Reference : Sedimentary development and correlation of long-term off-reef to shallow-water Devoni...
Dissertations and theses : Doctoral thesis
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
Sedimentary development and correlation of long-term off-reef to shallow-water Devonian carbonate records in Europe
Pas, Damien mailto [Université de Liège > Département de géologie > Pétrologie sédimentaire >]
Université de Liège, ​Liège, ​​Belgique
Docteur en Sciences
Boulvain, Frédéric mailto
Javaux, Emmanuelle mailto
Da Silva, Anne-Christine mailto
Suttner, Thomas
Yans, Johan
Devleeschouwer, Xavier
[en] The Devonian Period was characterized by extensive shallow-marine regions, with the largest carbonate platform development of the Phanerozoic Eon. The research carried out in this thesis integrates field work, petrographic analysis, conodont biostratigraphy, elemental and carbon isotope geochemistry, magnetic susceptibility and magnetic hysteresis measurement. The aim, to better understand and characterize the environmental conditions that led to the development of three of the largest European Devonian carbonate platforms. This multi-disciplinary study also proposes to validate the use of magnetic susceptibility as a reliable tool for palaeoenvironmental reconstruction and long-distance correlation in marine carbonate.

Fieldwork was conducted on four key sections of the European Pre-Mesozoic massifs: the Ardennes (La Thure and Fromelennes-Flohimont), the Rheinisches Schiefergebirge (Burgberg) and the Carnic Alps (Freikofel). The large quantity and in-depth analysis of rock samples and thin-sections has demonstrated the fascinating environmental diversity that shaped the carbonate platforms in the Rhenohecynian and Paleotethys oceans towards the mid-late Devonian times.

The aforementioned analysis has enabled the development of reconstructed sedimentary models and large-scale shallowing-deepening histories for each section. New and published biostratigraphic data provided reliable age constraints for the foremost environmental changes evident in each of the sections. δ13C results from the Frasnian – Famennian boundary in the Burgberg and Freikofel sections have revealed Kellwasser events in limestone lithologies.

Based on the analysis of ±1800 samples, a high-resolution magnetic susceptibility (MS) curve for each section has been developed, highlighting the strong link between the MS signatures and the syn-sedimentary parameters, such as carbonate productivity/sedimentation rate, water agitation and siliciclastic input. The comparison between MS and elemental geochemistry datasets has demonstrated the inherent-parallel link existing between the siliciclastic input proxies and the variation in MS signature in each of the sections. Magnetic hysteresis measurements have shown that ferromagnetic minerals such as magnetite control the MS signal. By comparing our data sets with published data we could confirm that our MS signal is remagnetized. However links between siliciclastic input proxies and MS, and between MS and environmental parameters have proven a relatively good preservation of the primary depositionally-induced MS signal.

Finally, by integrating complete data and establishing a correlation chart including the four long-term MS curves, it is apparent that on a regional scale long-term MS trends can be correlated, as long as the evolution of the main depositional setting in the sections studied remains comparable. The significant impact of syn-sedimentary parameters on the final MS signature seems to obscure the imprint of parameters driving variations in continental erosion (e.g., climate, sea-level and tectonic variations) and therefore limiting the inter-regional correlations. This collaborative project on time-series analysis of long-term high-resolution MS records in the Dinant Syncline has revealed the imprint of astronomical parameters, giving rise to a more accurate estimate of the Givetian Stage’s duration.
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