Biometric calibration of the evolutionary lineage Eoparastaffella ovalis to E . simplex (Foraminifera), a high-resolution biostratigraphic tool for identifying the Tournaisian-Visean boundary
| Authors | |
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| Year of publication | 2005 |
| Type | Article in Proceedings |
| Conference | LYELL MEETING, APPLIED PHYLOGENIES HOW FAR CAN YOU GO? FEBRUARY 9TH 2005, Oral presentations |
| MU Faculty or unit | |
| Citation | |
| Web | http://www.nhm.ac.uk/hosted_sites/tms/pdf/Lyell%202005%20abstracts.pdf |
| Field | Geology and mineralogy |
| Keywords | evolution; foraminifers; high resolution stratigraphy |
| Description | The VisŠan Stage is the middle stage of the Mississippian (Lower Carboniferous) Subsystem. A stratotype for its base located in the Dinant Basin in Southern Belgium was adopted at the 6th International Carboniferous Congress in 1967. The horizon then selected is marked by the appearance of the foraminifer Eoparastaffella simplex. However, the entry of that taxon in the stratotype section is cryptic and occurs in a thin tempestite bed with shallow water bioclasts intercalated in a succession of otherwise deeper water limestone characterized by a depauperate foraminiferal fauna. Other species of Eoparastaffella preceding E. simplex had been reported earlier from Russia and have now been found in many places across Eurasia including Belgium (Ondrackova, 2001; Devuyst et al., 2003). The present study is part of a research effort initiated in 1995 with the creation of a working group to find a new criterion and/or GSSP for the base of the Visean by the Subcommission on Carboniferous Stratigraphy (SCCS) of the ICS. This work recently resulted in the proposal to use the lineage E. ovalis to E. simplex to define the base of the VisŠan and in the proposal of the Pengchong section, southern China, as a new GSSP (Devuyst et al., 2003). Latest Tournaisian microfauna containing primitive Eoparastaffella with a rounded periphery found in Southern China were first shown to constitute the parent evolutionary stock of E. simplex by Hance & Muchez (1995). The idea had been previously suggested by Vdovenko (1964) based on fauna from the Dnieper- Donets and Donbass basins but had not been demonstrated in a single section. Hance & Muchez (1995) introduced a morphometric index to differentiate the more rounded late Tournaisian primitive forms (morphotype 1) and the more pointed Visean ones (morphotype 2) and proposed that the base of the Visean should be selected on that basis. This innovative proposal presented many advantages and rapidly gained support. However, the reference material was relatively limited and the morphometric coefficient needed more testing to show that it could be used reliably. We present here extensive new material collected from sections widely distributed around the Paleo-Tethys, including Pengchong, which document the evolutionary lineage which leads to E. simplex. This material allows us to describe accurately the species involved in the lineage and to propose an improved morphometric coefficient that can be used by nonspecialists as an aid in identifying the base of the Visean. We also show that the genus Eoparastaffella as a whole has great potential for very high-resolution biostratigraphy in the late Tournaisian to early Visean interval. |
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