, sediment provenance, and paleoclimate history of the Qaidam Basin and reveals a prolonged history of Qilian-Nan Shan deformation and uplift, which may have accelerated during the late Miocene.

U-Pb ages of detrital zircons in lower Permian sandstone and siltstone of the Permian Basin, west Texas, USA: Evidence of dominant Gondwanan and peri-Gondwanan sediment input to Laurentia

Abstract The Permian Basin of west Texas, one of the most economically significant hydrocarbon basins in the United States, formed along the southwest margin of Laurentia in the foreland of the Ouachita-Marathon orogen during the late Paleozoic. While its stratigraphic record temporally coincides with syn- and post-orogenic Ouachita-Marathon sedimentation, sediment provenance, sediment routing and dispersal, and paleo-drainage evolution have remained controversial. This study presents more than 2000 new detrital zircon U-Pb ages from 16 samples across the Permian Basin to elucidate early Permian sediment provenance and basin-fill evolution. The data show that Wolfcampian sandstones are dominated by 950–1070 Ma and 500–700 Ma detrital zircon U-Pb ages, whereas Leonardian sandstones and siltstones are dominated by 500–700 Ma and 280–480 Ma detrital zircon U-Pb ages. Most of these age clusters are not typical Laurentian basement ages, but rather indicative of a southern Gondwanan and peri-Gondwanan sources of Mexico and Central America. This interpretation is corroborated by zircons with peri-Gondwanan and Gondwanan rim-core relationships, as well as major age components of euhedral zircons, matching Maya block basement ages. Regional comparison of these new detrital zircon results with published data from Carboniferous and Permian sedimentary rocks in various terranes of Mexico and Central America, Appalachian foreland basins, Ouachita orogenic belt, midcontinent of United States, and Fort Worth Basin (Texas), indicates that most sediment influx to the Permian Basin during the early Permian (Wolfcampian and Leonardian) was derived from basement or recycled upper Paleozoic strata associated with Gondwanan and peri-Gondwanan terranes in modern Mexico and Central America. North American basements such as the Appalachian Grenville (950–1300 Ma), Granite-Rhyolite (1300–1500 Ma), and Yavapai-Mazatzal (1600–1800 Ma) provinces, appear to have provided only minor amounts of sediment. In light of depositional age constraints, the timing of Marathon-Ouachita collision, and careful detrital zircon U-Pb age spectra comparison, the sediment provenance shift from Wolfcampian to Leonardian points to a diachronous, oblique continent-continent collision between Gondwana/peri-Gondwanan terranes and Laurentia.

Sediment grain size does matter: implications of spatiotemporal variations in detrital zircon provenance for early Paleozoic peri-Gondwana reconstructions

A comprehensive understanding of the relationship between the Sino-Korean Craton (SKC) and the Gondwana supercontinent is crucial for accurate reconstruction of the tectonic evolution and early Paleozoic paleogeography of East Asia. To explore the link between the SKC and peri-Gondwana, we provide new detrital zircon U–Pb age data from litho- and bio-stratigraphically constrained lower Cambrian to Lower Ordovician sandstone deposits from the eastern margin of the SKC (Taebaeksan Basin). Results indicate that the two distinct age spectra of detrital zircon resulted from provenance change combined with a strong function of sediment grain size within host siliciclastic rocks of the Taebaek Group. The age spectra from coarse-grained sandstones display Paleoproterozoic (1.9 Ga) and Neoarchean (~ 2.5 Ga) peaks, indicating that the sediments were supplied from the basement rocks of the SKC. Conversely, age spectra from fine-grained siliciclastics contain late Mesoproterozoic (~ 1.0 Ga) and Neoproterozoic (~ 0.6 Ga) peaks, with or without a Paleoproterozoic signal, consistent with a Gondwanan sediment origin. These different age populations have been documented in multiple Cambrian and Ordovician sequences of the SKC and are consistently well correlated with sediment grain size. Coarse-grained sediments, sourced primarily from local basement rocks, were deposited in coastal, nearshore, and shelf environments, whereas fine-grained sediments were derived from more distal sources (i.e., the Gondwana mainland and/or the Gyeonggi Marginal Belt) and deposited in inner to outer shelf settings. Therefore, the repeated occurrence of sediment with two distinct provenances in the Cambrian–Ordovician siliciclastics of the SKC is likely a result of provenance shift integrated with changing depositional environments in an epeiric platform. This yielded variations in sediment grain size and source rock provenance, with and/or without a tectonic activity. Consequently, our results indicate that the SKC was adjacent to Gondwana during the early Paleozoic.

From intrabasinal volcanism to far-field tectonics: causes of abrupt shifts in sediment provenance in the Devonian–Carboniferous Drummond Basin, Queensland

The Drummond Basin of central Queensland preserves a large-volume succession of little studied, predominantly fluviatile, coarse-grained sedimentary rocks of mid-Mississippian age. The stratigraphy of the basin has been subdivided into three sedimentary cycles. The Cycle 1/Cycle 2 boundary records a distinct, but poorly understood change in provenance from a volcanic-dominated succession related to initial basin rifting (Cycle 1) to a quartz-rich, craton-derived succession (Cycle 2). Cycle 3 has been thought to mark a resumption of intrabasinal volcanism and related sedimentation. The purpose of this study was to enhance the understanding of the basin-wide siliciclastic sedimentation of Cycles 2 and 3, and causes for the changes in sediment provenance. This objective was achieved by constraining large-scale spatial and temporal depositional trends and investigating sediment transport pathways into and through the basin. Petrographic, QFL, paleocurrent and conglomerate clast analyses were undertaken. The observations presented here have several implications relevant to understanding the stratigraphy of the Drummond Basin and regional tectonic events at this time. Cycle 3 is revised here primarily to be a continuation of Cycle 2-style basement-derived sedimentation, rather than recording a resumption of volcanism in the area, as per prevailing models. Quartz-rich sedimentation in the Drummond Basin was, therefore, more long-lived than previously envisaged, and once established, was not significantly disrupted by volcanism. Cycle 2 formation thicknesses appear highly variable across the basin. This is unlikely to be a result of pre-existing rift-related topography as suggested in previous models. The thickness variations are more likely related to sediment bypassing and post-depositional deformation in the area. The distinctive coarse-grained, relatively quartz-rich sedimentation of Cycles 2 and 3 is unusual in its volume and extent. The sediment was transported into the basin from its southern/southwestern margin, implying long-distance transport and extrabasinal sediment supply. While the specific source terrain(s) remain unknown, one plausible tectonic driver was far-field influence of the intraplate Alice Springs Orogeny.