Tracing exhumation and drainage dynamics in Taiwan's orogenic belt using detrital zircon U–Pb geochronology

Onset of foreland basin deposition in the Neuquén Basin (34°-35°S): New data from sedimentary petrology and U–Pb dating of detrital zircons from the Upper Cretaceous non-marine deposits

This thesis aims to unravel the origin and tectonic evolution of fore-arc basement terranes in Zealandia. The study is focussed on Permian to Lower Cretaceous volcanic and volcaniclastic rocks from several terranes in New Zealand and New Caledonia. The results provide new constraints on the timing, provenance, palaeogeography, and tectonic setting of the sedimentary basins, as well as establishing the cyclic nature of arc magmatism in Zealandia. Ultimately, the thesis provides insights into geodynamic processes associated with basin formation and arc magmatism along the eastern Gondwanan margin.The origin of basement terranes in New Caledonia (Teremba, Koh-Central, and Boghen terranes) is constrained by g2000 new concordant U/Pb ages and trace-element data from detrital zircons. Results show abundant pre-Mesozoic zircon ages, but a lack of early Permian to Middle Triassic ages. The results indicate that detritus was derived from a local Paleozoic continental fragment that was rifted from the Gondwanan margin prior to the initiation of Permo-Triassic magmatism in eastern Australia. This implies that the dispersal of the eastern Gondwanan margins might have started already in the early Permian, much earlier than previously thought.The Brook Street Terrane in South Island, New Zealand, was investigated by geological mapping in the Takitimu Mountains and UnPb zircon petrochronology. Results suggest that this terrane was an oceanic arc during the early Permian, possibly during a phase of trench retreat and back-arc extension. New constraints on the timing of hypabyssal intrusive rocks (White Hill Intrusive Suite; 288.6 p 6.0 Ma) coincide with the inferred biostratigraphic age of the Takitimu Group (290.1n272.3 Ma), and is substantially older than the age of the Longwood Suite magmatism (261n252 Ma) in the nearby Median Batholith. The White Hill Intrusive Suite, therefore, is spatially and temporally linked to the allochthonous Brook Street Terrane, which was amalgamated to the Gondwanan margin between 288 Ma and 261 Ma. Detrital zircon age spectra from the upper Permian to Middle Jurassic volcaniclastic successions match magmatic pulses in the adjacent Tuhua Intrusives, indicating that following terrane amalgamation, the Brook Street Terrane became a fore-arc basin.Detrital zircon data from the Murihiku Terrane, Dun Mountain-Maitai Terrane, and Kaka Point Structural Belt, show age spectra that match magmatic pulses in the adjacent Tuhua Intrusives (Median Batholith). Based on the cross-terrane and localized provenance links, we suggest that the Brook Street, Murihiku and Dun Mountain-Maitai terranes represent the proximal and distal parts of the same fore-arc basin along the Gondwanan margin. In the Murihiku Terrane, a change in the provenance of the detrital zircon, at 235n230 Ma, is indicated by a prominent change in the trace-element compositions (Th/U, Zr/Hf, U/Yb, Eu/Eu*, and zircon crystallization temperature). This change was coeval with the transition from the Longwood to Darran Suite magmatism in the Median Batholith. During this short period, at 235n230 Ma, magmatism, deformation, and uplift of basement rocks affected New Caledonia and eastern Australia (Hunter-Bowen Orogeny), thus suggesting that the Gondwanide Orogen was subjected to a large-scale secular change associated with a plate reorganization event.The cyclic nature of arc magmatism in Zealandia was investigated by combining detrital zircon geochronology with trace-element and new Hf isotope data. Zircon grains dated 360n160 Ma from New Zealand have a juvenile Hf isotope signature with temporal variations that suggest a geodynamic link to eastern Australia. During the Late Permian to Middle Triassic Gondwanide Orogeny, foreland basins were developed along the Gondwanan margin, and the oceanic Teremba Terrane arc (New Caledonia) was accreted. This arc accretion is reflected in a mix of juvenile and evolved Hf isotope signatures in 245n185 Ma zircon grains from New Caledonia.Based on the findings of this thesis, it is concluded that the evidence for proximal Zealandia sources for fore-arc basement terranes in Zealandia do not support (1) models that have invoked more distant or exotic sources, and (2) periods of margin-parallel tectonic transport to their present New Zealand position. Detrital zircons contain a reliable record of geodynamic processes occurring within the Zealandia continent, and are generally compatible with geodynamic processes record in east Australia. The demonstrated links between detrital zircon geochemistry and various geodynamic processes highlight its potential as an important tool in understanding the evolution of accretionary orogenic belts.n

