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2022 Vol. 33, No. 6

2022, 33(6)
2022, 33(6)
Guest Editors: Claire E. Reymond, Pamela Hallock and Hildegard Westphal
Tropical Large Benthic Foraminifera: Adaption, Extinction, and Radiation
Preface for "Tropical Large Benthic Foraminifera: Adaption, Extinction, and Radiation"
Claire E. Reymond, Pamela Hallock, Hildegard Westphal
2022, 33(6): 1339-1347. doi: 10.1007/s12583-021-1590-0
Evolution, Extinction, Homology and Homoplasy of the Larger Benthic Foraminifera from the Carboniferous to the Present Day, as Exemplified by Planispiral-Fusiform and Discoidal Forms
Marcelle K. BouDagher-Fadel
2022, 33(6): 1348-1361. doi: 10.1007/s12583-021-1596-7

Examples of evolution, extinction and homoplasy of the larger benthic foraminifera (LBF) occur throughout their history. Since the Carboniferous, LBF have thrived in carbonate-rich tropical and subtropical shallow-marine shelf environments. Their high abundance and diversity are due primarily to their extraordinary ability to inhabit a range of ecological niches and by hosting a variety of symbionts. Attaining relatively large, centimetre-scale sizes, made some forms very specialized and vulnerable to rapid ecological changes. For this reason, some LBF have shown a tendency to suffer periodically during major extinctions, especially when environmental conditions have changed rapidly and/or substantially. This, however, makes them valuable biostratigraphic microfossils and, in addition, gives invaluable insight into the spatial and temporal process of biological evolution, such as convergent/homoplasy and homology/iterative evolution. Here the evolutionary behavior of two important morphological types that occurred throughout the history of the LBF are discussed, namely the planispiral-fusiform test as typified by the fusulinids in the Late Paleozoic and the alveolinids in the Mid-Cretaceous and Neogene, and the three-layered discoid lenticular test as characterized by the orbitoids in the Mid- to Late Cretaceous, the orthophragminids in the Paleogene, and lepidocyclinids in the Oligocene to Quaternary. Understanding the propensity of these forms to convergent and iterative evolution, with the repeated re-occurrence of certain morphological features, is essential in understanding and constructing their phylogenetic relationships more generally within the main groups of the LBF. The insights gained from the history of these LBF have wider implications, and provide a more general understanding of the impacts of climate and ecological changes as driving forces for biological evolution.

Interpreting Morphologically Homogeneous (Paleo-)Populations as Ecological Species Enables Comparison of Living and Fossil Organism Groups, Exemplified by Nummulitid Foraminifera
Johann Hohenegger, Ana Ivis Torres-Silva, Wolfgang Eder
2022, 33(6): 1362-1377. doi: 10.1007/s12583-021-1567-z

Morphologically homogeneous groups, either living populations or fossil paleo-populations, must be regarded as ecological species, independent of their molecular genetic resemblance in living forms. Morphology is always expressed during development by structure genes initiated from a network of regulator genes acting at different times and intensities, additionally being subjected to epigenetic controls. Therefore, homogeneous populations influenced by the environment represent species better than the reproduction (biological species) or molecular-genetic approach using ancestral sequences like rDNA. Living and fossil representatives of nummulitid foraminifera were chosen to demonstrate complete reconstruction of morphology using metrical growth-invariant and growth-independent characters. Using these characters, 6 models were established to define ecological species in living and fossil species. Furthermore, a distinction between evolutionary and environmental effects in fossil forms was possible using discriminant analysis showing characters that are responsible for differentiating between evolutionary and environmental trends.

