Southern dispersal and Palaeoecological implications of woolly rhinoceros (Coelodonta antiquitatis): review of the Iberian occurrences

Cold-adapted large mammal populations spread southward during the coldest and driest phases of the Late Pleistocene reaching the Iberian Peninsula. Presence of woolly rhinoceros (Coelodonta antiquitatis) can be identified from 23 Iberian sites, which is compiled and analyzed herein, and the fossil specimens from seven of these sites are described here for first time.Morphological and biometrical analyses demonstrate that the Iberian woolly rhinoceros did not significantly differ from individuals of other European populations, but represent the westernmost part of a continuous Eurasian belt of distribution.The first presence of woolly rhino in the Iberian Peninsula has been identified during the late Middle Pleistocene and early Late Pleistocene. However, the highest abundance of this species is recorded during MIS 3 and 2. The latest Iberian occurrences can be dated around 20 ka BP. The presence of woolly rhinoceros in the Iberian Peninsula correlates with periods of extreme dry and cold climatic conditions documented in Iberian terrestrial and marine sediment sequences.From a palaeobiogeographic point of view, the maximum southern spread of C. antiquitatis on the Iberian Peninsula was registered during the late Middle Pleistocene or early Late Pleistocene, reaching the latitude of Madrid (about 40°N). Subsequently, during MIS 3 and 2, all Iberian finds were restricted to the Northern regions of Iberia (Cantabrian area and Catalonia). The southern expansion of C. antiquitatis during the Late Pleistocene in the Iberian Peninsula reached similar latitudes to other Eurasian regions.The ecological composition of fossil assemblages with presence of woolly rhinoceros was statistically analyzed. Results show that temperate ungulate species are predominant at Iberian assemblages, resulting in a particular mixture of temperate and cold elements different of the typical Eurasian cold-adapted faunal associations. This particular situation suggests two possible explanations: a) Eventual migrations during the coldest time spans, resulting in a mixing of cold and temperate faunas, instead a faunal replacing; b) Persistence of woolly rhinoceros populations in the Iberian Peninsula during interglacial episodes confined at cryptic southern refugia.     

Extinction of the woolly mammoth (Mammuthus primigenius) and woolly rhinoceros (Coelodonta antiquitatis) in Eurasia: Review of chronological and environmental issues

Kuzmin, Y. V. 2009: Extinction of the woolly mammoth (Mammuthus primigenius) and woolly rhinoceros (Coelodonta antiquitatis) in Eurasia: Review of chronological and environmental issues. Boreas, 10.1111/j.1502‐3885.2009.00122.x. ISSN 0300‐9483. The current evidence for date and environmental preferences of the extinction of two middle–late Pleistocene megafaunal species, the woolly mammoth (Mammuthus primigenius Blum.) and woolly rhinoceros (Coelodonta antiquitatis Blum.), is presented in this review. It is suggested that extinction of these large herbivores in Eurasia was closely related to landscape changes near the Pleistocene–Holocene boundary (c. 12 000–9000 uncalibrated radiocarbon years ago, yr BP), mainly involving the widespread forest formations in the temperate and arctic regions of northern Eurasia and the loss of grasslands crucial to the existence of woolly mammoth and rhinoceros. However, some woolly mammoth populations survived well into the Holocene (up to c. 3700 yr BP), showing that the process of final extinction was fairly complex, with delays in some regions of up to several millennia. The possible role of Palaeolithic humans in the extinction of Late Pleistocene megafauna is also considered.     

Arctic Siberia: refuge of the Mammoth fauna in the Holocene

Global climate change at the end of Pleistocene led to extinction in the huge territories of Northern Eurasia of the typical representatives of the Mammoth fauna: mammoth, woolly rhinoceros, wild horse, bison, musk-ox, and cave lion. Undoubtedly the Mammoth fauna underwent pressure from Upper Paleolithic humans, whose hunting activity could also have played a role in decreasing the number of mammoths and other representatives of megafauna. Formerly it was supposed that the megafauna of the “Mammoth complex” had become extinct by the beginning of the Holocene. Nevertheless the latest data indicate that extinction of the Mammoth fauna was significantly delayed in the north of Eastern Siberia. In the 1990s some radiocarbon dates established that mammoths existed in the Holocene on Wrangel Island—from 7700 until 3700 yBP. Radiocarbon data show that wild horses inhabited the north of Eastern Siberia 4600–2000 yBP. Muskoxen lived here about 3000 yBP. Some bison remains from Eastern Siberia belong to the Holocene. The following circumstances could promote the survival of representatives of Mammoth fauna. Cool and dry climate in this region promotes the maintenance of steppe associations—the habitats of those mammals. Late Paleolithic and Mesolithic settlements are not found in the Arctic zone of Eastern Siberia from Taimyr Peninsula to the lower Yana River; they are very rare in basins of the Indigirka and Kolyma Rivers. The small number of Stone Age hunting tribes in the northern part of Eastern Siberia was probably another factor that contributed to the survival of some Mammoth fauna representatives.     

