Programme: 2000 - 2001

© Craven & Pendle Geological Society

Field Meetings: cancelled due to FOOT & MOUTH

Indoor Meetings
Friday, 27th October
Chasing Dinosaurs across China
Martin Whyte Ph.D. Sheffield University

Friday, 24th November
Palaeobiology of Wenlock Crinoids
Rosanne Widdison B.Sc., Birmingham University

Friday, 8th December
Volcanic eruptions under ice - the plot thickens
Dave McGarvie Ph.D., Open University.  Christmas Jacob's Join

Friday, 26th January
Members Evening

Friday, 23rd February
New insights into glaciation
Bob Perris, BSc.

Friday, 16th March
The Burgess Shale - a pivotal time in the evolution of life
Will Watts B.Sc.(Hons), Yorkshire Museum

Two, three-week trips to China, in 1996 and 1997, provided contrasting experiences of the richness of China's dinosaur fossil record.

During the first tour, a private family holiday, the opportunity was taken to visit museums in Beijing, Zigong and Chengdu and in particular to look at exhibits of material from the Sichuan basin. The middle Jurassic dinosaur fauna of Sichuan is the best skeletal record of this age in the world and has some interesting parallels with, and perplexing differences from, the approximately coeval fauna represented by footprints in the Ravenscar Group of Yorkshire. The Zigong Museum is outstanding in having been built over and having preserved a quarry site from which large numbers of skeletons have been recovered. Skeletal mounts of sauropods, primitive stegosaurs and small theropods are also on display.

Later, in Zhengzhou, a chance was taken to meet members of the Henan Dinosaur Egg Research Group and after discussions a Collaborative Research Agreement was formulated with them. The second excursion, supported by the Systematics Association, initiated this joint work and allowed field and laboratory study of the upper Cretaceous dinosaur eggs of the Xixia Basin in Henan. The 2000m thick succession of the Xixia Basin is a red-bed succession of sandstones, silts and mudrocks with occasional gravels and breccias. These were deposited in a complex of fluvial, alluvial-fan and lacustrine environments in a semi-arid intra-montane basin within the Qinling Mountains. Abundant dinosaur eggs and scraps of dinosaur bone occur at several horizons and the Henan Research Group was set up not only to study the eggs but also as part of a series of measures aimed at discouraging the illicit trade in the eggs. Though eggs range in size from the large, 45cm long, Macroelongatoolithus eggs to eggs comparable in size to a large hen's egg, the dominant egg type studied was the ovate, 16cm long, eggs of Paraspheroolithus. These were often laid in large irregularly arranged clusters of which the largest recorded contained at least 26 eggs.

The next stage in the collaboration will commence soon when one of the Chinese research workers will spend a year in Sheffield on a Royal Society Scholarship.

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Palaeobiology of Wenlock Crinoids
Rosanne Widdison, Birmingham University

By the beginning of the Ordovician Crinoids began to flourish. They continued to evolve and prosper until the catastrophic Permo-Triassic Mass extinction event which wiped out 85% of all marine faunas. Only a single genus of crinoid is known from the early Triassic, which eventually gave rise to Articulate crinoids of modern times.

Although crinoids are the least understood of living echinoderms, their skeletal remains are among the most abundant and important of fossils. They appeared during the Lower Ordovician and underwent several major radiations during the Paleozoic Era. Crinoids were major carbonate producing organisms during the Paleozoic and Mesozoic.

A persistent, traditional view treats living crinoids as chiefly deep-sea organisms, relicts of their opulent Paleozoic past, holding off final extinction in remote abyssal habitats. This view is generally applied to stalked crinoids, or sea lilies, as typical of the entire group, because they most closely resemble their fossil forebears.

Most of a crinoid's body, in fact usually at least 80% or so, consists of a skeleton of calcium carbonate pieces, or ossicles, held together by ligaments and muscles. This skeleton explains both why crinoids make good fossils (calcium carbonate is basically limestone) and why not too many creatures subsist on a crinoid diet (they're highly crunchy).

All crinoids are passive suspension feeders. They produce no feeding/respiratory current but, rather, rely on ambient water movement. Diets include a variety of diatoms and other unicellular algae, foraminiferans, actinopods, invertebrate larvae, small crustaceans, and detrital particles.

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Volcanic eruptions under ice - the plot thickens
Dave McGarvie, Open University

Iceland exists only because there is an extra supply of magma - over and above that supplied by the spreading ridge. This extra supply of magma comes from a deep-seated mantle plume (a hot spot). As Iceland's highest point is a dormant stratovolcano which rises 2 km above sea level, and as normal spreading ridges lie some 4 km beneath sea level, this means that the mantle plume has contributed an additional 6 km of oceanic crust. All of which means that geologists can use Iceland to investigate oceanic magmatism without the need to delve into the depths of the ocean.

© Dave MCGarvie

Glaciers now only cover about 11% of Iceland, but during the last glacial period over 80% was ice-covered. When shield volcanoes erupt into ice they produce flat-topped table mountains, and when large fissure eruptions take place they build linear ridges. Complex successions of subglacial volcanics are found at some central volcanoes, where there have been repeated eruptions under ice. (Examples include Askja in a rift zone and Torfajökull in a flank zone.) In the past few decades Iceland has provided us with spectacular (and sometimes unusual) eruptions at regular intervals. Much of Iceland's volcanic activity is restricted to small-scale events. But at some time in the future there will be a large eruption, and if the wind blows ill for us, it's quite possible that we might find ourselves forcibly reminded of what our ancestors experienced back in 1783 - when Lakagigar erupted and caused famine and widespread civil unrest through western Europe.

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The Burgess Shale
Will Watts, Yorkshire Museum

In 1911, Walcott applied the name 'Burgess Shale' to an outcrop of Middle Cambrian rocks in the southern Canadian Rocky Mountains.  Little did he know that these Cambrian Burgess Shales of British Columbia would become perhaps the most celebrated fossil locality on Earth.  These faunas have been of great assistance to palaeontologists' in their piecing together of the details of the "Cambrian Explosion" -  a pivotal time in the evolution of life on Earth.

The superb diversity and preservation of soft-bodied fossils are to be found in calcareous grey-black shales.  On close examination of molecular data it is possible that animals evolved at least a billion years ago and therefore the known fossil record would have to be reconsidered.

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