Provenance Evolution Research Articles

Detrital zircon provenance record of the northern shelf in the Rakhine Basin, Bay of Bengal

The Cenozoic strata in the Rakhine Basin play a crucial role in hydrocarbon exploration; however, the provenance of these sedimentary rocks remains poorly investigated. In this study, we employed detrital zircon geochronology and geochemistry in the northern Rakhine shelf to investigate the provenance of sedimentary rocks and, combined with the previous studies, to identify their spatial and temporal variations and to elucidate the provenance evolution since the middle Miocene. The geochemical results of the zircons indicate that the primary source rocks of the sedimentary rocks are magmatic and metasedimentary rocks, particularly those of continental arc and post-collision granites. The origin of these rocks can be attributed to the Gangdese arc magmatic belt in the north, as well as the Indo-Burma Ranges in the east. The sedimentary rocks in the northern Rakhine yield zircon U-Pb age peaks primarily at 0–150 Ma, 400–600 Ma, 600–1000 Ma, and 1600–2100 Ma, with minor populations at 150–400 Ma and >2100 Ma. The detrital zircon provenance study shows that the zircons in the Miocene sedimentary rocks were primarily derived from the paleo-Brahmaputra River, with contributions ranging from 68.7% to 77.0%. During the Pliocene, the paleo-Brahmaputra River and the Chittagong-Tripura Fold Belt were the most significant sediment suppliers. Since the early Pleistocene, the northern Rakhine coastal region has played a significant role in their composition. The Brahmaputra River was the predominant contributor to upper Pleistocene rocks, and the Rakhine coastal region's contribution to the shelf intensified throughout the Pleistocene. In conjunction with regional tectonic evolution, our study underscores the importance of the Indian Plate subduction as a pivotal factor influencing the provenance transitions in the northeastern Bay of Bengal.

Fingerprint of Plio–Quaternary detrital zircon geochronology: Implications for sediment provenances and geomorphological evolution of the Yangtze Delta

The Yangtze (Changjiang) Delta serves as a prominent depocenter for siliciclastic sediments from the Tibetan Plateau and Yangtze Craton, providing essential data on sediment source-to-sink dynamics and geomorphological evolution of large river drainage systems. This study presents the detrital zircon geochronology of Plio–Pleistocene sediments in the Yangtze Delta, alongside the data from modern river sediments, to elucidate provenance evolution since the Pliocene. The zircon geochronology reveals a considerable shift in sediment provenance during the Pliocene–Pleistocene transition. The Pliocene sediments exhibit a straightforward and predominant zircon age spectrum characterized by a typical peak age of 100–200 Ma. This spectrum markedly differs from the modern upper–middle Yangtze River sediments but closely resembles those of local rivers in the lower Yangtze River region. This demonstrates that the Pliocene sediments originated from local mountainous rivers, indicating the paleo-Yangtze River channelization prior to the Quaternary. In contrast, the zircon age spectra of Pleistocene sediments in the present-day delta reveal several dominant age groups ranging from 11.9 ± 1 to 3643 ± 30 Ma, similar to those found in present-day upper–middle Yangtze River sediments. This implies that the Pleistocene sediments were mainly derived from the upper–middle Yangtze River, showing a diversity of source rocks with varying geological ages and origins. The presence of the upper Yangtze River provenance signal, characterized by Cenozoic (<65 Ma) zircons, in early Pleistocene strata (ca. 1.6 Ma) of the delta suggests that the paleo-Yangtze River transported Tibet-sourced sediments into the modern delta area no later than that time. These findings indicate the geomorphological evolution of the Yangtze River Delta from an intermontane basin in the Pliocene to an alluvial–fluvial plain during the Quaternary. This geomorphological and geographic evolution, along with changes in sediment source, directly reflect extensive tectonic subsidence in eastern China since the late Cenozoic.