Pleistocene vertebrates of the Yukon Territory

Unglaciated parts of the Yukon constitute one of the most important areas in North America for yielding Pleistocene vertebrate fossils. Nearly 30 vertebrate faunal localities are reviewed spanning a period of about 1.6 Ma (million years ago) to the close of the Pleistocene some 10 000 BP (radiocarbon years before present, taken as 1950). The vertebrate fossils represent at least 8 species of fishes, 1 amphibian, 41 species of birds and 83 species of mammals. Dominant among the large mammals are: steppe bison (Bison priscus), horse (Equus sp.), woolly mammoth (Mammuthus primigenius), and caribou (Rangifer tarandus) – signature species of the Mammoth Steppe fauna (Fig. 1), which was widespread from the British Isles, through northern Europe, and Siberia to Alaska, Yukon and adjacent Northwest Territories. The Yukon faunas extend from Herschel Island in the north to Revenue Creek in the south and from the Alaskan border in the west to Ketza River in the east. The Yukon holds evidence of the earliest-known people in North America. Artifacts made from bison, mammoth and caribou bones from Bluefish Caves, Old Crow Basin and Dawson City areas show that people had a substantial knowledge of making and using bone tools at least by 25 000 BP, and possibly as early as 40 000 BP. A suggested chronological sequence of Yukon Pleistocene vertebrates (Table 1) facilitates comparison of selected faunas and indicates the known duration of various taxa.     

Last straw versus Blitzkrieg overkill: Climate-driven changes in the Arctic Siberian mammoth population and the Late Pleistocene extinction problem

A set of radiocarbon dates on woolly mammoth were obtained from several regions of Arctic Siberia: the New Siberian Islands (n = 68), north of the Yana-Indigirka Lowland (n = 43), and the Taimyr Peninsula (n = 18). Based on these and earlier published dates (n = 201) from the East Arctic, a comparative analysis of the time-related density distribution of ¹⁴C dates was conducted. It was shown that the frequencies of ¹⁴C dates under certain conditions reflect temporal fluctuations in mammoth numbers. At the end of the Pleistocene the number of mammoths in the East Arctic changed in a cyclic manner in keeping with a general “Milankovitch-like” trend. The fluctuations in numbers at the end of the Pleistocene occurred synchronously with paleoenvironmental changes controlled by global climatic change. There were three minima of relative mammoth numbers during the last 50 000 years: 22 000, 14 500–19 000, and 9500 radiocarbon years ago, or around 26 000, 16–20 000, and 10 500 calendar years respectively. The last mammoths lived on the New Siberian Islands, which were connected to the continent at that time, 9470 ± 40 radiocarbon years ago (10 700 ± 70 calendar years BP). This new youngest date approximates the extinction time of mammoths in the last continental refugium of the Holarctic. The adverse combination of environmental parameters was apparently a major factor in the critical reduction in mammoth numbers. The dispersal of humans into the Arctic areas of Siberia no later than 28 000 radiocarbon years ago did not overtly influence animal numbers. Humans were not responsible for the destruction of a sustainable mammoth population. The expanding human population could have become fatal to mammoths during strong the minima of their numbers, one of which occurred at the very beginning of the Holocene.     

