Step-wise change of Asian interior climate preceding the Eocene–Oligocene Transition (EOT)

Understanding the global climate change from greenhouse to icehouse conditions at the Eocene–Oligocene Transition (EOT) 34 million years ago requires climatic records from oceanic as well as continental realms of the key Late Eocene “doubthouse” period preceding this switch. Here, we report integrated stratigraphic results from well-dated Late Eocene continental mudflat to saline lake paleoenvironments of the Xining Basin (northeastern Tibetan Plateau, western China) recording regional and global change. Cyclostratigraphic analysis strongly suggests continuous dominance of the 41-kyr obliquity cycle in the whole late Eocene interval down to the base of polarity chron C18n.2n at 39 Ma with additional input of the ~ 100-kyr eccentricity cycle up to the base of chron C13r at ~ 34.7 Ma. This might imply that high-latitude climates dominated the area long before the EOT, probably related to incipient ice-volume fluctuations. Furthermore, our results reveal two paleoenvironmental deterioration steps preceding the Eocene–Oligocene Transition. The first step occurs in the top of chron C17n.1n at ~ 36.6 Ma. This age closely corresponds to (1) the high-altitude pollen appearance in chron C16.2r at ~ 36.4 Ma in the same section, (2) the recently dated final retreat of the Tarim Sea in western China, and (3) a shift from precession to obliquity dominance in the Atlantic Ocean. This near co-occurrence suggests global change at this time. We hypothesize this change is related to an increase in incipient ice sheet volume leading to passing threshold conditions for the high-altitude pollen appearance and Tarim Sea retreat, finally leading to decreased moisture availability in the Xining Basin. At the second step, in the base of chron C13r at ~ 34.7 Ma, a substantial increase in clastic sedimentation rates is observed. This might relate to increased climate variability preceding the greenhouse to icehouse transition at the EOT that prevented landscapes to attain equilibrium configurations.     

Miocene pollen record of KC-1 core in the Qaidam Basin,NE Tibetan Plateau and implications for evolution of the East Asian monsoon

Thick Cenozoic deposits in the Qaidam Basin provide great potential for understanding the tectonic history, paleoclimatic changes, and evolution of the East Asian Monsoon. This study examines the pollen record from the KC-1 core for the interval covering the later Early to Late Miocene (18–5 Ma). Thermophilic taxa percentages are high between 18 and 14 Ma and decrease after this time, a pattern which fits well with the Middle Miocene Climatic Optimum (MMCO) between 18 and 14 Ma and global climatic cooling after 14 Ma. During the same period, xerophytic taxa percentages gradually increase and those of the conifers gradually decrease, suggesting an aridification process in the Qaidam region driven by the gradual strengthening of the East Asian winter monsoon (EAWM) and weakening of the East Asian summer monsoon (EASM). The global climate cooling process appears to have driven the climatic development of the Qaidam Basin region throughout the Miocene, but the uplift of the Tibetan Plateau also contributed.     

Holocene foraminiferal assemblages from Firth of Tay,Antarctic Peninsula: Paleoclimate implications

The 77 m sediment core from Firth of Tay provides complete record of glacial retreat and Holocene climate change on the Weddell Sea side of the Antarctic Peninsula that began ~ 9400 yr BP. Benthic foraminiferal data indicate significant environmental changes as recorded at ~ 600 m water depth at the drill site. Three foraminiferal assemblages (FAs): Globocassidulina spp.–Fursenkoina fusiformis FA, Miliammina arenacea FA, and Paratrochammina bartrami–Portatrochammina antarctica FA reflect increasingly glacier-distal conditions. They started with most glacier-proximal conditions that lasted until ~ 8800 yr BP, which is indicated by Cribroelphidium cf. webbi, and continued with elevated input of coarse glacial sediment until ~ 7750 yr BP. The Mid-Holocene Climatic Optimum between 7750 and 6000 yr BP appears to be the time of highest primary production, which led to higher corrosiveness of bottom waters, and biased species composition of the M. arenacea FA. It was terminated by minor cooling. The Neoglacial, that took place after ~ 3500 yr BP, is marked by an increase in P. bartrami and P. antarctica, the major constituents of the P. bartrami–P. antarctica FA. This FA became periodically dominant after ~ 900 yr BP indicating increasingly glacier-distal conditions due to cooling coinciding with increasing aridity, rising altitude of the glacial equilibrium line, and less glacial influence on marine biota. Episodic high-abundances of a fourth foraminiferal assemblage (Globocassidulina biora FA) that occurs practically throughout the core is difficult to interpret explicitly. Although there are some concerns if G. biora FA represents in situ fauna, it appears to be an opportunistic fauna that dominated during periods of more glacial sediment input and sediment remobilization leading to better carbonate preservation.     