Provenance of the Permo–Carboniferous sediments in the northern Alxa and its tectonic implications for the southernmost Central Asian Orogenic Belt

The tectonic setting of the southwestern Sichuan foreland basin, China, changed rapidly during the Paleogene period, and records from this period may provide crucial information about the formation and tectonic processes that affected the Sichuan Basin. To constrain the provenance and to reconstruct the paleogeography of the Paleogene successions, we conducted a detailed analysis of the petrology, geochronology, and sedimentary facies of rocks from the southwestern Sichuan foreland basin. The detrital components of the three analyzed sandstone samples indicate moderately to highly mature sediment that was primarily derived from a recycled orogen provenance. Five major age populations were identified in the U-Pb age spectra: Neoarchean to Siderian (2524–2469 Ma and 2019–1703 Ma), Neoproterozoic (Tonian to Cryogenian, 946–653 Ma), Ordovician to Carboniferous (Katian to lower Pennsylvanian, 448–321 Ma), and Carboniferous to Triassic (306–201 Ma). Each of these age populations corresponds to one or several potential sources around the southwestern Sichuan foreland basin. A multidimensional scaling analysis indicated that the Paleogene zircons were mainly derived from recycled sediments of the Songpan-Ganzi terrane and the Sichuan Basin, with minor input from the Yidun terrane, Kangdian terrane, Qinling orogenic belt, and Jiangnan-Xuefeng orogenic belt. More specifically, the sediment supply from the Songpan-Ganzi terrane to the foreland basin decreased significantly from the Mingshan stage to the Lushan stage, and the Sichuan Basin simultaneously became the most important source area. In addition, there is a high correlation between the detrital zircon U-Pb age spectrum of the southwestern Sichuan Basin and that of the Xichang Basin, which may suggest that a wider and unified Paleo-Yangtze Basin existed during the Late Cretaceous-early Paleogene.

The results of U–Pb dating and Hf isotopic analyses of detrital zircons from the Penglai Group in the Jiaobei terrane of the North China Craton (NCC) gave age populations of 1300–1000, 1500–1300, 1700–1500, 1800–1700 and >1800 Ma. The age spectra, variations in U and Th contents, Th/U ratios and Hf isotopic compositions of the detrital zircons of the Penglai Group are identical to those of the Tonian strata of the southeastern NCC. The Penglai Group rocks also have a similar litho- and biostratigraphy and tectonic setting to these Tonian strata, suggesting that the Penglai Group has a tectonic affinity with the NCC and was deposited during the Tonian. The detrital zircon age populations of the Penglai Group are consistent with the multiple magmatic and thermal metamorphic events in the NCC, especially the 1300–1000 Ma intermediate–acid and/or acid igneous rocks of the Korean Peninsula, and we therefore propose that the Penglai Group is mainly sourced from the NCC. The detrital zircon populations of 1300–1000, 1500–1300, 1700–1500 and 1800–1700 Ma show both positive and negative ε Hf(t) values, which, combined with late Paleoproterozoic–Neoproterozoic basic magmatism represented by large volumes of diabase sills in the NCC, suggests that the NCC experienced strong crust–mantle interactions that might have triggered continuous, multi-stage rifting in the NCC during the late Paleoproterozoic (1.8 Ga)–Neoproterozoic. Supplementary material: LA-ICP-MS U-Th-Pb analyses data and Lu-Hf isotopes analytical data are available at: https://doi.org/10.6084/m9.figshare.c.4816317

Taiwan orogeny: thin-skinned or lithospheric collision?