A new site from the Spanish Middle Pleistocene with cold-resistant faunal elements: La Parte (Asturias,Spain)

The La Parte (Asturias) northern Spain site contains a cold-adapted mammal faunal assemblage that corresponds to a level radiometrically dated to a minimum age of 150 ka. It represents the most ancient site with cold resistant fauna in the Iberian Peninsula.Among the species recorded in La Parte, Coelodonta antiquitatis and Rangifer tarandus represent the typical cold-adapted large mammal association.The presence of the woolly rhino at La Parte provides relevant environmental information about the Mammoth Steppe. This species was not as abundant in the Middle Pleistocene as during the Late Pleistocene, when its cold-adapted features can be studied from an evolutionary perspective. The remains attributed to R. tarandus suggest an open steppe ecosystem.The presence of Marmota sp. is also confirmed in La Parte. A first interpretation would suggest an alpine or periglacial ecosystem, but based on recent results which do not support the correlation between phylogeny and climatic tolerance for extant species of Marmota (López and Cuenca, 2002. Palaeogeography, Palaeoclimatology, Palaeoecology 186, 311), we propose the presence of this rodent suggests an open landscape with cold conditions.The rest of the taxa included in the La Parte assemblage (Crocuta crocuta, Panthera leo, Cervus elaphus, Megaloceros cf. giganteus, Bison priscus and Equus caballus) are usually associated with typical cold-adapted faunas, but they are also found in woody temperate zones so they do not characterize by themselves a cold period. The faunal association from La Parte suggests a combination of steppic and open woodland ecological conditions.     

Zonal stratigraphy and biogeography of the West Siberian Oxfordian based on ammonites

The Oxfordian Stage of West Siberia contains Boreal ammonites Cardioceratidae. The authors’ bank of paleontological data includes ~ 500 definitions of Cardioceratinae, permitting a considerable refinement of the official Oxfordian regional zonal scale. The lower substage is divided into the Cardioceras (Scarburgiceras) obliteratum, C. (S.) scarburgense, and C. (S.) gloriosum Zones instead of beds with C. (S.) spp., whereas the C. (Cardioceras) percaelatum and C. (C.) cordatum Zones are recognized instead of beds with C. (C.) spp. We have found new ammonites typical of the Middle Oxfordian C. (Subvertebriceras) densiplicatum and C. (Miticardioceras) tenuiserratum Zones. The first of these zones is divided into two subzones. The Upper Oxfordian includes the Amoeboceras glosense and A. serratum Zones instead of beds with A. spp., and the A. regulare Zone and beds with A. rosenkrantzi are recognized instead of the A. ex gr. regulare Zone. The genus Ringsteadia (Aulacostephanidae) is observed only in the northwestern part of the region, along the eastern slope of the North Urals; therefore, two upper units of the biostratigraphic scale correspond to beds with Ringsteadia marstonensis.In the Oxfordian, West Siberia and northern Siberia belonged to the North Siberian province of the Arctic realm. Only in the latest Oxfordian did the northwestern West Siberian basin become part of the Boreal-Atlantic realm, as evidenced by the distribution of Ringsteadia on the eastern slope of the Cis-Polar Urals.     

Geochronology and paleomagnetism of mafic igneous rocks in the Olenek Uplift, northern Siberia: Implications for Mesoproterozoic supercontinents and paleogeography

We present a new, reliably dated Mesoproterozoic paleopole for Siberia, based on a combined geochronological and paleomagnetic study of mafic rocks within the Mesoproterozoic Sololi Group of the Olenek Uplift in northern Siberia. Ion microprobe (SHRIMP) U–Pb analysis yields crystallisation ages of 2036 ± 11 Ma for zircon from a basement granite and 1473 ± 24 Ma for baddeleyite from a large dolerite sill within the Kyutingde Formation. The baddeleyite result indicates that the lower Sololi Group is significantly older than was suggested by previous K–Ar results. Paleomagnetic analysis of the dolerite sill and related mafic intrusive rocks yields a paleopole at 33.6°N, 253.1°E, A₉₅ = 10.4°. A positive baked-contact test between the Kyutingde sill and sedimentary country rocks shows that the magnetisation is primary. Comparison of this paleopole with coeval results for Laurentia provides a revised reconstruction between Siberia and Laurentia, and implies that these two continents were parts of a single Mesoproterozoic supercontinent since at least 1473 Ma. We argue that Siberia, Laurentia, and Baltica belonged to the same supercontinent between 1473 Ma and mid-Neoproterozoic time.     

