Contribution
Palynological, geochemical, and mineralogical characteristics of the Early Jurassic Liasidium Event in the Cleveland Basin, Yorkshire, UK
Hesselbo, Stephen P.; Hudson, Alexander J.L.; Huggett, Jenny M.; Leng, Melanie J.; Riding, James B.; Ullmann, Clemens V.
Newsletters on Stratigraphy Volume 53 Number 2 (2020), p. 191 - 211
publié: Mar 25, 2020
publication en ligne: Jun 29, 2019
manuscrit accepté: Mar 21, 2019
révision final du manuscrit reçu: Mar 19, 2019
révision du manuscrit demandée: Feb 4, 2019
manuscrit reçu: Jan 2, 2019
Open Access (article peut être télechargé gratuitement)
Abstract
A previously proposed hyperthermal episode in the Early Jurassic (mid-Sinemurian) is investigated from the shallow marine succession at Robin Hood’s Bay, Cleveland Basin, Yorkshire, UK. Palynological study confirms that the stratigraphical extent of the distinctive dinoflagellate cyst Liasidium variabile corresponds very closely to the oxynotum Zone. The range of Liasidium variabile also corresponds to an overall negative excursion in carbon-isotopes measured in bulk organic matter, which here exhibits a double spike in the middle oxynotum Zone. Additionally, Liasidium variabile abundances track overall transgressive-regressive facies trends with peak abundance of dinoflagellate cysts corresponding to deepest water facies and maximum flooding. Lithological cycles (parasequences), defined by visual description and hand-held X-ray fluorescence analysis of powdered samples, match previously suggested short eccentricity cycles, and allow a total duration for the event of at least one million years to be suggested. Changes in clay mineralogy throughout the section determined by whole rock X-ray diffraction and scanning electron microscopy are shown to be largely related to authigenic processes, and neither support nor refute the proposition of coeval palaeoclimate changes. The combined characteristics of the Liasidium Event described from Robin Hood’s Bay are similar to, but much less extreme than, the Early Jurassic Toarcian Oceanic Anoxic Event albeit, at this locality, there is no evidence for the development of significant bottom water deoxygenation.
Mots-clefs
carbon-isotope excursion • Early Jurassic • hyperthermal • Liasidium Event • Liasidium variabile • Yorkshire