Detrital-zircon U-Pb and (U-Th)/He double-dating provenance signatures in the Jaca foreland basin: interplay of direct vs. recycled sources during Pyrenean orogenic growth

ABSTRACT The Eocene to Miocene clastic wedge of the south Pyrenean basin constitutes a reference model to understand the progressive evolution of sediment provenance and source-to-sink dynamics in a foreland basin. We present new detrital-zircon (DZ) U-Pb and U-Pb-He (ZHe) double-dating data from the Jaca basin and the Ebro basin, providing insights into the evolution of the sedimentary systems that record a major tectonic and drainage reorganization from the late Eocene to Miocene. Three distinct DZ U-Pb signatures have been identified: i) Variscan dominated, ii) mixed Cadomian–Variscan, iii) Cadomian dominated, and two DZ ZHe signatures: i) Pyrenean dominated, ii) pre-Pyrenean dominated. Coupling DZ U-Pb, ZHe, and petrographic data allows us to discriminate among distinct Pyrenean sources as well as to understand how DZ signatures are propagated in a source-to-sink system. Our results indicate that while the eastern Jaca basin was fed from eastern source areas located in the central and eastern Pyrenees, the western Jaca basin was fed from the Basque massifs and the Urbasa–Andía Sierra (Basque–Cantabrian Pyrenees).

Evolution of provenance and sedimentary records in multiphase rift basins: Insights from petrology, detrital zircon geochronology, and seismic reflections of Oligocene Liaozhong Depression, Bohai Bay Basin, China

Sedimentary provenance in multiphase rift basins exhibits rapid variations during distinct tectonic sub-stages, and a close association exists between alterations in sediment source, geomorphology, and tectono-depositional records. This study comprehensively integrates sandstone petrology, heavy mineral assemblages, detrital zircon characters, drill cores, well logs, and seismic reflections to investigate the evolution of provenance and sedimentary records within a complete rifting episode in a lacustrine basin. Three tectono-depositional models for different tectonic sub-stages have been established. During the early strengthened stage of Rifting Episode IV (Sqd3), sediments were primarily sourced from the Liaoxi Uplift, serving as an intrabasinal provenance. These sediments mainly consist of medium-to coarse-grained sandstones with short-distance transportation, forming a transversely-sourced fan-delta and gravity-flow depositional system. Additionally, wedge-shaped seismic configurations were observed along the flow direction. In the middle stage of Rifting Episode IV (Sqd2), the Liaoxi Uplift was submerged, and sediments originated from the Qinhuangdao, Suizhong, and Liaodong Uplift regions. Lake basin expanded during this period, resulting in axially and transversely-sourced river deltaic deposits in a multi-stage superimposed manner, associated with gravity-flow deposits. The sediments are predominantly composed of medium-to fine-grained sandstones that underwent long-distance transportation, accompanied by a significant increase in mudstone content. Simultaneously, sigmoid-oblique and sigmoidal geometries extensively developed. During the late weakened stage of Rifting Episode IV (Sqd1), sediments originated from the Qinhuangdao and Suizhong regions, forming a transversely-sourced shoal-water deltaic system enriched in medium-to fine-grained sandstone with limited mudstone. In comparison to Sqd3 and Sqd2, sediments within Sqd1 underwent intermediate-distance transport. Typically, a shingled seismic configuration developed, presenting a sharp contrast with the sigmoid-oblique and sigmoidal reflections within Sqd2. The detailed models of source-to-sink systems developed in this study are expected to enhance the comprehensive understanding of sedimentological responses to provenance evolution across various tectonic sub-stages in lacustrine rift basins.

Geochemical evidence for changes in provenance and paleoclimate during the Holocene obtained from a fluvial–eolian sequence in the southern Mu Us Desert, north-central China

