The Triassic period started more than 250 million years ago and spanned over 50 million years. We spoke to Professor Rossana Martini about her work in studying marine shallow-water (reefal) limestone from this period, and the importance of this research to understanding the biological and ecological changes that occurred during the Triassic.
Delving deep into the Panthalassa Ocean The Panthalassa Ocean covered around 70 percent of the Earth’s surface during the latter part of the Triassic period, an area much larger than the modern Pacific Ocean. The sediments deposited in this immense ocean are therefore the best record of the environmental and biological conditions during the Triassic. As the Principal Investigator of the REEFCADE project, Prof. Rossana Martini has deep expertise in the analysis of rocks and sediments dating from the Upper Triassic, from which new insights can be drawn about the environment and climate during this period. “The idea in the project has been to check the composition of limestone rocks originating in different parts of the world. We have found organisms that allow us to date rocks precisely as from the Upper Triassic,” she says. Much of the previous research on the sedimentary rocks and biodiversity of this period has focused on limestone deposited in the much smaller Tethys Ocean; now researchers aim to gather more information about the Panthalassa, then draw comparisons between deposits of reefal limestone in the two oceans. “This means the most accessible and well preserved limestone deposits that were deposited in the continental plateau during the Upper Triassic,” explains Prof. Martini. REEFCADE project A large number of samples have been gathered from all over the world during the project, including Japan, the Far East of Russia, as well as North and South Americas, which have then been subjected to rigorous analysis. These limestone rock samples were originally deposited in a fairly shallow waters, typically at a depth of less than 150 metres, with Prof. Martini and her PhD students looking for the presence of certain organisms that would allow them to date the rocks as precisely as possible. “I am a specialist in Permian and Triassic small Foraminifera, which are very valuable unicellular organisms to date rocks and specify rock depositional environments. We also use Conodonts, which are small pieces of very old vertebrates resembling eels, which lived in the sea from the Palaeozoic period to the end of the Triassic. Conodonts are also very useful for dating rocks, as they became extinct at the boundary between the Triassic and Jurassic
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Global reconstruction at 220 Ma (Norian) after the Panalesis model (Verard, 2019b); Robinson projection.
periods,” she outlines. By analysing these rocks, and looking at their isotopic composition, researchers hope to identify the different factors that affect how they are distributed and controlled within the oceans. “We have applied the same workflow in all the studied localities in the frame of REEFCADE,” says Prof, Martini. Researchers have conducted in-depth analysis of these rocks, looking for example at their diagenetic features and their chemical
studies also allow us to be more precise about the reservoirs of natural resources, of gas or oil for example,” she continues. The aim now is to bring various different strands of research in the project together and establish a clearer picture of what happened in the huge Panthalassa Ocean during the Upper Triassic period. One of the main goals is to understand how organisms were distributed around the Panthalassa Ocean at this time, a
The idea in the project has been to check the composition of rocks found in different parts of the world. We have found some organisms that allow us to date these rocks precisely as from the Upper Triassic. composition, and trying to gain deeper insights. Along with analysis, Prof. Martini and her research group have spent time out in the field. “We go out into the field, often exploring localities and outcrops for the first time, we collect samples and then we go back to the lab. We proceed to the preparation of the samples, which are very thin slices of rocks, and we look at them in the microscope, to see the components of the rocks and to date their deposition,” she says. This evidence provides a basis for Prof. Martini and her students to then effectively reconstruct the depositional systems during the Upper Triassic period. “We can reconstruct the environment in the past, the ecology at this time. There are also some applications to industry, since these
Upper Triassic - Lower Jurassic reef and carbonate build-up development as recorders of biotic, environmental and climatic changes
Origins of Triassic Foraminifera Researchers have been working to validate this hypothesis for Foraminifera, with many papers and PhD theses written on the subject over the course of the project. However, rather than validating the existing hypothesis, Prof. Martini and her colleagues have found that certain Foraminifera in fact originated in the Panthalassa and then moved towards the Tethys, so the picture is far more complex than had previously been thought. “At that time, there was no sea route to connect the Tethys and the Panthalassa to the West. This connection was established much later with the opening of the North Atlantic Ocean. All the connections, the movement, circulation and palaeocurrents, went from East to West and West to East,” she outlines. More than 25 papers, strictly related to the topics of the REEFCADE project, have been written over the course of the project, and a consistent picture has emerged. “We’ve found a very clear and homogenous frame of what happened in the Panthalassa. We can see also that shallowwater limestone from the Upper Triassic period are concentrated around what we can call the Palaeoequator,” continues Prof. Martini. The students themselves may be able to build further on this research should they choose to remain in academia, with Prof. Martini keen to encourage continued investigation. While some of Prof. Martini’s previous students have gone down the academic route, others have chosen to go into the private sector, demonstrating
Project Objectives
• Palaeoenvironmental and palaeogeographic evolution of the Panthalassa Ocean • Carbonates as an archive of global biological and ecological evolution during the Late Triassic and their implications on the T/J boundary crisis • Comparison at high stratigraphic resolution between Panthalassan and Tethyan provinces to disentangle the factors controlling different organisms distribution patterns and evolution • Taxonomy and systematic of foraminifers as a tool for assessing past depositional and ecological conditions
Project Funding Aulosina oberhauseri. Benthic foraminifer. Black Marble Quarry (Wallowa Mountains, Oregon, USA) – Age: Upper Carnian? – Lower-Middle? Norian. Diverse oblique sections (in Rigaud et al., Acta Paleont Pol 2013).
