RICERCA ITALIANA     

A multiproxy approach to the study of environmental changes: numerical simulation of sedimentary wedges evolution during the two global extintion events at the P-T and Fr-Fm boundaries, time-constrained and calibrated by the faunal dynamics

Università degli Studi di Bologna

Abstract

The main goal of the multidisciplinary research is quantitative evaluation of important climate-forced parameters (i.e. sea-level curve) which changed as a consequence of global environmental changes during two of the "Big Five" events: the Permian-Triassic (P-T) and the Frasnian-Famennian (Fr-Fm) global extinction events. Both are elegantly expressed in stratigraphic sequences in the Southern Alps.
We will model the architecture of P-T and Fr-Fm sedimentary wedges using a physically-based, parameter-rich model ("Basin"), calibrated by good regional stratigraphic data.
Analysis of the P-T boundary will be a pilot study, taking advantage of availability of a rich dataset on lithostratigraphy and facies, occurring as a near-continuum over a large area (Southern Alps), and well represented by the Bulla section.
In this work we plan to use conodonts and associated fossil groups such as palynomorphs for detailed analysis of evolutionary patterns of conodonts and associated fossil groups in relation to the pattern of environmental change. Interpretation of faunal dynamics in the investigated sequences will be based on taxonomic, biostratigraphic and sedimentologic data. Isotopic data from carbonate matrices and organic matter—specifying changes in ocean chemistry— will provide an additional dimension to the palaeontologic and sedimentologic data.
The modelling will be constrained by chronostratigraphic (radiometric dating) and palaeomagnetic data >>>

Principal Investigator

Enzo FARABEGOLI Università degli Studi di BOLOGNA

Research Objectives

-The main goal is to quantitatively evaluate some of the climatic parameters which showed pronounced variation before. during and after the major global extinction events associated with the Permian-Triassic (P-T) and Frasnian-Famennian (Fr-Fm) boundaries

First Results

-Sampling and measurement of stratigraphic sections at the Frasnian-Famennian and Permian-Triassic boundaries.

-Preparation of samples collected in continuum - providing polished slabs and thin sections for microfacies and diagenesis analyses as

Timescale

24 months

National and international background

Historically the boundaries of the main chronostratigraphic intervals of the geological time-scale were made to coincide with phases of extinction and/or rapid increase of taxonomic diversity. Changes in biodiversity, when seen in detail, are complex. Qualitative and quantitative studies of variation at low taxonomic level and on local or regional scale are necessary to verify how they fit in with or depart from gross global trends, and how they relate to changes in environmental parameters (climate, sea-level fluctuations, volcanic activity, tectonics, and oceanic circulation) (Valentine 1985, Signor 1990).
Conodonts, as prominent components of the Palaeozoic fauna, are known to reflect major changes in biodiversity (Sweet, 1988).
Five grand-scale extinction events (the "Big Five") have been discriminated within the Phanerozoic. These include the major biological crises at the Frasnian-Famennian (Fr-Fm) and Permian-Triassic (P-T) boundaries. A plethora of global causes have been postulated for these events and other life crises, among them transgression-regression events, climate change connected with orbital variations, tectonics, massive volcanism, and extraterrestrial causes (meteorites, comets). The last has been the ruling hypothesis for the massive extinction event at the Cretaceous-Paleocene boundary.
The Late Devonian extinction at the Frasnian-Famennian (Fr-Fm) boundary has been intensively investigated, particularly in the last decade (House >>>