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Mike Walker is a highly experienced, script writer of drama and documentary for film, radio and television. He has won several Sony Awards for Best Play as well as a Royal Television Society Gold Medal and other awards including ones from the Society of Authors and Writers Guild. He has also written several novels and non-fiction works and teaches creative writing at Morley College London.

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The Quaternary is the most recent major subdivision of the geological record, covering the last 2.5 million years or so of earth history and extending to the present day. Over the course of the Quaternary, the earth's global climate system oscillated between glacial and interglacial modes. A reliable chronology is key to our understanding not only of the dramatic changes in the physical and biotic landscapes that resulted from these major climatic shifts, but also of the important human evolutionary and dispersal events that occurred during this period. Quaternary Dating Methods describes the different techniques that can be employed to establish a Quaternary timescale, and shows the wide range of contexts in which these can be applied.

The book begins with a review of the history of Quaternary dating from the early attempts based on biblical genealogies to recent developments involving radiometric methods. The basics of radioactivity and concepts of Quaternary stratigraphy are also introduced. Subsequent chapters cover the different dating techniques, beginning with those based on the radioactive decay of certain chemical elements, through the use of annually-banded records such as tree-rings and varves, to methods that enable materials either to be ranked in terms of relative order of antiquity or to be correlated using time-parallel marker horizons in different sedimentary sequences.

This book:

• Introduces each dating technique in a clear and straightforward manner, with a minimum of technical detail.
• Discusses the strengths and weaknesses of each method.
• Focuses on the practical aspects of dating, with specific examples that show the versatility of the different approaches.
• Covers a broad field, including Quaternary Science, Earth Science and Archaeology.

This book is essential reading for second and third-year undergraduates in Physical Geography, Environmental Science, Earth Science and Archaeology, and for students taking courses in Quaternary Studies, Geochronology, and Palaeoclimatology. It is equally important for professionals in the fields of Earth, Environmental and Archaeological Sciences, who need to know about the range of dating techniques that are available, and about their strengths, limitations and potential applications.

Aus dem Klappentext

The Quaternary is the most recent major subdivision of the geological record, covering the last 2.5 million years or so of earth history and extending to the present day. Over the course of the Quaternary, the earth's global climate system oscillated between glacial and interglacial modes. A reliable chronology is key to our understanding not only of the dramatic changes in the physical and biotic landscapes that resulted from these major climatic shifts, but also of the important human evolutionary and dispersal events that occurred during this period. Quaternary Dating Methods describes the different techniques that can be employed to establish a Quaternary timescale, and shows the wide range of contexts in which these can be applied.

The book begins with a review of the history of Quaternary dating from the early attempts based on biblical genealogies to recent developments involving radiometric methods. The basics of radioactivity and concepts of Quaternary stratigraphy are also introduced. Subsequent chapters cover the different dating techniques, beginning with those based on the radioactive decay of certain chemical elements, through the use of annually-banded records such as tree-rings and varves, to methods that enable materials either to be ranked in terms of relative order of antiquity or to be correlated using time-parallel marker horizons in different sedimentary sequences.

This book:

• Introduces each dating technique in a clear and straightforward manner, with a minimum of technical detail.
• Discusses the strengths and weaknesses of each method.
• Focuses on the practical aspects of dating, with specific examples that show the versatility of the different approaches.
• Covers a broad field, including Quaternary Science, Earth Science and Archaeology.

This book is essential reading for second and third-year undergraduates in Physical Geography, Environmental Science, Earth Science and Archaeology, and for students taking courses in Quaternary Studies, Geochronology, and Palaeoclimatology. It is equally important for professionals in the fields of Earth, Environmental and Archaeological Sciences, who need to know about the range of dating techniques that are available, and about their strengths, limitations and potential applications.

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Quaternary Dating Methods

John Wiley & Sons

Chapter One

Whatever withdraws us from the power of our senses; whatever makes the past, the distant or the future, predominate over the present, advances us in the dignity of thinking beings. Samuel Johnson

1.1 Introduction

The Quaternary is the most recent period of the geological record. Spanning the last 2.5 million years or so of geological time and including the Pleistocene and Holocene epochs, it is often considered to be synonymous with the 'Ice Age'. Indeed, for much of the Quaternary, the earth's land surface has been covered by greatly expanded ice sheets and glaciers, and temperatures during these glacial periods were significantly lower than those of the present. But the Quaternary has also seen episodes, albeit much shorter in duration, of markedly warmer conditions, and in these interglacials the temperatures in the mid- and high-latitude regions may have exceeded those of the present day. Indeed, rather than being a period of unremitting cold, the hallmark of the Quaternary is the repeated oscillation of the earth's global climate system between glacial and interglacial states.

