Based in Mahone Bay, nova scotia, agile libre is an independent publisher of technical books about the subsurface.  

Hardgrounds

I still vividly remember the relaxed and beautiful day on the west coast of Malaysia, bathing in bright sunlight. We took a small boat to a recommended snorkelling spot along the coast of an island. I was prepared for the underwater beauty of coral reefs and colourful fishes, but I wasn’t prepared for what I saw when I jumped into the water. I was actually overlooking something very similar to a subtropical 53-million-year-old shallow-water and wave-dominated hardground environment, complete with the same fauna that occurred in the sediment-starved areas of the Early Eocene Roda fan delta! The morphologies of the wave-resistant lobate coral colonies were exactly the same, the thick-walled shallow-burrowing bivalves looked very similar, and the many turriform, turbinoform, and conical gastropods together with the spiny echinoids completed the image. Amazing.

Shortly before this trip, I had finished my master’s degree looking at the fauna–substrate relationships of the hardgrounds found on top of some of the large, rapidly deposited sandstone bodies in the Roda Formation of the Spanish Pyrenees. An exciting topic that I had pursued as if I was Sherlock Holmes trying to reconstruct an ancient scene of rise to, and subsequent fall from, glory. I had used some modern and some old-fashioned, but still effective, techniques to collect data, develop the palaeoenvironmental model, and decipher the relationship with sediment dispersal patterns over time. Some of it was straightforward, but much of it had to be deduced and interpreted. Sudden shifts in the locus of sand deposition happened frequently and had a profound impact on the palaeoecological conditions locally causing the gradual development or, contrarily, rapid cessation of richly populated invertebrate palaeocommunities.

On the hardgrounds, the abundantly occurring fossil Goniaraea coral colonies are generally well preserved, and over the years the many visitors to these parts of the Roda outcrops have significantly reduced their surviving number. (Which, by the way, is a plea to field-trip participants to better protect outcrops!) Rays, sharks, and sea turtles patrolled the waters, and the various Eocene Conus species so commonly occurring on the hardgrounds were likely as venomous then as they are today. Colour, though, was the one striking feature that was missing: the preserved Roda hardground fossils are uninspiringly brownish grey. So, when I dipped my head beneath the waves near the Malaysian island the transformation was complete. I was relocated back in time — not using a DeLorean, but a small motor boat.

Why does palaeontology never cease to fascinate me? It is the sheer beauty and intricacy of past ecosystems and their diversity, the interdependency and interactions of the physical environment, and the biological adaptations to it. It is the understanding and comprehension of why that particular ecosystem ceased to exist, what the factors were that controlled it, and what we can deduce from it that might have meaning for our current environments. I am excited by the view through a ‘window to a past world’ that is much larger and more multidimensional than my own life observations and experiences allow. I find it intriguing to realize that environmental conditions may change — gradually or dramatically — but that life will return and continue albeit in different ways and forms.

Relatively sudden and high-impact environmental changes are common in life’s history. Maybe we should be reassured that, from an ecological point of view, we don’t need to feel despair about the environmental calamities and challenges we are facing. Which brings me back to the fascinating life forms, their mutual dependencies and interactions with the physical environment, and the Malaysian island — there to be enjoyed and cherished.

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