Rhaetian magneto-biostratigraphy from the Southern Alps (Italy): Constraints on Triassic chronology

New Late Triassic–earliest Jurassic magneto-biostratigraphic data have been obtained from three overlapping sections in the Southern Alps, Italy (Costa Imagna, Brumano, Italcementi Quarry), composed of ~ 520 m of shallow-marine carbonates outcropping in stratigraphic continuity. Characteristic magnetic components of presumed depositional age record a sequence of 9 normal and reverse polarity magnetozones (as defined by at least three stratigraphically superposed samples) linked by conodont and palynofloral evidence from this study and the literature to Rhaetian to Triassic–Jurassic boundary age. This represents a significantly larger number of polarity zones than previously recognized in more condensed Rhaetian sections from the literature, and by inference represents more time. These data are placed in a broader Late Triassic temporal framework by means of correlations to published magneto-biostratigraphic data from the Tethyan marine Pizzo Mondello section and the Newark astronomical polarity time scale (APTS). This framework is consistent with a position of the Norian–Rhaetian boundary (as defined at Brumano and Pizzo Mondello by the first appearance of Misikella posthernsteini) within Newark magnetozones E17r–E19r in the ~ 207–210 Ma time interval, in basic agreement with the position originally estimated in the Newark using pollen biostratigraphy (E18 at 208–209 Ma). This framework is also consistent with the position of the Triassic–Jurassic boundary interval (placed at Italcementi Quarry at the acme of Kraeuselisporites reissingeri coincident with a negative carbon isotope excursion) correlative to just above Newark magnetozone E23r and just below the oldest CAMP lavas dated at ~ 202 Ma. Hence, we estimate the duration of the Rhaetian to be ~ 5.5–8.5 Myr (or even longer if the Triassic–Jurassic boundary is instead placed above the negative carbon isotope excursion as at Kuhjoch, which is the designated GSSP for the base of the Hettangian), and encompassing 9 magnetozones. This duration contrasts with a duration of ~ 2 Myr and only ~ 4 magnetozones in several alternative published magneto-biostratigraphic schemes.     

Environmental and climatic changes in the central Mediterranean Sea (Siculo–Tunisian Strait) during the last 30 ka based on dinoflagellate cyst and planktonic foraminifera assemblages

A high resolution micropalaeontological study of the core MD 04-2797 CQ recovered in the Sicilian–Tunisian Strait provides insights into the paleoclimatic history of the Mediterranean Sea at the transition between the western and eastern basin over the last 30 ka. Using the analysis of dinoflagellate cyst and planktonic foraminiferal assemblages, we reconstruct the paleoenvironmental changes that took place in this region. High abundances of cold temperate dinocyst species (Nematosphaeropsis labyrinthus, Spiniferites elongatus, Bitectatodinium tepikiense) and the polar planktonic foraminifera Neogloboquadrina pachyderma (left coiling) reveal three major cooling events synchronous with North Atlantic Henrich events 1 and 2 (H1 and H2) and the European and North Atlantic Younger Dryas event. During the Holocene, the presence of warm dinocyst species (Spiniferites mirabilis and Impagidinium aculeatum) and planktonic foraminifera (Globorotalia inflata and Globigerinoides ruber), reflects a significant increase of sea surface temperatures in the western Mediterranean basin, but a full warming was not recorded until 1500 years after the onset of the Holocene. Moreover, our results show that the Holocene was interrupted by at least four brief cooling events at ~ 9.2 ka, ~ 8 ka, ~ 7 ka and ~ 2.2 ka cal. BP, which may be correlated to climatic events recorded in Greenland ice cores and in the Atlantic Ocean.     