Identifying the sources and weathering degree of sediments in the northern deserts of China is crucial to understand the evolution of the Asian monsoon system and corresponding induced changes in surface processes. Great progress has been made in the reconstruction of paleoclimate and paleoenvironment from the Early Holocene onwards based on chronostratigraphy and proxies of aeolian sedimentary sequences in the Mu Us Desert (MUD). However, previous studies have given rise to some controversial over the timing of the Holocene optimum period, and there is a scarcity of studies on the sediment provenance evolution of the desert during the Holocene and its internal relationship with the East Asian summer (EASM) and winter (EAWM) monsoons. Here, we provide new elemental geochemical data from a fluvial–aeolian sedimentary sequence in the southern MUD; we then combine these data with other available elemental data and hydroclimatology information to investigate the characteristics of sediment source evolution and their possible connection with the EASM and EAWM on the southern margin of the MUD-desert/loess transition zone since the latter part of the Early-Holocene. The elemental composition and geochemical characteristics of the studied sedimentary sequence differed markedly in the periods before and after 6.4 ka BP, suggesting a change in the source of the sediments across this boundary. From the late Early-Holocene (10.6 cal. ka BP), sediments were dominated by the chemical weathering products of local source material, with a gradual increase in chemical weathering over time, indicating a gradual strengthening of the EASM; the EASM reached its peak Holocene strength at 8.4–6.4 ka BP, accompanied by a moderate level of chemical weathering. After 6.4 ka BP, with the weakening of monsoon precipitation, the EAWM began to strengthen, and long-distance transport of source material from the west and northwest increased; however, chemical weathering of local source material driven by the EASM remained dominant until 4.0 ka BP. After 4.0 ka BP, the EAWM became dominant, and sediments showed strong sedimentary cycles, mainly transported from long-distance sources by aeolian activity, and the MUD became an important sedimentary sink for the northern-central deserts. After 0.7 ka BP, the sediments in the MUD became a mixture of different-age sediments due to river scouring and the transport of pre-existing sediments along the shoreline. Collectively, the elemental geochemical and other proxy data from Holocene sediments on the southern margin of the MUD record an inverse relationship between the EASM and EAWM; these two monsoonal circulations have alternated in their control of the sedimentary source characteristics and geomorphological environmental evolution processes across the southern margin of the MUD during the Holocene.

U–Pb detrital zircon ages from late Eocene to early Oligocene Pinghu formation of the East China Sea Shelf Basin: Inferences on synergistic effects between East Asia offshore sedimentation and major rivers supply

Our understanding of the late Eocene to early Oligocene provenance evolution of the East China Sea Shelf Basin has been limited, which hampers our study of the synergistic effects between East Asia offshore sedimentation and major rivers. To address this, we compared newly acquired detrital zircon chronological data from the East China Sea with published detrital U–Pb ages of major rivers in East Asia. Through this analysis, we have been able to reconstruct the provenance changes of sediments in the East China Sea during this crucial period. We have identified two large-scale and three small-scale denudation surfaces that developed in the Pinghu and lower Huagang Formations. These surfaces indicate that sediments were also derived from underlying strata and bedrock, particularly in the lower Pinghu and lower Huagang Formations. The newly acquired detrital zircon U–Pb age range was found to be roughly similar, ranging from 36.2 ± 0.7 to 2954.0 ± 30.3 Ma. The age peaks of the lower Pinghu Formation were more consistent, while the middle, upper Pinghu Formation, and lower Huagang Formation exhibited multiple age peaks. Comparing the compiled zircon U–Pb age peaks of the Chuanjiang segment of the upper Yangtze River with those of the East China Sea Shelf Basin, we found relative similarity. Additionally, the younger zircon grains with ages <500 Ma in the east Cathaysia catchment showed similarities with the East China Sea Shelf Basin. In terms of provenance contribution, the sediments of the lower Pinghu Formation were predominantly provided by the adjacent uplifts in the east Cathaysia catchment, with the Chuanjiang segment also playing a significant role. From the middle Pinghu Formation onwards, the provenance from the Chuanjiang segment became dominant, accounting for over 90 % of the sediments. However, this influence was limited to the northern part of the study area. This suggests a substantial increase in the Yangtze River catchment during this period, potentially related to the complete connection of the modern Yangtze River.