SE Asian Cenozoic Larger Foraminifera: Taxonomic Questions, Apparent Radiation and Abrupt Extinctions
Peter Lunt, Xiwu Luan
2022, 33(6): 1378-1399. doi: 10.1007/s12583-022-1614-4

The Cenozoic larger foraminifera are important for biostratigraphy in SE Asia. This review examines the taxonomic inconsistencies of this group and especially the confusion over concepts of evolution, migration, radiation and extinction. It is proposed that from the Mediterranean to Indo-Pacific, Latest Eocene through Miocene, larger foraminifera populations were more homogenous than previously believed. Lineages show a slow morphological radiation interrupted by several extinctions. This pattern is superimposed on a long-term decline in larger foraminiferal abundance. The dating of the major biostratigraphic events are qualified. The main lineages of larger foraminifera can be classified by their evolutionary style. The classically "large" genera have highly peramorphic trends achieved through strong orthoselection, and these lineages were the most severely hit by a series of Mid-Eocene to Mid-Miocene extinction events. Other carbonate facies taxa that are traditionally grouped with the larger foraminifera are characterised by weak paramorphism, and these were much less affected by the extinction events. Some of these weakly peramorphic forms underwent Latest Miocene to recent radiation to and locally become rock-forming organisms. The three major and one minor larger foraminiferal extinction events since the Mid Eocene coincide with abrupt tectonic events across SE Asia. However, there are probably multiple causes for these extinctions, including global climatic changes.

Stable Adult Growth but Reduced Asexual Fecundity in Marginopora vertebralis, under Global Climate Change Scenarios
Claire E. Reymond, Frances Patel, Sven Uthicke
2022, 33(6): 1400-1410. doi: 10.1007/s12583-022-1657-6

Large benthic foraminifera are an integral component of shallow-water tropical habitats and like many marine calcifiers, are susceptible to ocean acidification (OA) and ocean warming (OW). In particular, the prolific Symbiodiniaceae-bearing and high-magnesium calcite Marginopora vertebralis has a low threshold compared to several diatom-bearing and low-magnesium calcite species. In this multi-year mesocosm experiment, we tested three RPC 8.5 climate change scenarios (i) present day, (ii) the year 2050, and (iii) 2100. To enable a realistic epiphytic association, these experiments were uniquely conducted using natural carbonate substrate, living calcifying alga, and seagrass. In contrast to previous studies, we detected no reduction in surface-area growth under future climate conditions compared with present day conditions. In terms of calcification, M. vertebralis' epiphytic association to primary producers (i.e., calcifying algae and seagrasses) potentially ameliorates the effects of OA by buffering against declines in boundary layer pH during periods of photosynthesis (i.e., CO2 removal). Importantly for population maintenance, we observed a strong reduction in asexual fecundity under the 2100 scenario. We propose the additional energy needed to maintain growth might be one reason for drastically reduced asexual reproduction. An alternative explanation could be that the 2 ℃ temperature increase interfered with the environmental synchronization that triggered asexual multiple fission. We conclude that the low levels of reproduction will reduce populations in a high CO2 environment and reduce a valuable source of CaCO3 sediment production.

Operculina and Neoassilina: A Revision of Recent Nummulitid Genera Based on Molecular and Morphological Data Reveals a New Genus
Maria Holzmann, Johann Hohenegger, Laure Apothéloz-Perret-Gentil, Raphael Morard, Sigal Abramovich, Danna Titelboim, Jan Pawlowski
2022, 33(6): 1411-1424. doi: 10.1007/s12583-021-1595-8

The genus Operculina, a large symbiont-bearing benthic foraminifer, is characterized by high morphological variability showing thick involute to intermediate semi-involute to flat evolute tests. Different morphotypes are either considered as ecophenotypes or distinct species. In order to test the hypothesis of ecophenotypes versus different species, a single cell high throughput sequencing approach was applied to assess the interspecific diversity of Operculina. This results in two groups of ribotypes, one corresponding to Operculina ammonoides/Operculina discoidalis, the other containing Operculina complanata/Operculina elegans. These groups can also be separated morphologically. Therefore, O. complanata and O. elegans represent a single species and the latter can be regarded as a junior synonym of O. complanata. Operculina ammonoides and O. discoidalis also form a single species, which makes the latter a junior synonym of O. ammonoides. Because generic differences in Operculina species are manifested in morphology and molecular genetics, the genus Neoassilina with the designated species Neoassilina ammonoides is installed. Additional analysis of ribosomal SSU rDNA data of eight recent nummulitid genera confirms the obtained high troughput sequencing results and further shows that Palaeonummulites venosus builds a clade with O. complanata that branches at the base of other Nummulitidae containing Planostegina, Planoperculina, Cycloclypeus, Heterostegina, Operculinella and Neoassilina.

