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Ground‐penetrating radar facies as an aid to sequence stratigraphic analysis: application to the archaeology of Clonmacnoise Castle, Ireland
Author(s) -
Ruffell Alastair,
Geraghty Louise,
Brown Colin,
Barton Kevin
Publication year - 2004
Publication title -
archaeological prospection
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.785
H-Index - 38
eISSN - 1099-0763
pISSN - 1075-2196
DOI - 10.1002/arp.240
Subject(s) - geology , facies , ground penetrating radar , sequence stratigraphy , stratigraphy , sequence (biology) , fluvial , paleontology , context (archaeology) , fault scarp , onlap , geomorphology , radar , fault (geology) , tectonics , structural basin , telecommunications , genetics , biology , computer science
This paper describes the advantages of interpreting ground‐penetrating radar (GPR) facies in a sequence stratigraphic context. These data have been collected adjacent to the River Shannon at Clonmacnoise Castle in central Ireland and demonstrate that stratigraphy is not necessarily made up of horizontal isochronous surfaces; some reflective surfaces are more important than others in interpretation and that two‐dimensional sections must be interpreted with caution. Radar facies analysis and thus sequence stratigraphy can be used to both interpret the sedimentary record in terms of palaeoenvironments as well as identify important (key) surfaces. Bright, continuous surfaces are often found at horizons of palaeoenvironmental change and have distinctive reflector shapes and terminations (or stratal patterns) above and below. Such stratal patterns define and reflect linked fluvial and human environments that have developed and been preserved through the creation of accommodation space. Key surfaces have been identified when sedimentation was altered, thus reflecting a natural or anthropogenic palaeoenvironmental change. In anthropogenically modified or created successions, such as those seen at Clonmacnoise, key surfaces have produced changes in dielectric constants in the sediments that are seen as radar reflections. Natural activity includes lateral migration of point‐bars and fluvial onlap. Anthropogenic activity has created accommodation space (the moat), a major sequence boundary and subdwelling surface disruption of reflectors. A pre‐moat fault can be observed on GPR data that is along strike of a surface scarp to the southwest of Clonmacnoise Castle. The results demonstrate the enhanced interpretive and predictive use of radar facies in sequence stratigraphy. Copyright © 2004 John Wiley & Sons, Ltd.