Paleoceanographic changes during the early Cretaceous (Valanginian–Hauterivian): evidence from oxygen and carbon stable isotopes
Introduction
During the late Jurassic and early Cretaceous, a carbonate platform of considerable extent developed along the northern Tethyan margin [1], [2]. The evolution of this platform system was punctuated by several phases of platform drowning, most notably during the late early Valanginian to early Hauterivian, and the Aptian. Within the sections preserved in the Helvetic Zone of the northern Alps, the drowning phases are documented by erosional surfaces, hiati, and condensed glauconitic and phosphatic beds, which have been described in numerous publications [1], [2], [3], [4], [5], [6], [7], [8], [9].
The large drowning unconformities formed during the late early Valanginian to early Hauterivian (D1 in [2]), the late early to early late Aptian (D4), and latestmost Aptian to earlymost Albian (D5) correspond in time to major positive excursions in the stable carbon isotope record [10], [11]. This correlation was used to propose a model for the development of the drowning unconformities, which includes major changes in the global carbon budget. In this model, the formation of the large flood basalt provinces at Paraña, Kerguelen, and especially Ontong Java is inferred to have led to major increases in atmospheric CO2 during the Valanginian and Aptian, thereby triggering a row of negative feedback mechanisms, which led to a decrease in atmospheric CO2 contents. These mechanisms include increases in rates of continental biogeochemical weathering, mobilization of nutrients and especially phosphorus, productivity and sedimentary burial of organic matter, whereas the rates of carbonate production were decreased leading to phases of widespread platform drowning and phosphogenesis [2], [11].
Since the publication of this model, new age models have been developed for several key areas and further detailed studies have been accomplished in the area of platform deposition [8], [12]. During these studies, the following subjects were shown to be critical and in need of further elaboration:
Section snippets
Correlation between the Helvetic realm and other regions
Whereas the drowning unconformities are well expressed in the Helvetic realm, they are less well traceable in more proximal areas, such as the Jura Mountains in western Switzerland and eastern France, and more distal areas, such as the Vocontian Trough. This is due to the prevalence of erosional processes during the drowning phases in the proximal areas and to the deposition of more complete, hemipelagic sections in the distal areas, beyond the platform margin (e.g., [1], [8]). Correlation of
The Hauterivian
The sections from which we sampled material for stable carbon and oxygen isotope analyses are exposed in southeastern France, in the region near Digne-les-Bains (Alpes de Haute Provence) and Nyons (Drôme, Fig. 1C). The sediments sampled for this stable isotope study were deposited along the western margin of the Tethys in a narrow inlet, known as the Vocontian Basin (Fig. 1A,B).
The lithology consists of alternations of hemipelagic calcareous marlstones and micritic limestones. In addition to
Methods
Stable carbon and oxygen isotope analyses were performed on bulk rock samples from the limestone intervals and on belemnites mostly from the marly intervals for all four sections. The whole rock samples were taken from fresh outcrops; powder was drilled out of the micritic matrix, avoiding bioturbation fabrics. The belemnites were cleaned in 1% HCl and cut along the alveolic line if their size allowed for this. Powder was drilled avoiding the outside laminae and the alveolus, because it has
Carbon and oxygen stable isotopes
The data obtained by Hennig et al. [12] for the Vocontian Basin show that the Valanginian positive carbon isotope excursion commences in the Campylotoxus Zone, and reaches its maximum in the earliest late Valanginian (Verrucosum Zone, +2.5‰). During the late Valanginian δ13C values gradually decrease. Our study indicates that δ13C values derived from bulk rock material decrease further to reach a minimum at the early-late Hauterivian boundary (Nodosoplicatum Zone, +0.59‰), after which they
Conclusions
It seems that every phase of platform drowning has to be viewed in the light of its own set of paleo-environmental controls. The model established for the Valanginian and Aptian platform drowning events [2], [11] does not necessarily apply to the Hauterivian and Albian. The early Valanginian carbonate platforms suffered from widespread regression and the shedding of siliciclastics onto the shelf. Organic carbon was stored in coastal and continental settings. The transgression that followed
Acknowledgements
We are greatly indebted to Thierry Adatte for fruitful discussion and improvement of the manuscript. We also would like to thank Sebastian Ryser of the University of Neuchâtel for performing the AAS analyses. Jan Veizer and Gregory Price are thanked for reviewing this paper and for making useful comments.[AH]
References (47)
- et al.
Correlation of Early Cretaceous carbon isotope stratigraphy and platform drowning events; a possible link?
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1998) - et al.
Palaeotemperatures indicated by Upper Jurassic (Kimmeridgian–Tithonian) fossils from Mallorca determined by oxygen isotope composition
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1994) - et al.
‘Warm’ palaeotemperatures from high Late Jurassic palaeolatitudes (Falkland Plateau); ecological, environmental or diagenetic controls?
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1997) High northern palaeolatitude Jurassic–Cretaceous palaeotemperature variation; new data from Kong Karls Land, Svalbard
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1997)- et al.
Oxygen isotope composition of Upper Cretaceous chalk at Laegerdorf (NW Germany); its original environmental signal and palaeotemperature interpretation
Cretaceous Res.
(1991) - et al.
The Barremian–Aptian arid phase in Western Europe
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1990) - et al.
3-D, 40Ar–39Ar geochronology in the Parana continental flood basalt province
Earth Planet. Sci. Lett.
(1996) - H.P. Funk, K.B. Föllmi, H. Mohr, Evolution of the Tithonian–Aptian Carbonate Platform along the Northern Tethyan...
- et al.
Phosphogenesis, carbon-isotope stratigraphy, and carbonate-platform evolution along the Lower Cretaceous northern Tethyan margin
Geol. Soc. Am. Bull.
(1994) - A. Heim, Monographie der Churfirsten-Mattstock-Gruppe, in: Beiträge zur Geologische karte der Schweiz, Neue Folge,...
Garschella-Formation und Goetzis-Schichten (Aptian–Coniacian); neue stratigraphische Daten aus dem Helvetikum der Ostschweiz und der Vorarlbergs
Eclogae Geol. Helvet.
Der frühkretazische helvetische Schelf im Vorarlberg und Allgäu
Jahrb. Geol. Bundesanst. Vienna
The Valanginian carbon isotope event; a first episode of greenhouse climate conditions during the Cretaceous
Terra Nova
C-Isotope stratigraphy, a calibration tool between ammonite- and magnetostratigraphy: the Valanginian–Hauterivian transition
Geolog. Carpath.
Le cadre stratigraphique du Valanginien superieur et de l’Hauterivien du Sud-Est de la France; definition des biochronozones et caracterisation de nouveaux biohorizons
Geol. Alp.
Diagenesis and construction of the belemnite rostrum
Palaeontology
Chemical signatures of belemnites
Neues Jahrb. Geol. Palaeontol. Abh.
Carbon- and oxygen-isotope stratigraphy of the English Chalk and Italian Scaglia and its palaeoclimatic significance
Geol. Mag.
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