We present new LA-ICP-MS detrital zircon U-Pb age and trace element data of the Late Mesozoic sedimentary sequences from the western Shandong and Tanlu fault zone, with the aim to constrain the depositional ages and sedimentary sources. The samples from the western Shandong have similar U-Pb age spectra, which can be divided into three major age groups, peaking age at circa 2,475–2,540 Ma, 1820–1870 Ma and 257–285 Ma, with minor Mesoproterozoic, Neoproterozoic and Paleozoic detrital zircon grains. The sample JN recovered from the Tanlu fault zone has an overwhelming majority of the Early Cretaceous detrital zircons with the age peak at circa 125 Ma, whereas the Archean and Paleoproterozoic detrital zircons are subordinate. The weighted average age of the youngest zircons show that the Santai Formation probably had begun deposition at circa 158 Ma and terminated deposition at circa 150 Ma, and the Tianjialou Formation of the Dasheng Group had begun deposition at circa 122 Ma. Our study indicates that the activity of the dinosaurs might occur during the Late Jurassic rather than the Cretaceous in the Shandong province. In addition, most detrital zircons of the studied samples are characterized by the high Th/U ratios and left-inclined REE patterns, revealing a magmatic origin. Morphologically, most detrital zircon grains characterized by angular to sub-rounded shapes indicate a middle-short distance transport from the source regions, whereas minor detrital zircon grains show rounded shapes, indicating a long-distance transport or multiphase recycling. According to detrital age populations in this study, combined with previously published data, we conclude that depositional provenances of the Santai Formation were mainly derived from the western Shandong and Jiao-Liao Belt, and minor detritus were derived from the northern part of the North China Craton and Xing-Meng orogenic belt. The sediments deposited in the Tanlu fault zone were mainly derived from the volcanic and subvolcanic rocks of the Qingshan period in the eastern Shandong, and subordinate depositional sources were from the Jiao-Liao and the basement uplift of the western Shandong, with minor supplier being derived from the Yinshan-Yanshan orogenic belt. The detrital provenance of the Santai Formation indicates that extension of the eastern NCC occurred during the Late Jurassic. The Neoproterozoic detrital zircons play a minor role in the studied strata, indicating that the large sinistral movement of the Tanlu fault zone might have occurred at the Early-Middle Jurassic and formed a paleogeographic separation of the western Shandong and eastern Shandong (Sulu orogenic belt).

The Murree Formation is the oldest continental sequence in the Himalayan foreland basin and holds significant information about the Himalayan exhumation following the India-Asia collision. This study explains the provenance of the Murree Formation using detrital zircon U-Pb geochronology supplemented with sandstone petrography to unravel the Himalayan exhumation in Pakistan. The sandstone provenance indicates the sediment was sourced from recycled orogen and suture belts, supporting a post-collisional origin. The source rocks, shown by the ternary plot (QpQnuQu), comprise plutonic and medium to high-rank metamorphic rocks prevalent in the Higher Himalaya (HH), Tethyan Himalayan (TH), and Lesser Himalaya (LH). The zircon ages are mainly ~ 1200–400 Ma, with two minor clusters (~1900–1400 Ma and ~ 2600–2300 Ma). This pattern is compatible with a Himalayan source mainly from the TH, HH, and partly from LH. Notably, the age populations < 200 Ma are in minor percentages, which indicates the hindrance from the Kohistan – Ladakh Arc (KLA) (Asian source) to the foreland basin due to the uplift of the TH and HH blocks. Combining the petrography and zircon U – Pb geochronology, a tectonic model is proposed, which suggests fold – thrust belt propagation to the south after the India – Asia collision. During the deposition of the Murree Formation in the foreland basin, TH and HH blocks were already uplifted in the western Himalaya, which provided major detritus. Along with this significant contribution, a minor contribution from a part of the LH is also suggested. This suggestion is based on the presence of Cambro – Ordovician detrital zircon ages, mainly from the plutonic source indicative of erosion of the Cambro – Ordovician granites and metamorphic rocks due to the initial phase of uplift along the Panjal fault.