Revisiting the stratigraphical, sedimentological and provenance evolution of Lingshan Island, offshore of east China: Implications for the destruction of the north China craton

The Cretaceous strata of Lingshan Island, offshore of East China, are a key sedimentary archive for understanding the destruction of the North China Craton (NCC). However, there has been limited progress in characterizing its stratigraphical, sedimentological and provenance evolution in the context of the progressive lithospheric thinning and magmatism associated with the destruction of the NCC. We report field logging data, sandstone framework petrography, and detrital and volcanic zircon U–Pb geochronology data from the Cretaceous strata of Lingshan Island, and correlate these data with coeval sediments in the Jiaolai Basin and volcanic units in the East China. Our results indicate rapid deposition of the Laiyang and Qingshan groups from c. 124–123 Ma with an upward thickening and coarsening succession from the lacustrine turbidites of the Laiyang Group to the deltaic rocks of the Qingshan Group, accompanied by an increase in volcanic activity up-section. Sandstone petrology and detrital zircon U–Pb ages indicates that the source areas for the Laiyang and Qingshan Groups were syn-depositional volcanic rocks and plutonic rocks, with some contributions from the Yangtze Craton and Sulu terrane. Our compilation of detrital zircon U–Pb ages (n = 8513) from the Cretaceous strata of Lingshan island and the Jiaolai Basin in the hinterland implies provenance contributions from four different sources. The zircon Th/U ratios from this large dataset suggests that Cretaceous magmatic zircons formed in an extensional setting (Th/U ratios >1 but with significant variation). The Eu anomalies in magmatic zircons (n = 550) from the Jiaodong Peninsula indicate continuous lithospheric thinning in Eastern China since c. 130 Ma, leading to the destruction of the NCC. Based on all available data, Lingshan Island most likely was a rift basin during the Cretaceous.

Provenance Evolution and Its Response to Sea Level Change in the South Yellow Sea since 1.0 Ma

The sediments provenance of the South Yellow Sea is controlled by many factors such as sea level change, ocean circulation, and neotectonic movement. The short time scale sediments provenance changes in this region since the Holocene have been revealed well, and a unified understanding has been formed that the central muddy area in the South Yellow Sea is a mixed area of the Yellow River sediments and the Yangtze River sediments. However, the contribution of different rivers to the sediments of the South Yellow Sea since late Quaternary is still ambiguous. Through comparative analysis of several boreholes with precise annual data constraints in the central mud area, the process of sediments provenance change at different periods since the late Early Pleistocene (1.0 Ma) was reconstructed, and the coupling mechanism of sediments provenance change and sea level change was established. It is found that during the period from 1.0 to 0.88 Ma, the seawater entered the South Yellow Sea along the Yellow Sea trough from the southeast to north as a channel, and there were different phenomena at the same time in different regions. Since 0.88 Ma, the sea water has been advancing from east to west. In addition, the sediments in the western of Jeju Island are mainly from China, and the sediments in the eastern are mainly from the Korean Peninsula, which roughly coincides with the boundary between the silty area and the sandy area on the eastern of the South Yellow Sea. In the surface sediments, the boundary line between the Yellow River sediments and the Yangtze River sediments is approximately 33.4° N.

Recycling effects in detrital zircon U[sbnd]Pb signatures in a foreland basin: Identifying the multicyclic sediment sources of the Eocene-Miocene Jaca basin (southern Pyrenees, Spain)

This work deals with the provenance evolution of the mid Eocene to early Miocene clastic deposits of the Jaca basin (southern Pyrenees), which record a main drainage network reorganization during the progressive tectonic uplift of the Pyrenean orogen. We present new detrital zircon UPb data which show a Variscan-dominated detrital zircon signature for the Lutetian Hecho Group turbidites, while the overlying late Eocene to early Miocene alluvial fan sediments record a Cadomian-dominated detrital zircon signature, allowing to document a major change in the source area. Moreover, a tectono-stratigraphic cyclicity can be identified in each of the turbidite systems that conform the upper Hecho Group, featuring an enrichment of the Variscan detrital zircon signal at the base of the system, which can be interpreted as the result of an efficient sediment transfer from distant Axial Zone sources during relative sea-level lowstands, while a dilution of this signal occurs during highstands, at the top of each system, due to the reduced erosion capability of the fluvial network. Integration of detrital zircon UPb data with sandstone petrography allows for improved resolution of the source-area shifts, for discrimination between first-cycle and multi-cycle zircons, and to identify that the detrital zircon signal of the alluvial fans does not fully represent the source area configuration. This study illustrates the importance of combining petrography with detrital zircon UPb data to improve provenance reconstructions and to identify the role of sediment recycling during progressive foreland evolution.

