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Two New Reviews

Bedrock geology UK North, by P. Stone
Bedrock geology UK South by A.A. Jackson
Published by: British Geological Survey
Publication date: 2008
ISBN: 978 085272585 6 & 978 085272586 3
List Price £10 each and £15 each with folded map in plastic wallet (25% academic discount)
www.bgs.ac.uk


BGS SouthSince these maps were first published in 1948, with indispensable 10km grid lines, there have been considerable advances in our understanding of the bedrock stripped bare of any superficial Quaternary deposits. The maps have been completely overhauled and many (geological!) faults have been added to give a sense of tectonic grain without becoming overwhelming. Furthermore, while the maps can be mounted together and cover the whole of Northern Ireland, they now have a generous 80km overlap across Cumbria and North Yorkshire along with a number of informative cross sections. In addition, an excellent pair of attractive, well written and concise explanatory booklets has been produced to go with each sheet.

The Precambrian units are placed into a revised framework with modern terminology so they are subsumed into a combined sedimentary and metamorphic index with key horizons dated to within a million years. Only the igneous and meta-igneous rocks remain separated into age-classified intrusive and extrusive columns beneath the main key. While this overall scheme is very simple, quite subtle variations in rock types can be shown by the use of different colour tones to add complexity for those who seek it, without becoming off-putting for causal users. Compared with earlier editions the most striking change is to the southeast of the Great Glen fault in Scotland, where most of the country rocks in the Grampian Mountains are now assigned to the Dalradian.

UK North In much of the North West Highlands the line work has often been completely re-jigged and clearly linked to various thrusts which are neatly traced across country. Though 1:50,000 sheet lines are neatly shown in red, dividing lines for historic Scottish sheets are not shown, as since metrication they are usually published in two halves.

Unfortunately the sea is left blank and the coast highlighted by a white zone which ignores and even omits some outlying islands and rocks (Skerryvore for example), and many coastal place names are left unlabeled unlike earlier editions. Conversely, Lough Neagh in the middle of Northern Ireland is coloured in and not even subdued with pale tones. While the shores of large lakes can usually be picked up, this is disconcerting.

In northern England the recently revised distribution of the Lias to the west of Carlisle has been omitted, though the Isle of Man is now mainly Ordovician sediments, which was apparent long before the 4th edition was published in 2001. Compared with earlier editions the Jurassic has been simplified, while the Carboniferous has been improved with additional units and the monolithic Lower Old Red Sandstone replaced with four units which cast Herefordshire in a totally different light. Clearly, like Mid-Wales, Cornwall and South Devon have undergone a radical overhaul as the use of regional variations in the index and addition of a series of southward dipping thrusts and linking faults present a much more coherent picture.

The next priority must be to produce a pair of maps showing superficial deposits at this scale.  This will take some doing, as along with ongoing mapping this requires a modern synthesis as radical in its own way as the overhaul of the Precambrian coverage on these excellent bedrock geology maps.

David Nowell New Barnet, Hertfordshire

 

Geological History of Greenland – Four Billion Years of Earth Evolution
Niels Henriksen
Published by: Geological Survey of Denmark and Greenland (GEUS)
ISBN: 978-87-7871-211-0
List price: £43.99
272pp
www.gazellebookservices.co.uk


HenriksenThis beautifully produced volume summarises the results of more than 60 years of geological investigations in Greenland and the surrounding shelf areas. Greenland’s exceptionally well exposed mountainous arctic landscape preserves evidence for close to four billion years of Earth evolution and continues to attract significant international research interest. The substantial areas of Precambrian basement exposed have in particular yielded crucial insights into the evolution of the early Earth. Generations of UK university researchers have participated in the summer expeditions that mapped this remote terrain and contributed to present understanding.

The key features of the volume include its generous size (30 x 25cm), the splendid photographic images and accessible colour diagrams, and the way in which has been presented in a form that is suitable not only for the general, interested reader, but also for students and geologists without specialist knowledge of Greenland geology. Introductory chapters set the scene, with a brief review of Greenland’s geological evolution from the Eoarchaean to the Quaternary, a history of research, and a synthesis of the way in which ice has moulded the landscape. Then follow chapters that deal in turn with the crystalline basement, the Gardar Province, Proterozoic to Ordovician sedimentary basins, the development of the Caledonian and Ellesmerian fold belts, Upper Palaeozoic to Palaeogene basins, and Palaeogene volcanism. Summaries of the geology offshore and the Quaternary glacial history are followed by chapters on mineral, oil and gas resources. All are copiously illustrated with a mix of field photographs (including numerous stunning images of mountain-scale structures and rock successions), palaeogeographic maps and other specially drawn colour diagrams (e.g. sketch cross-sections, sedimentary logs, geophysical profile).

The diversity of geology within Greenland means that no major processes are left untouched within the book. Highlighted blocks of text accompanied by well presented and easily readable diagrams explain basic geological concepts for the non-specialist as the book progresses. These include subjects as wide-ranging as basic rock identification, geological mapping, deep-sea drilling, and the generation of oceanic crust. This is a particularly strong feature of the book. Indeed, it could be argued that this is just as effective an introductory text book for geology undergraduates as any of the commonly used examples in the UK and abroad. In summary, this is an outstanding contribution to the Earth sciences literature. It is one of the best books available on geology for a broader public, but will still manage to satisfy the academic or industry-based geologist who wishes for an update on the geology of this perennially fascinating piece of the Earth’s crust. No library should be without a copy.

Rob Strachan, Portsmouth