Redox-Optimized ROS Balance and the relationship between mitochondrial respiration and ROS

The Redox-Optimized ROS Balance [R-ORB] hypothesis postulates that the redox environment [RE] is the main intermediary between mitochondrial respiration and reactive oxygen species [ROS]. According to R-ORB, ROS emission levels will attain a minimum vs. RE when respiratory rate (VO₂) reaches a maximum following ADP stimulation, a tenet that we test herein in isolated heart mitochondria under forward electron transport [FET]. ROS emission increased two-fold as a function of changes in the RE (~ 400 to ~ 900 mV·mM) in state 4 respiration elicited by increasing glutamate/malate (G/M). In G/M energized mitochondria, ROS emission decreases two-fold for RE ~ 500 to ~ 300 mV·mM in state 3 respiration at increasing ADP. Stressed mitochondria released higher ROS, that was only weakly dependent on RE under state 3. As a function of VO₂, the ROS dependence on RE was strong between ~ 550 and ~ 350 mV·mM, when VO₂ is maximal, primarily due to changes in glutathione redox potential. A similar dependence was observed with stressed mitochondria, but over a significantly more oxidized RE and ~ 3-fold higher ROS emission overall, as compared with non-stressed controls. We conclude that under non-stressful conditions mitochondrial ROS efflux decreases when the RE becomes less reduced within a range in which VO₂ is maximal. These results agree with the R-ORB postulate that mitochondria minimize ROS emission as they maximize VO₂ and ATP synthesis. This relationship is altered quantitatively, but not qualitatively, by oxidative stress although stressed mitochondria exhibit diminished energetic performance and increased ROS release.     

New marine mammal faunas (Cetacea and Sirenia) and sea level change in the Samlat Formation,Upper Eocene,near Ad-Dakhla in southwestern Morocco

The Samlat Formation is well exposed in coastal sections bordering the Atlantic Ocean south of Ad-Dakhla in southwestern Morocco. Here some 22 m of rhythmically-bedded, chert-rich, marine siltstones and marls are overlain by 1–1.5 m of vertebrate-bearing microconglomeratic sandstone, another 4–8 m of rhythmically-bedded siltstone and marl, and finally a second 3–6 m unit of vertebrate-bearing muddy sandstone. The microconglomeratic and muddy sandstones represent low sea stands in what is otherwise a deeper water sequence. Cetacean skeletons are rare but cetacean vertebrae are common in the lower sandstone (bed B1), where many show the effects of reworking. The cetaceans in bed B1represent a minimum of five species, from smallest to largest: cf. Saghacetus sp., cf. Stromerius sp., Dorudon atrox, cf. Dorudon sp., and Basilosaurus isis. Bed B1 yields rib fragments that may represent sirenians, but sirenians, if present, are rare. The only identifiable cetacean found in the upper sandstone (bed B2) is Basilosaurus sp. Dugongid sirenians identified as cf. Eosiren sp. are the most common mammal in bed B2. We interpret co-occurrence of the typically Early Priabonian species Dorudon atrox and Basilosaurus isis with smaller species more like Middle Priabonian genera Saghacetus osiris and Stromerius nidensis to indicate that bed B1 was deposited during low sea stand Pr-2 between the Early and Middle Priabonian (between the early and middle Late Eocene). Bed B2 is separated from B1 by an interval of deeper water sediment accumulation. Bed B2 could represent a later phase of Pr-2 or a subsequent Priabonian low sea stand (possibly Pr-3).     

A new stage 3 millennial climatic variability record from a SW France speleothem

We present a new high resolution speleothem stable isotope record from the Villars Cave (SW-France) that covers part of marine isotope stage (MIS) 3. The Vil14 stalagmite grew between ~ 52 and 29 ka. The δ¹³C profile is used as a palaeoclimate proxy and clearly shows the interstadial substages 13, 12 and 11. The new results complement and corroborate previously published stalagmite records Vil9 and Vil27 from the same site. The Vil14 stalagmite chronology is based on 12 Th-U dating by MC-ICP-MS and 3 by TIMS. A correction for detrital contamination was done using the ²³⁰Th/²³²Th activity ratio measured on clay collected in Villars Cave. The Vil14 results reveal that the onset of Dansgaard–Oeschger (DO) events 13 and 12 occurred at ~ 49.8 ka and ~ 47.8 ka, respectively. Within uncertainties, this is coherent with the latest NorthGRIP time scale (GICC05-60 ka) and with speleothem records from Central Alps. Our data show an abrupt δ¹³C increase at the end of DO events 14 to 12 which coincides with a petrographical discontinuity probably due to a rapid cooling. As observed for Vil9 and Vil27, Vil14 growth significantly slowed down after ~ 42 ka and finally stopped ~ 29 ka ago where the δ¹³C increase suggests a strong climate deterioration that coincides with both North Atlantic sea level and sea surface temperature drop.     