Petrogenesis of Middle-Eocene granitoids and their Mafic microgranular enclaves in central Urmia-Dokhtar Magmatic Arc (Iran): Evidence for interaction between felsic and mafic magmas

Whole rock major and trace element geochemistry together with zircon U-Pb ages and Sr-Nd isotope compositions for the Middle Eocene intrusive rocks in the Haji Abad region are presented. The granitoid hosts, including granodiorite and diorite, yielded zircon U-Pb ages with a weighted mean value of 40.0 ± 0.7 Ma for the granodiorite phase. Mafic microgranular enclaves(MMEs) are common in these plutons, and have relatively low SiO_2 contents(53.04-57.08 wt.%) and high Mg#(42.6-60.1), probably reflecting a mantle-derived origin. The host rocks are metaluminous(A/CNK = 0.69-1.03), arc-related calc-alkaline, and I-type in composition, possessing higher SiO_2 contents(59.7-66.77 wt.%) and lower Mg#(38.6-52.2); they are considered a product of partial melting of the mafic lower crust. Chondritenormalized REE patterns of the MMEs and granitoid hosts are characterized by LREE enrichment and show slight negative Eu anomalies(Eu/Eu* = 0.60-0.93). The host granodiorite samples yield(⁸⁷Sr/⁸⁶Sr);ratios ranging from 0.70498 to 0.70591,positive eNd(t) values varying from +0.21 to +2.3, and TDM2 ranging from 760 to 909 Ma, which is consistent with that of associated mafic microgranular enclaves(⁸⁷Sr/⁸⁶Sr)i = 0.705111-0.705113, ε_Nd(t)= +2.14 to +2.16, T_DM2 = 697-785 Ma). Petrographic and geochemical characterization together with bulk rock Nd-Sr isotopic data suggest that host rocks and associated enclaves originated by interaction between basaltic lower crust-derived felsic and mantlederived mafic magmas in an active continental margin arc environment.     

Six new stromatolitic microbiotas from the Proterozoic of the Soviet Union

Diverse assemblages of cellularly preserved Precambrian microorganisms have been discovered in cherty stromatolitic sediments from six formations in the Soviet Union: Sukhotungusin Fm. (Middle Riphean, Siberia); Valukhtin Fm. (Middle Riphean, Siberia); Shorikha Fm. (Upper Riphean, Siberia); Minyar Fm. (Upper Riphean, Bashkiria); Olkhin Fm. (Upper Riphean, Siberia); and Chichkan Fm. (Vendian, Kazakstan). These cyanophyte-dominated microbial communities, occurring in both stratiform (cf. Stratifera) and columnar stromatolitic deposits (Baicalia hirta and Conophyton gaubitza), are the first stromatolite-building microbiotas to be reported from the Soviet Union; collectively they comprise more than one-fifth of all such Precambrian assemblages now known.     

Revised radiocarbon ages on woolly rhinoceros (Coelodonta antiquitatis) from western central Scotland: significance for timing the extinction of woolly rhinoceros in Britain and the onset of the LGM in central Scotland

Woolly rhinoceros bones, from a number of sites in Britain, have been AMS radiocarbon dated following ultrafiltration pre-treatment. These determinations give a coherent set of ages between >50 and c. 35 cal ka BP. The youngest (35,864–34,765 cal BP) come from the area around Bishopbriggs in western central Scotland and are derived from glaciofluvial sand and gravel overlain by till, both deposited during the Last Glacial Maximum (LGM) glaciation. A previous radiocarbon date from the site suggested that woolly rhinoceros lived c. 27 ¹⁴C ka BP and the region was ice-free at the time. This date has had significant influence on the timing of extinction of woolly rhinoceros and the onset of glaciation over Britain during the LGM. The new dates revise this earlier determination and confirm that woolly rhinoceros became extinct in Britain after c. 35 cal ka BP, that central Scotland was ice-free at this time, and glaciation extended across this region sometime after 35 cal ka BP.     

