The GSSP of the Second （Upper） Stage of the Lower Ordovician Series： Diabasbrottet at Hunneberg, Province of Vaeistergoetland, Southwestern Sweden

Diabasbrottet, selected by the International Subcommisson on Ordovician Stratigraphy and in 2002 ratified by the International Commission on Stratigraphy as the GSSP of the Second (Upper) Stage of the Lower Ordovician, is located on the Hunneberg Mountain in southwestern Sweden. The stratigraphic succession represents an outer shelf environment near the Baltic Shield margin. The shale-dominated, biostratigraphically complete, richly fossiliferous boundary interval is completely exposed in a disused quarry. The GSSP is in the lower TФyen Shale 2.1 m above the top of the Cambrian and is marked by the first appearance of the graptolite Tetragraptus approximatus Nicholson. The boundary interval contains a diverse graptolite fauna and biostratigraphically diagnostic conodonts and trilobites that make it possible to define the boundary in terms of zone schemes based on these groups. In this respect, the Diabasbrottet and nearby sections are unique in the world among described localities having this boundary interval. Based on the appearance of T. approximatus, the base of the Second Stage can be identified in many graptolitiferous successions round the world but this level is currently more difficult to recognize precisely in some carbonate sequences outside Baltoscandia. We propose the Second Stage be called the Floan Stage. It is named for the Village of Flo, which is situated about 5 km southeast of the GSSP.     

The Global Boundary Stratotype Section and Point for the base of the Turonian Stage of the Cretaceous： Pueblo, Colorado, U.S.A.

Following the recommendation of the International Commission on Stratigraphy (16 votes Yes [94%], 1 abstention, 2 votes not received), the Global boundary Stratotype Section and Point (GSSP) for the base of the Turonian Stage of the Cretaceous System is defined as the base of bed 86 of the Bridge Creek Limestone Member of the Greenhorn Limestone Formation at the western end of the Denver and Rio Grande Railroad cut near the north boundary of the Pueblo Reservoir State Park Recreation Area, west of Pueblo, Colorado, USA. This GSSP horizon is also exposed and protected in the adjacent state recreation area. It coincides with the first occurrence of the ammonite Watinoceras devonense, is in the middle of a global positive excursion in Carbon-13 isotopes, and is bracketed by widespread bentonites that have yield edages of 93 to 93.5 Ma.     

The Global Stratotype Section and Point （GSSP） for the base of the Holocene Series/Epoch （Quaternary System/Period） in the NGRIP ice core

The Greenland ice core from NorthGRIP （NGRIP） contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision.     

A proposed Global Stratotype Section and Point （GSSP） for the base of the Upper （Late） Pleistocene Subseries （Quaternary System/Period）

Following the precedence already established during the INQUA Congress in 1932, the Middle/Upper （Late） Pleistocene boundary is defined at the base of the Last Interglacial, the Eemian Stage. It is proposed that a high-resolution core sequence from the Amsterdam Terminal （the Eemian Stage parastratotype） should constitute the Global Stratotype Section and Point （GSSP） for the base of the Upper （Late） Pleistocene Subseries （Quaternary System/Period）.     

Retrogressive Microstructures of the Eclogites from the Northern Dabie Mountains, Central China： Evidence for Rapid Exhumation

The ultrahigh-pressure eclogites from the northern Dabie Mountains in central China occurred as tectonic lens or blocks within granitic gneisses or meta-peridotites. Petrologic studies suggest that the studied eclogites experienced strongly retrogressive metamorphism and produced a series of characteristic retrogressive microstructures. The retrograde structures mainly include: (1) oriented needle mineral exsolution, e. g. , quartz needles in Na-clinopyroxene and rotile, clinopyroxene and apatite exsolution in garnet formed under decreasing pressure conditions during exhumation; (2) symplectite, especially, two generations of symplectites developed outside the garnet grains, which are called ““double symplectite““ here; (3) compositional zoning of minerals such as garnet and clinopyroxene; (4) minerals with a reaction rim or retrograde rim, e.g. , omphacite with a diopside rim, diopside with an amphibole rim and rutile with a rim of ilmenite. These retrograde textures, especially mineral zoning and symplectite, provide important petrologic evidence for the exhumation process and uplift of high-grade metamorphic rocks such as eclogite in the northern Dabie Mountains, indicating a rapid exhumation process.     

The Global Boundary Stratotype Section and Point （GSSP） for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France

Following the unanimous recommendation of the International Commission on Stratigraphy, the Global boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage is defined at a level 36 metres below the top of the Marnes Bleues Formation, a level that corresponds to the the first appearance of the planktonic foraminiferan Rotalipora globotruncanoides Sigal, 1948, on the south side of Mont Risou, east of Rosans, Haute-Alpes, France, where it can be placed in the context of a series of secondary marker levels based on nannofossils, planktonic foraminifera, ammonites,and an ornate δ^13C curve.     

