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Zhe-kun Zhou - One of the best experts on this subject based on the ideXlab platform.
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calocedrus shengxianensis a Late Miocene relative of c macrolepis cupressaceae from south china implications for paleoclimate and evolution of the genus
Review of Palaeobotany and Palynology, 2015Co-Authors: Jian Huang, Jianwei Zhang, Ashalata Drozario, Jonathan M Adams, Zhe-kun ZhouAbstract:The diversification of the relict genus Calocedrus Kurz (Cupressaceae) in the Neogene of eastern Asia has remained unknown due to lack of fossil evidence. A Late Miocene species, Calocedrus shengxianensis (He, Sun et Liu) Zhang et Zhou comb. nov., is described on the basis of new fossil material from the Wenshan flora in SE Yunnan, SW China. The species was originally described as Fokienia shengxianensis He, Sun et Liu from the upper Miocene Shengxian flora in E Zhejiang, SE China. The new fossil material includes well-preserved compression of leafy shoots and associated impression of seed cones. Based on the comparisons, this fossil species bears most similarities to the modern Calocedrus macrolepis Kurz, which is presently endemic to eastern Asia, in N India, Laos, NE Myanmar, NE Thailand, Vietnam and S China, but does not occur in SE Yunnan and E Zhejiang. The difference between them lies primarily in the morphology of apex of Lateral as well as facial leaves. With the global cooling and uplift of the Qinghai–Tibet PLateau since the Late Miocene, the climate in eastern Asia has changed profoundly. This has led to the disappearance of C. shengxianensis from SE Yunnan and E Zhejiang, and the leaf morphological shifts in C. macrolepis: the acute or acuminate leaf apices in the modern C. macrolepis, which are in contrast to the blunt or obtuse ones in the Late Miocene C. shengxianensis, have evolved probably to adapt to the humid climate since the Late Miocene.
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Late Miocene vegetation dynamics under monsoonal climate in southwestern china
Palaeogeography Palaeoclimatology Palaeoecology, 2015Co-Authors: Limi Mao, Zhe-kun Zhou, Robert A Spicer, Julie Lebretonanberree, Mei SunAbstract:To better understand vegetation dynamics and the Asian monsoonal climate in the Neogene, we reconstructed the vegetational succession and climate of Wenshan basin in southwestern China during the Late Miocene (11.62-5.33 Ma). We used newly available palynological data and the results of a quantitative bioclimatic analysis. The Late Miocene palynoflora in Wenshan basin resembles that of modern evergreen broadleaf vegetation in subtropical East Asia. Based on pollen elements and reconstructed palaeoclimates in 72 samples, we found the composition of the vegetation in the Wenshan basin fluctuated during the Late Miocene and was likely driven by natural climate variability. Quantitative estimates suggest that the mean annual temperature (MAT) ranged from 16.6 to 17.5 degrees C; the mean annual precipitation (MAP) was similar to 1500 mm; and the monsoon intensity index (MSI) ranged from 11.3 to 17.1. Our results indicate that the Wenshan basin experienced a warm, wet, and temperate to subtropical climate. By comparison with other Late Miocene sites in Yunnan, we show that temperatures differed slightly from region to region and, overall, annual and seasonal precipitation levels were higher in the Late Miocene than at present, but with a weaker monsoon intensity than in the Wenshan basin today. (C) 2015 Elsevier B.V. All rights reserved.
