Palaeontology and life history

Numerous Variscan syntectonic calcite veins cross-cut Palaeozoic rocks in the Moravian Karst. A structural, petrographic and stable isotopic analysis of the calcite veins and a microthermometric study of fluid inclusions in these vein cements have been carried out to determine the origin of the Variscan fluids and their migration during burial and deformation. The isotopic parameters of white (older, more deformed) and rose (younger) calcites are: 87Sr/86Sr is between 0.7078 and 0.7082 (white) and 0.7086 (rose), δ18O is between +17.7 and +26.1 (white) and between +14.8 and +20.7 ‰ SMOW (rose), δ13C ranges from +0.1 to +2.5 (white) and from −0.3 to +1.6 ‰ V-PDB (rose). The isotopic signatures point to precipitation in an older fluid system buffered by the host rock (white calcites) and to an open, younger fluid-dominated system (rose calcites). Parent fluids (H2O–NaCl system) had salinities between 0.35 and 17.25 eq. wt % NaCl. The pressure-corrected and confined homogenization temperatures suggest formation of the calcite veins from a fluid with a temperature between 120 and 170 °C, a pressure of 300–880 bar at a depth between 2.1 and 3.2 km. The fluids were most likely confined to a particular sedimentary bed as a bed-scale fluid migration (white older calcite veins) or, later, to a pile of Palaeozoic sediments as a stratigraphically restricted fluid flow (rose younger calcite veins). The low temperatures and pressures during precipitation of calcites, which took place close to a peak of burial/deformation, confirm the distal position of the Moravian Karst region within the Variscan orogen.

Analysis of the grain-scale deformation mechanisms in folded rocks of the Dongargarh Supergroup, central India, reveals that deformation was accomplished by a combination of pressure solution, microfracturing and dislocation creep processes. The finite strain was assessed using the Rf/ϕ method (X/Z ≈ 2). Partitioning of strain into various deformation mechanisms revealed that dislocation creep and pressure solution were the major contributors to the finite strain, followed by microfracturing. Analyses of microstructures suggest a sequence of dislocation creep followed by pressure solution and microfracturing, that ultimately gave way to microfracturing and limited crystallization or recrystallization. Overall constancy in volume during deformation is suggested from the balance between fracture-related grain-scale dilatancy and solution-related volume loss. Observations on cleavage spacing within various lithologies in a specific structural setting suggest that lithology played a vital role in cleavage development. Cleavage development in sandstones of the Dongargarh Supergroup required thin shale interbeds (for competency contrast) and grain size <0.036 mm (4.75 ϕ).

Summary

Mankind has always been fascinated by fossils, by their beauty and their mystery, their charm and their strangeness, their mute testimony to lives and worlds lost unimaginably long ago. In prehistoric times, our forebears not only collected fossils, but evidently treated them as valued artefacts, as indicated, for example, by the discovery of an ammonite at an Upper Palaeolithic burial site in Aveline's Hole in Burrington in the West Country (Rahtz, 1993), and numerous different types of fossil at Cro Magnon sites in the V´ez`ere valley in the P´erigord region of France, truly the birthplace of European civilisation (many of which are now displayed in the magnificent Museum of Prehistory in Les Eyzies). The habit persisted both in so-called primitive and so-called advanced societies through historical times (Mayor, 2000).

Palaeontology, that is, the scientific study of fossils, may be said to have originated at least as long ago as the sixteenth century (Thackray, in Briggs and Crowther, 1990), and, obviously, continues to be practised to the present day. The earliest written observations on fossils were made by the German Bauer, or Agricola, in his book De natura fossilum, and the earliest illustrations by the Swiss Gesner in his book De rerum fossilium lapidum et gemmarum, both of which date from the sixteenth century. The usage by these and other early observers of the term ‘fossil’, from the Latin fodere, meaning ‘to dig’, pertained to literally anything dug up from the ground or mined, including what we would now classify as minerals, crystals and gemstones. The earliest interpretations as to the nature of what we would now accept as fossils were made by the Danish anatomist Stensen, or Steno, working in the Medici court in Florence, in his publications dating from the latter part of the seventeenth century (Cutler, 2003). Steno applied Descartes’ ‘method of doubt’ and his own deductive logic to demonstrate that the so-called glossopetrae or ‘tongue stones'much valued in medieval Europe for their supposed medicinal properties were in fact not the tongues of snakes turned to stone by St Paul, as was the superstition, but the fossilised equivalents of the shark's teeth he was familiar with from his dissection work.