A Study on the Geological—Geochemical Dynamics of Hydrothermal Ore Deposition as Exemplified by the Muping—Rushan Gold Deposit Belt,Eastern Shandong,China

This paper presents a method of establishing a hydrothermal ore-forming reaction system.On the basis of the study of four typical hydrothermal deposits,the following conclusions concerning geochemical dynamic controlling during hydrothermal mineralization have been sions concerning geochemical dynaamic controlling during hydrothermal mineralization have been drawn:(1)The regional tectonic activities control the concentration and dispersion of elements in the ore-forming process in terms of their effects on the thermodynamic nature and conditions of the ore-forming reaction system.(2)During hydrothermal mineralization the activites of ore-bearing faults can be divideb into two stages:the brittle splitting stage and the brittle-tough tensing stage,which would create characteristically different geodynamic conditions for the geochemical thermodynamic ore-forming system.(3)The hydrothermal ore-forming reaaction system is an open dynamic system.At the brittle splitting stage the system was so strongly supersaturated and unequilibrated as to speed up and enhance the crystallization and differentiation of ore-forming fluids.And at the brittle-tough tensing stage,the ore-forming system was in a weak supersaturated state;with decreasing temperature and pressure the crystallization of oreforming material would show down,and it can be regarded as an equilibrated state.(4)In the lates stages of hydrothermal evolution,gold would be concentrated in the residual ore-forming solution.The pulsating fracture activite in this stage led to the crush of pyrite ore and it was then filled with gold-enriched solution,forming high-grage“fissure”gold ore.This ore-forming process could be called the coupling mechanism of ore formation.     

REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin, NW China： A Potential REE Proxy for Ancient Seawater

Rare earth element compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied. Most dolomite samples are more or less contaminated by clay minerals. Their rare earth element compositions have been consequently changed, showing both seawater-like and non-seawater-like features. The clay contamination should be disposed before the REE data are used. Through ICP-MS and ICP-AES analyses, the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation, trace elements and REE contents. The dolomites, at least in the Tarim Basin, are thought to be pure when their total LREE contents are less than 3×10^-6. Through comparison, the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone, which indicates that dolomitization may slightly change the REE compositions. Nevertheless, whatever the change is, the pure dolomites may act as a potential REE proxy for Ordovician seawater, which would be significant for ancient massive dolomite strata that lack limestone.     

Ordovician Granitoids and Silurian Mafic Dikes in the Western Kunlun Orogen, Northwest China: Implications for Evolution of the Proto-Tethys

The western Kunlun orogen in the northwest Tibet Plateau is related to subduction and collision of Proto-and Paleo-Tethys from early Paleozoic to early Mesozoic. This paper presents new LA-ICPMS zircon U-Pb ages and Lu-Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotopes of two Ordovician granitoid plutons(466–455 Ma) and their Silurian mafic dikes(～436 Ma) in the western Kunlun orogen. These granitoids show peraluminous high-K calcalkaline characteristics, with(⁸⁷Sr/⁸⁶Sr)_i value of 0.7129–0.7224, ε_Nd(t) values of -9.3 to -7.0 and zircon ε_Hf(t) values of -17.3 to -0.2, indicating that they were formed by partial melting of ancient lower-crust(metaigneous rocks mixed with metasedimentary rocks) with some mantle materials in response to subduction of the Proto-Tethyan Ocean and following collision. The Silurian mafic dikes were considered to have been derived from a low degree of partial melting of primary mafic magma. These mafic dikes show initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7101–0.7152 and ε_Nd(t) values of -3.8 to -3.4 and zircon ε_Hf(t) values of -8.8 to -4.9, indicating that they were derived from enriched mantle in response to post-collisional slab break-off. Combined with regional geology, our new data provide valuable insight into late evolution of the Proto-Tethys.     

A Middle–Upper Devonian Boundary Section in the Open Platform,Platform Margin Facies of Guilin, South China

Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common–rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 “standard” conodont zones are recognized across the Givetian–Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni–cristatus Zone, the Lower hermanni–cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle–Upper Devonian (Givetian–Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.     

U-Pb zircon age from the base of the Ediacaran Doushantuo Formation in the Yangtze Gorges,South China： constraint on the age of Marinoan glaciation

The reported new U-Pb age by sensitive high-resolution ion microprobe (SHRIMP Ⅱ) on zircon was obtained from a tuff sample at the basal Doushantuo Formation in the Jiuqunao section, which situated at the western limb of the Huangling anticline in the Yangtze Gorges in Zigui, Hubei, South China. Eighteen spots of zircons were analyzed and they form two clusters: one includes three spots, with an inherited age of 784+ 15 Ma (MSWD=0.05); the other consists of 15 spots and gives a weighted mean ^206pb/^238U age of 628.3±5.8 Ma (MSWD=0.86). It is the first SHRIMP U-Pb zircon age obtained nearly the base of the Doushantuo Formation of Ediacaran and represents a maximum age of the Doushantuo Formation It also forms an age constraint on the upper limit age of the Nantuo (Marinoantype) glaciation.