Application of impulse radar to continuous profiling of tephra-bearing lake sediments and peats: An initial evaluation

Abstract

Subsurface interface radar (SIR), or impulse radar, uses electromagnetic pulses for continuous stratigraphic profiling. It has been applied to lake sediments (dy-gyttja) and peat deposits containing a sequence of thin, late Quaternary, ashgrade tephras at Lake Maratoto, North Island, New Zealand. The SIR system is very rapid, precise, and reasonably accurate compared with conventional coring and probing methods, but still requires good stratigraphic control for reliable interpretation. Radar penetration depths of up to 10 m were attained. Interfaces between lake bottom and lake sediments and underlying volcanogenic materials of varying lithologies could be readily discerned, as could many of the tephra layers preserved within the lake sediments. Peat depths and positions of stumps or logs on the surface of the subpeat materials could also be determined. Given adequate calibration by drilling, the SIR system appears useful for various shallow subsurface exploration studies, particularly those involving tephrostratigraphy and paleoenvironmental reconstructions from limnic and peat deposits, and in projects on buried wood.

Keywords:

• subsurface interface radar
• radar methods
• electromagnetic logging
• pyroclastics
• stratigraphy
• lake sediments
• peat
• limnology
• paleolimnology
• Lake Maratoto
• Rukuhia
• bogs
• organic materials