Summary

Palaeobiology deals with the documentation, analysis and interpretation of the relationships of fossils to evolving earth and life processes and environments, and their application to the elucidation thereof. This chapter deals with applications of fossils in the interpretation of earth and life processes (excluding evolution, covered in Chapter 5), and environments. Readers interested in further details of the principles and practice of palaeobiology are referred to the works of Briggs and Crowther (1990), Dodd and Stanton (1990), Bosence and Allison (1995), Brenchley and Harper (1998), Erwin and Wing (2000), Gastaldo and DiMichele (2000), Briggs and Crowther (2001) and Cohen (2003).

Life strategy

There are a number of theoretical biological models of population dynamics, one of the most elegant and influential of which involves only two variables, r and K, at either end of a continuum (Pianka, 1970). Of these, r refers to the theoretically initially limitless rate of increase of the population of a species, assuming no competition, for example, on occupying a new environmental niche; K to the ultimately limiting, carrying capacity of that niche. Whether a species or a higher-level taxon selects in favour of a strategy that tends to maximise K, through the ability to compete, or r, through the ability to reproduce at a high rate, will depend on a number of factors, including population density etc. K-strategy selection typically involves slow development to reproductive maturity, at large size, sexual reproduction, small numbers of progeny, typically in more than one issue or confinement (iteroparity), long generation time, and a long lifespan; r-strategy selection, rapid development to reproductive maturity, at small size, asexual reproduction in some groups, large numbers of progeny, typically in one issue (semelparity), short generation time and a short lifespan.

In general, there appears to be a tendency towards conservative, or specialist, K-strategy selection in stable environments, and radical, or generalist opportunistic, r-strategy selection in unstable or otherwise stressed environments. Interestingly, environments that are both stable and stressed favour selections involving a combination of components of both strategies. For example, deserts favour plants characterised by a K-type tolerance of long periods of drought, and an r-type ability to react by reproducing rapidly whenever it rains.

Summary

Biostratigraphy deals with the documentation, analysis and interpretation of the ordered succession of fossils, their relationships to evolving earth and life history, and their application to the elucidation thereof (Emery and Myers, 1996; Jones, 1996; Doyle and Bennett, 1998; Backman, in Briggs and Crowther, 2001; Bowring and Martin, in Briggs and Crowther, 2001; Marshall, in Briggs and Crowther, 2001; Rawson, in Briggs and Crowther, 2001; Coe, 2003; Harries, 2003; Gradstein et al., in Gradstein et al., 2005; McGowran, in press). Together with sequence stratigraphy, it is one of the principal bases for chronostratigraphic subdivision and correlation of lithological units, thus providing a spatiotemporal context for their interpretation, and is a fundamental building-block of earth science. This chapter deals with applications of biostratigraphy and sequence stratigraphy in the interpretation of earth – and life – history.

Biostratigraphy

The stratigraphic distributions of the principal fossil groups discussed in Chapter 3 are summarised in Fig. 6.1. The ranges over which they are stratigraphically useful are shown by broad bands. It is evident that most are only useful over certain time intervals, and then only in the appropriate facies. Note also that the potential biostratigraphic usefulness of fossils can be impaired by natural factors, such as post-mortem transportation and diagenetic effects (see Section 2.2), and reworking. The biostratigraphic usefulness of fossils can also be impaired by artificial factors, such as sample acquisition and processing, and subjectivity in specific identification.