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paleoclimatic estimation reveals a weak winter monsoon in southwestern china during the Late Miocene evidence from plant macrofossils
Palaeogeography Palaeoclimatology Palaeoecology, 2012Co-Authors: Zhe-kun Zhou, Torsten Utescher, Yaowu Xing, Frederic M B Jacques, Yusheng Liu, Yongjiang HuangAbstract:The Late Miocene Xianfeng flora of Yunnan Province, southwestern China, was chosen to reconstruct the paleoclimate and the intensity of the Asian monsoon. Three available quantitative climate reconstruction methods from fossil plants, i.e. Leaf Margin Analysis (LMA), the Climate Leaf Analysis Multivariate Program (CLAMP), and the Coexistence Approach (CA) were used in this study. MATs (mean annual temperatures) resulting from these three approaches (i.e., LMA: 17.2 +/- 2.38 degrees C; CLAMP: 15.43 +/- 1.25 degrees C; CA: 17.2-21.7 degrees C) appear to have been higher than the present (14.9 degrees C), suggesting a much warmer climate in the Late Miocene. Both the growing season precipitation (GSP) from CLAMP (1908.7 +/- 217.7 mm) and mean annual precipitation (MAP) from CA (1206.0-1613.0 mm) estimates are higher than modern values (1003.2 mm (GSP) and 1038 mm (MAP) respectively) indicating a more humid climate during the Late Miocene. By comparing these with climates reconstructed from neighboring Late Miocene floras, we conclude that the general Late Miocene climate appears warmer and more humid than present conditions in southwestern China. Furthermore, the evident differences in estimated monthly temperatures between the summer and winter, and precipitations between the humid and dry seasons indicate the existence of seasonality, though not as strong as that of today. Difference in precipitation of dry season indicates a marked strengthening in the winter monsoon since the Late Miocene. A new monsoon intensity index has also been defined based on precipitation seasonality to investigate the intensity of the Asian monsoon. (C) 2012 Elsevier B.V. All rights reserved.
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quantitative reconstruction of the Late Miocene monsoon climates of southwest china a case study of the lincang flora from yunnan province
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Frederic M B Jacques, Yaowu Xing, Yusheng Liu, Yongjiang Huang, David K Ferguson, Shuangxing Guo, Zhe-kun ZhouAbstract:The Miocene Lincang leaf assemblage is used in this paper as proxy data to reconstruct the palaeoclimate of southwestern Yunnan (SW China) and the evolution of monsoon intensity. Three quantitative methods were chosen for this reconstruction, i.e. Leaf Margin Analysis (LMA), Climate Leaf Analysis Multivariate Program (CLAMP), and the Coexistence Approach (CA). These methods, however, yield inconsistent results, particularly for the precipitation, as also shown in European and other East Asian Cenozoic floras. The wide range of the reconstructed climatic parameters includes the Mean Annual Temperature (MAT) of 18.5-24.7 degrees C and the Mean Annual Precipitation (MAP) of 1213-3711 mm. Compared with the modem Lincang climate (MAT, 17.3 degrees C; MAP, 1178.7 mm), the Miocene climate is slightly warmer, wetter and has a higher temperature seasonality. A detailed comparison on the palaeoclimatic variables with the coeval Late Miocene Xiaolongtan flora from the eastern part of Yunnan allows us to investigate the development and interactions of both South Asian and East Asian monsoons during the Late Miocene in southwest China, now under strong influence of these monsoon systems. Our results suggest that the monsoon climate has already been established in southwest Yunnan during the Late Miocene. Furthermore, our results support that both Southeast Asian and East Asian monsoons co-occurred in Yunnan during the Late Miocene. (C) 2010 Elsevier B.V. All rights reserved.
