Upper Ordovician chitinozoan biostratigraphy from the type Ashgill area (Cautley district) and the Pus Gill section (Dufton district, Cross Fell Inlier), Cumbria, Northern England

Abstract

Seventy-five samples from the classic sections through the historical type area of the Ashgill Series in the Cautley district and along Pus Gill in the Cross Fell Inlier have been examined for chitinozoans. The results of this study allowed the recognition of five internationally recognized biozones and the definition of two new Avalonian chitinozoan zones. From bottom upwards, these are: the Fungochitina spinifera, the Tanuchitina bergstroemi?, the Conochitina rugata, the Spinachitina fossensis, the Bursachitina umbilicata sp. n., the Ancyrochitina merga and the Belonechitina postrobusta zones. One new species is described: Bursachitina umbilicata sp. n. This biozonation enables a correlation between the Cautley district and the Baltoscandia and Gondwana palaeocontinents based on chitinozoans. The Baltoscandic chitinozoan zones are, therefore, now better correlated with the British chronostratigraphical scheme, which is still widely used. It is stratigraphically significant that the base of the Ashgill in its type area does not fall within the Tanuchitina bergstroemi Zone, as widely believed before, but in the Fungochitina spinifera Zone. In addition, chitinozoans from the Onnian (Caradoc) section of the Cross Fell Inlier provide a link with the type Caradoc section in Shropshire.

Graptolites of the Králův Dvůr Formation (mid Katian to earliest Hirnantian, Czech Republic)

“…Chen et al 2005) previously identified as N. angustus are actually referable to Styracograptus (Goldman et al 2011) (Chen et al 2000), the Dicellograptus ornatus and P. pacificus zones in western Laurentia (Štorch et al 2011), and in the D. anceps Zone of eastern Laurentia (Williams 1982 (Vandenbroucke et al 2005), on the other hand, suggest correlation with the D. anceps Zone interval in Baltica (Ainsaar et al 2010), consistent with the inferences above about the age of the D. laticeps-bearing interval in the upper Králův Dvůr Formation.…”

Chitinozoan biostratigraphy of the Upper Ordovician of Faulx-les-Tombes (central Condroz Inlier, Belgium)

“…prussica Eisenack, 1931 are recovered (one specimen of each). It is only at a level, estimated at a stratigraphic position of less than 20 m higher than JVM 03-066 that the next indicative species occurs: Bursachitina umbilicata Vandenbroucke et al, 2005 (sample JVM 03-085, E brook section). It is also recognised from samples in the Rue du Bois Grand-Pré section and probably also in the W brook section.…”

“…Vanmeirhaeghe and Verniers (2004) studied the chitinozoans of the Fosses Formation in the western part of the Condroz Inlier (including the Puagne Inlier) and recognised the presence of the Baltoscandian Tanuchitina bergstroemi and Conochitina rugata chitinozoan biozones by the index species. These two biozones are also identified in the Avalonian type Ashgill area, Cautley District, U.K. (Vandenbroucke et al, 2005). Further, the Spinachitina fossensis and Bursachitina umbilicata (as Bursachitina sp.…”

“…Further, the Spinachitina fossensis and Bursachitina umbilicata (as Bursachitina sp. 1 in Vanmeirhaeghe and Verniers, 2004) Avalonian biozones (defined by Vandenbroucke et al, 2005) were discovered in the upper part of the Bois de Presles Member here (Vanmeirhaeghe and Verniers, 2004). The Baltoscandian Biozones indicate an upper Vormsi to middle Pirgu age for the lowermost sampled to the middle part of the Bois de Presles Member.…”

“…The Baltoscandian Biozones indicate an upper Vormsi to middle Pirgu age for the lowermost sampled to the middle part of the Bois de Presles Member. Correlation with the biozones of the Avalonian type Ashgill area (Vandenbroucke et al, 2005) provided a Cautleyan to Rawtheyan age for the studied part of the Bois de Presles Member.…”