Paleo-reef reconstructions

The need for paleo-ecological studies

Reefs are increasingly impacted by ongoing anthropogenically-caused climate change & the intensifying local human pressures that jeopardize the ability of coral reefs to persist in the near future. However, changes in coral ecosystems have predated human underwater investigations. Fortunately, fossil reefs & the calcified remains within, are unique witnesses of the past, holding important physical, biological & chemical information. Studying these remains, in particular fossilized corals, allows scientists to reconstruct the functioning of the coral ecosystems prior to any anthropogenic exploitation. The scientific community critically needs these pieces of past knowledge to adequately preserve reef functioning & ultimately ensure the survival of this crucial ecosystem.

Exploring river banks for fossilized marine remains
Dr. Lin & myself looking at a fossil reef along the coastline of Kenting National Park (KNP, southern Taiwan)

Kenting National Park (KNP) paleo-reef descriptions

Numerous outcrops of well-preserved Holocene reefs can be observed along the coastlines of KNP. These outcrops provide perfect survey sites for us to reconstruct the past diversity & global structure of Taiwanese reefs thousands of years before the Anthropocene era. At certain locations, these outcrops can be over 3 m tall & more than 5 m wide without discontinuity or obstruction, where past reef materials can be accessed with minimal cost. On the other hand, fossilized materials from these outcrops are exposed to weathering, making them unlikely to be ideal candidates for isotopic measurements & subsequent paleo-climate reconstructions. Such studies will most likely require drillings of less exposed sections of the paleo-reefs, which could be found a few meters inland from these exposed outcrops.

Four outcrops in two locations on the western side of KNP have already been selected as targeted study sites for this project. A Structure from Motion (SfM) model for one of the selected outcrops has already been built (a preview video of this model is available on the right).

3D model of a fossil reef outcrop in KNP, using Structure from Motion (SfM) method

Late Miocene Dendrophyllia fossils in North Taiwan

During field investigations along the Dahan river bed in Shulin district (樹林), numerous small & fragile scleractinian fossils were found & identified as Dendrophyllia sp. (Ribas-Deulofeu et al. 2021). The fossils were collected from the lowest part of the Late Miocene Tapu Formation. The absolute age of the boundary between the Tapu Formation and the underlying Nanchuang Formation is 8 Ma, providing indications of the maximum age possible for the found Dendrophyllia fossils. The marine ecosystem in which the sampled specimens grew was probably a turbid shallow coastal environment with muddy to sandy bottom, likely at the vicinity of a river estuary, as suggested by the combined presence of numerous Ariidae and Sciaenidae otoliths. To our knowledge, these are the first record of Dendrophyllia fossils from Taiwan.

Supplementary figure from Ribas-Deulofeu et al. 2021. 3D model of Dendrophyllia specimen ASIZF0100147 (h= ~1.3 cm, w= 1 cm)

Fossil description from boreholes: Consulting for Pr. Le Béon (National Central University, Taiwan)

Recently, Pr. Le Béon from the National Central University (Taiwan) contacted me to consult on some boreholes from Southern Taiwan. Porites sections from Gunshuiping
Pr. Le Béon's team works on active tectonics with a particular focus on seismic hazard & fault displacement assessment. In the boreholes obtained near a mud volcano in Gunshuiping (滾水坪, Qiaotou district), Pr. Le Béon's team found fossil reef sequences from 16 m to 44 m deep. This layers contains numerous fragments of corals, including Acroporidae, Fungiidae, & Merulinidae. The sequences also include large Porites & a few other coral colonies pieces exceeding 30 cm in length (up to > 1 m). A dozen of coral fragments have already been selected along the core sequences for U/Th dating. In addition, two Porites (50 cm & 30 cm long) were sliced to test their suitability for isotopic studies (collaboration with Pr. Huang & Pr. Liu, Academia Sinica)

Gunshuiping cores (32-36 m deep)

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