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quantitative climate reconstructions of the Late Miocene xiaolongtan megaflora from yunnan southwest china
Palaeogeography Palaeoclimatology Palaeoecology, 2009Co-Authors: Ke Xia, Frederic M B Jacques, Yaowu Xing, Yusheng Liu, Zhe-kun ZhouAbstract:The Late Miocene Xiaolongtan megaflora from Kaiyuan in southeast Yunnan (23 degrees 48'45 '' N, 103 degrees 11'52 '' E, 1050 m a.s.l.) was chosen for palaeoclimatic reconstruction using three quantitative techniques, i.e. the Coexistence Approach (CA), Leaf Margin Analysis (LMA), and the Climate-Leaf Analysis Multivariate Program (CLAMP). The reconstructed climatic parameters are also compared with those of the two adjacent Miocene floras currently available in Yunnan, i.e. the early to middle Miocene carpological Mangdan flora (24 degrees 24'N, 97 degrees 49'E, 1620 m a.s.l.) and the Late Miocene Luhe palynoflora (25 degrees 10'N, 101 degrees 22'E, 1930 m a.s.l.). Quantitative analyses of the Xiaolongtan flora supports the previous qualitative results of a southern, humid subtropical climate, being more humid and having a slightly higher mean annual temperature (MAT) than today. The MATs calcuLated by CA, LMA, and CLAMP overlap (16.7-19.2 degrees C, 22.3 +/- 2.05 degrees C, 18.1 +/- 1.2 degrees C, respectively) and are close to the present day value (19.7 degrees C). The overlapping of temperatures derived using the three techniques is unusual and probably reLated to the low latitude of the Xiaolongtan area and the southern subtropical nature of its vegetation. Both the mean temperatures of the warmest month (WMT) and of the coldest month (CMT) reconstructed by CA (WMT=25.4-26.0 degrees C, CMT=7.7-8.7 degrees C) and CLAMP (WMT=25.9 +/- 1.6 degrees C, CMT=10.8 +/- 1.9 degrees C) are similar to those of today (WMT=24.3 degrees C, CMT=12.8 degrees C), but great changes appear in the mean annual precipitation (MAP). The CLAMP results suggest a higher precipitation (1964 +/- 335.9 mm) than CA (1215-1639 mm), but they are much higher than the present MAP (820.5 mm). This is consistent with results from the Luhe palynoflora, which also developed under a warmer subtropical climate with higher precipitation (803.6-1254.7 mm) than that of today (815.9 mm). In contrast, the Mangdan flora, situated in a more complicated topographic region to the west of Xiaolongtan and near the Sino-Myanmar border, implies a slightly lower precipitation (1170-1300 mm) than that of today (1300-1400 mm). Overall, the wetter climate during the Late Miocene around the Xiaolongtan area suggests that the Himalayas had not yet uplifted to its present altitudes at that time. (C) 2009 Elsevier B.V. All rights reserved.
Bernard A Housen - One of the best experts on this subject based on the ideXlab platform.
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rapid exhumation of the eastern himalayan syntaxis since the Late Miocene
Geological Society of America Bulletin, 2016Co-Authors: Karl A Lang, Katharine W. Huntington, Russell F Burmester, Bernard A HousenAbstract:The Himalayan syntaxes are exceptionally dynamic landscapes characterized by high-relief topography and some of the most rapid and focused crustal exhumation on Earth. In the eastern Himalayan syntaxis, it has been hypothesized that thermo-mechanical feedbacks between erosion by the Yarlung River and growth of a crustal-scale antiform may have locally sustained exhumation rates exceeding 5 km/m.y. during the Late Pliocene and Pleistocene. However, young (younger than 3 Ma) cooling histories from syntaxial bedrock samples restrict interpretations of the timing and mechanism initiating feedback development. To extend this record of landscape evolution, we reconstructed an exhumation history since the Late Miocene from analysis of detrital minerals in Himalayan foreland basin deposits. We combined magnetostratigraphy, detrital white mica 40Ar/39Ar thermochronology, and coupled zircon U-Pb and fission-track geothermochronology from a 4.6-km-thick stratigraphic section proximal to the eastern syntaxis. We used a simple thermal model to interpret the combined provenance and lag-time data set, concluding that rock exhumation rates in the core of the syntaxis increased by a factor of 5–10 in the Late Miocene and have sustained extremely rapid exhumation rates (>5 km/m.y.) since 5 Ma. This onset significantly postdates the first appearance of Tibetan detritus in the Himalayan foreland, suggesting that thermo-mechanical feedbacks sustaining rapid exhumation are unreLated to river integration. Instead, such feedbacks may develop where large, antecedent rivers sustain elevated erosion rates across a region of enhanced rock uplift. Compilation of similar data sets across the Himalaya demonstrates extraordinary syntaxial exhumation histories, potentially resulting from peculiar geodynamics at these orogenic margins.
