Upper Cretaceous radiolarians reworked in the Eocene London Clay Formation, SE England

Tom Fer,Taniel Danelian,Haydon W Bailey

doi:10.1144/jmpaleo2014-033

Abstract

Radiolarians were recently discovered in the lower Eocene London Clay Formation of the London Basin from samples in a drainage borehole in the River Thames. They come from a c. 10 m thick sequence of silty shales in the lower part of the formation. The radiolarians are, in general, rather poorly preserved, with the exception of six samples that yielded moderately preserved radiolarians that allowed the identification of eighteen taxa. All radiolarians observed are of Late Cretaceous age and they are therefore reworked into the lower part of the Eocene London Clay Formation. The best preserved sample yielded an assemblage of twelve morphospecies, including Diacanthocapsa ovoidea , Theocapsomma amphora and Theocapsomma sp. aff. T . amphora sensu Popova-Goll et al. 2005, suggesting an original Santonian–Campanian age, and more likely only the Campanian. However, the stratigraphic origin of these radiolarians from the Upper Cretaceous sequence of the London Basin is uncertain.

Highlights

Over the last 20 years a large number of taxonomic and biostratigraphic studies have been devoted to Cretaceous radiolarians from Europe, but the majority of them concern Tethyan basins in Spain and Italy (Jud 1994; O’Dogherty 1994), Montenegro (Gorican 1994), Greece (Danelian et al 2002; Danelian 2008), Poland (Bak 1995, 1996; Bak & Sawlowicz 2000) and the Czech Carpathians (Smreckova 2011)
Cretaceous radiolaria from the NW European and Boreal realm are much less well known; the few data available come from the Danish Trough, where radiolarians have been described from Coniacian to Santonian sequences (Packer & Hart 2005)
In the UK, rare radiolarians were reported at the end of the nineteenth century (Rüst 1888; Hill & Jukes-Browne 1895; Holmes 1900) from the Upper Cretaceous, mainly Turonian, chalk (Melbourn Rock) of the London Basin (Fig. 1), but there is no modern taxonomic study

Summary

Introduction

Over the last 20 years a large number of taxonomic and biostratigraphic studies have been devoted to Cretaceous radiolarians from Europe, but the majority of them concern Tethyan basins in Spain and Italy (Jud 1994; O’Dogherty 1994), Montenegro (Gorican 1994), Greece (Danelian et al 2002; Danelian 2008), Poland (Bak 1995, 1996; Bak & Sawlowicz 2000) and the Czech Carpathians (Smreckova 2011). In the UK, rare radiolarians were reported at the end of the nineteenth century (Rüst 1888; Hill & Jukes-Browne 1895; Holmes 1900) from the Upper Cretaceous, mainly Turonian, chalk (Melbourn Rock) of the London Basin (Fig. 1), but there is no modern taxonomic study. They come from the London Clay Formation (Fig. 2), which is Ypresian (early Eocene) in age and rather rich in microfossils where they are preserved. The Eocene Harwich Formation overlies the Lambeth Group; it is mainly composed of sand, clayey sand and pebbles This thin formation is overlain by the Ypresian London Clay Formation which is composed of brownish clay and silty clay 90–130 m thick (Ellison et al 2004). It is in the London Clay Formation that radiolarians were found during this study

Methods

Discussion

Conclusion