Contributions of Trimorphic Life Cycles to Dispersal and Evolutionary Trends in Large Benthic Foraminifers
Pamela Hallock, Claire E. Reymond
2022, 33(6): 1425-1433. doi: 10.1007/s12583-022-1707-0

The basic life cycle of Foraminifera has long been recognized as alternation between sexual and asexual generations; a common modification is several successive asexual generations. Production and release of flagellated gametes also has been documented as the basic sexual-reproductive mode in extant lineages. Research on population dynamics, local spatial distributions, and biogeography of Amphistegina spp. and Heterostegina depressa have been augmented by culture studies over the past 50 years, providing insights that have been widely used in paleoecological and paleoenvironmental interpretations. Hypotheses are proposed suggesting how stages in the life cycle might contribute to understanding biogeographic and evolutionary trends commonly observed in large benthic foraminifers. Recruitment of sexually-produced cryptobiotic propagules, followed by successive asexual generations (schizogeny), can potentially establish viable, locally-adapted populations within literally years, consistent with the concepts of both allopatric speciation and reticulate evolution associated with isolation and reconnection of local basins. The review concludes with the recommendation that future studies utilizing genomics, proteonomics, geochemistries, scanning technologies, and other approaches can promote greater understanding of both modern and fossil larger benthic foraminiferal lineages.

Local Persistence of Large Benthic Foraminifera (LBF) under Increasing Urban Development: A Case Study from Zanzibar (Unguja), East Africa
Gita R. Narayan, Natalia Herrán, Claire E. Reymond, Yohanna W. Shaghude, Hildegard Westphal
2022, 33(6): 1434-1450. doi: 10.1007/s12583-022-1702-5

Coastal marine management is vital for socio-ecological sustainability of developing, tropical ecosystems, which calls for diverse tools to monitor and assess water quality. The carbonate-dominated habitats off Zanzibar were chosen for study due to potential water quality degradation in a rapidly developing tourist destination heavily reliant on its coral reefs. These reefs are largely unmonitored and subject to local and global stressors. A widely used method for assessing reef health, as an early detection method of ecological changes, is the application of large benthic foraminiferal bioindicators, i.e., the FoRAM Index. We expected to find poor water quality conditions in the unmanaged reefs supported by stress-toelerant (opportunistic) foraminiferal assemblages. The dissolved inorganic nitrogen and phosphate values derived from untreated sewage effluent from Stone Town were highly variable (ranging 0.05–3.77 and 0.05–1.45 μM, respectively), moderate, and occasionally approached or exceeded critical threshold values for oligotrophic ecosystems. The analysis of total assemblages indicated an abundance of symbiont-bearing large benthic foraminifera, dominated by prolific Amphistegina species, comparatively low-moderate diversity, high FI values (7.6 on average), and high coral cover. A water quality gradient was reflected by subtle assemblage differences, suggesting that LBF can provide early warning signals of benthic changes, indicating the importance of long-term monitoring programs in vulnerable, rapidly developing coastal ecosystems exposed to increasing pressures.

A New Foraminiferal Bioindicator for Long-Term Heat Stress on Coral Reefs
Alexander F. Humphreys, Sam J. Purkis, Chuyan Wan, Matthew Aldrich, Sarah Nichols, Jazmin Garza
2022, 33(6): 1451-1459. doi: 10.1007/s12583-021-1543-7

