Quantifying exhumation from apatite fission-track analysis andvitrinite reflectance data: precision, accuracy and latest results from the Atlantic margin of NW Europe
Published:January 01, 2002
Paul F. Green, Ian R. Duddy, Kerry A. Hegarty, 2002. "Quantifying exhumation from apatite fission-track analysis andvitrinite reflectance data: precision, accuracy and latest results from the Atlantic margin of NW Europe", Exhumation of the North Atlantic Margin: Timing, Mechanisms and Implications for Petroleum Exploration, A. G. Doré, J. A. Cartwright, M. S. Stoker, J. P. Turner, N. White
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In areas where significant unconformities are present, palaeotemperatures derived from apatite fission-track analysis (AFTA) and vitrinite reflectance (VR) data through a vertical rock section can be used to estimate palaeogeothermal gradients and (by extrapolation to an assumed palaeo-surface temperature) amounts of exhumation (palaeo-burial). AFTA also provides a direct estimate of the timing of exhumation. These parameters can be used to reconstruct more complete histories than those based purely on the preserved rock record.
Precision and accuracy of these estimates are controlled by a range of theoretical and practical factors, perhaps the most important being the use of appropriate kinetic models. In extracting thermal history information from fission tracks in apatite, it is essential to use models that can describe variation in response between apatite grains within a sample. It is also important to recognize the limitations of the methods. AFTA and VR are dominated by maximum temperatures, preserving no information on events prior to a palaeo-thermal maximum. Recognition of this allows definition of key aspects of the history with greater precision.
Results from NW Europe define a series of regionally synchronous palaeo-thermal episodes, with cooling beginning in Early Cretaceous, Early Tertiary and Late Tertiary times. Latest results show that Early Tertiary palaeo-thermal effects in NW England can be understood as being due to a combination of higher basal heat flow and deeper burial, and emphasize the importance of obtaining data from a vertical sequence of samples. Comparison with similar results from other parts of the world suggests that events at plate margins exert a key influence on the processes responsible for regional exhumation, as recognized through Mesozoic and Cenozoic times across NW Europe.
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Exhumation of the North Atlantic Margin: Timing, Mechanisms and Implications for Petroleum Exploration
Northwest Europe has undergone repeated episodes of exhumation (the exposure of formerly buried rocks) due to such factors as post-orogenic unroofing, rift-shoulder uplift, hotspot activity, compressive tectonics, eustatic sea-level change, glaciation and isostatic readjustment. The main observational legacy of this exhumation around the North Atlantic is preserved in the comparatively young (Mesozoic and Cenozoic) geological record of this region. Despite a rapid increase in the understanding of the exhumation of this area, there are still many unknowns: the relative intensity of the various phases and their geographical variation; mechanisms of uplift; primary causes of exhumation. Tied to these problems is the larger-scale question of whether the circum-North Atlantic is unique or whether its behaviour is typical for passive margins.
There have been several attempts in recent years to bring together researchers to address these questions, but these have often focused on one particular geographical area or one particular exhumation phase. Before an integrated story can emerge, disciplines that have traditionally remained apart need to come together: geomorphology and offshore seismic interpretation; Palaeogene and Neogene studies; Scandinavian and British-Irish research schools. This volume represents a first step in this direction by providing an inter-disciplinary set of studies over a wide latitudinal range of the NW European margin.
The studies presented here are based on a variety of techniques that have been employed to address the main concerns of North Atlantic exhumation history, including timing, mechanisms and the sedimentary response of the continental margin. The 25 papers presented in this volume have been arranged in four sections to reflect the highly varied approach to this subject and the commercial implications. Part 1 is concerned with exhumation mechanisms, focusing primarily on the Iceland Plume. Parts 2 and 3 present ongoing research on the continental margin record offshore Scandinavia, Britain, Ireland and the Faroes. The papers in these two parts illustrate the communication that is now occurring between the two regional research schools and the acknowledgement of a multiphase Cenozoic denudation chronology for both areas. Part 4 contains five papers describing the significant changes to the hydrocarbon systems that occur in exhumed basins, detailing the implications for hydrocarbon-bearing basins.
Exhumation of the North Atlantic Margin: Timing, Mechanisms and Implications for Petroleum Exploration is the most up-to-date and complete volume integrating all aspects of the Mesozoic-Cenozoic exhumation of North Atlantic borderlands. Itwill be of interest to those within the oil industry, geomorphologists and other workers with an interest in NW European regional geology.