SHRIMP zircon U–Pb ages from coal beds across the Permian–Triassic boundary, eastern Yunnan, southwestern China

The first SHRIMP zircon U–Pb ages from coal beds close to the end-Permian mass extinction are reported from the C1 coal seam in the Yantang Mine in Laibin Town, Xuanwei County, eastern Yunnan Province. Zircons were extracted from kaolinite claystone layers, defined as tonsteins (volcanic ash deposits), in the sub-seam B1 and B3 of the coal seam C1. The U–Pb ages are 252.0 ± 2.3 Ma and 250.3 ± 2.1 Ma for the sub-seam B1 and B3, respectively. Within analytical uncertainties, these U–Pb ages include the time period of the onset of the mass extinction at 251.941 ± 0.037 Ma, which was obtained from the marine Meishan section in Zhejiang Province, ∼1600 km away from the Yantang Mine. These new ages represent not only the first and closest ages to the PTB mass extinction in terrestrial coal beds, but also ages from the nearest site to the Emeishan volcanoes investigated so far. Therefore these new data provide the most accurate stratigraphic horizon of terrestrial facies of the end-Permian extinction in South China. The Emeishan volcanoes were likely the source of volcanic ash in the coal seams at the Xuanwei County and broader areas in South China. Furthermore, the minerals and geochemistry characteristics of the C1 coal seam also implied the influences of contemporaneous volcanic activities

The Quaternary Period

The Quaternary Period, comprising the Holocene and Pleistocene Epochs, encompasses the last ~2.6 Ma during which time Earth’s climate was strongly influenced by bi- polar glaciation and the genus Homo first appeared and evolved. The base of the Quaternary System/Period and Pleistocene Series/Epoch is defined by the GSSP for the Gelasian Stage at Monte San Nicola section in Italy. The base of the Holocene Series/Epoch is defined at a depth of 1492.45 m in the NGRIP ice core from Greenland, with an age based on annual layer counting, of 11 700 years b2k (before AD2000), with a 2s uncertainty of 99 years; it is the first and only GSSP to be defined in an ice core

Geomorphology, soils and palaeosols of the Chencha area (Gamo Gofa, south western Ethiopian Highlands)

The landscape of the Chencha Highland (south western Ethiopia) is characterized by flat plateau bordered by steep slopes affected by landslides and dissected by concave valleys and gullies. Coalescing alluvial fans are found along the eastern piedmont at the transition to the Lake Abaya shores. A major rift-plateau escarpment, with minor synthetic and antithetic faults, is located along the eastern slopes of the highlands. Soil erosion is a widespread process and the soil cover is usually thin and discontinuous. Immature Cambisols formed on colluvial deposits containing lithic tools, pottery fragments and charcoal represent the most recent phase of soil formation. They are related to the clearance of the original forest cover and the introduction of extensive agricultural and pastoral practices. On the slopes these soils locally unconformably overlie reddish, strongly weathered buried Nitisols and Luvisols that can be classified as Palaeoedlisols with formation of saprolite. Thicker and better preserved Palaeoeldisols can be found on the summit plateau, due to reduced runoff erosion. Different generations of clay illuviation indicate that they underwent polycyclic processes, recording soil processes probably older than Holocene. Along the slopes, gully erosion exhumed a palaeo-gully system infilled by colluviums of soils and buried soils containing Middle Stone Age artifacts suggesting that important slope degradational processes occurred also during the Late Pleistocene. Buried brownish soils in these infillings show moderate clay illuviation that indicates short-lived climatic amelioration and phases of slope stability

Conduits, timing and processes of sediment delivery across a high-relief continental margin: Continental shelf to basin in Late Quaternary, Gulf of Papua

© 2016 Elsevier Ltd. The Gulf of Papua (GoP), between Australia and Papua New Guinea, is the receiving basin for multiple substantial rivers draining southern Papua New Guinea with collective sediment discharge \u3e\u3e 220 million metric tons (Mt) per year, comparable to a continental-scale river, but draining a combined catchment area of only ~160,000 km2. This study of the deepest marginal basins in the Gulf of Papua was undertaken to build a regional late Quaternary lithofacies and stratigraphic framework to better understand processes, timing, and conduits of sediment delivery from terrestrial and shelf settings to deep marginal basins, using the GoP as a natural laboratory. Methods include observations of sediment-core stratigraphy and physical properties, accelerometer mass spectrometry (AMS) C-14 dates, core x-radiographs and thin sections.Six lithofacies across the deep water Gulf of Papua (GoP) are identified based on core visual and textural observation. Chronological constraints permit an assessment of changes in sediment supply and depositional environments across time and space, from marine isotope stage (MIS) -3 to -1, or in the last 40 cal ka. The sediment delivery to the deep water GoP is dominated by two mechanisms, gravity-driven flows down slopes and into deep sea basin primarily during lowstands in the western portions of the study area, and hemipelagic sediment accumulation during transgression and highstand. Although the sediment flux appears to be overall dominated by sediment-gravity flows, hemipelagic sediment delivery is widespread during periods of sea level highstand. In the eastern portions of the study area, off-shelf sediment delivery continued into the Holocene in sufficient local volumes to produce turbidity currents. This late, localized sediment delivery appears to have been facilitated by oceanographic processes that allowed seaward sediment transport after flooding of the shelf.A simple sediment budget comparing basinal sediment accumulation to modern estimated river-sediment discharge indicates that peak sediment accumulation in proximal basins occurred during MIS-2; and declined thereafter, generally shifting to upper slope locations, except for the eastern margin of Moresby Trough. There, turbidite deposition continued until 7.4 cal ka, well after drowning of the shelf edge. This continued Holocene deep-sea sediment delivery is likely explained by the local narrow shelf width, and the presence of oceanographic processes capable of transporting sediments from shore to shelf edge