Silurian sites

From Palaeos

Silurian period 444-416
Llandovery 444-428			Wenlock 428-423		Ludlow 423-419		Pridoli 419-416
Rhuddalian 444-439	Aeronian 439-436	Telychian 436-428	Sheinwoodian 428-426	Homerian 426-423	Gorstian 423-421	Ludfordian 421-419
Silurian topics: Stratigraphy | Geography | Climate | Life | Important Fossil Sites | References | Links

3) Much Wenlock

The Silurian Much Wenlock exposures are located near the town of the same name in Shropshire, England, on the Welsh Borderlands. This was the edge of a vast Middle Silurian reef, now exposed as a limestone ridge, the Wenlock Edge -- just one more set of wooded Shropshire hills in a now absurdly civilized setting.

The Ordovician and Silurian have left us few famous sites. We chose the Much Wenlock site because it is one of the best of a bad lot. At that, its not really so bad. Well over 600 species of invertebrates have been found there. These include crinoids, corals, brachiopods, trilobites, algae and bryozoans. Much Wenlock may be less famous than the two Cambrian sites because there are few vertebrates. No one expects vertebrates in the Cambrian, but the early Silurian is part of the dark age of hidden vertebrate diversity, and its rather frustrating that so few are to be found at Much Wenlock. A more serious problem with the Much Wenlock exposures is that many are in limestone quarries (such as the Farley Quarry in the image) which are long abandoned and now filled with water.

As a paleontological site, Much Wenlock is about as old as geology itself. It is part of the region from which the Silurian System was first described by Murchison in the late 1830's. The astute reader may already have deduced as much from the fact that the "Middle Silurian" is officially named the Wenlock. From northwest to southeast, virtually the entire Silurian system is laid out in a series of gently sloping ridges. The impact of Much Wenlock on paleontology lies partly in that early discovery and partly in the early opportunity it gave geologists to put together a the components of a fairly complete Paleozoic ecosystem.

4) Saaremaa Island

If its Silurian vertebrates you're after, this is the better choice. Saaremaa Island is located just off the coast of Estonia, in the Baltic Sea. The entire island rests on Wenlock to Ludlow reef limestones which were buried under Baltic marine sediments until early Holocene times. The topography is quite low, so exposures are relatively rare except on a few bluffs referred to locally (and rather optimistically) as "cliffs." During most of the last century, it was the private preserve of a few scientists from Moscow, Talinn, and occasionally Stockholm.

Saaremaa is not particularly well known, although it has yeilded any number of often beautifully preserved jawless fishes, in addition to eurypterids and other shelled invertebrates. Perhaps we over-rate its importance; but perhaps not. Our belief is that more systematic exploration of Saaremaa and some even more obscure sites in Poland, has the potential to transform our understanding of vertebrate evolution.

5) Spitsbergen

This location is sometimes spoken of in the same breath as Saaremaa. Spitsbergen is actually a bit large to be referred to as a "site." It is the largest member of the Svalbard, a large arctic archipelago located well north of Norway. It is unreasonably cold and beautiful and is inhabited entirely by scientists and polar bears. At least that is the impression one gets. Undoubtedly this is an exaggeration, and many of the polar bears will turn out to be Norwegian scientists -- or vice versa. The base of the sedimentary sequence at Spitsbergen is the Red Bay Formation, largely of Ludlow and Pridoli age. The exposures continue right into the Cenozoic in various localities. For paleontologists, however, most of the interest is in the Red Bay and Early Devonian Wood Bay groups, both exposed in the relatively glacier-free center of the island.

These are immense exposures. Collection collections are difficult, and vertebrate fossils are seldom common in any Paleozoic site. However, with whole mountains of Ludlow and Early Devonian sediments available, remarkable finds have been made. Fossil prospecting has been going on here since approximately the 1880's. Some well-known results of that work are the three-dimensional fossils of Osteostracan headshields -- with the internal cartilage so perfectly preserved that Janvier, Wängsjö, and others have been able to trace, in detail, the branching paths of the cranial nerves in fishes dead for 400 My.

Palaeos com - Paleozoic

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