Coral reefs are in terminal decline. For conservation to be effective, naturally depauperate reefs must be distinguished from those recently degraded by humans. Traditional reef monitoring is time consuming and lacks the longevity to make this distinction. Success in using foraminifera as bioindicators for reef health has hitherto levered their response to nutrients. Because ocean heat waves are the dominant driver of coral bleaching and death, there is compelling motivation to develop new foraminiferal bioindicators that inform on temperature stress over meaningful timescales. This study focuses on identifying which foraminifera respond systematically to the temperature stress that kills corals. Statistical models were used to compare endosymbiont-bearing foraminiferal families, collected along a heat-stress gradient spanning the Solomon Islands and New Caledonia, to live coral cover at the same sites. Results indicate that Amphisteginidae foraminifera and coral cover show a significant decline in abundance as heat stress increases along the transect sites. Furthermore, ocean productivity and salinity, both recognized environmental influences on foraminifera, are shown to be subordinate to temperature in their sway of this ecological patterning. These findings indicate the potential for using foraminifera to develop new indices capable of quantifying long-term thermal impacts on reefs.

Light is an Important Limiting Factor for the Vertical Distribution of the Largest Extant Benthic Foraminifer Cycloclypeus carpenteri
Kazuhiko Fujita, Yoji Kanda, Takashi Hosono
2022, 33(6): 1460-1468. doi: 10.1007/s12583-022-1612-6

Cycloclypeus carpenteri is the largest extant benthic foraminifer, dwelling in the deep euphotic zone (a water depth between 60 and 130 m) of the warm oligotrophic Indo-West Pacific. This foraminifer harbors diatom endosymbionts and the foraminifer-microalgal association acts like a holobiont. To verify that light is an important limiting factor controlling the vertical (depth) distribution of living Cycloclypeus holobionts, their physiological responses to light intensity were examined by short-term metabolic measurements and long-term incubations. Net oxygen production (OP) rates measured under different light levels using an oxygen microelectrode indicate that Cycloclypeus holobionts are daily net primary producers adapted to low light levels, with slight photoinhibition (reduced net OP rates relative to a light-saturated rate) over 100 μmol photons m-2 s-1. Long-term growth increments of asexually reproduced juveniles incubated for two months at different light levels ranging from 0 to 100 μmol photons m-2 s-1 show that Cycloclypeus holobionts are adapted to a low light level (~5 μmol photons m-2 s-1), but can be acclimatized to a certain low light ranges (< 50 μmol photons m-2 s-1). These experimental results confirm that light is an important environmental gradient affecting the vertical distribution of Cycloclypeus holobionts.

Proteome-Based Clustering Approaches Reveal Phylogenetic Insights into Amphistegina
Marleen Stuhr, Bernhard Blank-Landeshammer, Achim Meyer, Vera Baumeister, Jörg Rahnenführer, Albert Sickmann, Hildegard Westphal
2022, 33(6): 1469-1479. doi: 10.1007/s12583-022-1609-1

Foraminifera are highly diverse and have a long evolutionary history. As key bioindicators, their phylogenetic schemes are of great importance for paleogeographic applications, but may be hard to recognize correctly. The phylogenetic relationships within the prominent genus Amphistegina are still uncertain. Molecular studies on Amphistegina have so far only focused on genetic diversity within single species and suggested a cryptic diversity that demands for further investigations. Besides molecular sequencing-based approaches, different mass spectrometry-based proteomics approaches are increasingly used to give insights into the relationship between samples and organisms, especially as these do not require reference databases. To better understand the relationship of amphisteginids and test different proteomics-based approaches we applied de novo peptide sequencing and similarity clustering to several populations of Amphistegina lobifera, A. lessonii and A. gibbosa. We also analyzed the dominant photosymbiont community to study their influence on holobiont proteomes. Our analyses indicate that especially de novo peptide sequencing allows to reconstruct the relationship among foraminiferal holobionts, although the detected separation of A. gibbosa from A. lessonii and A. lobifera may be partly influenced by their different photosymbiont types. The resulting dendrograms reflect the separation in two lineages previously suggested and provide a basis for future studies.

