Glimpses of the past

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Ammonites are extinct relatives to modern day octopuses and squids. The shells are chambered, in contrast to the shells of snails. The shapes of the septa, the dividing walls, are distinct characteristics of the separate species on the basis of which they have been classified.

In general I write about living natural elements, but a treasure trove of information on ancient life lies hidden within Curaçao’s rock record as well, for us to discover and unravel.

As a geologist, I am always fascinated by fossils, those – sometimes only subtle – imprints left behind within sedimentary rocks, the result of preservation of remains of ancient organisms. The process of fossilization is actually one of rare chance. The chances of plant or animal remains ending up within exactly those favorable conditions for fossilizations to be successful are minute. The harder parts, like shells, teeth or bones, have a fair chance to end up in the rock record, but soft tissue is another matter altogether. The work of a paleontologist is therefore somewhat that of a CSI (crime scene investigator). He has to unravel the way of life, and the cause of death of the fossilized organisms on the basis of those remains alone.

Ammonites were active hunters, and were able to propel themselves through the water column by means of ‘jet power’, like their modern day relatives. The ones shown here are not that big, about 2 centimeters across, but fossils have been found elsewhere on the planet of some species that reached huge sizes, of 1.5 meters across or even more!

The accompanying pictures are of the oldest fossils to be found on Curaçao, and these are actually quite special. The foundation of the Island consists of volcanic rocks, a thick succession of basalts that erupted in a submarine environment. Only in one location a small section of sedimentary rocks have been found within this succession, indicating that the eruptions were quite continuous (interruption of the eruption cycles would have allowed time for more sediments to settle in between those cycles). These layered rocks contain remains of several organisms, of which ammonites are the most conspicuous. This group died out at the end of the Cretaceous period, together with the dinosaurs, about 65.5 million years ago. Radiometric age determinations of several samples of the Curacao Lava Formation produced an age of about 86-87 million years, so the ammonites within this small section are at least as old.

Geologists juggle with millions of years with ease. But these ages are actually mind boggling. No one is able to visualize these enormous ages and geological processes. We are just mere humans, small and just one of the elements of the giant cycles of nature. Just like the ammonites, dinosaurs or myriads other extinct species, our species is destined to disappear one day as well. This is just the nature of nature….

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