The Huanghuachang section near Yichang, southern China meets the requirements of Global Stratotype Section and Point (GSSP) for the base of the Middle Ordovician Series and the yet-to-be-named third stage of the Ordov...The Huanghuachang section near Yichang, southern China meets the requirements of Global Stratotype Section and Point (GSSP) for the base of the Middle Ordovician Series and the yet-to-be-named third stage of the Ordovician System (or lower stage of Middle Ordovician Series). The conodont succession at the section is complete across the Lower to Middle Ordovician series boundary and several excellent phylogenetic lineages of Baltoniodus, Trapezognathus, Periodon, and Microzarkodina are represented. The definition of the base of the Middle Ordovician is proposed to be the first appearance datum (FAD) of Baltoniodus? triangularis in the section. It is followed closely by the FAD of Microzarkodina flabellum, which is taken as a reasonable proxy for the boundary. This level approximates the boundary between the lower and upper intervals of the Azygograptus suecicus graptolite Biozone, and nearly coincides with the base of the Belonechitina henryi chitinozoan Biozone.The proposed GSSP for the base of the international Middle Ordovician Series is located in a roadside exposure at the base of Bed (SHod) 16, 10.57 m above the base of the Dawan Formation in the measured Huanghuachang section near Yichang City, southern China. The same faunal succession is also recorded from the Chenjiahe (formerly Daping) section, 5 km to the north of the Huanghuachang section. The proposed boundary horizon can be recognized and correlated globally with high precision in both relatively shallow-water carbonate facies as well as in deep-water graptolite facies.展开更多
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 Turoni...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.展开更多
文摘The Huanghuachang section near Yichang, southern China meets the requirements of Global Stratotype Section and Point (GSSP) for the base of the Middle Ordovician Series and the yet-to-be-named third stage of the Ordovician System (or lower stage of Middle Ordovician Series). The conodont succession at the section is complete across the Lower to Middle Ordovician series boundary and several excellent phylogenetic lineages of Baltoniodus, Trapezognathus, Periodon, and Microzarkodina are represented. The definition of the base of the Middle Ordovician is proposed to be the first appearance datum (FAD) of Baltoniodus? triangularis in the section. It is followed closely by the FAD of Microzarkodina flabellum, which is taken as a reasonable proxy for the boundary. This level approximates the boundary between the lower and upper intervals of the Azygograptus suecicus graptolite Biozone, and nearly coincides with the base of the Belonechitina henryi chitinozoan Biozone.The proposed GSSP for the base of the international Middle Ordovician Series is located in a roadside exposure at the base of Bed (SHod) 16, 10.57 m above the base of the Dawan Formation in the measured Huanghuachang section near Yichang City, southern China. The same faunal succession is also recorded from the Chenjiahe (formerly Daping) section, 5 km to the north of the Huanghuachang section. The proposed boundary horizon can be recognized and correlated globally with high precision in both relatively shallow-water carbonate facies as well as in deep-water graptolite facies.
文摘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.