Stratigraphic distribution of the radiolarian Spongodiscus biconcavus Haeckel at IODP Site U1340 in the Bering Sea and its paleoceanographic significance

The temporal and spatial distributions of the radiolarian species Spongodiscus biconcavus Haeckel are investigated to understand the paleoceanographic evolution of the Bering Sea region during the last 4.3 Myr based on extensive study of samples collected at Site U1340 during the IODP Expedition 323. The biostratigraphic resolution for the region is also improved by multidisciplinary studies of radiolarians, diatoms, dinoflagellates, ebridians, and silicoflagellates. The results demonstrate that the abundance variation of S. biconcavus during the last 4.3 Myr is closely related to global climate changes, and the species can be used as a warm water and climate proxy in the Bering Sea. Based on the downhole profiles of S. biconcavus and other parameters, we conclude that the southern Bering Sea was associated with a warm water mass prior to 3.147 Ma but it gradually cooled thereafter. From 2.793 Ma to 0.889 Ma, a cold water mass and sea-ice predominated in the Bering Sea, in response to the early Northern Hemisphere glaciation (NHG). Furthermore, the climate suddenly became much cooler post 0.889 Ma. Nevertheless, a reversal of this cooling trend occurred after the Mid-Pleistocene Climatic Transition (∼1.2 Ma), marked by reoccurrence of warm water and reduced sea-ice in the Bering Sea until the final retreat of warm water mass from the Bering Sea after 0.239 Ma. These processes are correlated with biogeographic expansion and retreat of warm water planktonic species.     

Cenozoic long-term terrestrial climatic evolution in Germany tracked by δ18O of rodent tooth phosphate

Even though the Cenozoic has been recognized as a period of important climate change, long-term climatic changes that took place in the continental domain are still questioned. For an area, southern Germany, for which other long-term palaeoclimatic records exist, analysis of oxygen isotope composition of small mammal teeth has been carried out for localities ranging in age from the late Eocene (c.36 Ma) to the middle Miocene (c.10 Ma). Comparison of this long-term continental δ¹⁸O record with the marine record reveals comparable trends. The major Cenozoic climatic events are thus recognized in the continental oxygen isotope record.Through comparison with other quantitative palaeoclimatic reconstructions available for the studied area, temperatures in southern Germany are broadly estimated to have fluctuated between 12 °C and 25 °C from late Eocene to early late Miocene. According to the different available chronological frameworks, either a ～ 2 °C (considering the classical biostratigraphy) or a ～ 6 °C (considering a revised biostratigraphy) decrease in mean air temperature is estimated for the Eocene/Oligocene boundary.     

Monomerization and aggregation of β-lactoglobulin under adverse condition: A fluorescence correlation spectroscopic investigation

β-Lactoglobulin is one of the major components of bovine milk and it remains in a dimeric form under physiological conditions. The present contribution elucidates the structural change of β-lactoglobulin at pH 7.4 under the action of guanidine hydrochloride (GnHCl) and heat at the single molecular level. The only free cysteine (Cys-121) of β-lactoglobulin has been tagged with 7-diethylamino-3-(4-maleimidophenyl)-4-methylcoumarin (CPM) for this purpose. The dimeric structure of β-lactoglobulin found to undergoes a monomerization prior to the unfolding process upon being subjected to GnHCl. The hydrodynamic diameter of the native dimer, native monomer and the unfolded monomer has been estimated as ~ 55 Å, ~ 29 Å and ~ 37 Å, respectively. The free energy change for the monomerization and denaturation are respectively 1.57 kcal mol^− 1 and 8.93 kcal mol^− 1. With change in temperature, development of two types of aggregates (small aggregates and large aggregates) was observed, which is triggered by the formation of the monomeric structure of β-lactoglobulin. The hydrodynamic diameters of the smaller and larger aggregates have been estimated to be ~ 77 Å and ~ 117 Å, respectively. The formation of small aggregates turns out to be reversible whereas that of larger aggregates is irreversible. The free energy associated with these two steps are 0.69 kcal mol^− 1 and 9.09 kcal mol^− 1. Based on the size parameters, the smaller and larger aggregates have been proposed to contain ~twenty and ~sixty monomeric units. It has also been concluded that the monomeric subunits retain their native like secondary structure in these aggregates.     

