The first discovery of Hypsodontus (Artiodactyla, Bovidae) from the Early Miocene of Linxia Basin, Gansu Province, China

Late cretaceous to recent palaeoenvironments of the Saudi Arabian Red Sea

Orogeny in Action: Tectonic Evolution and Stratigraphy of Sabah, Seismic and Outcrop Evidence

The distribution of foraminifera in the Uscari, Rio Banano, Moin Formations of the Limon Basin, Costa Rica, is the subject of this study. Heterostegina antillea and Lepidocyclina (L.) waylandvaughani place the basal Uscari Formation of Quebrada Terciopelo in Zone N3 of the latest Oligocene. The overlap of Orbulina universa and Globorotalia fohsi peripheroronda places the type section Uscari Formation in the early Middle Miocene (zones N9 to N10). The overlapping ranges of planktonic foraminifera and the ostracods Radimella ovata in the sandstones places that unit in Zone N18 of Early Pliocene. Globorotalia truncatulinoides excelsa indicates a Pleistocene age for the Moin Formation. The algal-foraminiferal limestones of the basal Uscari Formation were deposited on a shallow shelf receiving volcaniclastic sediment from the emerging islands of the Central American arc. During the Late Oligocene and Early Miocene the Linon Basin quickly subsided. In the Quebrada Terciopelo reference section of the Uscari Formation, Early Miocene foraminiferal indicators of a middle to upper bathyal environment include Siphogenerina transversa and Melonis pompilioides; late early and early Middle Miocene faunas (Uvigerina peregrina, Bolivina pseudoplicata, and Buliminella bassendorfensis indicate progressive shoaling. For the Early Miocene Rio Reventazon section of the Uscari Formation, species such as Cibicides wuellerstorfi and Melonis pompilioides indicate depths near 2000 meters. The type section of the Uscari Formation in Quebrada Uscari is dominated by an outer shelf assemblage containing Hanzawaia concentrica and Fursenkoina pontoni. The Early Pliocene sandstones of the Rio Banano Formation were deposited on a shallow, current-swept continental shelf. These rocks contain a mixture of open marine, nearshore, and a few reefal species, including Cibicidoides floridanus, Amphistegina gibbosa, Articulina mayori, and Elphidium discoidale. The claystones of the Pleistocene Moin Formation contain outer shelf to upper slope species, such as Gyroidina soldani, Cibicidoides floridanus, and Cassidulina curvata. The foraminiferal record of the Rio Banano sandstones suggests land was emergent in the southern Limon Basin, separating the Caribbean and Pacific basins, by 5 mybp, before such an event occurred in Panama.

The Uscari Formation (Torito and Calvario rivers, 3X, Peralta and Alto Guayacán), shows a shallowing from lower bathyal zones to neritic zones during the Early Miocene. In the Middle Miocene there was a change back to bathyal zones, but not as deep as those found in the 3X area during the previous interval.During the Early Miocene bathyal zones were characterized by eutrophic to mesotrophic environments deposited under oceanic upwelling and turbidity flows conditions, except for the 3X area that had a more stable fauna. The shallowing towards neritic zones is characterized by oligotrophic environments with hard substrates and high-energy sands, with the presence of reefs, algae and warm waters. During the Middle Miocene, bathyal zones were oligotrophic and diversity was low possibly due to increased predation or a change in the circulation of intermediate waters by the influence of Northern Component Water (NCW), a precursor of the current North Atlantic Deep Water (NADW), which is characterized by oxygenated waters, is carbonate-rich and is low in nutrients.The bathyal zone of the study area correlates with the bottom of the Terciopelo creek section and Early Miocene Period of the Reventazón river. Both the bathyal and abyssal deposits of the Reventazón river section, and the mid bathyal zone of the Terciopelo creek section were subject to turbidites flows which brought shallow taxa into deep water. During the late Early Miocene and early Middle Miocene, the middle and upper Terciopelo creek section was deposited in the upper slope to shelf environments transition. The early Middle Miocene type section of the Uscari creek was deposited on the continental shelf and is tentatively correlated to the top of the Terciopelo creek section.

