Abstract
Abstract. This paper documents a warming event across the middle–upper Albian interval in a ∼ 22 m long section from the Gault Clay Formation of Copt Point, Folkestone (UK). Evidence for the event comes from three independent datasets: calcareous nannofossils, ammonites, and the bulk sediment carbon and oxygen stable isotope record, which collectively indicate a brief period (∼ 500 kyr) of significant surface water warming (in excess of 6 ∘C) at around 107.5 Ma (the base of the Dipoloceras cristatum Ammonite Zone). A surface water productivity increase based on high percentages of the eutrophic nannofossil Zeugrhabdotus noeliae is found to be concomitant with this warming event, suggesting that surface waters were nutrient-rich and the warming was associated with increased precipitation and run-off, delivering more nutrients into the basin.
Highlights
The Albian stage (12.5 Myr duration; Ogg and Hinnov, 2012) is broadly characterized by global warming, rising sea levels, and greenhouse climates
The Gault Clay samples are middle to late Albian in age and can be assigned to Nannofossil Zone BC24 through Subzone BC25b of Bown et al (1998), based upon the following events in stratigraphic order (Fig. 3, Table S1): (i) presence of Tranolithus orionatus in the lowest sample (1.6 m); (ii) the FO of Axopodorhabdus albianus in the sample at 3.6 m; (iii) the LO of Ceratolithina bicornuta in the sample at 9.0 m; and (iv) the absence of Eiffellithus monechiae and E. turriseiffelii in the samples
A minor hiatus at the middle–upper Albian boundary based on missing ammonite zones and subzones likely represents less than 10– 20 kyr but is not apparent in the nannofossil biostratigraphy, which includes subzone BC25a–BC25b at this level (Bown et al, 1998)
Summary
The Albian stage (12.5 Myr duration; Ogg and Hinnov, 2012) is broadly characterized by global warming, rising sea levels, and greenhouse climates. Our understanding of Albian palaeoclimates largely comes from studying short-term perturbations in the global carbon cycle, known as oceanic anoxic events 1b, 1c, and 1d (e.g., Leckie et al, 2002; Galeotti et al, 2003; Giraud et al, 2003; Herrle et al, 2003, 2004; Jenkyns, 2010; Coccioni et al, 2014) using geochemical data (carbon and oxygen isotopes) and often related to biotic turnovers among marine planktonic and benthic organisms from pelagic deep-sea drilling sites and/or the proto-North Atlantic and western Tethys epicontinental basins (e.g., Erbacher et al, 1999; Herrle and Mutterlose, 2003; Watkins et al, 2005; Wagner et al, 2007, 2008; Huber and Leckie, 2011; Friedrich et al, 2012).
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