Late Miocene paleoenvironmental changes in North Africa and the Mediterranean recorded by geochemical proxies (Monte Gibliscemi section,Sicily)

The astronomically tuned marls of the Monte Gibliscemi section, Sicily, constitute an archive to trace the late Miocene palaeoenvironmental conditions (~ 9.7–7.0 Ma) in North Africa. Here we have utilised carbonate content and Al-normalised geochemical proxies to trace changes in terrigenous source area and bottom-water ventilation. The terrigenous input into the section is dominated by North African river systems draining into the Eastern Mediterranean. The proxy parameters indicate that the palaeoenvironmental conditions in North Africa were humid from 9.5 Ma onward with high fluvial input to the Mediterranean. Increases in the Si/Al and Mg/Al ratios occurred from 8.4 to 8.2 Ma and from 8.05 to 7.75 Ma, with maximum values similar to those of Messinian diatomites. These peaks indicate conditions of enhanced biosiliceous productivity and the presence of authigenic clay formation. Sluggish water circulation in the Mediterranean during those times is inferred from the Mn/Al and V/Al behaviour. Late Miocene changes of the Betic (southern Spain) and Rifian (Morocco) Mediterranean–Atlantic gateways are interpreted as the driving force for the changes in water circulation and the transgression associated with the opening of the Rifian corridor is interpreted to occur at 7.8 Ma.     

Palaeogene marine stratigraphy in China

Palaeogene deposits are widespread in China and are potential sequences for locating stage boundaries. Most strata are non‐marine origin, but marine sediments are well exposed in Tibet, the Tarim Basin of Xinjiang, and the continental margin of East China Sea. Among them, the Tibetan Tethys can be recognized as a dominant marine area, including the Indian‐margin strata of the northern Tethys Himalaya and Asian‐margin strata of the Gangdese forearc basin. Continuous sequences are preserved in the Gamba–Tingri Basin of the north margin of the Indian Plate, where the Palaeogene sequence is divided into the Jidula, Zongpu, Zhepure and Zongpubei formations. Here, the marine sequence ranges from Danian to middle Priabonian (66–35 ma), and the stage boundaries are identified mostly by larger foraminiferal assemblages. The Paleocene/Eocene boundary is found between the Zongpu and Zhepure formations. The uppermost marine beds are from the top of the Zongpubei Formation (~35 ma), marking the end of Indian and Asian collision. In addition, the marine beds crop out along both sides of the Yarlong Zangbo Suture, where they show a deeper marine facies, yielding rich radiolarian fossils of Paleocene and Eocene. The Tarim Basin of Xinjiang is another important area of marine deposition. Here, marine Palaeogene strata are well exposed in the Southwest Tarim Depression and Kuqa Depression. They comprise mostly neritic and coastal lagoon facies of the Tethyan realm. Palaeontological evidence suggests that the Paleocene/Eocene boundary here is in middle of the Qimugen Formation. The Tarim Basin was largely drained by Late Oligocene. To the east, the marine offshore Palaeogene strata are widespread in the North Taiwan and East Zhejiang depressions of the continental shelf basin of East China Sea. Abundant fossils including foraminifera, calcareous nannofossils, ostracods, pollen and bivalves occur in the marine environment. Biostratigraphically, the sequence is well correlated with the international planktonic foraminiferal and nannofossil zonations.     

Sulforaphane improves dysregulated metabolic profile and inhibits leptin-induced VSMC proliferation: Implications toward suppression of neointima formation after arterial injury in western diet-fed obese mice

