Orogen Project Integrated: Learnings & Perspectives
Author: Emmanuel Masini, M&U
Questions & Answers
The succession of these orogenic stages is not random and follow a logical order what defines a “lifecyle”. From this point of view, any orogenic system is getting mature through time going across “maturity” stages and critical events. Present-day orogenic systems can be representative of different maturity stages as far orogenesis can stop prematurely if plate convergence stops. This can explain part of the observed worldwide diversity of mountain belts. The same “maturity” concept can also apply to the pre-orogenic divergence evolution that precedes the formation of an orogen by convergence. Different maturity stages can also be defined from early continental rifts to mature oceanic basins. In the OROGEN research program, we propose that the combination of the divergence and convergence maturity of an orogenic system defines the “OROGENIC ID” of a mountain belt in a new “genetic” orogenic nomenclature – Oro-genetics -. We further think that the first order geological characteristics of an orogenic system can be predicted from its determined “Orogenic ID”.
1) How can we determine the orogenic track of an orogenic system depending on its divergence and convergence maturities (what we refer as the “Oro-genic ID”).
2) How does the orogenic track impact the development / preservation / distribution of a petroleum system (i.e. which oro-genic ID applies).
To solve question 1, surface/sub-surface geological data is required to determine at what divergent and convergent maturities the plate boundary stopped during the last “Wilson Cycle”. The key observations that enable to determine the Orogenic IDs will be provided within the OROGEN “head paper” to be released before the end of the year. An algorithm to tackle this is in development at M&U.
Question 2 cannot be solved before obtaining the answer to question 1. Then, each parameter of a petroleum system needs to be linked with the genesis of the orogenic system. The maturity stage at which it develops, the tectonic domain at which it deposits and what tectonic domains were destroyed by orogenesis until present-day. This approach provides keys to predict where a layer of rock was deposited and what overprints may have suffered after its deposition during the different tectonic domains of the orogen.
Thus, this approach is focused on determining the consequences that the different tectonic stages have for the development, preservation and potential destruction of a petroleum system.
An alternative way to get an image of the pre-collisional topographies is to study fossilized example of early orogenic systems that failed to reach a mature collision. In the Pyrenean system, the best example may be the present-day Basque belt as suggested by Ducoux et al. (2019) and Mirò et al (2020, PhD). These authors suggest that this part of the Pyrenean system never reached a mature collisional stage and stopped while inverting the rift (until the necking zone). Present-day (and Cenozoic) topographies are not related to crustal overthickening (collision) but rather due to the thin-skinned shortening of Meso-Cenozoic rocks above a near top-basement salt décollement. This would correspond to expectations as reliefs for this transitional orogenic phase.
You can use the contact form HERE to make comments or ask additional questions. We will be delighted to answer here shortly!
M&U, all right reserved / Last Edits: March 2021
Masini, E. (2021, March). Orogen Project Integrated: Learnings and Perspectives. Retrieve from http://mandu-geology.fr/?page_id=869