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rapid exhumation of the eastern himalayan syntaxis since the Late Miocene
Geological Society of America Bulletin, 2016Co-Authors: Karl A Lang, Katharine W. Huntington, Russell F Burmester, Bernard A HousenAbstract:The Himalayan syntaxes are exceptionally dynamic landscapes characterized by high-relief topography and some of the most rapid and focused crustal exhumation on Earth. In the eastern Himalayan syntaxis, it has been hypothesized that thermo-mechanical feedbacks between erosion by the Yarlung River and growth of a crustal-scale antiform may have locally sustained exhumation rates exceeding 5 km/m.y. during the Late Pliocene and Pleistocene. However, young (younger than 3 Ma) cooling histories from syntaxial bedrock samples restrict interpretations of the timing and mechanism initiating feedback development. To extend this record of landscape evolution, we reconstructed an exhumation history since the Late Miocene from analysis of detrital minerals in Himalayan foreland basin deposits. We combined magnetostratigraphy, detrital white mica 40Ar/39Ar thermochronology, and coupled zircon U-Pb and fission-track geothermochronology from a 4.6-km-thick stratigraphic section proximal to the eastern syntaxis. We used a simple thermal model to interpret the combined provenance and lag-time data set, concluding that rock exhumation rates in the core of the syntaxis increased by a factor of 5–10 in the Late Miocene and have sustained extremely rapid exhumation rates (>5 km/m.y.) since 5 Ma. This onset significantly postdates the first appearance of Tibetan detritus in the Himalayan foreland, suggesting that thermo-mechanical feedbacks sustaining rapid exhumation are unreLated to river integration. Instead, such feedbacks may develop where large, antecedent rivers sustain elevated erosion rates across a region of enhanced rock uplift. Compilation of similar data sets across the Himalaya demonstrates extraordinary syntaxial exhumation histories, potentially resulting from peculiar geodynamics at these orogenic margins.
Walter Landini - One of the best experts on this subject based on the ideXlab platform.
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killer sperm whale a new basal physeteroid mammalia cetacea from the Late Miocene of italy
Zoological Journal of the Linnean Society, 2006Co-Authors: Giovanni Bianucci, Walter LandiniAbstract:Zygophyseter varolai, a new genus and species of Physeteroidea (Cetacea, Odontoceti), is based on an almost complete skeleton from the Late Miocene (Tortonian) in southern Italy. The extreme elongation of the zygomatic process of the squamosal and the circular supracranial basin (probably for housing the spermaceti organ) delimited by a peculiar anterior projection of the supraorbital process of the right maxilla are the most distinctive features of this bizarre sperm whale. Large body size, large teeth present in both lower and upper jaw, and anteroposteriorly elongated temporal fossa and zygomatic process of the squamosal indicate that this cetacean (for which we suggest the English common name killer sperm whale) was an active predator adapted to feeding on large prey, similarly to the extant killer whale (Orcinus orca). A phylogenetic analysis reveals that Zygophyseter belongs to a Middle–Late Miocene clade of basal physeteroids, together with Naganocetus (new genus for the type of ‘Scaldicetus’shigensis). Moreover, the phylogenetic analysis shows evidence of a wide physeteroid radiation during the Miocene and that the extant Physeter and Kogia belong to two distinct families that form a clade representing the crown-group Physeteroidea. © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society, 2006, 148, 103–131.
Yohannes Haile-selassie - One of the best experts on this subject based on the ideXlab platform.
