Friday, 12 October 2012

Past forward: Mangroves, reefs and Archaeopteryx?


The present can be a key to the past. This is something that the 18th Century Scottish Geologist James Hutton raised when viewing the surficial processes that have sculpted the land-shapes of the United Kingdom. This idea was refined and liberally applied by the famous 19th Century geologist Charles Lyell whose pivotal book, Principles of Geology, accompanied a young Charles Darwin on his voyage of discovery. This basic assumption that many palaeontologists apply to the fossil record relies on the uniformity of natural and physical laws that have governed our planet in both the past and present. This principle of 'uniformitarianism' often drive my colleagues and I to study the tissues, behavior, environments and ecology of living species, so that we may better understand the same in extinct organisms.

This week, I find myself on Grand Cayman…I just pinched myself…and yes, I am still sat on Grand Cayman. I am here to explore some of the most pristine carbonate environments in this corner of the world, so that I might better understand similar environments that I often sample from the fossil record. The submarine ridge that supports the Cayman Islands defines its geology, topography, as well as the rich environments that support a diverse flora and fauna. The carbonate shelf that fringes the islands support prolific coral reef communities while the lagoons and mangrove swamps inland support a vibrant terrestrial community. It is times like this that I realize how little we have to work with when reconstructing ancient communities, of which a fossil assemblage only represents but a fraction of the extinct ecosystem.

Stingrays at Stingray City (Grand Cayman) Image courtesy of Jim 'Rayman' Gobetz

The geological record of life also has a nasty habit of time-averaging samples, so that a fossil assemblage might represent hundreds or even thousands of years, albeit in a single unit of lithified sediment (rock). At the same time, the subtle variation in species and their distribution through time and space can be blurred due to the cumulative affects of taphonomic processes acting upon and concentrating, filtering and/or refining a fossil assemblage…all this and more adding to the difficulties of unpicking the past for palaeontologists. Hopefully, my wading through lagoons, swimming with stingrays, trekking through mangrove swamps and diving into reef systems will provide me with some new insights on this particular fraction of life on Earth…and not a dinosaur in sight! However, I am VERY keen to see if a seabird manages to meet a sticky end in one of the back-bay hypersaline lagoons…maybe a gentle echo of similar environments and taphonomic processes that preserved its distant Jurassic ancestor Archaeopteryx. I am sure that James Hutton would approve.

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