Lower Cambrian helcionelloid macromolluscs from South Australia

Early Cambrian univalve molluscs are predominantly represented by microscopic forms (body length of 1–3 mm), preserved mainly as phosphatised internal moulds with limited definable features. Macromolluscs (≥ 5 mm) are generally rare, occur in low abundance and are poorly preserved, often lacking apical features and ornament which hinders taxonomic assessment. New and previously undescribed material from lower Cambrian Hawker Group carbonates of the Flinders Ranges in South Australia includes four new taxa, Minastirithella silivreni gen. et sp. nov., Galeacalvus coronarius gen. et sp. nov., Helcionella histosia sp. nov., and Ilsanella enallaxa sp. nov. Three-dimensional silicified shell material preserved with intact apices offers new insight into protoconch morphology, growth habit (isometric vs. allometric) and developmental mode. This material supports previous suggestions that some micromollusc taxa may in fact be early ontogenetic stages (juveniles) of larger macroscopic taxa; such that the millimetric size range of helcionelloids conforms to the dimensions of earliest apical portion in some macromolluscs documented herein. However, taphonomic limitations associated with phosphatisation show that the morphology (especially height vs. width) of the apex can greatly influence the probability of steinkern formation and preservation potential for both micro- and macro-scale helcionelloids. Artificial inflation in the appearance of millimetric helcionelloids with an optimal morphology for phosphatisation is thus directly linked to taphonomic biases in the fossil record.     

Integrated stratigraphy of the Lower and Middle Cenomanian in a Tethyan section (Blieux,southeast France) and correlations with Boreal basins

A detailed stratigraphic analysis was carried out on the Lower–Middle Cenomanian hemipelagic deposits of the Blieux section (Alpes-de-Haute-Provence; southeast France) in order to identify the Middle Cenomanian event I (MCE I) in the Vocontian Basin. These deposits are represented by five bundles composed of limestone–marl alternations that are separated by thick marly intervals. The Blieux section, which is well exposed, very thick, continuous and relatively rich in macrofauna, provides an ideal succession for an integrated approach. Biostratigraphy by ammonoids and sequence stratigraphy have been established for the whole succession whereas calcareous nannofossil and geochemical analyses have been carried out on a restricted interval across the Lower/Middle Cenomanian boundary. The uppermost part of the Mantelliceras mantelli Zone, the Mantelliceras dixoni Zone and the lower part of the Acanthoceras rhotomagense Zone have been recognized. The appearance of the genus Cunningtoniceras (C. inerme or C. cunningtoni) is used to place the base of the A. rhotomagense Zone and the Lower/Middle Cenomanian boundary. This boundary is also well characterized by the presence of nannofossil Subzone UC2C. Two orders of hierarchically stacked depositional sequences have been identified. Medium- and large-scale sequences correspond to 400 ky eccentricity cycles and to third-order cycles, respectively. The duration of the interval studied (from the uppermost part of the M. mantelli to the lower part of the A. rhotomagense zones) is estimated to be 2.8 my. Carbon-isotope values determined from bulk carbonate sediments show a first positive excursion (+0.6‰) corresponding to the MCE Ia, in the lower part of the A. rhotomagense Zone. A subsequent increase (+1.1‰) is recorded and could correspond to MCE Ib, but a sharp return to baseline values as expected in an excursion is not observed. The duration of the MCE I is estimated to be less than 400 ky. The Blieux section is correlated with some classical sections of the Anglo-Paris (Southerham, Folkestone, Cap Blanc-Nez) and Lower Saxony (Baddeckenstedt and Wunstorf) basins using ammonoid biostratigraphy, sequence stratigraphy, and chemostratigraphy. It is proposed as a candidate for the Middle Cenomanian GSSP (Global Boundary Stratotype Section and Point).     

The extant genus Eutheia (Coleoptera: Staphylinidae: Scydmaeninae) discovered in Upper Cretaceous Taimyr amber

The Eutheiini includes over 90 extant species classified in seven genera and distributed predominantly in the Northern Hemisphere. So far only one extinct genus and species unambiguously placed in this tribe has been known, Archeutheia, from Albian of Spain. We report the discovery of Eutheia, a member of the largest extant genus of Eutheiini, in Santonian of northern Siberia. Extant species of Eutheia are primarily defined on the basis of male genital characters, and the specimen discovered in Taimyr amber is a female; consequently it is described as Eutheia sp. The new finding remarkably extends the known range of Eutheiini during Cretaceous over the area of about 6 thousand kilometers, from the Iberian Plate to northern Siberia. A long morphological stasis in Eutheia suggests that this genus was associated with stable mesic microhabitats of the upper soil layers or rotten wood for at least 83 my.     