Sulforaphane (SFN), a dietary phase-2 enzyme inducer that mitigates cellular oxidative stress through nuclear factor erythroid 2-related factor 2 (Nrf2) activation, is known to exhibit beneficial effects in the vessel wall. For instance, it inhibits vascular smooth muscle cell (VSMC) proliferation, a major event in atherosclerosis and restenosis after angioplasty. In particular, SFN attenuates the mitogenic and pro-inflammatory actions of platelet-derived growth factor (PDGF) and tumor necrosis factor-α (TNFα), respectively, in VSMCs. Nevertheless, the vasoprotective role of SFN has not been examined in the setting of obesity characterized by hyperleptinemia and insulin resistance. Using the mouse model of western diet-induced obesity, the present study demonstrates for the first time that subcutaneous delivery of SFN (0.5 mg/Kg/day) for ~ 3 weeks significantly attenuates neointima formation in the injured femoral artery [↓ (decrease) neointima/media ratio by ~ 60%; n = 5–8]. This was associated with significant improvements in metabolic parameters, including ↓ weight gain by ~ 52%, ↓ plasma leptin by ~ 42%, ↓ plasma insulin by ~ 63%, insulin resistance [↓ homeostasis model assessment of insulin resistance (HOMA-IR) index by ~ 73%], glucose tolerance (↓ AUC_GTT by ~ 24%), and plasma lipid profile (e.g., ↓ triglycerides). Under in vitro conditions, SFN significantly decreased leptin-induced VSMC proliferation by ~ 23% (n = 5) with associated diminutions in leptin-induced cyclin D1 expression and the phosphorylation of p70S6kinase and ribosomal S6 protein (n = 3–4). The present findings reveal that, in addition to improving systemic metabolic parameters, SFN inhibits leptin-induced VSMC proliferative signaling that may contribute in part to the suppression of injury-induced neointima formation in diet-induced obesity.     

Sap flow and water use in African baobab (Adansonia digitata L.) seedlings in response to drought stress

The African baobab (Adansonia digitata L.) is an important multi-purpose fruit tree with high potential for domestication in drier Africa. Although adult individuals are well-known to be drought resistant, only little has been reported on how young baobab trees can survive drought. Therefore, the aim of this study was to examine short-term soil drought effects on water relations of baobab seedlings. Baobab seedlings used a limited amount of stored water to buffer daily water deficits (~ 8.5 g d^− 1), which contributed up to only ~ 17.5% of daily water use and ~ 6% of total plant water. Under drought, a strong reduction in stomatal conductance (~ 85%) resulted in a midday leaf water potential of − 1 MPa and zero stem sap flow followed by significant leaf loss. Plant anatomy evidenced the presence of water storage tissues and the vulnerability to xylem embolism. The taproot was the most important plant part for water storage (68% of total plant water), suggesting root-succulence rather than stem-succulence. When drought intensified, limitation of leaf transpiration and/or root water uptake led to drought-enforced dormancy. Despite the large amounts of water stored in the taproot (~ 90%) and the stem (~ 75%), only a limited amount of stored water appeared to be used to sustain upper leaves and plant metabolism during the dormant period, and to facilitate recovery following water supply. Drought avoidance, conservative water use and the presence of internal stored water allow baobab seedlings to survive drought.     

Tsuga seed cones from the late Paleogene of southwestern China and their biogeographical and paleoenvironmental implications

Six Tsuga ovuliferous/seed cone impression fossils were discovered from the late Eocene (34.6 ± 0.8 Ma) Lawula Formation in Mangkang County, eastern Tibet and the early Oligocene (32 ± 1 Ma) lacustrine deposits in Lühe Basin, Nanhua County, Yunnan Province. These two fossil sites are both located in southwestern China, ∼800 km apart from each other. These fossils represent the oldest records of this genus in southwestern China, even earliest reliable macrofossil records of this genus in the world. These well-preserved seed cones provide sufficient materials for the establishment of Tsuga asiatica Wu et Zhou n. sp. to accommodate five specimens, leaving one to be assigned to T. cf. dumosa Eichler (cf. Wu et Zhou). Both qualitative and quantitative comparisons with other cone fossils and cones of all living species of the genus suggested that T. asiatica shares more similarities with one of the basal species of the genus T. heterophylla. The discovery of late Paleogene macrofossil records of Tsuga in southwestern China supports the previous hypothesis of the early disposal routes of this coniferous genus predicted by phylogenetic analysis. The elevation ranges and the climate requirements of living species that are closely related to our fossils suggest that the southeastern edge of the Qinghai-Tibetan Plateau should be much warmer, and wetter in late Paleogene than nowadays.     

