Waterloo Bay, Larne, Northern Ireland: a potential GSSP for the base of the Jurassic System

• Autorzy: Simms M. , Jeram A.
• Konferencja: International Congress on the Jurassic System (7 ; 06-18.09.2006 ; Kraków, Poland)
• Języki publikacji: EN

Abstrakty

EN

Northern Ireland is the type area for two basal Jurassic ammonites, Psiloceras sampsoni (Portlock 1843) and Caloceras intermedium (Portlock 1843). However, with its small and patchy exposures of Triassic and Jurassic strata the region has subsequently been largely overlooked compared with sites in SW England. A foreshore section at Waterloo Bay, Larne, on the east coast of Northern Ireland, exposes an almost uninterrupted succession from the upper part of the Mercia Mudstone Group (Triassic, Norian) through to the Bucklandi Zone of the Lias Group (Jurassic, Sinemurian). Recent study has established that the boundary section here is superior in many respects to that at St. Audrie's Bay, SW Britain, a long-standing candidate GSSP for the base of the Jurassic System. What has the Larne section to offer? 1. Exceptionally thick succession across the Triassic/Jurassic boundary. The boundary succession is significantly thicker, and deposition demonstrably more continuous, at Larne than anywhere else in NW Europe. 2. Potential biohorizon stratotypes for the Planorbis Zone. Clearly definable biohorizons can be recognised for Psiloceras erugatum, Neophyllites imitans, N. antecedens, Psiloceras planorbis/sampsoni and P. plicatulum. This site would make an ideal stratotype for the first three of these, for which currently no surface stratotypes are proposed (Bloos & Page 1998). Ammonites are very common in this section, and preservation by pyrite, or in nodules, is often excellent. 3. Diverse non-ammonite macro- and microfauna, already partly documented. A rich fauna of bivalves, gastropods, echinoids, crinoids, trace-fossils and occasional vertebrates are present at this site. Preliminary stratigraphic distribution of the fossil macrofauna, and of palynomorphs, through correlative strata in the nearby Larne borehole has already been published (Ivimey-Cook 1975; Warrington & Harland 1975). 4. Potential for correlation. Sedimentary cycles, of two orders, are clearly developed here. Combined sequence and cyclostratigraphic analysis indicates that the cycles reflect eustatic fluctuations, and therefore have significant potential for global correlation. A major seismite unit and associated desiccation-cracked bed in the Penarth Group provides an important datum correlated across the UK (Simms 2003).

Słowa kluczowe

EN

Triassic; Jurassic; ammonites; stratotypes; biohorizons

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Volumina Jurassica
• Rocznik: 2006
• Tom: Vol. 4, no. 1
• Strony: 297--298
• Opis fizyczny: Bibliogr. 4 poz.

Twórcy

autor

Simms M.

autor

Jeram A.

• Department of Geology, Ulster Museum, Botanic Gardens, Belfast BT9 5AB, Northern Ireland,

Bibliografia

• 1. Bloos G. and Page K. N. 1998. The basal Jurassic ammonite succession in the North-west European Province - Review and new results. Georesearch Forum, 6: 27-40.
• 2. Ivimey-Cook H. C. 1975. The stratigraphy of the Rhaetic and Lower Jurassic in east Antrim. Bulletin of the Geological Survey of Great Britain, 50: 51-69.
• 3. Simms M. J. 2003. Uniquely extensive seismite from the latest Triassic of the UK: Evidence for bolide impact? Geology, 31: 557-560.
• 4. Warrington G. and Harland R. 1975. Palynology of the Trias and Lower Lias of the Larne borehole. Bulletin of the Geological Survey of Great Britain, 50: 37-50.