Holocene provenance evolution of the northern South China Sea inferred from detrital zircon U-Pb geochronology and Hf isotopes

Holocene provenance evolution of the northern South China Sea inferred from detrital zircon U-Pb geochronology and Hf isotopes

Late Eocene—early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

Late Eocene—early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

Mid‐Cretaceous Exhumation of the Central Qiangtang Mountain Range Metamorphic Rocks as Evidenced by the Abushan Continental Redbeds

AbstractMetamorphic rocks and surrounding Paleozoic strata in central Tibet compose the core of an anticlinorium associated with the Central Qiangtang Mountain Range. The analysis of Mesozoic strata flanking the anticlinorium provides insights into the geological and landscape evolution of the range, which is important in determining the Mesozoic evolution of central Tibet and the paleo‐elevation of the Tibetan Plateau. Here we present a detailed stratigraphic study of the Shuanghu Conglomerate and over 1‐km‐thick mid‐Cretaceous continental redbeds of the Abushan Formation, which non‐conformably overlie the Qiangtang metamorphic belt. Pollen assemblages and detrital zircon ages along with published magnetostratigraphic results indicate a mid‐Cretaceous depositional age for the Abushan Formation. The Shuanghu Conglomerate is undated but may have been coeval with the Abushan Formation as suggested by foraminiferal assemblages contained within limestone clasts. The Abushan Formation shows a fining‐ and deepening‐upward megasequence, changing from braided river delta‐plain conglomerate and sandstone to lacustrine delta‐plain and delta‐front sandstone, siltstone and carbonate rocks. Both the Abushan Formation and Shuanghu Conglomerate received metamorphic detritus, indicating that the exhumation of the Qiangtang metamorphic belt to the surface took place at or before mid‐Cretaceous time. The lower member of the Abushan Formation contains dominant limestone clasts, whereas quartz, metamorphic, and volcanic clasts increase in percentage up‐section reflecting an unroofing sequence. The stratigraphic, sedimentologic, and provenance evolution suggests that exhumation of the Central Qiangtang Mountain Range metamorphic rocks may have occurred primarily by tectonic extension after the end of a long period of late Mesozoic Lhasa‐Qiangtang convergence.

Petrography and mineralogy of the Oligocene flysch in Ionian Zone, Albania: Implications for the evolution of sediment provenance and paleoenvironment

Abstract In this study, the reconstruction of the formation condition in the Oligocene flysch (Berati and Zhitomi section), in the Berati anticline structure, north-eastern part of the Ionian tectonic zone (Albania), is elucidated using petrographic–mineralogical characteristics and grain size analysis. Outcrops from the Berati and Zhitomi and the drilled wells were selected for sampling based on previous stratigraphic and paleontological studies. The mineralogical study of the flysch deposits made it possible to evidence for the first time three mineralogical zones: (a) quartz–garnet (b) serpentine, epidote with mica, and (c) feldspar zone, and three these petrographic zones: (a) quartz, (b) quartz–serpentine, and (c) quartz with mica and feldspars. The reconstruction of the depositional environment is based on the petrographic study of rock types, their textural characteristics, and grain size statistics. The granulometry coefficients like mean, sorting, skewness, and kurtosis are calculated arithmetically and the C/M diagram as well. Referring to the mineralogical composition of the sandstones and siltstones, the obtained data were used for the correlation of the sections and the delineation of the leaching area and the direction of the sediment movement. The mineralogic and petrographic characteristics show that during the Oligocene, the region has been under continuous paleogeographic change and under intensive orogenic activity, which has influenced the character of the mineralogical–petrographic composition of these deposits. Based on the pebbles petrography present in the slump horizons and on heavy mineral assemblages, it was evidenced that the eastern tectonic zones of Kruja, Krasta, and Mirdita (Albania) were the main suppliers of sedimentary material. The Passega C/M diagram suggests suspension and saltation as the main mode of sediment transport prior to deposition.

