Qi Yuping (祁玉平)

Foraminiferal Biostratigraphy of the Visean–Serpukhovian (Mississippian) Boundary Interval At Slope and Platform Sections In Southern Guizhou (South China)

Abstract The Visean–Serpukhovian boundary is not yet defined by a Global Stratotype Section and Point (GSSP) but it is recognizable operationally by the appearance of the conodont Lochriea ziegleri in the L. nodosa–L. ziegleri chronocline. Foraminiferal successions across this boundary in the type area of the Serpukhovian Stage (Moscow Basin, Russia), elsewhere in Russia and in the central United States suggest that the appearances of Asteroarchaediscus postrugosus, Janischewskina delicata, Eolasiodiscus donbassicus, and specimens controversially referred to “Millerella tortula” are reliable, auxiliary indices to the base of the Serpukhovian. In southern Guizhou Province, China, Visean–Serpukhovian rock sequences from slope and platform settings have yielded rich associations of conodonts and foraminifers, respectively. The Nashui section is a leading candidate for the Serpukhovian GSSP because its slope deposits contain an uninterrupted record of conodont occurrences including the L. nodosa–L. ziegleri transition. Foraminifers recovered from the Nashui section are comparatively rare and include none of the basal Serpukhovian indices. In contrast, the nearby Yashui section represents a platform interior setting in which foraminifers flourished and conodonts were nearly absent. The base of the Serpukhovian at Yashui is marked approximately by the appearance of “tortula-like” specimens. Although it is not possible to correlate biostratigraphically between the Nashui and Yashui sections, the occurrence of “tortula-like” specimens at the Yashui section allows correlation with the mid-Venevian Substage of the Moscow Basin at a level coinciding with the appearance of L. ziegleri. Together, the slope and platform sections comprise an informative biostratigraphic reference area for micropaleontologic characterization of the Visean–Serpukhovian boundary in southern Guizhou.

Serpukhovian conodont sequence and the Visean-Serpukhovian boundary in South China

This paper describes in detail the conodont sequence of Upper Visean (equivalent to Tatangian of China), Serpukhovian (equivalent to Duwuan of China) and the base of Bashkirian (equivalent to Luosuan of China) in South China. The following conodont zones can be recognized in descending order: Declinognathodus noduliferus, Gnathodus bilineatus bollandensis, Lochriea cruciformis, L. ziegleri and L. nodosa zones. The first occurrences of Lochriea ziegleri and D. noduliferus (or D. lateralis ) are considered as the bases of Serpukhovian and Bashkirian, respectively. The correlation of the conodont sequence from Upper Visean to the base of Bashkirian between South China and the Moscow Basin, South Urals, Great Britain, Ireland and North America is discussed.

CAMBRIAN CONODONTS ACROSS THE PRE-FURONGIAN TO FURONGIAN INTERVAL IN THE GSSP SECTION AT PAIBI, HUNAN, SOUTH CHINA

The conterminant base of the Furongian Series and Paibian Stage (Cambrian), as ratified in 2003, is in dark carbonate slope deposits of the Paibi section, Hunan, China, at the FAD of the agnostid trilobite Glyptagnostus reticulatus . Sampling in the boundary interval reveals 38 taxa of protoconodonts and paraconodonts, including two new species, Prosagittodontus telli and Furnishina miao , and some species in open nomenclature. In the investigated interval, Westergaardodina is a minor component of the conodont associations, whereas Furnishina is common. The interval can be subdivided into two informal assemblages: 1) the Furnishina miao assemblage, which extends from the base of the investigated interval to just below the FAD of G. reticulatus ; followed by 2) the Furnishina quadrataiV Furnishina longibasis assemblage, which extends from just above the FAD of G. reticulatus to the top of the studied interval. The conodont succession correlates with trilobite biozones, and approximately correlates with conodont zones previously recognized in South China and North China. The occurrence of Furnishina longibasis allows long distance correlation because it has a short stratigraphic range and has been reported from Sweden and Poland.

Evolution of carbon isotope composition in potential global stratotype section and point at Luoyixi, South China, for the base of the unnamed global seventh stage of Cambrian System

Abstract This work deals with the evolution of carbon isotope composition in the Luoyixi Section, a candidate of the Global Standard Stratotype-section and Point (GSSP), defining the base of the as-yet-undefined seventh stage of Cambrian System at the first appearance of the cosmopolitan agnostoid Lejopyge laevigata. This level is favored in a vote of International Subcommission on Cambrian Stratigraphy (ISCS) as the biohorizon for defining the base of a global stage. Two hundred and sixty-four samples for carbon and oxygen isotope analysis have been collected from the carbonate successions at an interval of 0.25 to 0.5 m in this section. Results of the carbon isotope data exhibit a remarkable disciplinarian trend. The pattern of the carbon isotope evolution is gently undulant with a relatively long period during the underlying Drumian Stage, and then the values of δ13C fluctuate sharply with a short period in provisional seventh stage. The onset of sharp fluctuation in the δ13C values begins at the proposed GSSP level, defining the base of the global seventh stage, where δ13C values change from a gentle trend to a sharp trend. Distinct covariant-relationships among δ13C, δ18O, and sea level fluctuations suggest that a warming change in paleoclimate took place during the early global seventh stage, which led to a positive shift in δ13C values.