Conodont Biostratigraphic Constraint on the Lower Taiyuan Formation in Southern North China and Its Paleogeographic Implications
Yuan Wang, Jianghai Yang, Dong-Xun Yuan, Jia Liu, Rui Ma
2022, 33(6): 1480-1493. doi: 10.1007/s12583-021-1526-8

The Late Paleozoic Taiyuan Formation in North China is mainly composed of a mixed shallow-marine carbonate and terrigenous clastic deposits. Its basal limestones have been constrained in the late Pennsylvanian to Early Permian. To further constrain the age of the lowest Taiyuan Formation, we obtained two genera and 16 species of conodonts from the bottom limestones of the Taiyuan Formation in two sections in Henan Province, southern North China. The fauna includes Idiognathodus hebeiensis, Streptognathodus isolatus, S. elongatus, S. cf. longus, S. acuminatus, S. cf. recreatus, S. cf. cristellaris, S. bellus, S. invaginatus, S. wabaunsensis, S. glenisteri, S. conjunctus, S. binodosus, S. fuchengensis, S. nodulinearis, and S. sp. A genus of Streptognathodus dominated conodont assemblage with some Idiognathodus elements. It indicates a late Gzhelian (latest Pennsylvanian) age for the lowest Taiyuan Formation in southern North China. This is consistent with recently published high-precision zircon U-Pb ages from ash layers. Based on conodont biostratigraphy, the basal limestones of the Taiyuan Formation in Henan Province (southern North China) can be correlated with the upper part of Miaogou limestones of the Taiyuan Formation in Shanxi Province (northern North China). This correlation might reflect a significant sea-level rise in North China, possibly corresponding to a deglaciation event at the Permo-Carboniferous transition.

Towards the Triassic Configuration of Western Paleotethys
Darko Spahić
2022, 33(6): 1494-1512. doi: 10.1007/s12583-021-1578-9

The tectono-paleogeograhic inheritance of barely documented Paleotethyan influence on the Southern Carpathian-Balkan belt is herein reappraised to highlight complex processes occurring along an alternative branched configuration of Triassic fossil subduction zone interfaces. The absence of Paleotethyan oceanic accretionary complexes, and the unavailability of rocks returned from poorly traceable Triassic subduction zones allow no conventional insights into its internal structure. In contrast, the adjoining Dinarides and investigated western Southern Carpathian-Balkan belt contain metamorphic rocks ejected from the precursory Late Paleozoic Paleotethyan active margin. An inventory and reappraisal of Variscan and Cimmerian imprints, far-field effects place the peri-Moesian Southern Carpathian-Balkan belt into the overriding plate position above the Triassic Paleotethyan active margin. Ongoing Permian–Early Triassic dragging of underlying Paleotethyan crustal material beneath external segments of the continental margin is contemporaneous with the onset and formation of several episutural back-arc oceans. These include the Maliac Ocean with a here introduced NNW-SSE striking Lower–Middle Triassic marginal shallow-water clastic-carbonate basin of Getic Unit (Gornjak nappe) that is spatially in line with the "Volvi-Therma" western Rhodope aborted Triassic rift system. The carbonate platform deposition was interrupted by a change in the geodynamic regime at the end of the Middle Triassic (inducing mild compressional deformations and the regional uplift resulting in missing of Upper Triassic sediments). The constraints on the investigated sequences yield that the lagged Paleotethyan closure in the Balkan sector occurred during the late Ladinian-Carnian interval.

Compositional Features of Fine Sediments Involved in the Montescaglioso Landslide (Southern Italy)
Vito Summa, Rosa Sinisi, Eleonora Paris, Agnese Emanuela Bonomo
2022, 33(6): 1513-1525. doi: 10.1007/s12583-021-1579-8

