Late Jurassic (Kimmeridgian-Tithonian) stable isotopes (delta O-18, delta C-13) and Mg/Ca ratios: New palaeoclimate data from Helmsdale, northeast Scotland

The data presented here provide the first detailed stable isotope (delta O-18, delta C-13) and geochemical (Mg/Ca) investigation of Kimmeridgian-Tithonian belemnites from the Helmsdale Coast, Scotland, UK Oxygen and carbon stable isotope values from well preserved specimens range from 28 to + 0 3 parts per thousand and from 2 3 to + 2 8 parts per thousand. respectively. The oxygen isotope data are consistent with palaeotemperatures of up to 24 degrees C in the Early Kimmeridgian cymodoce Zone and down to 11 degrees C in the Mid Tithonian rotunda-fittom Zones. These estimates are strongly supported by the Mg/Ca data, which also indicate a cooling episode (and very similar palaeotemperatures. 11-22 degrees C) at this time. The cooling event is associated with an approximately 5 parts per thousand decline in delta C-13 ratios This shift towards more negative delta C-13 values has also been recorded in the Tethys and on the Russian Platform, confirming that this event was of global origin Such globally synchronous records can provide a valuable tool for stratigraphic correlation. The Helmsdale delta C-13 data are therefore combined here with other published belemnite isotope data from the Jurassic of Scotland (from the Callovian-Kimmeridgian of the Isle of Skye and the Toarcian-Aalenian of Raasay) The resultant belemnite delta C-13 curve provides a detailed record of the Toarcian-Tithonian British Boreal Realm that can be compared with coeval records to investigate regional differences in Jurassic carbon isotope stratigraphy (C) 2010 Elsevier B.V. All rights reserved