Neogene–Quaternary Mammalian Paleobiogeography of the Indian Subcontinent: An appraisal

A biostratigraphic evaluation of the Indian subcontinent Neogene–Quaternary mammal genera at 1 Ma intervals reveals a strong correlation between faunal turnovers (first and last appearances and immigrations), diversity and major tectonic and climate-induced sea level and vegetation changes at 23–22, 20–18, 17–16, 15–14, 11–10, 9–8, 3–2 and 1–0 Ma. The Early Miocene collision of Afro-Arabian and Eurasian Plates, followed by the Middle Miocene Climate Optima and the presence of evergreen rainforests, most likely facilitated the dispersals into and out of the subcontinent from the west along the coast and included African proboscideans, primates, creodonts, thryonomyid rodents and Asian chalicotheres, rhinos, suids, anthracotheres, carnivores and muroid rodents. The Late Miocene and Early Pleistocene cooler and drier conditions, the spread of grasslands and sea level drops may have influenced the exchange of African monkeys, Eurasian carnivores, bovids, equids, camelid, and South Asian suids, leporids and murids. Immigrations from the east (East and SE Asia) occurred mostly during the Miocene and involved primarily small mammals.     

Palaeoenvironmental evolution of Lake Gacko (Southern Bosnia and Herzegovina): Impact of the Middle Miocene Climatic Optimum on the Dinaride Lake System

In the Early to Middle Miocene, a series of lakes, collectively termed the Dinaride Lake System (DLS), spread out across the north-western part of the Dinaride–Anatolian continental block. Its deposits, preserved in numerous intra-montane basins, allow a glimpse into the palaeoenvironmental, palaeobiogeographic and geodynamic evolution of the region. Lake Gacko, situated in southern Bosnia and Herzegovina, is one of the constituent lakes of the DLS, and its deposits are excellently exposed in the Gra?anica open-cast coal-mine. A detailed study of the sedimentary succession that addresses facies, sediment petrography, geophysical properties, and fossil mollusc palaeoecology reveals repetitive changes in lake level. These are interpreted to reflect changes in the regional water budget. First-order chronologic constraints arise from the integration of radio-isotopic and palaeomagnetic data. ⁴⁰Ar/³⁹Ar measurements on feldspar crystals from a tephra bed in the upper part of the sedimentary succession indicate a 15.31 ± 0.16 Ma age for this level. The reversed magnetic polarity signal that characterises the larger part of the investigated section correlates to chron C5Br of the Astronomically Tuned Neogene Timescale. Guided by these chronologic data and a detailed cyclostratigraphic analysis, the observed variations in lake-level, evident as two ~ 40-m and seven ~ 10-m scale transgression–regression cycles, are tuned to ~ 400-kyr and ~ 100-kyr eccentricity cycles. From the tuning, it can be inferred that the sediments in the Gacko Basin accumulated between ~ 15.8 and ~ 15.2 Ma. The economically valuable lignite accumulations in the lower part of the succession are interpreted to indicate the development of swamp forests in conjunction with lake-level falls corresponding to ~ 100-kyr eccentricity minima. Pedogenesis, rhizoliths and palustrine carbonate breccias in the upper part of the section reveal long-term aridity coinciding with a ~ 400-kyr eccentricity minimum. Eccentricity maxima are interpreted to trigger lake-level high-stands. These are accompanied by eutrophication events caused by enhanced denudation of the surrounding basement and increased detrital input into the basin. The presented age model proves that Lake Gacko arose during the Middle Miocene Climatic Optimum and that the optimum climatic conditions triggered the formation of this long-lived lake.     

Mixed carbonate-clastic facies in the Eocene Kalatar Formation of the southwest Tarim Basin (NW China): tectonic and climatic controls

During the Eocene, the southwest Tarim Basin was a large epicontinental sea as a part of the Turun Sea in the eastern Paratethys. The marine succession of the Kalatar Formation is exposed along the piedmonts of the southern Tian Shan and western Kunlun Shan, and can be subdivided into three members. On the southern side of the Tarim Basin, a non-barrier shore-to-shelf, siliciclastic-dominated system, locally with carbonates and oyster biostromes, developed along the western Kunlun Shan, where river input led to a seaward arrangement of alluvial fan, foreshore, shoreface, and offshore facies. In contrast, on the northern side of the Tarim Basin, a carbonate ramp system formed along the southern Tian Shan, including shallow bioclastic-oolitic grainstone shoals, oyster beds, and red algal rudstones along with a number of evaporite units, which formed under hypersaline tidal-flat and lagoonal conditions. The basin center was a largely moderate deep and low-energy embayment facies. Deposition of the mixed carbonate-siliciclastic Kalatar Formation was controlled by tectonic activity, in particular the development of the Himalayan orogeny with the closure of Paratethys sea-level fluctuations, and arid-humid climate variations.