Geochemical characteristics and provenance of the detrital sediments in the junction area of Yinggehai and Qiongdongnan basins, South China Sea

Together, the Yinggehai and Qiongdongnan basins have received a large amount of terrigenous sediments, but the provenance evolution of Cenozoic sediments in the two basins remains disputable. Combined with previous studies in the Yinggehai and Qiongdongnan basins, the elemental geochemistry of Oligocene to Pliocene sediment samples in the junction area of the two basins were analyzed to explore the tectonic implications, parent rock characteristics, and provenance evolution of the two basins during the Cenozoic. The results reveal that all the sediment samples were derived from continental island arc to passive continental margin settings. The light REE enrichment and stable content of heavy REE with large negative Eu anomalies indicate that they were probably derived from Hainan Island. The reconstructed provenance evolution model showed that the Red River Source (RRS) provided sedimentary materials for the Central Depression of Yinggehai Basin from the Oligocene to the Pliocene, and Hainan Island Source (HIS) was also one of the sources for sediments deposited in the Central Depression of Yinggehai Basin during the Miocene. However, most of the sediments preserved in the Yingdong Slope and Qiongdongnan Basin were derived from the HIS from the Oligocene to the Pliocene, and sediments deposited in the Yingdong Slope were also derived from the RRS during the Miocene. Furthermore, the junction area of the two basins had a mixed source of the RRS and HIS during the Cenozoic.

Detrital zircon U–Pb age constraints on the provenance of submarine channels in Ledong area, Yinggehai Basin, South China Sea

To better understand the provenance and its evolution of the submarine channels of Huangliu and Yinggehai Formation in the Ledong area, the Yinggehai Basin, 200 single detrital zircons from two sandstone samples were collected from submarine channels, and the U–Pb dating was carried out. The results show that the detrital zircon ages from the submarine channel of Huangliu Formation have a narrow range from 78 to 264 Ma with two major age peaks at ca. 96 and 235 Ma, accompanied by two subordinate age peaks at ca. 78 and 159 Ma. In contrast, the detrital zircon ages from the submarine channel of Yinggehai Formation have a wide range from 94 to 3076 Ma with three major age peaks at ca. 95, 235, and 449 Ma, accompanied by five subordinate age peaks at ca. 144, 177, 376, 549 and 801Ma. The characteristics of provenance evolution for submarine channels were furtherly analyzed using 3-MDS and source unmixing methods. The sediments in the submarine channel of Huangliu Formation were originated from the Changhua River, Beili River, Wanglou River, and Ningyuan River in the west of Hainan Island, and their relative contributions for the submarine channel were 65%, 3.5%, 6.4%, and 25.1%, respectively. The sediments in the submarine channel of Yinggehai Formation were provided with mixed source by the Red River, Wanglou River, and Ningyuan River, and their relative contributions for the submarine channel were 82.6%, 4.3%, and 13.1%, respectively. The transition of submarine channel provenance from near source of Huangliu Formation to distant source of the Yinggehai Formation may be due to the uplift of the Tibet Plateau during Pliocene.

Environmental and provenance change since MIS 2 recorded by two sediment cores in the central North Jiangsu Plain, East China

In order to reveal the evolution of sediment provenance and paleoenvironment of the central North Jiangsu Plain (NJP) since marine isotope stage 2 (MIS 2), we analyzed lithology, accelerator mass spectrometry (AMS) 14C dating, macrofossils and foraminifera, grain size, and geochemical compositions of sediments from two sediment cores (Core M and Core Y) recovered in the northern side of the Yangtze River. Our results show that fluvial environments prevailed in the central NJP during MIS 2, followed by alternations of coastal-marsh environments and shallow-bay environments in north central NJP and coastal-marsh environments in south central NJP during MIS 1. Provenance analysis suggests a major change in sediment provenance from the Yangtze River to the Yellow River at early MIS 1 in north central NJP; these Yellow River sediments might be transported from previously deposited sediments by strong tidal currents and intense waves to this area or be a reflection of a southward shift of the Yellow River during this period. However, the Yangtze River-derived sediments dominated the south central NJP since MIS 2. The depositional succession and sediment supplies since MIS 2 were dominantly controlled by sea-level fluctuations, regional geomorphic patterns, shift of the rivers, etc.

