Bryozoans in the English Chalk

Dr Paul D Taylor (UK) We are very fortunate in Britain to host one of the most remarkable deposits in the entire geological record, the Chalk. The Late Cretaceous Chalk (with a capital ‘C’) is an extremely pure limestone, famous for the White Cliffs of Dover and responsible for the landscape of rolling hills and dry valleys, forming the ‘downs’ and ‘wolds’ that stretch through England from Devon in the southwest, to Yorkshire in the northeast. The economic importance of the Chalk to the early human inhabitants of Britain was enormous because the flints contained within it could be fashioned into axe heads and hard cutting tools. Why is the Chalk so special geologically? It is a rare example of a pelagic sediment – an open ocean sediment – that was deposited over the continental shelf. This occurred at a time when global sea-level was high and the supply of terrigenous clastic sediment into the sea was minimal. The Chalk is an oceanic ooze composed mainly of the disaggregated plates – coccoliths – of coccolithophores, planktonic microalgae with exquisitely engineered skeletons of calcite. Unfathomable numbers of coccolithophores sank to the seabed over a period of some 35 million years to produce the thick accumulation of Chalk that today extends over northern Europe and into western Asia. The Chalk is a favourite hunting ground for fossil collectors, yielding beautifully preserved specimens, especially of echinoids. But closer inspection of the Chalk shows that the dominant macrofossils are often bryozoans. These colony-forming invertebrates … Read More

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Fossil folklore: Echinoderms

Dr Paul D Taylor (UK) The distinct five-fold – or pentameral – symmetry of echinoderms makes them particularly striking fossils. Some even have a vaguely mystical appearance. Modern echinoderms – starfish (asteroids), sea urchins (echinoids), feather stars and sea lilies (crinoids), sea cucumbers (holothurians) and brittle stars (ophiuroids) – are all animals of the oceans. As no echinoderms inhabit freshwater environments, it is difficult to envisage what ancient people living far distant from the coast and who had never visited the sea might have thought when finding a fossil echinoderm with peculiar star-like marks on its surface. How could such a stone have been formed? What was its significance? Did the star markings point to a heavenly origin? Could the stone possess magical or mystical properties? Even today, many folklore beliefs about echinoderms persist. For example, the echinoid, Eurhodia matleyi, is found in west-central Jamaica around Stettin, where it can be abundant on bedding planes of the Eocene Yellow Limestone Group. These fossils are locally referred to as ‘lucky stones’, because of the distinctive star-shaped pattern of the ambulacra (SK Donovan, pers. comm, July 2003). Fossil echinoderms must have seemed worthy of collecting and treasuring regardless of how they were viewed. Indeed, some were even worn as amulets to protect against evil. Not surprisingly, echinoderms have a folklore that is matched only by that of ammonites (see Fossil folklore: Ammonites). Pre- and unscientific beliefs about various kinds of fossil echinoderms abound and a plethora of folklore names have been given … Read More

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