Stable isotope evidence for resource partitioning in extinct marine carnivores

Miocene, Pliocene, and Pleistocene strata were deposited in two embayments in the central Atlantic Coastal Plain, the Salisbury to the north and Albermarle to the south. Both embayments underwent local tectonics, and no single area within either has a continuous section. Deposition in both embayments began in early Miocene time. In the Salisbury embayment, the early deposits were largely biogenic (Fairhaven Member of the Calvert Formation), and the center of deposition was located in Maryland. Relatively continuous clastic deposition commenced in the late early Miocene and continued through the middle Miocene (Plum Point Marl Member of the Calvert Formation and the Choptank and St. Marys formations). Deltaic deposition began in the northern part of the embayment, as seen in the Calvert and Kirkwood formations and influenced environments west of the delta lobe. The center of deposition in the Salisbury embayment shifted southward into Virginia during late Miocene time (“Virginia St. Marys” beds) and continued there through the early and middle(?) Pliocene (Yorktown Formation); only the southeastern part of the embayment received sediments in the late Pliocene and early Pleistocene (uppermost part of the “Yorktown” Formation). Environments throughout this time were largely inner shelf (less than 60-m depths), and some marginal-marine to nonmarine intervals. The Albemarle embayment in North Carolina received largely biogenic and biochemical deposition during the early and early middle Miocene (Pungo River Formation). This was followed by uplift in the late middle and late Miocene. Clastic sedimentation started near the Miocene-Pliocene boundary and continued with minor hiatuses throughout much of the Pliocene and into early Pleistocene (Yorktown, uppermost part of the “Yorktown,” Duplin, Croatan, and Waccamaw formations). Some Pungo River strata formed in middle-shelf environments as deep as 100 m; most younger strata were deposited in inner-shelf environments (less than 60-m depth), but some in marginal-marine intervals.

Based on foraminiferal biostratigraphy of the Neogene sedimentary sequences of Shmidta Peninsula at the northern tip and the Makarov region in southeastern Sakhalin, Russian Far East, paleoenvironment and ages are discussed. In the Makarov region, the history of environmental changes is roughly delineated, as follows: warm non-marine environment in late Early Miocene, transgression around early Middle Miocene, abrupt deepening into bathyal depth in Middle Miocene, and regression during Late Miocene and Pliocene. This succession is quite similar to those in Hokkaido and the northern Honshu in Japan. In the Pil'vo section at the west coast of Shmidta Peninsula, the similar bathymetric changes are recognized at the same time as in the Makarov region, although this section is regarded as being in the bathyal depths throughout Early to Middle Miocene.The occurrences of some temperate-water species give evidence of the influence of warm-surface water during the Miocene period. Ammonia spp. survived in early Middle Miocene (the transition period between the MNCO and the following cooler stage in early Middle Miocene) in the Makarov region. A planktonic foraminifer, Globorotalia cf. miozea conoidea was found in the middle part of the Pili Formation (early Middle Miocene) of the Pil'vo section. This is the first discovery of keeled Globorotalia in Sakhalin, and is important for the consideration of the geohistory of the Northwest Pacific, in particular the first appearance of subarctic climate and cold Oyashio water.

Correlation of pollen sequences in the Neogene palynofloristic regions of China

Palaeoenvironmental significance of Miocene larger benthic foraminifera from the Xisha Islands, South China Sea

BackgroundMammalian fossils from the Eppelsheim Formation (Dinotheriensande) have been a benchmark for Neogene vertebrate palaeontology since 200 years. Worldwide famous sites like Eppelsheim serve as key localities for biochronologic, palaeobiologic, environmental, and mammal community studies. So far the formation is considered to be of early Late Miocene age (∼9.5 Ma, Vallesian), representing the oldest sediments of the Rhine River. The stratigraphic unity of the formation and of its fossil content was disputed at times, but persists unresolved.Principal FindingsHere we investigate a new fossil sample from Sprendlingen, composed by over 300 mammalian specimens and silicified wood. The mammals comprise entirely Middle Miocene species, like cervids Dicrocerus elegans, Paradicrocerus elegantulus, and deinotheres Deinotherium bavaricum and D. levius. A stratigraphic evaluation of Miocene Central European deer and deinothere species proof the stratigraphic inhomogenity of the sample, and suggest late Middle Miocene (∼12.5 Ma) reworking of early Middle Miocene (∼15 Ma) sediments. This results agree with taxonomic and palaeoclimatic analysis of plant fossils from above and within the mammalian assemblage. Based on the new fossil sample and published data three biochronologic levels within the Dinotheriensand fauna can be differentiated, corresponding to early Middle Miocene (late Orleanian to early Astaracian), late Middle Miocene (late Astaracian), and early Late Miocene (Vallesian) ages.Conclusions/SignificanceThis study documents complex faunal mixing of classical Dinotheriensand fauna, covering at least six million years, during a time of low subsidence in the Mainz Basin and shifts back the origination of the Rhine River by some five million years. Our results have severe implications for biostratigraphy and palaeobiology of the Middle to Late Miocene. They suggest that turnover events may be obliterated and challenge the proposed ‘supersaturated’ biodiversity, caused by Middle Miocene superstites, of Vallesian ecosystems in Central Europe.

Vertebrate microfossils from the Upper Freshwater Molasse in the Swiss Molasse Basin: Implications for the evolution of the North Alpine Foreland Basin during the Miocene Climate Optimum

Deciphering how modern precipitation patterns became established in monsoon‐dominated East Asia and the arid interior Asia is crucial for predicting future precipitation trends under accelerated global warming and increased climate extremes. However, this effort is hindered by a scarcity of quantitative paleo‐precipitation data in this region. Here we reconstruct the pattern of Middle to Late Miocene paleo‐precipitation across an east‐to‐west transect from the summer monsoon‐dominated East Asian region through the transition zone and into interior Asia. Our work is based on a newly established precipitation calculation equation and quantitative pollen‐based precipitation conversion. Analysis indicates a common trend of precipitation across the studied region prior to ca, 11 Ma, followed by a clear divergence of precipitation variations between East and interior Asia since at least 11–9 Ma. This divergence is characterized by increasing precipitation in East Asia, but a coeval decrease in rainfall in the transition zone and interior Asia. The timing of this precipitation divergence was contemporaneous with intense tectonic activity in the northern Tibetan Plateau, which differentially affected the efficacy of water vapor transport into East and interior Asia. Modeling work using different topographic settings corroborates this tectonic influence. Our study demonstrates the early establishment of modern‐like precipitation patterns in East‐interior Asia at least in the early Late Miocene.