Provenance identification and source-to-sink studies from an intrabasinal subaqueous uplift in the Eocene western Bohai Bay Basin, eastern north China

Intrabasinal subaqueous uplifts around small positive structural units are important targets of high-quality reservoirs in the Eocene Bohai Bay Basin (BBB). The western BBB was filled with sediments from northern and southern source regions. The southern sources are the Paleozoic rocks deposited in marine and costal settings, which are widely exposed along the Chengzikou uplift and stacked with Mesozoic igneous rocks. The northern sources are pre-Cambrian metamorphic rocks from the western Shaleitian uplift. To determine the origin of the Eocene sediments in the intrabasinal subaqueous uplift, eight sediment samples were collected from drill cores in the Shaxinan structural belt of Shanan sag, western BBB for detrital zircon U–Pb dating. We conduct detrital zircon U–Pb dating to shed new light on Eocene provenance evolution and analyze sediment dispersal characteristics of the lacustrine beach-bar sandstones by integrating lithology, wire-line logs and 3-D seismic data in the Shaxinan structural belt. The obtained ages vary between the Archaeological and Mesozoic (2692 ± 42 Ma to 79.8 ± 1.0 Ma). Dominant provenance for the Shahejie Formation has evolved temporally, that is, from the early Shaleitian uplift to the late Chengzikou uplift. The beach-bar sand bodies developed on the subaqueous uplift in the Shahejie Formation (from base to top: member 3 of the Shahejie Formation, Es3, and members 1 and 2 of the Shahejie Formation, Es12), while the gravel-rich fan delta-beach bar sand bodies mainly from the northern Shaleitian uplift in the Es3 transitions to the mixed sand-mud braided delta-beach bar sand bodies mainly influenced by southern Chengzikou uplift in the Es12. Types of intrabasinal subaqueous uplift (gentle palaeoslope), strong hydrodynamic environment, abundant multiple sediment provenance and the Eocene-Oligocene evolution collectively control beach bar sediment dispersal patterns in the deposit area.

Zircon U–Pb age constraints on the provenance and response to tectonics: Lower Oligocene of the western Qiongdongnan Basin, South China Sea

Provenance changes and tectonic activity during the Early Oligocene in the Qiongdongnan Basin are responses to the evolution of the northwestern South China Sea. However, the provenance of the Lower Oligocene (Yacheng Formation) in the Qiongdongnan Basin is poorly understood owing to a lack of available borehole samples and poorly constrained stratigraphy. Here, combined with published data from wells of different part of the basin, we apply U–Pb dating of detrital zircons on samples nearby the western boundary fault of the basin to analyse the provenance of the Yacheng Formation and its regional tectonic implications. The zircon U–Pb age spectra of the sediments in three different members of Yacheng Formation show different features. A single U–Pb age peak at ca. 235 Ma occurs in the Third Member of the Yacheng Formation, whereas the U–Pb age spectra in the stratigraphically younger Second Yacheng Formation show different zircon U–Pb age spectra features: an age pattern has two major peaks at ca. 248 Ma and 441 Ma and lacks zircons younger than 200 Ma, and another pattern has two major peaks at ca. 95 Ma and 252 Ma. The Early Oligocene provenance evolution of the western Qiongdongnan Basin is reconstructed by comparing the zircon U–Pb age spectra of the sediments in the different samples to potential sources nearby. Abrupt changes in the U–Pb ages throughout the Lower Oligocene in the western Qiongdongnan Basin suggest that sediment supply in the Second Member of Yacheng Formation was dominated by rivers from western Hainan Island and Central Vietnam. By contrast, Hainan Island and local structural highs within the Qiongdongnan Basin were the main sources in the Third and First Members of the Yacheng Formation, respectively. The difference in the U–Pb age spectra between sediments in the Qiongdongnan Basin and the Red River implies that the time at which the Red River system entered the Qiongdongnan Basin was later than the Early Oligocene. Paleorivers sourced from Central Vietnam entered into the western Qiongdongnan Basin and did not reach the central or eastern part of the basin until ca. 31.5–29.9 Ma. An examination of the activity of the Red River Fault showed that the transition of provenance in the study area during the Early Oligocene could be a response to sinistral strike-slip motion along the Red River Fault.

