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The Green Point Formation of the Cow Head Group in western Newfoundland (Canada) 24 represents the Global Stratotype Section and Point (GSSP) for the Cambrian-Ordovician 25 boundary on Laurentia. The formation consists of the Martin Point (lower) and the Broom Point 26 (upper) members, which constitute a thick (~170 m) deep subtidal to slope marine carbonate 27 sequence. Preservation of the micritic carbonates of the Green Point Formation was evaluated by 28 multiple petrographic and geochemical screening tools. The δ 13 C and δ 18 O values of near-29 primary micrites range from-4.7 ‰ to +1.7‰ (VPDB) and from-8.7 ‰ to-5.5 ‰ (VPDB), 30 respectively, with no significant correlation (R 2 = 0.002). Similarly, the δ 13 C values show no significant correlation with Mn/Sr ratios or total REE contents, which suggest that the investigated carbonates retain their near-primary δ 13 C signatures that can be utilized to construct 33 a high-resolution carbon-isotope profile for the GSSP. The δ 13 C carb profile about the GSSP trends 34 generally positive into Bed 22 of the Green Point Formation. The top of the C. intermedius Zone 35 marks the onset of a negative δ 13 C carb shift to about 6.0 ‰ culminating in the upper part of the zone. Subsequently, the δ 13 C carb profile trends positive with a 'double switch-back' about the boundary point and then continues on to a most positive value in the uppermost part of Bed 23. In addition, based on 87 Sr/ 86 Sr and Ce*/Ce values, the GSSP is defined by ratios of 0.709623 and <0.9, respectively, suggesting generally dysoxic waters before, during, and immediately after the boundary. The high-resolution chemostratigraphic results, curve, and trends covering the GSSP should facilitate correlation of the Cambrian-Ordovician boundary sections/sequences from other locations.

In 2000, the International Union of Geological Sciences (IUGS) ratified the decision from the International Working Group on the Cambrian-Ordovician Boundary (COBWG) to place the Global boundary Stratotype Section and Point (GSSP) for the base of the Ordovician System in the Green Point section, Newfoundland, Canada, at a point coinciding with the first appearance of the conodont Iapetognathus fluctivagus. However, a restudy of the conodont successions from Green Point shows that this species is not present at the boundary interval, and as a consequence the section does not fulfil the biostratigraphical requirements of a GSSP. The GSSP horizon as now defined is based on a level part-way through the range of I. preaengensis- a species with lower first appearance datum (FAD). The true FAD of I. fluctivagus is above the FAD of planktonic graptolites and well above the FAD of I. preaengensis. As a consequence of these problems, a restudy of the GSSP section and the other sections in the Cow Head Group is necessary. A redefinition of the GSSP horizon is suggested. The following four alternative horizons have potential as new horizons for the GSSP level: the FAD of Cordylodus intermedius; the FAD of Cordylodus andresi; the FAD of Eoconodontus notchpeakensis; and the FAD of the agnostoid Lotagnostus americanus

International Commission on Stratigraphy and the IUGS Executive Committee have recently approved a Global Standard Stratotype-section and Point (GSSP) defining the base of the second stage of the Furongian Series, Cambrian System. This stage is named the Jiangshanian Stage, after Jiangshan City, western Zhejiang Province, China, where the GSSP is located. The GSSP is exposed in a natural outcrop near Duibian Village. It is defined at the base of a limestone (wackestone) layer 108.12 m above the base of the Huayansi Formation in the Duibian B section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis (base of the A. orientalis Zone). The GSSP is at a position of 28° 48.977´N latitude and 118º 36.887´E longitude. Secondary global markers at or near the base of the stage include the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata, which coincides with the FAD of the primary marker in the stratotype section, and near the end of a large positive carbon isotopic excursion (SPICE excursion). Faunal turnovers close to the base of the Jiangshanian Stage have been recognized as being at the base of the Iverian Stage in Australia, the Gonggrian Stage in Korea, and the Agnostotes orientalis-Irvingella perfecta Zone in Siberia, and near the base of the Aksayan Stage in Kazakhstan, the Sunwaptan Stage in Laurentia, and the Parabolina brevispina Zone in Baltica.

each series it is expected that two to three stages whose boundaries correspond to horizons that can be correlated with a high degree of confidence through all paleocontinents will be recognized. As emphasized by Geyer and Shergold (2000), communication of timestratigraphic information will be maximized if the internal subdivisions of the system correspond to horizons recognizable on all paleocontinents. Traditional, regional stratigraphic schemes, based principally on unit stratotypes, do not meet this goal, and it is for this reason that the ISCS is now engaged in further developing our understanding of key horizons for correlation within the Cambrian, and newly defined series and stages that are readily traceable among Cambrian regions. The newly defined chronostratigraphic units are based on the principle of boundary stratotypes, in which the base of one unit (marked by a Global boundary Stratotype Section and Point, or GSSP) automatically delimits the top of the underlying unit. So defined, these intervals differ in substance from unit stratotypes, which have been variously defined in Cambrian regions (Geyer and Shergold, 2000; Peng et al., 2004a, 2006; Babcock et al., 2005). Apart from the Guzhangian Stage (discussed here), the boundary positions relevant to the Cambrian (Figure 1) that have been ratified are: 1, the conterminant base of the Paleozoic Erathem, Cambrian System,