Lower Jurassic (Hettangian–Pliensbachian) microfossil biostratigraphy of the Ballinlea-1 well, Rathlin Basin, Northern Ireland, United Kingdom

Boomer, Ian; Azmi, Azrin; Copestake, Philip; Raine, Robert. 2021 Lower Jurassic (Hettangian–Pliensbachian) microfossil biostratigraphy of the Ballinlea-1 well, Rathlin Basin, Northern Ireland, United Kingdom. Proceedings of the Geologists' Association, 132 (6). 657-666. https://doi.org/10.1016/j.pgeola.2020.06.002

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Official URL: http://dx.doi.org/10.1016/j.pgeola.2020.06.002

Abstract/Summary

The thickest section of Early Jurassic strata known from onshore Ireland (total Jurassic thickness 566 m) is reported from the Ballinlea-1 well (Rathlin Basin) situated on the north coast of Northern Ireland. A biostratigraphical and palaeoenvironmental assessment is presented for this section largely based on calcareous benthic microfossils (foraminifera and ostracods). The Early Jurassic Waterloo Mudstone Formation (Lias Group) of Northern Ireland has previously received little micropalaeontological attention, therefore this work provides an opportunity to enhance palaeogeographic and palaeoenvironmental understanding for the Early Jurassic of the province, and this paper illustrates the key microfossil taxa of this age from Ireland for the first time. The records, based on ditch-cuttings samples, demonstrate a stratigraphical range from Hettangian to Early Pliensbachian, consistent with other wells and boreholes in this basin. The assemblage compositions are comparable to those elsewhere in the European boreal Atlantic realm. Hettangian to earliest Sinemurian microfossil assemblages are generally of low diversity and are numerically dominated by metacopid ostracods with occasional influxes of foraminifera. Gradually, foraminiferal abundance (often dominated by species of the Lagenida) come to exceed those of the ostracods in the Early Sinemurian reaching their greatest diversity in the Late Sinemurian. The sediments are considered to represent an inner to mid-shelf environment throughout while the record thickness for this region indicates ongoing syn-sedimentary fault movement along the basin margins within this period.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.pgeola.2020.06.002
ISSN:	00167878
Date made live:	06 Oct 2020 11:43 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/528643

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.pgeola.2020.06.002

ISSN:

00167878

Date made live:

06 Oct 2020 11:43 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/528643