Ordovician acritarchs of China and their utility for global palaeobiogeography

Abstract

Abstract. -Since the 1970s, acritarch workers have recognized two distinct geographic acritarch assemblages in the Ordovician. The first assemblage occurs in the late Tremadoc in low latitude areas. This assemblage, recently redefined by Volkova [1997], has been attributed to warm-water environments.

Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle Ordovician)

“…A review of the available literature reveals an ambiguous picture. Li and Servais (2002) place the North China block on the northeastern edge of Gondwana close to Australia and in the northern hemisphere. In these models the closest neighbors to the Precordilleran terrane are Laurentia to the northeast, Baltica to the east, and West Gondwana to the south.…”

“…Ty chsen and Harper (2004) locate the North China block in the Southern Hemisphere somewhere between Baltica and the eastern margin of Gonwana, but no specific data are given for the Pre cordillera. Li and Servais (2002) place the North China block on the northeastern edge of Gondwana close to Australia and in the northern hemisphere. In the paleomagnetic reconstructions of Huang et al (2000) and Yang et al (2002), the North China block separated from the eastern margin of Gondwana in the earliest Ordovician and moved eastward in the middle latitudes of the southern hemisphere toward the Argentinian margin of Gond wana.…”

“…However, the time span of this ''domain'' comprises the entire Ordovician, and thus is hardly useful in tracing the Early-Middle Ordovician paleogeographic movements of the Precordillera. Li and Servais (2002) placed the Early-Middle Ordovician acritarchs of Argentina in their peri-Gondwana province, but gave no information from which region their Argentina data were obtained. These conodont data are comparable with ''temperate'' and unrestricted marine environments.…”

“…These conodont data are comparable with "temperate" and un restricted marine environments. Li and Servais (2002) placed the Early-Middle Ordovician acritarchs of Argentina in their peri-Gondwana province, but gave no information from which region their Argentina data were obtained.…”

Biostratigraphy and paleoenvironmental characterization of the Middle Ordovician from the Sierras Subandinas (NW Argentina) based on organic-walled microfossils and sequence stratigraphy

“…Q. Acanthodiacrodium costatum (Burmann, 1968 localities (Vavrdová, 1974;Volkova, 1997;Tongiorgi and Di Milia, 1999) and the other, formerly named "Mediterranean Province" (Vavrdová, 1974;Li, 1987Li, , 1989Martin, 1982) and successively renamed "peri-Gondwanan province" (Albani, 1989; see exhaustive review in Playford et al, 1995), is distributed along the periphery of Gondwana from Argentina to north Africa including Iran, Pakistan and southern China. This "province" occurs close to the south pole but also reaches intermediate latitudes (i.e., the Yangtze Platform in South China: Li, 1987;Tongiorgi et al, 1995), therefore its distribution was probably not entirely controlled by climatic zones, but also by oceanic currents (Tongiorgi et al, 1998) as well as by continental configuration (Li and Servais, 2002).…”