This paper presents the multidisciplinary study of the southern Italy Plio-Pleistocene sediments involved in the large Montescaglioso Landslide. The principal aim of the work is to assess the compositional characters (i.e., grain-size, mineralogy, petrography and geochemistry) and some rheological features (Atterberg's limits, plasticity index and activity) of these sediments to enrich our knowledge about the Montescaglioso fine sediments and correlation among the lithological properties studied. Two types of sediments, from a deep geognostic borehole and from the surrounding landslide area, were collected and analysed. No significant compositional differences have been found between the core and landslide area sediments. Conversely, some changes have been detected in sediments along the core. Particularly, the -15 to -20 m lithostratigraphic level hosts the highest percentages of phyllosilicates and clay fraction (CF), commonly considered as possible hazard factors for the landslide triggering. Further more, in the studied core sediments, the CF contents correlate with the Atterberg's liquid and plastic limits and a CF value of about 38% was suggested as threshold value for the changing of index properties of sediments. Other factors, such as the weathering degree and clay mineral type, do not show significant correlations with the rheological properties of sediments here studied.

Cretaceous Meteorite Impact-Induced Initial Subduction: Records of highly Siderophile Element Abundances and Re-Os Isotopes in Ophiolites
Benxun Su
2022, 33(6): 1526-1534. doi: 10.1007/s12583-022-1734-x

Compiled global ophiolite data reveal that Cretaceous ophiolites exhibit broaden variations in 187Re/188Os and 187Os/188Os values, increases in Re concentrations and thus Re/Os ratios in all peridotites and chromitites, and additional increased PPGE/IPGE (Pd-subgroup platinum-group element (PGE)/Ir-subgroup PGE) ratios in chromitites and dunites relative to pre-Cretaceous ophiolites. These compositional changes in Cretaceous ophiolites, which mostly formed in subduction initiation settings, cannot be attributed solely to involvement of subducting or previously subducted crustal materials. Here, the author proposes a Cretaceous meteorite impact model that led to impact-induced disruption of oceanic lithosphere, asthenosphere upwelling, subduction initiation at edges of laterally spreading anomalies. High-pressure and high-temperature conditions during the impacts caused melting of the meteorites and the ambient crustal and mantle rocks, producing hybrid melts containing partially unmelted fragments. Crustal materials contributed to the elevated 187Os/188Os values, Re and Re/Os ratios, whereas the undifferentiated meteorite accounted for the increases in the PPGE/IPGE and decreased 187Os/188Os ratios. Shock pressure and super-reduced phases were likely generated by this process and were subsequently transported into the newly formed mantle peridotites and chromitites of future ophiolites. The remaining meteoritic and lithospheric fragments most likely sank deeper and were distributed widely in the convecting mantle to produce the observed global compositional heterogeneities.

Mineral Chemistry of Biotite and Its Petrogenesis Implications in ca. 2.5 Ga Wangjiazhuang Granitic Pluton, North China Craton
Junpeng Wang, Kang Jiang, Deng Xiao, Fenfang Li, Fupeng Li, Xiaofeng Li, Song Jin, Guanghuo Tao
2022, 33(6): 1535-1548. doi: 10.1007/s12583-020-1376-9

The Wangjiazhuang granitic pluton is located in the central Zanhuang Domain, the central part of the North China Craton, which is mainly composed of biotite monzogranite with few mafic microgranular enclaves. Biotite is an important ferromagnesian mineral in most of the intermediate-felsic igneous rocks, and its mineral chemistry can record the properties of magma and the petrogenetic physicochemical conditions. In this study, we carried out a detailed petrographic study by electric probe microanalysis on biotite for the biotite monzogranite and mafic microgranular enclaves, to discuss the source, physicochemical conditions, and the magma mingling/mixing processes of the Wangjiazhuang granite. The results show significantly different chemical compositions from the biotite monzogranite and mafic microgranular enclaves. The crystallization of these biotite grains from the biotite monzogranite and mafic microgranular enclaves all occurred in low oxygen fugacity. The biotite grains in biotite monzogranite are rich in Fe, poor in Mg, which belong to siderophyllite. The ratios of [(Fe3+ + Fe2 +)/(Fe3+ + Fe2+ + Mg2+)] are between 0.78 and 0.86. The average of FeOT (total FeO)/MgO of biotite grains in biotite monzogranite is 9.02. The MF values [2 × Mg/(Fe2+ + Mg + Mn)] of biotite monzogranite are between 0.31 and 0.47, suggesting biotite monzogranite derived from crustal source rocks (metasedimentary rocks). The formation of granitic rocks including the Wangjiazhuang granite was related to the subduction event at ca. 2.5 Ga which resulted in the melting event, and then induced the early partial melting of TTGs and metasedimentary rocks. The biotite in mafic microgranular enclaves varies from siderophyllite to ferrobiotite, and MF values range from 0.63 to 1.06, suggesting that magma of mafic microgranular enclaves had experienced magma mixing/mingling in various degrees. Biotite monzogranite and parts of mafic microgranular enclaves have a similar crystallized condition, while other mafic microgranular enclaves are different from biotite monzogranite. The differences between biotite monzogranite and mafic microgranular enclaves may be a consequence of continuous interaction between granitic and mafic magmas.