Establishing the timing of these climatic changes, and of their effects on the earth's environment, is a key element in Quaternary research. Whether it is to date a particular climatic episode, to estimate the rate of operation of past geological or geomorphological processes, or to determine the age of an artefact or cultural assemblage, we need to be able to establish a chronology of events. The aim of this book is to describe, evaluate and exemplify the different dating techniques that are applicable within the field of Quaternary science. It is not, however, a dating manual. Rather, it is a book that is written from the perspective of the user community as opposed to that of the laboratory expert. It is, above all, a book that lays emphasis on the practical side of Quaternary dating, for the principal focus is on examples or case studies. To paraphrase the words of the actor John Cleese, it is intended to show just what Quaternary dating can do for us!

In this chapter, we examine the development of ideas relating to geological time and, in particular, to Quaternary dating. We then move on to consider the ways in which the quality of a date can be evaluated, and to discuss some basic principles of radioactive decay as these apply to Quaternary dating. Finally, we return to the Quaternary with a brief overview of the Quaternary stratigraphic record, and of Quaternary nomenclature and terminology. These sections provide important background information, and both a chronological and stratigraphic context for the remainder of the book.

1.2 The Development of Quaternary Dating

Early approaches to dating the past were closely associated with attempts to establish the age of the earth. Some of the oldest writings on this topic are to be found in the classical literature where the leitmotif of much of the Greek writings is the concept of an infinite time, equivalent in many ways to modern day requirements for steady-state theories of the universe (Tinkler, 1985). This position contrasts markedly with that in post-Renaissance Europe where biblical thinking placed the creation of the world around 6000 years ago, and when the end of the universe was predicted within a few hundred years. This restricted chronology for earth history derives from the biblical researches of James Ussher, Archbishop of Armagh, who in 1654 published his considered conclusion, based on Old Testament genealogical sources, that the earth was created on Sunday 23 October 4004 BC, with 'man and other living creatures' appearing on the following Friday. Another momentous event in the Old Testament, the 'great flood', occurred 1656 years after the creation, between 2349 and 2348 BC.

In his magisterial review of the history of earth science, Davies (1969) has observed that although modern researchers have tended to scoff at Ussher's chronology he was, in fact, no fanatical fundamentalist but rather a brilliant and highly respected scholar of his day. It is perhaps for this reason that his chronology had such a pervasive influence on scientific thought, although it is perhaps less clear to modern geologists why it still forms a cornerstone of contemporary creationist 'science'! During the eighteenth and nineteenth centuries, however, with the development of uniformitarianist thinking in geology, the pendulum began to swing once more towards longer timescales for the formation of the earth and for the longevity of operation of geological processes, a view encapsulated by James Hutton's famous observation in his Theory of the Earth (1788) that '... we find no vestige of a beginning, no prospect of an end'.

The difficulty was, of course, that pre-twentieth-century scientists had no bases for determining the passage of geological time. One of the earliest attempts to tackle the problem was William McClay's work in 1790 on the retreat of the Niagara Falls escarpment, which led him to propose an age of 55 440 years for the earth (Tinkler, 1985). Others tried a different tack. The nineteenth-century scientist John Joly, for example, calculated the quantity of sodium salt in the world's oceans, as well as the amount added every year from rock erosion, and arrived at a figure of 100 million years for the age of the earth. Increasingly, however, came an awareness that even this extended time frame was simply not long enough to account for the entire history of the earth and, moreover, for organic evolution, a view that was underscored by the publication of Darwin's seminal work Origin of Species in 1859. Further challenges to the Ussher timescale and to its successors came from the field of archaeology, with noted antiquarians such as John Evans (and his geological colleague Joseph Prestwich) arguing, on the basis of finds of ancient handaxes, for a protracted period of human occupation extending into a period of antiquity'.... remote beyond any of which we have hitherto found traces' (Renfrew, 1973).

It was into this atmosphere of chronological uncertainty that Louis Agassiz introduced his revolutionary idea of a 'Great Ice Period', which arguably marks the birth of modern Quaternary science. This notion, first propounded in 1837, was initially received with a degree of scepticism by the geological establishment, but the idea not only of a single glaciation but, indeed, of multiple glaciations rapidly gained ground. By the beginning of the twentieth century, most geologists were subscribing to the view that four major glacial episodes had affected the landscapes of both Europe and North America, although the basis for dating these events remained uncertain. An early attempt at establishing a glacial-interglacial chronology was made by the German geologist Albrecht Penck, using the depth of weathering and 'intensity of erosion' in the northern Alpine region of Europe to estimate the duration of interglacial periods. On this basis, an age of 60 000 years was assigned to the Last Interglacial and 240 000 years to the Penultimate Interglacial, the duration of the Quaternary being estimated at 600 000 years (Penck and Bruckner, 1909). An alternative approach using the astronomical timescale based on observed variations in the earth's orbit and axis...