Provenance Variability in Coeval Slope Channel Systems: Hermod S2 Member Sandstone (Eocene), South Viking Graben (North Sea)

Conventional and varietal heavy mineral studies of the earliest Eocene Hermod S2 Member (Mbr) sandstones in the Greater Alvheim area of the northern North Sea have revealed marked lateral variations and more subtle vertical evolution in provenance signature. Major variations are of geographic rather than stratigraphic nature as biostratigraphy reveals that all investigated sandstones are coeval. The provenance variations show an organized pattern, with sandstones in the north showing a different signature than those in the south. The position of the sandstones relative to the East Shetland Platform (ESP) is inferred to be the main control on provenance, with sediment input from at least two different point sources. Sediment supplied from both catchments is predominantly recycled in nature, given the mineralogical maturity of the heavy mineral assemblages, consistent with the evidence for widespread Permo-Triassic and Devonian sediments on the ESP. However, some direct supply from metasedimentary (Moine and Dalradian) basement is implied by the sporadic occurrence of unstable minerals. The southern catchment incorporated a greater exposure of Permo-Triassic sandstones than the northern catchment. The Permo-Triassic part of the catchment can be reconstructed as comprising equivalents of the Foula and Otter Bank sandstones present to the west of Shetland, with the majority of the Foula section having been stripped off prior to Hermod S2 deposition, exposing Otter Bank equivalents for erosion and redeposition. However, remnant Foula-like sandstones remained exposed further south on the ESP until at least the earliest Eocene since Foula-type garnet signatures are found in the Forties Sandstone Mbr of the central North Sea. In addition to lateral differences, stratigraphic evolution of provenance can also be detected in the Hermod S2 Mbr, with variations in key provenance-sensitive parameters related to a sea-level rise that reduced the extent of alluvial storage and altered the geological framework of the hinterland.

Unraveling an alkaline lake and a climate change in Northeastern Brazil during the Late Aptian

The Codó Formation is an Aptian marine-influenced lacustrine depositional system in the Parnaíba Basin (Brazil). This unit is an important sedimentary succession because of the high organic matter content and for being an ancient analog for the depositional systems of the Brazilian Pre-salt interval. However, mineralogical and lithogeochemical studies have not been sufficiently carried out on the Codó Formation, which hinders detailed sedimentological knowledge. We report new mineralogical and lithogeochemical data that allow a better understanding of the environmental, climatic, and provenance evolution of the Codó deposits. Mineralogical and lithogeochemical studies were performed on 50 lutite samples collected from the 1-UN-32-PI core and 13 outcrop lutite samples obtained from sites close to the Grajaú and Imperatriz regions. A magnesium-sulfate-rich shallow alkaline hypersaline lake was identified in the lower Codó Formation based on the identification of a clay mineral assemblage composed of authigenic saponite and detrital illite. Hydrothermal processes were interpreted as the magnesium source of this alkaline lake. A salinity-alteration event was identified at the upper limit of the alkaline lake and was interpreted as the first marine ingression in the Codó Formation. This event changed the lake's pH from alkaline to acid, inhibiting the formation of Mg-smectites, and changing its hydrochemical conditions, originating a marine-influenced sulfate-rich acid saline/hypersaline sabkha. This facies succession coincides with a clay mineral assemblage composed of detrital montmorillonite, illite and kaolinite. A regional paleoclimate humidification process was identified from the sabkha to a lagoon facies succession in the upper Codó Formation. This last succession reveals the marine-dominated interval of the Codó Formation and coincides with a clay mineral assemblage composed of detrital kaolinite, montmorillonite and illite. Based on lithogeochemical data, a common post-Archean intermediate source area was also interpreted for these three environments.