Platform-induced clay-mineral fractionation along a northern Tethyan basin-platform transect: implications for the interpretation of Early Cretaceous climate change (Late Hauterivian-Early Aptian)

Abstract

Kaolinite Climate change Early Cretaceous Carbonate platform Jura Mountains Vocontian Trough a b s t r a c tHigh-resolution clay-mineral analyses were performed on upper Hauterivian to lower Aptian sediments along a platform-to-basin transect through the northern Tethyan margin from the Neuchâtel area (Switzerland), to the Vocontian Trough (France) in order to investigate links between climate change, carbonate platform evolution, and fractionation patterns in clay minerals during their transport. During the Hauterivian, the northern Tethyan carbonate platform developed in a heterozoan mode, and the associated ramp-like topography facilitated the export of detrital material into the adjacent basin, where clay-mineral assemblages are dominated by smectite and kaolinite is almost absent, thereby suggesting dry-seasonal conditions. During the Late Hauterivian Balearites balearis ammonite zone, a change to a more humid climate is documented by the appearance of kaolinite, which reaches up to 30% of the clay fraction in sediments in the Vocontian Trough. This prominent change just preceded the Faraoni Oceanic Anoxic Event and the onset of the demise of the Helvetic Carbonate Platform, which lasted to the late early Barremian. From the Late Barremian onwards, the renewed growth of the northern Tethyan carbonate platform in a photozoan mode and the associated development of a marginally confined platform topography fractionated the clay-mineral assemblages exported into hemipelagic settings: kaolinite particles were preferentially retained in proximal, platform settings, due to their size and their relatively high specific weight. In the inner platform environment preserved in the Swiss Jura, an average of 32% of kaolinite in the clay fraction is observed during the latest Barremian-earliest Aptian, whereas clay-mineral assemblages of coeval sediments from deeper depositional settings are dominated by smectite and show only minor amounts of kaolinite. This signifies that besides palaeoclimate conditions, the morphology and ecology of the carbonate platform had a significant effect on the distribution and composition of clay assemblages during the Late Hauterivian-Early Aptian along the northern Tethyan margin.

Reconciling strontium-isotope and K–Ar ages with biostratigraphy: the case of the Urgonian platform, Early Cretaceous of the Jura Mountains, Western Switzerland

“…The ages discussed here are conform with recently published dating obtained both by ammonite and nannofossil biostratigraphy, sequence stratigraphy, the correlation of platform drowning pattern in the western Swiss Jura with that of the well-dated Helvetic platform succession, and trends in kaolinite and phosphorus contents (Godet et al 2008(Godet et al , 2010. Especially the age for the onset of the Urgonian platform (middle Late Barremian) seems compatible with similar ages in the Helvetic realm (Bodin et al 2006b;Föllmi et al 2007) and southeastern France (Arnaud et al 1998;Arnaud 2005).…”

Bridging the Faraoni and Selli oceanic anoxic events: late Hauterivian to early Aptian dysaerobic to anaerobic phases in the Tethys

“…This time period is characterised by increasing P burial rates and generally high kaolinite depositional rates (Fig. 10), which may indicate continuing humid climate conditions, with an increasing tendency towards the end of the early Barremian (Deconinck and Bernoulli, 1991;Godet et al, 2008). The δ 18 O records in Italy and France show a tendency towards heavier values relative to the late Hauterivian (Sprovieri et al, 2006;Godet et al, 2006;Bodin et al, 2009;Stein et al, 2011), whereas the French belemnite record is characterised by a trend towards lighter values for most of the early Barremian (Bodin et al, 2009;Fig.…”

“…Even if the kaolinite record does not show a change in the Vocontian basin record, increases have been established on the adjacent carbonate platform (Godet et al, 2008;Stein et al, 2012). This phase is followed by a decrease in organiccarbon burial and a second episode in Urgonian platform build up.…”

“…The late Hauterivian is characterised by a minimum in the Italian δ 18 O whole-rock record ( Fig. 10; Weissert and Erba, 2004;Godet et al, 2006;Bodin et al, 2009) and the onset in kaolinite deposition (in southeast France, Godet et al, 2008;Fig. 10;cf.…”

“…From left to right: calculated laminated mudstone layer density for the Breggia and Capriolo sections; estimated laminated mudstone layer density for the Gorgo a Cerbara section using the stratigraphic logs from Gorin and Fiet (2000) and Stein et al (2011); occurrence of laminated mudstone layers in the Lower Saxony Basin: the Barremian and Aptian occurrences are from the basin margin (Mutterlose et al, 2010) and the Hauterivian occurrence from the basin centre (Mutterlose et al, 2009); evolution of the Helvetic segment of the northern Tethyan carbonate platform (modified after Föllmi et al, 2007); δ 13 C record on whole-rock carbonate, from the Cismon outcrop and Cismon Apticore (Menegatti et al, 1998;Erba et al, 1999); low-resolution phosphorus burial record (Föllmi, 1995;Bodin et al, 2006a); δ 18 O records from whole-rock carbonate from central Italy (in green; Sprovieri et al, 2006;Stein et al, 2011) and southeast France (in red; Godet et al, 2006;Bodin et al, 2009) and δ 18 O record from belemnites from southeastern France (in blue; Bodin et al, 2009); and kaolinite record from southeastern France (Godet et al, 2008). contents; Bodin et al, 2006aBodin et al, , 2007. The Faraoni anoxic episode coincides also with important evolutionary change in rudists (Masse and Fenerci-Masse, 2008), ammonite faunas (Hoedemaeker and Leereveld, 1995;Company et al, 2005), planktonic foraminifera (Venturati, 2006), radiolaria (O'Dogherty andGuex, 2002;De Wever et al, 2003), and calcareous nannofossils (Company et al, 2005;Tremolada et al, 2009).…”