Ballad of the Borders

books & arts ballad of the borders

death of an ocean: part of the palaeocontinent of Laurentia. And mountain belt mostly happened before A geological England and Wales belonged with Africa and ocean closure. In Britain, anyway, formation borders ballad South America as part of the palaeocontinent of the Scottish uplands did not involve a of Gondwana. As these ancient continents climactic continental collision. Clarkson and by Euan Clarkson and approached one another, the ocean between Upton correctly narrate how the Southern Brian Upton them was destroyed, leaving behind the Uplands’ sedimentary rocks were scraped off Caledonian–Appalachian mountain belt the Iapetus oceanic plate in the 30 million to mark the join. These tectonic ideas have years before ocean closure. They could also DuneDin ACADeMiC mostly stood the test of time. have stressed that the strong deformation PRess: 2010. 210 PP. Clarkson and Upton have faced the on the English margin, once attributed to £25.00 challenge of explaining, to the non-geologist, the closure of the Iapetus Ocean, actually generic principles such as plate tectonics, occurred a further 30 million years after stratigraphy and igneous processes, as closure, due to an unrelated cause. Thus the he Scottish Borders contain key well as the specific local details of Scottish Scottish–English border is one of the few geological evidence that a wide ocean geology and landscape. They have met this places in Britain where the closure of the Tonce separated Scotland from England challenge by writing well-crafted informative Iapetus Ocean can be dated. around 420 million years ago. But this text and using well-designed diagrams My second addition to the book evidence is complex, cryptic and obscured and photos. They have resisted the natural would have been a chapter on the period by later geological events. In Death of an urge of geological historians simply to allot between the Carboniferous wetlands, Ocean, Euan Clarkson and Brian Upton successive chapters to consecutive time slices. about 300 million years ago, and the bravely explain to the general reader the Instead, the history is pieced together more Quaternary ice age of the past couple of events that led to the disappearance of this indirectly through a series of topical essays. million years. This long period gets only a ocean. By decoding the rocks of the Scottish Several of these chapters are entertainingly passing mention by Clarkson and Upton, Southern Uplands, they show how the biographical; James Hutton famously perhaps quite reasonably, as no depositional disappearance of an ancient ocean welded used the unconformities in his native rock record of this period exists. However, Scotland together with England and Wales. Scottish borders to deduce the immensity it would have been interesting to chart how In 1966, Tuzo Wilson proposed that an of geological time, and Charles Lapworth the topographic plateau of the Scottish ocean existed in place of the present-day refined the use of graptolite fossils for Southern Uplands survived the Mesozoic North Atlantic Ocean over 420 million years subdividing the Southern Uplands rocks, and crustal rifting that essentially defined the ago. This idea marked a radical change in thereby early Palaeozoic time in general. shape of the British Isles, and how the late our understanding of the formation and We can forgive Clarkson and Upton some Cretaceous seas probably lapped over the geological history of Britain. This ancient overemphasis of their respective specialisms Scottish Borders. ocean, named the Iapetus Ocean, bisected of fossils and igneous rocks. Such personal Around 60 million years ago, and towards Ireland and cut through Britain along the enthusiasms bring geology to life. My the end of this gap in our records, the border between England and Scotland, personal interest in regional tectonics might intrusion of igneous melt into the Scottish explaining why the old rocks of the two have promoted further aspects of Scottish crust caused regional uplift, and rejuvenated countries are very different. Before the geology. Specifically, the deformation the upland plateaux of northern and closure of the Iapetus Ocean, Scotland was that turned the continental margins of western Britain. The Scottish mountains attached to Greenland and North America as the Iapetus Ocean into the Caledonian are too often equated directly with the Caledonian mountain belt that marked the Iapetus Ocean closure. Death of an Ocean avoids this implication, but it misses a chance to advertise that the British uplands have a multistage geological origin, and are not simply the result of a continental collision that resulted from the closure of this ancient ocean. Minor reservations aside, Death of an Ocean is an illuminating, entertaining and authoritative read for the non-specialist interested in the ancient geological history of Britain, and in the fundamental act of union between Scotland and England. ❐

Reviewed by Nigel woodcock Nigel Woodcock is in the Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK.

nature geoscience | VOL 3 | MARCH 2010 | www.nature.com/naturegeoscience 145