Evolution of trilobite biofacies in Cambrian basins of the Siberian Platform

Abstract

Cambrian biotic zonation on the Siberian Platform reflects differentiation of the depositional environments (inner shelf, outer shelf and open basin). The combination of the chart of trilobite biofacies replacement and the curve of sea-level fluctuations shows that trilobite biofacies replacement occurs as a rule at times of sign reversal and distinct change in the rates of sea-level rise or fall. The boundaries of major Siberian platform Cambrian chronostratigraphic units, such a stages and series, frequently coincide with the boundaries of biofacies in stratigraphic succession related to sea-level fluctuations. If these fluctuations are gradual and restricted, then the boundaries of the Cambrian stages and series cannot be isochronous levels at a global scale. The known levels for intercontinental correlation on the Siberian Platform include boundaries of the adjacent Triplagnostus gibbus and Tomagnostus fissus Zones from the uppermost Amganian Stage (Middle Cambrian) and the Glyptagnostus stolidotus and Glyptagnostus reticulatus Zones of the lower Upper Cambrian. Both levels correspond to boundaries between highstands and lowstands on the Siberian Platform and appear to serve as boundaries of high rank. Evolution of the trilobite biofacies zonation is illustrated by genera typical for each of the various Cambrian paleogeographic environments on the Siberian Platform.

Fallotaspidoid trilobite assemblage (Lower Cambrian) from the Esmeralda Basin (western Nevada, U.S.A.): The oldest trilobites from Laurentia

“…The Fritzaspis zone provides a useful and convincing correlation with the trilobites of the Fallotaspidoidea biofacies in the open shelf carbonates on the middle reaches of the Lena River, southeastern Siberian Platform (Pegel 2000). Profallotaspis?…”

Cambrian trilobite biostratigraphy and its role in developing an integrated history of the Earth system

“…; Peng ; Ahlberg & Ahlgren ; Geyer & Shergold ; Geyer et al . ; Pegel ; Peng & Robison ; Ahlberg ; Peng et al . ,b, ; Peng et al .…”

The first record ofDinesus(Trilobita, Dinesidae) in the Cambrian of the Mediterranean region

“…The scheme for Laurentia reflects the latest modifications by Sundberg & McCollum (2003) and Sundberg (2005). Cambrian) of Australia (Brock et al 2000, Paterson 2005); Lermontovia grandis Zone to Kounamkites Zone (upper lower Cambrian and lower middle Cambrian) of the Siberian Platform and Altay-Sayan Fold Belt (Russia), generally as Erbia (see Tchernysheva 1971, Savitsky et al 1972, Repina & Romanenko 1978, Egorova et al 1976, Astashkin et al 1991, 1995, Repina et al 1999, Pegel 2000, Varlamov et al 2008; Lungwangmioan Stage (upper lower Cambrian) of China (see Lin 2008) and, probably, Taijiangian Stage (middle Cambrian) of China (see Peng 2008); Montezuman and Dyeran stages (lower Cambrian) of Alaska and Canada (Palmer 1968, Fritz 1973; and lower Cambrian of Kazakhstan (Ivshin 1978, Repina et al 1999. The specimen described herein is the first record of the genus from Spain (Mediterranean subprovince) in the Acadobaltic province (sensu Sdzuy 1972).…”