Some of the more stratigraphically useful fossil groups are the dinoflagellates, diatoms, calcareous nannoplankton, acritarchs, Bolboforma, foraminiferans, radiolarians, calpionellids, plants, archaeocyathans, ammonoids, belemnites, tentaculitids, trilobites, graptolites, chitinozoans, conodonts and mammals (see appropriate sections in Chapter 3; see also Sub-section 6.1.1). Other groups are only locally important.

Significantly, the more stratigraphically useful fossil groups share two common characteristics: firstly, relatively rapid rates of evolutionary turnover, and hence restricted stratigraphic distributions, and/or essentially isochronous first and last appearances; and secondly, essentially unrestricted ecological distributions (for example, throughout the marine realm, and across a range of biogeographic provinces, in the case of many planktonic or nektonic forms). The most useful groups for practical purposes are also, typically, abundant, well preserved, and easy to identify. These are referred to as ‘marker fossils’ or ‘index fossils’. Conversely, the less stratigraphically useful groups characteristically exhibit relatively slow rates of evolutionary turnover, and/or diachronous or time-transgressive first and last appearances.

Summary

This chapter deals with the generalities and specifics of the evolutionary and extinction events and trends that have controlled past and present, and will control future, biodiversity on Earth.

Readers interested in further details of a general nature are referred to Nisbet (1991), van Andel (1994), Moore et al. (1996), Smith and Szathmary (1999), Stanley (1999), Wicander and Monroe (2000), Groombridge and Jenkins (2002), Conway Morris (2003), Southwood (2003), Dawkins (2004), Erwin, in Moya and Font (2004), Prothero and Dott (2004) and Cowen (in press).

Evolution and extinction

The history of life on Earth, insofar as it can be captured in words, can be said to have been one of general evolutionary diversification intermittently interrupted by mass extinction and recovery (Benton, 1995; Rosenzweig, 1995; Foote, in Erwin and Wing, 2000; Miller, in Erwin and Wing, 2000; Benton, in Briggs and Crowther, 2001; Groombridge and Jenkins, 2002). Certain of the difficulties in description arise from difficulties in quantifying diversity, in part in turn arising from uncertainties as to the representativeness of the fossil record, and from biases and inconsistencies in sampling and interpreting same (see Box 5.1). There are particular problems associated with taxonomic bias and inconsistency, that is, the definition of taxa across different fossil groups. The two main models that have been proposed to date for the evolution of diversity are the equilibrium model, which assumes – logistic – diversification only up to and not beyond a critical point, and the expansion model, which assumes continuous – either additive or exponential – diversification (Benton, in Briggs and Crowther, 2001).

Evolution

This is not the appropriate forum for a detailed discussion of the complex and contentious subject of evolution, that is, the process whereby species and higher-level taxa evolve – or are transformed – into and replaced by others. Suffice it to say here that empirical observations of the fossil record should leave little doubt, even in the mind of the most ardent creationist, that evolution has manifestly evidently been taking place throughout geological time. The difficulties that sceptics have in understanding and accepting evolution perhaps arise in part from the fact that the process cannot actually be observed, other than under artificial laboratory conditions, as it occurs over generations (Lazarus, in Briggs and Crowther, 2001).

This book was first published in 2006. Palaeontology has developed from a descriptive science to an analytical science used to interpret relationships between earth and life history. Applied Palaeontology adopts a holistic, integrated approach to palaeontology, highlighting its key role in the study of the evolving earth, life history and environmental processes. After an introduction to fossils and their classification, each of the principal fossil groups are studied in detail, covering their biology, morphology, classification, palaeobiology and biostratigraphy. The latter sections focus on the applications of fossils in the interpretation of earth and life processes and environments. It concludes with case histories of how our knowledge of fossils is applied, in industry and elsewhere. This is a valuable reference for anyone involved in the applications of palaeontology, including earth, life and environmental scientists, and petroleum, minerals, mining and engineering professionals.