Since the collision between the Indian and Asian plates, several peripheral foreland basin were formed, and started to accumulate the sediments from the hinterland Himalayan orogeny. The sediments deposited at the northern tip of the Greater India have been uplifted, exhumed after the activation of several south propagating thrusts and finally transported to the foreland basin by southward flowing fluvial system. We present petrography and detrital zircon dating for the interpretation of possible provenance of the Neogene Siwalik foreland basin sediments in far western Nepal. The QFL ternary plot for provenance analysis show a 'recycled orogeny' field for the studied sandstone samples, indicating Tethys Himalaya, Higher Himalaya and Lesser Himalaya as the source of the foreland basin sediments. The detrital zircon U-Pb ages of the studied samples have shown that during the time of deposition there was dominant numbers of detritus supplied from the Tethys and upper Lesser Himalaya. Subsequently the amount of the Higher and Lower Lesser Himalaya increased during the time of deposition of the Middle Siwalik.

Detrital zircon age spectra of the Gurvan Sayhan accretionary complex in South Mongolia: Constraints on the Late Paleozoic evolution of the southern Central Asian Orogenic Belt

In this issue of Geology, Fuentes et al. (2009, p. 379) present a new subsidence plot and age data from detrital zircons that help to constrain the date of initiation of the foreland basin in Montana (United States). They offer these data as evidence for the resolution of a controversy regarding the initiation of foreland basin sedimentation in the Western Interior. However, their discussion raises the question of what geological data constitute the defi nitive evidence of the foreland basin style of sedimentation, and therefore the criteria that should be used to defi ne its commencement. A useful defi nition of a foreland basin is that it is a depression that develops adjacent and parallel to a mountain belt. Foreland basins form because the mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric fl exure. At convergent plate margins, foreland basins develop behind the marginal arc (retroarc or retroforeland type; Jordan, 1995) or above the downgoing continental plate adjacent to a collision zone (peripheral or proforeland type; Miall, 1995). The downward fl exure is accompanied by the uplift of a forebulge in the basement, typically a few hundred kilometers out from the fold-thrust belt, and beyond that there is a shallow depression called the backbulge basin. The relationship between crustal loading and basin formation was fi rst articulated by Price (1973) with respect to the foreland basin of southern Alberta, and subsequent modeling of the Alberta Basin by Beaumont (1981) demonstrated the quantitative link between fl exural loading, the formation of a crustal depression, and its fi lling by syntectonic sedimentation. Jordan (1981) demonstrated another key criterion for the defi nition of the foreland basin style of subsidence and sedimentation: the distinctive isopach pattern of the basin fi ll, elongated parallel to the mountain front and asymmetric in cross section, with a depocenter located close to the contemporaneous fold-thrust belt, the uplift of which serves as the proximal sediment source. Cross (1986) used this criterion to distinguish foreland basin subsidence from that due to subcrustal mantle loading, which yields a much broader, wider pattern of basinal subsidence. The Western Interior basin (of which the Alberta basin and the Rocky Mountain basin are parts) was initiated as a retroarc basin as a result of a fi rst-order change in the plate kinematics of Pangea. This supercontinent, assembled by multiple plate convergence and suture between Ordovician and Permian time, began to fragment by rifting in the Triassic, and by early Middle Jurassic time, oceanic crust was forming off what is now the Atlantic coast of the United States. The North American continent began a long process of northwestward drift, which carried the plate some 70° of longitude westward, relative to the Pacifi c plate, and, some 40° of latitude northward until Paleocene time, followed by a change in trajectory and a subsequent southward drift of ~10° up to the present day (Engebretson et al., 1985). There are numerous indicators of a fi rst-order change in magmatic, tectonic subsidence and sedimentation patterns associated with this change in plate kinematics. The fi rst appearance of westerly-derived detritus from a rising arc or orogen has long been accepted as providing the timing of initiation of the Western Interior foreland basin. Prior to the establishment of the basin, the western continental margin was miogeoclinal in character, with sediment derived from easterly sources (the craton and the Canadian Shield). Ron Blakey and I (in Miall, 2008), designated the