Provenance of Uranium Mineralization of the Yuqia Area, Northwest China: Constraints from Detrital Zircon U-Pb Geochronology and Hf Isotopes
Guangwen Huang, Jiayong Pan, Fei Xia, Jie Yan, Chengyong Zhang, Dehai Wu, Ying Liu
2022, 33(6): 1549-1570. doi: 10.1007/s12583-022-1654-9

Many sandstone-type uranium mineralization sites have been identified along the northern margin of the Qaidam Basin in North China. Intense tectonism and multistage magmatism that occurred there have restricted the use of conventional techniques (petrogeochemistry) to deduce the sources of detritus and uranium in these sediments, and to further explore the sandstone-type uranium deposits. In this study, U-Pb geochronological and Hf isotopic analyses were conducted on detrital zircon grains collected from Jurassic to Paleogene sandstones exposed in the Yuqia area of the Qaidam Basin. The results indicate that the U-Pb ages of the analyzed zircon grains are clustered into four groups, 285–229, 498–401, 999–806, and 2 520–2 305 Ma. The εHf(t) of the analyzed zircon grains ranges from -21.9 to +10.5, with two-stage Hf model ages (TDM2) concentrated between 2.1 and 1.3 Ga. Based on paleocurrent studies and results of petrological, detrital zircon geochronology, and Hf isotopic analyses, the Jurassic sediments in the Yuqia area were likely derived from the tectonic belt along the northern margin of the Qaidam Basin, such as the Qilian Mountains and the Quanji Block. In contrast, the Paleogene sediments were probably sourced from the northern margin of the Qaidam Basin and the Qilian Mountains. The uranium and thorium content and Th/U value of the rock mass and sedimentary strata in the source area show that the Indosinian Early Paleozoic uranium-rich granites and the Middle Jurassic uranium-rich strata of the northern margin of the Qaidam tectonic belt in the source area provide dual uranium sources for the Yuqia sandstone-type uranium mineralization. Therefore, the study area appears to be favorable for sandstone-type uranium mineralization and may have potential for uranium prospecting.

Tracing the Methane Events by Stable Carbon Isotopes of Benthic Foraminifera at Glacial Periods in the Andaman Sea
Yue Cen, Jiasheng Wang, Xuan Ding, Dorrik Stow, Zhou Wang, Can Chen, Xiaochen Ma
2022, 33(6): 1571-1582. doi: 10.1007/s12583-022-1750-x

Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment studies. However, studies about the shells of benthic foraminifera in methane-hydrate-bearing sediments as reliable geochemical proxies to reconstruct the potential methane release events in the geologic past are rare. In this study, we present the stable carbon and oxygen isotopes of fossil benthic foraminifera including one epifaunal species (Cibicidoides wuellerstorfi) and two infaunal species (Bulimina mexicana and Uvigerina peregrina) from the Site U1447 of IODP 353 Expedition to trace methane events in the Andaman Sea, where one of the thickest and deepest gas hydrate stability zones was discovered. The δ13C values of benthic foraminifera show that there are eight distinct intervals with negative values in the last ~10 Myr, interpreted as a record of long-term fluctuations in methane emission. Six of these methane events occurred during the glacial sea-level lowstands in the last ~1.1 Myr. We, therefore, infer that the trigger mechanism for these events might be the hydrate destabilization caused by sea level fall. The methane events that occurred at ~2.11 and ~5.93 Ma are more likely related to the sudden changes in sedimentation, either slide events or marked variations in sedimentation rate.