The distribution and abundance of chironomids in high-latitude Eurasian lakes with respect to temperature and continentality: development and application of new chironomid-based climate-inference models in northern Russia

The large landmass of northern Russia has the potential to influence global climate through amplification of climate change. Reconstructing climate in this region over millennial timescales is crucial for understanding the processes that affect the global climate system. Chironomids, preserved in lake sediments, have the potential to produce high resolution, low error, quantitative summer air temperature reconstructions. Canonical correspondence analysis of modern surface sediments from high-latitude lakes, located in northern European Russia and central Siberia, suggests that mean July air temperature is the most significant variable explaining chironomid distribution and abundance. This strong relationship enabled the development of a chironomid-based mean July air temperature-inference model based on 81 lakes and 89 taxa which has a r_jack² = 0.92 and RMSEP = 0.89 °C. Comparison of taxon responses to July temperature between this Russian and existing Norwegian data-sets shows that the temperature optima of individual taxa were between 1 and 3 °C higher in the Russian data regardless of modelling technique. Reconstructions based on fossil assemblages from a Russian tundra lake core (VORK5) using a Norwegian chironomid-based inference model provide mean July air temperature estimates that are 1.0–2.7 °C colder than from the 81-lake Russian model and are also lower than the instrumental record from a nearby meteorological station. The Norwegian model also did not reconstruct decadal-scale fluctuations in temperature seen in the instrumental record. These observations suggest that chironomid-based inference models should only be applied to sediment cores which have similar climate regimes to the geographic area of the training set. In addition a 149 lake, 120 taxa chironomid-based continentality inference model was also developed from the modern Norwegian and Russian training sets. A 2-component WA-PLS model was the minimal adequate model with r_jack² = 0.73 and RMSEP = 9.9 using the Gorczynski continentality index. Comparison of reconstructed continentality indices from the tundra lake, VORK5, show close agreement with local instrumental records over the past 70 years and suggest that the model is reliable. Recent warming in the Arctic has been spatially and seasonally heterogeneous; in many areas warming is more pronounced in the spring and autumn leading to a lengthening of the summer, while summer temperatures have remained relatively stable. A continentality inference model has the potential to detect these seasonal changes in climate.     

Biometry of the Late Cretaceous Arkhangelskiella group: ecophenotypes controlled by nutrient flux

This study focuses on the morphometry and taxonomy of the Late Cretaceous coccolith genus Arkhangelskiella. Sixty samples from the Campanian–Maastrichtian interval of DSDP Hole 390A (Blake Nose) were investigated for their contents of Arkhangelskiella spp. In each sample one hundred specimens of Arkhangelskiella spp. were examined by measuring the coccolith length and width, as well as the length and width of the central area. In the samples investigated the Arkhangelskiella group exhibits a large size variation, specimens length varies from 4.95 μm to 14.52 μm. Former taxonomic concepts, based on morphometry, subdivided the Arkhangelskiella group into three species: Arkhangelskiella maastrichtiana, Arkhangelskiella confusa and Arkhangelskiella cymbiformis. Our data show a large variability of the morphometric data (coccolith length, width of the outer rim). There is no indication for three independant species; two of the quoted taxa (1. thick outer rim = Arkhangelskiella maastrichtiana; 2. very thin outer rim = Arkkhangelskiella cymbiformis) seem to be extreme forms of a continuous morphometric lineage. The lower part of the investigated succession (139.92–133.42 mbsf) is dominated by small specimens with an average length of 6.8 μm whereas the upper part (132.86–126.15 mbsf) is characterized by larger specimens (mean 8.7 μm). In DSDP Hole 390A the size increase appears to be very abrupt, within two samples (samples 133.42 mbsf, 132.86 mbsf) the mean size increases by 1.51 μm. Previous morphometric studies of Arkhangelskiella indicate a more continuous size increase throughout the late Campanian–Maastrichtian. The abrupt size increase observed here hints toward a minor hiatus in DSDP Hole 390A separating upper Campanian from lower Maastrichtian sediments. It seems likely that the size increase of Arkhangelskiella reflects changes of various environmental factors like nutrient supply and sea water chemistry (Mg/Ca ratio; Ca concentration). A comparison of morphometric results with previous palaeoecological studies documents a nutrient control for the growth of Arkhangelskiella. Small specimens can be related to more mesotrophic conditions whereas large specimens are linked to oligotrophic surface waters.     

