ABOUT OUR PROJECT

The mission of  the DEEPTREE project

Terrestrial ecosystems have significantly influenced Earth's climate and the ocean-atmosphere system since the colonisation of land by plant life. Vegetation is an often neglected yet particularly powerful agent in the alteration of the hydrological cycle, weathering, and elemental fluxes between land and ocean which in turn affects marine biota as well. As global climate change proceeds, it is expected that the climatic conditions will alter landscape, vegetation composition and subsequently the ecological connectivity (physical, chemical, biological processes) between land and sea. The geological past provides a unique insight into long-term biotic responses to ecological disturbances and rebound, attributed to abrupt climatic change, usually rapid global warming. Studying these events can shed light on crisis mechanisms and recovery patterns to help predict how life adapts to a warmer world or rapid climate changes. Examples from past global warming episodes like the End Permian mass extinction (EPME) or the Jenkyns Event have already demonstrated a strong ecological coupling between land and sea, as florals diebacks or turnovers were influencing weathering, landscape stability and elemental and energy transfer (nutrients, clastic material) between the two realms. 

In the DEEPTREE project, we are targeting the Early Triassic (~251–246 Ma) period when plant life on Earth underwent drastic evolutionary changes after the EPME. Despite unprecedented recovery, this period was further punctuated by significant biotic crises, such as the Late Smithian Thermal Maximum (LSTM) – or the Smithian–Spathian boundary extinction (SSB) event. Simultaneously with the marine recovery, this period is marked by an abrupt change in terrestrial vegetation from pioneer lycopsid-dominated floral assemblages to more complex forests with conifers. This period can shed light on how changes in the vegetation composition could stabilize landscape and weathering on land, influencing climate on a long-term and how it contributed to marine recovery by controlling land to sea elemental and nutrient fluxes. 

To expand our knowledge on the land-sea ecological interactions from the Early Triassic, we propose to collect an integrated dataset on vegetation changes from plant microfossils (palynology), marine organisms (foraminifers, ostracods, phytoplankton, molluscs) coupled with geochemical analyses (stable isotopes, main and trace element), biomarkers, and mineralogical composition (clay mineralogy) derived from the same sampled horizons to disentangle the intricate relationship between environmental dynamics and biogeochemical cycles. Shallow marine to transitional-coastal successions deposited at tropical latitudes in the Western Tethys will be investigated in Croatia and Hungary. To establish a wider correlation of biotic events, the dataset will be expanded by including Permian–Triassic successions from China. 

Earlier research on Early Triassic environments and recovery patterns in Croatia 

In southern Croatia, there are several areas with well exposed Lower Triassic deposits. One of these areas is in Central Dalmatia, on the road between villages Muć and Ogorje, where Lower Triassic clastic and carbonate deposits were studied along 230 m thick succession (Fio Firi et al., 2022). Studies included sedimentological logging, determination of facies associations (FA) and paleontological analyses, including micro- and  macrofossils, as well as trace fossils. Determined biota and trace fossils of low diversity suggested restoration of benthic ecosystems from the Dienerian to the Spathian. Seven determined facies associations suggested multiple oscillations in relative sea level and environmental changes throughout the succession. Gained data enabled interpretation of paleoenvironmental conditions and comparison of the Muć–Ogorje succession with other Lower Triassic sections in Croatia, Slovenia, Italy and Hungary. This research contributed to the understanding of the depositional conditions and environmental changes on the epicontinental shelf of Gondwana during the Early Triassic. 

Fio Firi, K., Gobo, K., Marković, F., Sremac, J. (2022): Changes in environmental conditions, present biota and depositional pattern within Lower Triassic clastic and carbonate deposits, Muć–Ogorje, Central Dalmatia (Croatia). Palaios, 37, 16–33.

The other one is the Plavno section near Knin. It is a more than 900 m thick, almost continuous Early Triassic succession, ranging from the Early Griesbachian into the Anisian. The section presents great potential to determine pollen associations and reconstruct climatic perturbations in the western Tethys after the end-Permian mass extinction. Conodonts, bivalves, and ammonoids date the succession, which is linked to a continuous carbonate carbon isotope curve that records characteristic Early Triassic excursions. This allowed the first recognition of Early Triassic substage boundaries in the Dinarides and enables correlation with sections in the Southern Alps and Hungary. The section was deposited on a storm-influenced epeiric ramp under long-term transgression. It comprises three informal members: a dolostone member (Early Griesbachian), a siliciclastic member (Late Griesbachian–Smithian), and a lime mudstone member (Spathian). Feldspar-bearing sandstones indicate arid to semi-arid hinterland weathering, and the abrupt Smithian–Spathian change from red siliciclastics to grey carbonates marks a major environmental shift. Combining this well-constrained time frame and sedimentary context with palynological analysis, the project aims to link changes in terrestrial vegetation to Early Triassic climatic and environmental perturbations.

Aljinović, D., Horacek, M., Krystyn, L., Richoz, S., Kolar-Jurkovšek, T., Smirčić, D. & Jurkovšek, B. (2018): Western Tethyan epeiric ramp setting in the Early Triassic: an example from the Central Dinarides (Croatia), Journal of Earth Science, 29, 4, 806-823.

Earlier palynological studies and Early Triassic palynostratigraphy from the Transdanubian Range, Hungary  

Both the Croatian and Hungarian successions have been studied in the past, with established sedimentological and biostratigraphic frameworks. Pilot palynological studies performed in Hungary already revealed well-preserved spore-pollen and phytoplankton assemblages. Góczán et al (1986) and Brugman (1986) used the palynological record to provide the palynostratigrohic subdivision of the strata, while Looy et (1999) based on the late Olenekain-Anisian segment of the Bakonyszűcs-3 core documented the protracted recovery of equatorial forests on the basis of palynological data with frequent occurrence of opportunist Pleuromeiaceae (Densoisporites nejburgii) and other enigmatic palynomorphs such as Scythiana spp. Unpublished data also indicate phytoplankton bloom events in Hungary simultaneously with some variation in vegetation patterns across the Induan and early Olenekian. Considering also the frequent variation in depositional style, these vegetation changes already predict potential changes in land-sea connections.

Brugman, W.A. (1986) Ph.D. thesis (Utrecht Univ., Utrecht, The Netherlands).

Góczán, F., Oravecz-Scheffer, A. & Szabó, I. (1986) Acta Geol. Hung. 29, 233–259.

Looy, C.V, Brugman, W.A., Dilcher, D.L., Visscher, H. (1999) PNAS 96, 13857-13862.