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Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution
Science, 2004Co-Authors: Yohannes Haile-selassie, Suwa, Tim D. WhiteAbstract:Late Miocene fossil hominid teeth recovered from Ethiopia's Middle Awash are assigned to Ardipithecus kadabba . Their primitive morphology and wear pattern demonstrate that A. kadabba is distinct from Ardipithecus ramidus . These fossils suggest that the last common ancestor of apes and humans had a functionally honing canine–third premolar complex. Comparison with teeth of Sahelanthropus and Orrorin , the two other named Late Miocene hominid genera, implies that these putative taxa are very similar to A. kadabba . It is therefore premature to posit extensive Late Miocene hominid diversity on the basis of currently available samples.
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Late Miocene hominids from the Middle Awash, Ethiopia
Nature, 2001Co-Authors: Yohannes Haile-selassieAbstract:Molecular studies suggest that the lineages leading to humans and chimpanzees diverged approximately 6.5–5.5 million years (Myr) ago, in the Late Miocene1,2,3. Hominid fossils from this interval, however, are fragmentary and of uncertain phylogenetic status, age, or both4,5,6. Here I report new hominid specimens from the Middle Awash area of Ethiopia that date to 5.2–5.8 Myr and are associated with a wooded palaeoenvironment7. These Late Miocene fossils are assigned to the hominid genus Ardipithecus and represent the earliest definitive evidence of the hominid clade. Derived dental characters are shared exclusively with all younger hominids. This indicates that the fossils probably represent a hominid taxon that postdated the divergence of lineages leading to modern chimpanzees and humans. However, the persistence of primitive dental and postcranial characters in these new fossils indicates that Ardipithecus was phylogenetically close to the common ancestor of chimpanzees and humans. These new findings raise additional questions about the claimed hominid status of Orrorin tugenensis8, recently described from Kenya and dated to ∼6 Myr9.
Tim D. White - One of the best experts on this subject based on the ideXlab platform.
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Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution
Science, 2004Co-Authors: Yohannes Haile-selassie, Suwa, Tim D. WhiteAbstract:Late Miocene fossil hominid teeth recovered from Ethiopia's Middle Awash are assigned to Ardipithecus kadabba . Their primitive morphology and wear pattern demonstrate that A. kadabba is distinct from Ardipithecus ramidus . These fossils suggest that the last common ancestor of apes and humans had a functionally honing canine–third premolar complex. Comparison with teeth of Sahelanthropus and Orrorin , the two other named Late Miocene hominid genera, implies that these putative taxa are very similar to A. kadabba . It is therefore premature to posit extensive Late Miocene hominid diversity on the basis of currently available samples.
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geology and palaeontology of the Late Miocene middle awash valley afar rift ethiopia
Nature, 2001Co-Authors: Giday Woldegabriel, Yohannes Haileselassie, Paul R Renne, William K Hart, Stanley H Ambrose, Berhane Asfaw, Grant Heiken, Tim D. WhiteAbstract:The Middle Awash study area of Ethiopia's Afar rift has yielded abundant vertebrate fossils (≈ 10,000), including several hominid taxa1,2,3,4. The study area contains a long sedimentary record spanning Late Miocene (5.3–11.2 Myr ago) to Holocene times. Exposed in a unique tectonic and volcanic transition zone between the main Ethiopian rift (MER) and the Afar rift, sediments along the western Afar rift margin in the Middle Awash provide a unique window on the Late Miocene of Ethiopia. These deposits have now yielded the earliest hominids, described in an accompanying paper5 and dated here to between 5.54 and 5.77 Myr. These geological and palaeobiological data from the Middle Awash provide fresh perspectives on hominid origins and early evolution. Here we show that these earliest hominids derive from relatively wet and wooded environments that were moduLated by tectonic, volcanic, climatic and geomorphic processes. A similar wooded habitat also has been suggested for the 6.0 Myr hominoid fossils recently recovered from Lukeino, Kenya6. These findings require fundamental reassessment of models that invoke a significant role for global climatic change and/or savannah habitat in the origin of hominids.
