Cretaceous Research xxx (2017) 1e18 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Stratigraphy and ammonite faunas of the Cenomanian rocks of Northern Ireland, UK * A.S. Gale a, , M.J. Simms b, W.J. Kennedy c, d a School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, PO1 3QI, UK b Department of Natural Sciences, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, Co. Down, BT18 0EU, UK c Oxford University Museum of Natural History, Parks Road, Oxford, OX13PW, UK d Department of Earth Sciences, South Parks Road, Oxford, OX1 3AN, UK article info abstract Article history: A re-examination of surviving outcrops of the Cenomanian parts of the Hibernian Greensands Formation Received 31 January 2017 of south and east Antrim in Northern Ireland, together with a revision of the limited ammonite faunas, Received in revised form provide a basis for dating and interpreting the sequence. The lower part of the Belfast Marls Member 24 March 2017 yields an early Cenomanian Mantelliceras dixoni Zone assemblage, whilst other faunal elements suggest Accepted in revised form 25 March 2017 the upper part extends into the lower part of the middle Cenomanian. The succeeding Islandmagee Available online xxx Siltstones Member yields the index species of the middle Cenomanian Acanthoceras rhotomagense and A. jukesbrownei zones. The Collinwell Sands Member is in part, or whole, of late Cenomanian age on the Keywords: Cretaceous basis of the occurrence of the benthic foraminiferan Orbitolina. The erosion surface at the base of the fl Antrim Belfast Marls Member corresponds to the Ce3 maximum ooding surface recognised in the Anglo-Paris Hibernian Greensands Basin; the erosion surface at the base of the Islandmagee Siltstones to the Ce4 maximum flooding surface and the erosion surface at the base of the Collinwell Sands Member to the sub-plenus erosion surface at the base of the late Cenomanian Metoicoceras geslinianum Zone. © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). 1. Introduction (1982), who provided further details. Here we give detailed ac- counts of the three surviving sections, and supply an illustrated Cenomanian strata in Northern Ireland are restricted to south revision of the ammonite faunas. On this basis we discuss the and east Antrim, and crop out between Collinwell and Glenarm dating of the sequence in terms of the standard early and middle (Fig. 1). They form a thin, highly condensed succession, up to 20 m Cenomanian ammonite zonation developed in western Europe in thickness and comprising the lower part of the Hibernian (Fig. 3), and detailed knowledge of the stratigraphical distribution Greensands Formation, which underlies the Ulster White Lime- of non-ammonite elements of the fauna based on the records from stone Formation. The Hibernian Greensands have been divided into the ‘Lower Chalk’/Grey Chalk Subgroup of southern England three members (Fig. 2; see Griffith and Wilson, 1982). There are (Kennedy, 1969; Gale, 1990, 1995; Kennedy and Gale, 2006). currently outcrops at three localities; Collin Glen, Cloghfin Port and Detailed logs of the sections at Collin Glen, Clogfin Port and Port- Portmuck (Fig. 1). Early studies on the Cretaceous successions of muck are illustrated in Figs. 4, 5 and 6, respectively. Northern Ireland were reviewed by Tate (1865), who noted the presence of Ammonites varians (¼ Schloenbachia varians) in what he 2. Description of the sequence termed the Glauconitic Sands. The most significant subsequent account is that of Hancock (1961), who noted all of the Cenomanian 2.1. Belfast Marls Member ammonites then known from the sequence in his account of the Cretaceous System in Northern Ireland. There is a general review in This unit (Fig. 2), formerly known as the Glauconite Sands Wilson (1972), and a more detailed one in Griffith and Wilson (Hancock, 1961) comprises 2e3 m of dark, highly glauconitic, strongly bioturbated sandy clay, resting unconformably upon Triassic and Lower Jurassic strata; the basal part contains small * Corresponding author. quartz pebbles, while small phosphatic pebbles are present E-mail address: [email protected] (A.S. Gale). throughout. The unit is only developed along the outcrop between http://dx.doi.org/10.1016/j.cretres.2017.03.022 0195-6671/© 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Gale, A.S., et al., Stratigraphy and ammonite faunas of the Cenomanian rocks of Northern Ireland, UK, Cretaceous Research (2017), http://dx.doi.org/10.1016/j.cretres.2017.03.022 2 A.S. Gale et al. / Cretaceous Research xxx (2017) 1e18 Fig. 1. Map of the eastern portion of Northern Ireland to show the Cretaceous outcrop. Portmuck and Belfast (Fig. 1). Fossils occur throughout, but are Acompsoceras (Fig. 10AeC, F), together with Mantelliceras commoner in the higher part, being abundant at two named (Figs. 9IeJ; 10D, E) and Mariella (Fig. 7EeF) in the lower part of levels. the Belfast Marls fauna demonstrate that this is of Mantelliceras The first of these is termed the Carr's Glen Ammonite Bed. dixoni Zone age. Hancock (1961) collected composite moulds of the early Cen- The second named level is the Portmuck Oyster Bed. A con- omanian ammonites Schloenbachia, Mantelliceras and Mariella centration of oysters is present between 1.0 and 1.5 m beneath the from a bed in Carr's Glen, which lay close to the (unexposed) base top of the Belfast Marls at Collin Glen and Portmuck, which also of the Belfast Marls; the section is no longer available. A level yields common belemnites, calcitic bivalves and rare brachiopods. 