Hanspeter Funk’s research while affiliated with ETH Zurich and other places

During the Late Barremian and Early Aptian (about 120 million years ago) intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere, and resulted most probably in rising atmospheric carbon dioxide pressure. In order to document the response of the shallow water carbonate-producing communities to this pronounced disturbance of the carbon cycle we studied a Late Barremian to Early Aptian neritic carbonate succession deposited on the northern Tethyan shelf (Swiss Alps). The sedimentological and stable carbon and oxygen isotope records of two sections located along a N–S transect from proximal to more distal shelf environments were investigated. The sediments correspond to outer-, mid-, and inner-ramp deposits of a homoclinal carbonate ramp. Vertical facies variations within the two studied sections feature three progradation phases of the platform. A highly resolved correlation of the shelf sediments with a pelagic succession from the Southern Alps (Northern Italy) is based on both δ13C stratigraphy and biostratigraphy, and indicates that the drowning of the Helvetic carbonate platform coincided with a pronounced calcification crisis of calcareous nannofossils. The biocalcification crisis started before but culminated during the Aptian methane event recorded in a negative carbon-isotope spike. We propose that increased carbon dioxide concentrations in oceans and atmosphere related to volcanic activity and to sudden methane release reduced the marine calcium carbonate oversaturation and the calcification potential of benthic and planktonic organisms. Carbonate-producing shallow water communities on platforms and ramps suffering from additional environmental stress such as extreme temperatures or high nutrient levels could not survive during times of rising sea level, and, as a consequence, carbonate platforms drowned.

A new high-resolution carbon-isotope stratigraphy of the Late Jurassic has been generated from Tethyan carbonate sections. Sections chosen for this study are from the Helvetic nappes of the Swiss Alps, from the Jura Mountains, from the Provence (France) and from the Southern Alps (N. Italy). The limestones and marls used for this isotope geochemical investigation were deposited along the northern (Helvetics, Jura, Provence) and the southern (S. Alps) margin of the Alpine Tethys. Isotope curves were first established in well-dated sections of the Jura Mountains, the Southern Alps and the Vocontian Basin. Isotope curves generated from the poorly dated Helvetic nappe sections could then be correlated with the bisotratigraphically dated sections. This comparison produces greatly improved age control for the Helvetic sections and a more detailed composite δ 13C curve for the Late Jurassic than has been published previously. The composite δ 13C curve features two short-lived negative excursions in the Oxfordian, a δ 13C maximum in the Late Kimmeridgian and steadily decreasing δ 13C values throughout the Tithonian. These δ 13C events are consistent with previous, lower resolution data sets and are valuable tie-points, which can be used for correlating upper Jurassic successions among different lithologies and across different depositional settings. The new carbon isotope record is not only useful as a stratigraphic tool but it records fluctuations in Late Jurassic global carbon cycling. The negative carbon isotope events lasting up to a few 10 5 years are interpreted as primary perturbation signals recording anomalies in the atmospheric and marine carbon reservoirs. The perturbations of the global C-cycle were triggered by a sudden and massive release of methane stored in deep-sea gas hydrates. Positive carbon isotope excursions lasting up to millions of years record changes in carbonate and organic carbon production and sedimentation.

Tectonic evolution of the Alpine Tethys is controlled by the plate movements of Africa, Europe, and the Adriatic microplate. It is, however, unclear to which extent and at what times the motion of Adria was related to Africa. Kinematic models which assume a rigid connection between Africa and Adria have difficulties in explaining the Alpine rock record. Reconstructions based on the Alpine record are, on the other hand, in conflict with the involved kinematics. To resolve these conflicts, they require complicated motions or the introduction of additional microplates. Here we present a solution which is based on a rigid connection between Africa/Adria during Jurassic/Cretaceous times. Our model requires only four plates, involving Africa, Europe, Iberia, and Adria. It describes a self-consistent kinematic evolution of the western Tethyan microplate motions from Jurassic to Miocene times. The initial (Early Jurassic) plate configuration was found by iterative forward modeling. The resulting Jurassic plate configuration is unusual and provides new insights into Alpine geology. The obtained model is, however, in good agreement with the available geological data and suggests that the assumption of independent movements of Adria during Jurassic/Cretaceous times is not a necessity.

The paper distinguishes three different stages in the evolution of the Tithonian (Late Jurassic) to Aptian (Early Cretaceous) northern Tethyan carbonate platform: 1) carbonate production in the coral-oolite mode, 2) carbonate production in the crinoid-bryozoan mode, and 3) platform retrogradation and destruction, condensation, and phosphogenesis. The δ13C stratigraphies obtained from Valanginian-Hauterivian and Aptian-Albian hemipelagic successions beyond the platform correlate well with the Early Cretaceous pelagic δ13C record. -from Authors

In the region of Anzeindaz (Ct. Vaud, Switzerland) the sedimentary succession of the so-called "Urgonian" of the Schrattenkalk Formation (late Barremian to early Aptian in age) and of the Garschella Formation (early Aptian to late Cenomanian in age) is well developed. These outcrops in the helvetic Morcles nappe are particularly appropriate to study the drowning events that lead to the disappearance of the urgonian carbonate platform and the subsequent development towards a sedimentary regime of condensation and authigenesis. Cavities with infillings of Garschella Formation sediments penetrating the Schrattenkalk limestone up to 20 meters deep are interpreted as karstic erosional cavities and/or neptunian dikes. The most interesting finding was the special way in which the drowning of the urgonian carbonate platform is documented. At one outcrop (La Corde) thin relics of a bed interpreted as the Upper Orbitolina Bed seem to be integrated in the Garschella Formation since it separates relics of at least two phosphoritic beds, probably the Luitere Bed but also an older bed that was not described by Föllmi and Ouwehand (1987). In fact a diploma student at the University of Neuchâtel, François Gainon (2001) just recently rediscovered and correctly interpreted a similar but less condensed succession in the nearby Rawil region that was first described (but misinterpreted) by Schaub (1936). Gainon named this older phosphoritic horizon of the Rawil region "Plaine Morte Bed" and he was able to date it with an ammonite of the earliest Aptian Weissi/Tuarkyricus Zones. In both the Rawil and Anzeindaz regions the whole ensemble is deposited over an erosive unconformity cutting off the Schrattenkalk limestone. The sedimentary succession of the Garschella Formation in the Anzeindaz region contains equivalents of nearly all beds described and defined in the type outcrops of eastern Switzerland and Austria (Föllmi &Ouwehand 1987). The study of these sediments revealed new evidence for sedimentary processes related to condensation and authigenesis, especially cyclic processes comparable to Baturin Cycles. These observations allow for new interpretations about the character of the original sediment and the concept of condensation.