Zircon ages and Hf isotopic constraints on sources of clastic metasediments of the Slyudyansky high-grade complex,southeastern Siberia: Implication for continental growth and evolution of the Central Asian Orogenic Belt

We present results of combined in situ U–Pb dating of detrital zircons and zircon Hf and whole-rock Nd isotopic compositions for high-grade clastic metasedimentary rocks of the Slyudyansky Complex in eastern Siberia. This complex is located southwest of Lake Baikal and is part of an early Paleozoic metamorphic terrane in the eastern part of the Central Asian Orogenic Belt (CAOB). Our new zircon ages and Hf isotopic data as well as whole-rock Nd isotopic compositions provide important constraints on the time of deposition and provenance of early Paleozoic high-grade metasedimentary rocks as well as models of crustal growth in Central Asia. Ages of 0.49–0.90 Ga for detrital zircons from early Paleozoic high-grade clastic sediments indicate that deposition occurred in the late Neoproterozoic and early Paleozoic, between ca. 0.62–0.69 and 0.49–0.54 Ga. Hf isotopic data of 0.82–0.69 Ga zircons suggest Archean and Paleoproterozoic (ca. 2.7–2.8 and 2.2–2.3 Ga; Hfc = 2.5–3.9 Ga) sources that were affected by juvenile 0.69–0.82 Ga Neoproterozoic magmatism. An additional protolith was also identified. Its zircons yielded ages of 2.6–2.7 Ga, and showed high positive ε_Hf(t) values of +4.1 to +8.0, and Hf model ages t_Hf(DM) = t_Hfc = 2.6–2.8 Ga, which is nearly identical to the crystallization ages. These isotopic characteristics suggest that the protolith was quite juvenile. The whole-rock Nd isotopic data indicate that at least part of the Slyudyansky Complex metasediments was derived from “non-Siberian” provenances. The crustal development in the eastern CAOB was characterized by reworking of the early Precambrian continental crust in the early Neoproterozoic and the late Neoproterozoic–early Paleozoic juvenile crust formation.     

Age and petrogenesis of late Mesozoic intrusions in the Huoluotai porphyry Cu-(Mo) deposit,northeast China: Implications for regional tectonic evolution

Multi-stage igneous rocks developed in the recently discovered Huoluotai Cu-(Mo) deposit provide new insights into the controversial late Mesozoic geodynamic evolution of the northern segment of the Great Xing’an Range (NSGXR). Zircon U-Pb dating suggests that the monzogranite, ore-bearing granodiorite porphyry, diorite porphyry, and granite porphyry in the deposit were emplaced at 179.5 ± 1.6, 148.9 ± 0.9, 146.1 ± 1.3, and 142.2 ± 1.5 Ma, respectively. The Re-Os dating of molybdenite yielded an isochron age of 146.9 ± 2.3 Ma (MSWD = 0.27). The Jurassic adakitic monzogranite and granodiorite porphyry are characterized by high SiO₂ and Na₂O contents, low K₂O/Na₂O ratios, low MgO, Cr, and Ni contents, low zircon ε_Hf(t) values relative to depleted mantle, and relatively high Th contents. They were produced by partial melting of a subducted oceanic slab, with involvement of marine sediments in the magma source and limited interaction with mantle peridotites during magma ascent. The Late Jurassic diorite porphyry is characterized by moderate SiO₂ contents, high MgO, Cr, and Ni contents, and positive dominated ε_Hf(t) values, indicating it was produced by partial melting of a subduction-modified lithospheric mantle wedge and underwent limited crustal contamination during magma ascent. The early Early Cretaceous adakitic granite porphyry shows high SiO₂ and K₂O contents and K₂O/Na₂O ratios, low MgO, Cr, and Ni contents, enriched Sr–Nd isotopic compositions, and slightly positive zircon ε_Hf(t) values, suggesting it was produced by partial melting of thickened mafic lower crust. The NSGXR experienced a tectonic history that involved flat-slab subduction (200–160 Ma), and tearing and collapse (150–145 Ma) of the Mongol–Okhotsk oceanic lithosphere. The period of magmatic quiescence from ca. 160 to 150 Ma was a response to flat-slab subduction of the Mongol–Okhotsk oceanic lithosphere. Crustal thickening in the NSGXR (145–133 Ma) was due to the collision between the Amuria Block and the Siberian Craton.