0.6 m above the base of the unit at Collin Glen also yields am- This bed was also exposed in Carr's Glen (Hancock, 1961; material monites, which is thought to be a correlative level; however, they now in the Sedgwick Museum, Cambridge). At Portmuck this are much more poorly preserved there. The presence of yielded: Please cite this article in press as: Gale, A.S., et al., Stratigraphy and ammonite faunas of the Cenomanian rocks of Northern Ireland, UK, Cretaceous Research (2017), http://dx.doi.org/10.1016/j.cretres.2017.03.022 A.S. Gale et al. / Cretaceous Research xxx (2017) 1e18 3 Fig. 2. Litho- and biostratigraphical classification of the Hibernian Greensands Formation. Please cite this article in press as: Gale, A.S., et al., Stratigraphy and ammonite faunas of the Cenomanian rocks of Northern Ireland, UK, Cretaceous Research (2017), http://dx.doi.org/10.1016/j.cretres.2017.03.022 4 A.S. Gale et al. / Cretaceous Research xxx (2017) 1e18 Fig. 3. Ammonite zones and subzones of the lower and middle Cenomanian substages. Amphidonte obliquatum (Pulteney, 1813) (abundant) (M. dixoni Zone) and the lowest occurrence of T. costatus and Entolium orbiculare (J. Sowerby, 1817) (common) Acanthoceras rhotomagense, the Cunningtoniceras inerme Zone Neithea cf. gibbosa (Pulteney, 1813) (2) (Gale, 1995). In fact, it is the only level in the UK in which Cun- Neithea cometa (d'Orbigny, 1847) (1) ningtoniceras inerme is present. A single specimen of C. sp. (group of Oxytoma seminudum (Dames, 1874) common cunningtoni) from Sallagh Braes, Larne (Fig. 10C), may therefore Platythyris squamosa (Mantell, 1822) (1) possibly be from the Belfast Marls, although the matrix is sugges- Praeactinocamax primus (Arkhangelsky, 1912) common tive of the overlying Islandmagee Siltstones. Gryphaeostrea canaliculata (J. Sowerby, 1813) 2.2. Islandmagee Siltstones Member Additional species of bivalve, none of them age diagnostic, were recorded by Griffith and Wilson (1982) from unspecified localities. Formerly known as the Yellow Sandstone (Hancock, 1961), this The co-occurrence of P. primus and common E. orbiculare and unit comprises 5e10 m of well-indurated, poorly glauconitic silt- O. seminudum is strongly suggestive of precise correlation with the stones. On the coast, at Cloghfin Port and Portmuck, they are middle Cenomanian Cast Bed in southern England and its correla- conspicuously rhythmic on the scale of about 1 m, comprising hard tive level in France and Germany, to which P. primus is restricted beds of siltstone alternating with marly intervals. In contrast, they (Gale, 1990, 1995; Wilmsen, 2003; Wilmsen et al., 2007), and in are massive, with a few weak partings, in the inland exposure at which the other two species are abundant. In the Cast Bed, Collin Glen. The rhythms are similar to those developed in the Amphidonte occurs only as a rarity and N. cf. gibbosa is unknown. Lower Chalk of southern England and the hard beds have The Cast Bed, and underlying limestone, yield a fauna of Turrilites conspicuously burrowed tops. Macrofauna can be collected readily costatus Subzone age at Lewes (Sussex) and Folkestone (Kent). If at Cloghfin Port, and includes common serpulids (Rotularia sp.), less this correlation is correct, it suggests that the uppermost 1.5 m of common calcitic bivalves (Entolium sp., Merklinia sp.) and abundant the Belfast Marls are also of Turrilites costatus Subzone age. How- small corals (Micrabacia coronula (Goldfuss, 1826)), at the 6.5 m ever, in southern England, a level with common Cunningtoniceras level. Griffith and Wilson (1982) recorded additional species, spp. occurs between the uppermost occurrence of Mantelliceras including the echinoid Holaster cf. trecensis (Leymerie, 1842), from Please cite this article in press as: Gale, A.S., et al., Stratigraphy and ammonite faunas of the Cenomanian rocks of Northern Ireland, UK, Cretaceous Research (2017), http://dx.doi.org/10.1016/j.cretres.2017.03.022 A.S. Gale et al. / Cretaceous Research xxx (2017) 1e18 5 Fig. 4. The succession at Collin Glen, with possible sequence stratigraphic events indicated (UWLF: Ulster White Limestone Formation).