Summary

Palaeontology incorporates several, overlapping, areas, the principal of which are:

Summary

This chapter deals with how our knowledge of fossils and earth and life history is applied in industry and elsewhere.

7.1 Petroleum geology

Readers interested in further details are referred to Jones (1996), Laudon (1996), Selley (1998) and Gluyas and Swarbrick (2003). Those interested in the environmental impact of petroleum exploration and reservoir exploitation are referred to Evans (1997); those interested in impact mitigation, to his discussion of BP's Wytch Farm oilfield underlying Poole Harbour, Dorset, UK, and under development using shore-based ‘extended reach’ directional drilling.

Principles and practice of petroleum geology

Play components

There are essentially three components to a successful play, namely, a working petroleum source-rock and system, to provide the petroleum charge; a reservoir, to store, and ultimately to flow, same; and a cap-rock (seal) and trap, to prevent it from escaping. Each of these play components is discussed in more detail below. A discussion of stratigraphic control on play component distribution follows.

Petroleum source-rocks and systems

Petroleum source-rocks. Petroleum source-rocks are those from which petroleum is derived. They typically consist of abundant organic matter or kerogen, that can be of either terrestrial land-plant or humic, or marine algal or sapropelic, origin. This organic matter is transformed, or matured, into oil and gas by heating on burial. The product will depend on the nature of the source-rock, and on the transformation ratio, or degree of maturation, in turn determined by burial history and by basin type. Typically, oil is generated from so-called ‘type I’ or ‘type II’ source-rocks, whose organic matter is of marine algal origin; and gas either from these same source rocks subjected to more maturation, or from ‘type III” source-rocks, whose organic matter is of terrestrial land-plant origin. Maturation and migration can be modelled using various publicly available and proprietary one-, two- and three-dimensional basin-modelling software packages.

Petroleum systems. Apetroleum system has been variously defined as ‘a dynamic petroleum generating and concentrating system functioning in geological space and time’, or ‘a pod of active source rock and the resulting oil and gas accumulations’. As recently noted by Katz and Mello, in Mello and Katz (2000), although the term has been defined, it nonetheless still appears to mean different, albeit thematically related, things to different individuals and organisations.

Summary

This chapter essentially deals with what fossils are, how they form, how they are collected, and how they are classified and identified, described and illustrated, and curated.

Fossils

The word ‘fossil’ derives from the Latin fodere, meaning ‘to dig’. Its usage is in reference to any and all physical remains or other direct physical indications of past life. The physical remains of past life include not only what are often termed ‘body fossils’, that is, ‘hard parts’ of skeletons such as bones (Denys, in Briggs and Crowther, 2001) and shells (Meldahl, in Briggs and Crowther, 2001), but also, under exceptional circumstances, ‘soft parts’ of animals (Stankiewicz and Briggs, in Briggs and Crowther, 2001), parts of plants (van Bergen, in Briggs and Crowther, 2001), bacteria (Liebig, in Briggs and Crowther, 2001), and biomolecules such as fats, proteins and DNA (Briggs et al., in Erwin and Wing, 2000; Collins and Gernaey, in Briggs and Crowther, 2001; Evershed and Lockheart, in Briggs and Crowther, 2001; Poinar and Paabo, in Briggs and Crowther, 2001; Jones, 2001). Other direct physical indications of past life include ‘trace fossils’ (see separate section in Chapter 3).

The fossilisation process (taphonomy)