Numerical Investigation of Residence Time Distribution for the Characterization of Groundwater Flow System in Three Dimensions
Jiale Wang, Menggui Jin, Baojie Jia, Fengxin Kang
2022, 33(6): 1583-1600. doi: 10.1007/s12583-022-1623-3

How to identify the nested structure of a three-dimensional (3D) hierarchical groundwater flow system is always a difficult problem puzzling hydrogeologists due to the multiple scales and complexity of the 3D flow field. The main objective of this study was to develop a quantitative method to partition the nested groundwater flow system into different hierarchies in three dimensions. A 3D numerical model with topography derived from the real geomatic data in Jinan, China was implemented to simulate groundwater flow and residence time at the regional scale while the recharge rate, anisotropic permeability and hydrothermal effect being set as climatic and hydrogeological variables in the simulations. The simulated groundwater residence time distribution showed a favorable consistency with the spatial distribution of flow fields. The probability density function of residence time with discontinuous segments indicated the discrete nature of time domain between different flow hierarchies, and it was used to partition the hierarchical flow system into shallow/intermediate/deep flow compartments. The changes in the groundwater flow system can be quantitatively depicted by the climatic and hydrogeological variables. This study provides new insights and an efficient way to analyze groundwater circulation and evolution in three dimensions from the perspective of time domain.

Spatiotemporal Distribution of Microbial Tetraether Lipids in a Lake and Its Inflowing River: Implications for the Identification of Flooding Events
Xiuchang Zhu, Yongbo Wang, Xinyue Dang, Huan Yang, Shucheng Xie
2022, 33(6): 1601-1613. doi: 10.1007/s12583-021-1552-6

Microbial glycerol dialkyl glycerol tetraethers (GDGTs) in lacustrine sediments are widely used to reconstruct terrestrial paleoenvironments. However, lipids of diverse origin in lakes make it difficult to decipher environmental information, appealing for the necessity to evaluate the impact of terrigenous input on the distribution of GDGTs through long-term monitoring. In this study, we conducted two-year monitoring of GDGTs along the river, estuary, near shore, to the center of Lake Liangzi in central China. By comparing the spatiotemporal changes of GDGT distribution in suspended particulate matter (SPM) and surface sediments, we found that the archaeal isoprenoid GDGTs (isoGDGTs) were mainly produced in situ in the river-lake systems, and not affected by the soil input. In contrast, the bacterial branched GDGTs (brGDGTs) were affected, to some extent, by soil input, depending on the distance to the lakeshore. The soil input of brGDGTs was enhanced during an episode of abnormal rainfall (flood). Moreover, the large variation of isoGDGTs indicates the in situ production under the anoxic condition in lake water. The paired increase in the GDGT-0/Cren ratio and GDGT concentration might be diagnostic of flooding events in ancient times.

Notes for a History of Gas Geochemistry
Guodong Zheng, Giovanni Martinelli, Yanxin Wang, Shun Li, Xiangxian Ma
2022, 33(6): 1614-1623. doi: 10.1007/s12583-022-1758-2

During ancient times, human interest in naturally-occurring gases was religious, while it was scientific in the historical age and industrial in modern times. Gases were also utilized for practical purposes and more than 3 000 years before present day, Chinese populations made use of methane for salt extraction while in the 17th century it was observed that native Americans ignited methane seepages. The development of human thinking on gases followed the fundamental steps that characterized the natural sciences during the 18th century scientific revolution that was based on significant improvements in analytical methods. These improvements are still ongoing while present-day scientific publications evidence the spread of the field of interest and more cooperation with geophysical sciences to solve common interest problems. The existence of proper meetings and dedicated scientific journals confirms that gas geochemistry has ended this pioneering phase to enter a more mature condition.

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