The octodontoid rodent Acarechimys was abundant during the early Miocene and had the widest temporal and geographic distribution of any extinct caviomorph. Despite this extensive fossil record Acarechimys has not been well characterized. In this work, we systematically revise Acarechimys, describe new early—middle Miocene fossils from Argentina and Bolivia, corroborate its monophyly, and study its evolutionary history. Acarechimys has brachydont molars, retained deciduous premolars, four crests on upper molars, lowers with variably developed mesolophid and metalophulid II, and absence of mental foramen in the mandible. Acarechimys includes: Acarechimys leucotheae (late Oligocene, Chubut, Argentina), A. gracilis and A. constans (early Miocene, Chubut and Santa Cruz, Argentina), and A. minutus and A. minutissimus (early—middle Miocene of Patagonia Argentina, Bolivia, and Colombia). The temporal and geographic distributions suggest that Acarechimys could have evolved in Patagonia, by the early late Oligocene. Its acme was during the late early Miocene in Southern Patagonia. By the middle Miocene, Acarechimys decreased in diversity and was last recorded in high latitudes of South America (Patagonia). In lower latitudes, the oldest record is from the late early Miocene of Chucal, northern Chile, and during the late middle Miocene, the genus is recorded in localities of Colombia, Bolivia, and Peru. The available evidence suggests that Acarechimys was probably not present in lower latitudes (N of ~ 30° S) before the early Miocene. The reasons Acarechimys dispersed northward at this time remain to be elucidated, but the timing coincides with a massive disappearance of other octodontoids from Patagonia.

Lufengpithecus keiyuanensis from the Xiaolongtan Coal Mine is the earliest known Miocene fossil hominoids in southern China, yet its chronological context has long been subjected to disputes, in being either of late Middle Miocene or early Late Miocene age. This controversy is largely due to the uncertainty of the exact positions of previously discovered fossils in the outcrops, and the different chronological interpretations for some proboscidean and suid fossils from associated fossil faunal assemblages. Here we report the first discovery of Stegolophodon latidens from Xiaolongtan with an unambiguous stratigraphic provenance, which provides important evidence in constraining the age of Lufengpithecus keiyuanensis . Stegolophodon has a very high evolutionary rate of dental morphology, and exhibits a pronounced evolutionary trend with time: from the pentalophodont m3 of the Early Miocene or early Middle Miocene, to the pentalophodont M3 and hexalophodont m3 of the late Middle Miocene, to the 5.5-lophed (five principal lophs followed by an extreme well-developed cingulum) M3 and hexa- to heptalophodont m3 of the early Late Miocene, and to the hexalophodont M3 and hepta- to octalophodont m3 of the middle Late Miocene. The newly discovered Stegolophodon latidens bears a 5.5-lophed M3 and a heptalophodont m3, the second and subsequent lophs/lophids show a slight chevron structure, and the pretrite mesoconelets shift mesially and fuse with the corresponding pretrite anterior central conules, forming a “Y-shape”. These traits are similar to, or even slightly more derived than those of Stegolophodon from the lower part of the Dhok Pathan Formation (9.3−8.3 Ma) in the Middle Siwaliks of the Indian Subcontinent. The materials described here can all be assigned to Stegolophodon latidens which was originally discovered from the Yenangyaung fauna, the lower Irrawaddy Formation of Myanmar, deemed of early Late Miocene age. Revisions on the other proboscidean and suid materials also support an early Late Miocene age for Xiaolongtan Fauna. The new fossils were discovered from the upper part of the lignite layers, close to the bottom of the greyish marls of the Buzhaoba Formation. Based on the original records in the geological reports of the Xiaolongtan Coal Mine, the descriptions of the previous publications, as well as the accounts of the fossil finders, the Xiaolongtan coal mine possesses only one fossiliferous layer, which locates in the upper part on the Xiaolongtan Formation (lignite layers). Therefore, the new fossils situate possibly in the same layer as Lufengpithecus keiyuanensis that were found in the 1950’s and 1980’s. From the recent palaeomagnetic investigations, the age of this fossil layer should be 11.6/11.7 Ma, close to the boundary between the Middle and the late Miocene; however, seems to be slightly older than Stegolophodon latidens from the Siwaliks. Further investigations should be carried out to resolve this inconsistency.

Integrated biozonation based on palynology and ostracods from the Neogene of Solimões Basin, Brazil