The fossilisation process, whereby living individual organisms or communities are transformed after death into fossils or fossil assemblages, is termed taphonomy (Fursich, in Briggs and Crowther, 1990; Allison and Briggs, 1991; Donovan, 1991; Martin, 1999; Behrensmeyer et al., in Erwin and Wing, 2000; Wilson, in Briggs and Crowther, 2001; Holz and Simoes, in Koutsoukos, 2005). In fact, a range of biological, physical and chemical processes is involved, from decomposition (Allison, in Briggs and Crowther, 2001), through disarticulation, fragmentation and transportation (Anderson, in Briggs and Crowther, 2001), to compaction, thermal alteration and dissolution on burial (Briggs, in Briggs and Crowther, 1990; Tucker, in Briggs and Crowther, 1990; Jones, 1996; McNeil et al., 1996), and reworking. For a living organism to become fossilised requires that it can withstand the combined effects of these processes. In general, its chances of becoming fossilised are enhanced if it becomes buried immediately after death (and/or is otherwise protected from decomposition, perhaps by anoxic bottom conditions), and/or is and remains resistant to the destructive physical and chemical effects of the so-called diagenetic processes that enter into operation after burial (see also Sub-section 2.2.2).

Summary

This chapter includes sections on all of the highlevel divisions of organisms identified in Chapter 2 that are important in the fields of palaeobiology and biostratigraphy, namely bacteria, plant-like protists or algae, animal-like protists or protozoans, plants, fungi, invertebrate animals and vertebrate animals. It also covers trace fossils.

As far as practicable, a standard format has been adopted. Areas covered include: biology, morphology and classification; palaeobiology; and biostratigraphy.

Emphasis has been placed on the palaeobiological and biostratigraphic significance of the various groups, and their proven and potential applications in the interpretation of earth and life history and processes. Other areas are covered only if they are relevant to these applications, and only in a level of detail commensurate with applicability. Fossil groups with minimal applicability have not been included.

More or less familiar names have been used wherever practicable, and an attempt has been made to keep the amount of scientific jargon to a necessary minimum.

Micropalaeontology and palynology

The groupings used in this book are essentially natural, reflecting evolutionary relationships, and the arrangement is in at least approximate order of evolutionary advancement. It is worth noting here, though, that an alternative, entirely artificial grouping of microfossils also exists, which is useful for practical purposes, as it is based on size range, composition, and required methods of collection, preparation and study. This treats together the calcareous microfossils, that is, the calcareous algae, the calcispheres or oligosteginids, Bolboforma, foraminiferans, calpionellids, ostracods and otoliths; the siliceous microfossils, that is, the silicoflagellates, diatoms and radiolarians; the phosphatic microfossils, that is, the conodonts and ichthyoliths; the organic-walled microfossils or palynomorphs, that is, the dinoflagellates, acritarchs, plant spores and pollen, and chitinozoans; and the calcareous nannofossils (Jones, 1996). The study of microfossils is termed micropalaeontology; that of organic-walled microfossils or palynomorphs, palynology.

Innovative applications of palynology

Palynology has a number of applications in the fields of petroleum geology, mineral exploration and exploitation, coal mining, and archaeology (see appropriate sections below). It also has applications in a number of other fields.

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Variscan veins: record of fluid circulation and Variscan tectonothermal events in Upper Palaeozoic limestones of the Moravian Karst, Czech Republic

Grain-scale deformation in the Palaeoproterozoic Dongargarh Supergroup, central India: implications for shallow crustal deformation mechanisms from microstructural analysis

Preface

Summary

4 - Palaeobiology

Summary

6 - Biostratigraphy and sequence stratigraphy

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Index

5 - Key biological events in earth history

Summary

Applied Palaeontology

Dedication 2

1 - Introduction

Summary

Frontmatter

References

7 - Case histories of applications of palaeontology

Summary

2 - Fossils and fossilisation

Summary

Dedication 1

Acknowledgements

3 - Principal fossil groups

Summary

Contents

PROTHERO, D. R. 2005. The Evolution of North American Rhinoceroses. ix + 218 pp. Cambridge, New York, Melbourne: Cambridge University Press. Price £60.00, US $100.00 (hard covers). ISBN 0 521 83240 3

DASCH, P. (ed.) 2004. Icy Worlds of the Solar System. xiv + 202 pp. Cambridge, New York, Melbourne: Cambridge University Press. Price £30.00, US $45.00 (hard covers). ISBN 0 521 64048 2

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Applied Palaeontology

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