the wider relevance of this research. “Some students work in the geothermal energy field for example, looking at the composition of certain rocks, and their ability to store and/ or circulate hot water,” says Prof. Martini. The project’s research does hold wider relevance to industry, for example in assessing the quality of potential gas and oil reservoirs, yet Prof. Martini says her main motivation is scientific curiosity. “We want to improve the knowledge of this period at the end of the Triassic,” she stresses. “We have tried to characterise the Upper Triassic in terms of the forms of life and the depositional systems, just before the boundary with the Jurassic period. We can then compare these with those found from the Jurassic period, which is relatively well understood.”
Funded by the SNSF, which has been funding the long-term project REFFCADE (20072022, CHF 1.7M) to Rossana Martini.
Project Partners
• Prof. Bernard Lathuilière (http://georessources. univ-lorraine.fr/fr/content/lathuiliere-0) • Prof. Tetsujii Onoue (https://hyoka.ofc.kyushu-u. ac.jp/search/details/K007222/english.html) • Prof. Roberto Rettori (https://www.unipg.it/ personale/roberto.rettori) • Dr Sylvain Rigaud (https://dr.ntu.edu.sg/cris/ rp/rp00252) • Prof. George Stanley (http://hs.umt.edu/ geosciences/people/default.php?s=Stanley) • Prof. Hayato Ueda (http://www5b.biglobe. ne.jp/~ueta/main_eg.htm)
Contact Details
Principal Investigator, Professor Rossana Martini Director of the ELSTE University of Geneva – Department of Earth Sciences T: +41 22 379 66 12 E: Rossana.Martini@unige.ch W: https://orcid.org/0000-0002-0674-863X Professor Rossana Martini
Natural light and cathodoluminescence pictures of calcite cements and (A) the related impact points of LA-ICPMS measurements; (B) Impact points of SIMS me; (C) Cathodoluminescence image of A. (D) Cathodoluminescence image of B (in Peyrotty et al., Marine and Petrol Geol 2020).
Professor Rossana Martini, Principal Investigator of REEFCADE project, is an Associate Professor in the Department of Earth sciences at the University of Geneva, a position she has held since 2011. Her main research interests are carbonate sedimentology and Permian and Triassic biostratigraphy using foraminifera, of which she is one of the world’s leading specialists for the Triassic.
topic on which views have shifted over recent years. “Until around 15 years ago it was considered that the Tethys Ocean was the niche of biodiversity. It was assumed that marine life during the Triassic developed first in the Tethyan ocean,” says Prof. Martini. This was because the Tethys Ocean at that time was very shallow, in comparison to the Panthalassa, with a large zone on the continental shelf that was ideal for the development of life. “We know that more than 75 percent of life in the sea is nowadays developed on the continental shelf, and not in the deep. Nutrients and oxygenation are much more abundant in such environments, and the temperature is more conducive,” explains Prof. Martini. “This is one of the reasons why it was
EU Research
REEFCADE
thought that life developed in the Tethys, and then dispersed in the Panthalassa.”
www.euresearcher.com
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