Source-to-sink of Late carboniferous Ordos Basin: Constraints on crustal accretion margins converting to orogenic belts bounding the North China Block

Stratigraphic, provenance, and subsidence analyses suggest that by the Middle to Late Jurassic a foreland basin system was active in northwestern Montana (United States). U-Pb ages of detrital zircons and detrital modes of sandstones indicate provenance from accreted terranes and deformed miogeoclinal rocks to the west. Subsidence commenced ca. 170 Ma and followed a sigmoidal pattern characteristic of foreland basin systems. Thin Jurassic deposits of the Ellis Group and Morrison Formation accumulated in a backbulge depozone. A regional unconformity and/or paleosol zone separates the Morrison from Early Cretaceous foredeep deposits of the Kootenai Formation. The model presented here is consistent with regional deformation events registered in hinterland regions, and challenges previous interpretations of a strongly diachronous onset of Cordilleran foreland basin deposition from northwestern Montana to southern Canada.

Linking the Alxa Terrane to the eastern Gondwana during the Early Paleozoic: Constraints from detrital zircon U–Pb ages and Cambrian sedimentary records

The provenance of Middle Eocene clastic rock from the Gercus Molasse, NE Iraq was determined by detrital zircon (DZ) U-Pb geochronology. The Gercus Molasse in the Iraqi segment of the north-eastern Zagros Thrust Zone provides an ideal example of foreland system evolution with respect to the transition from passive margin to the accretionary complex terrene-flexural foreland basins. The DZ U-Pb age spectra from the Gercus Molasse suggest that the foreland sediments either influx from multiple provenances or are the result of recycling from the accretionary complex terrane. During pre-accretion, however, the radiolarite basin (Qulqula Radiolarite, 221 Ma) located along Arabian passive margin likely acted as an intermediate sediment repository for most or all of the DZ. Representative DZ U-Pb measurements revealed that the Gercus clastic rocks fall into several separable age population ranges of 92-102 (Albian-Cenomanian), 221 (Upper Triassic), 395-511 (Cambrian), 570- 645 (Neoproterozoic), 1111 (Mesoproterozoic), and lesser numbers of Paleoproterozoic (1622-1991 Ma) ages. The source of Proterozoic detrital Zircons is enigmatic; the age peaks at 1.1, 1.5, 1.6, and 1.9 Ga (Proterozoic) does not correspond to any known outcrops of Precambrian rocks in Iraq, and it may be useful to continue to search for such basement. The detrital zircons with age populations at 0.63–0.86 Ga probably originated from the Arabian-Nubian Shield. The age peak at 0.55 Ga correlates with Cadomian Magmatism reported from north Gondwana. The age peaks at ~0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys. The youngest ages populations at 93 Ma indicate that fraction of DZ were transported directly from the contemporaneously active magmatic arc (Zagros Ophiolite segments). The paleogeography and tectonic evolution of the Neogene Zagros foreland basin were reconstructed and divided into two tectonic stages. The early stage is defined by the Campanian accreted terranes (i.e. orogenic wedge) form loads sufficient to produce flexural basin with a deepest part is situated next to the tip of the loads. This flexural basin is filled by the flysch clastics of the Maastrichtian– Early Eocene (i.e. referred to by the Tanjero-Kolosh flysch sequence). The late stage is marked by a synchronized modification of the clastics fill of the basin and changes in dip directions to compensate for the reduction of the load by both erosion and extension and the basin, therefore, was sealed by a shallowing upwards depositional sequence ending with the terrestrial Gercus Formation.