Three-dimensional architecture and hydrostratigraphy of cross-cutting buried valleys using airborne electromagnetics, glaciated Central Lowlands, Nebraska, USA

Jesse T. Korus, R. Matt Joeckel, Dana P. Divine, Jared D. Abraham

Research output: Contribution to journalArticlepeer-review

Abstract

Buried valleys are characteristic features of glaciated landscapes, and their deposits host important aquifers worldwide. Understanding the stratigraphic architecture of these deposits is essential for protecting groundwater and interpreting sedimentary processes in subglacial and ice-marginal environments. The relationships between depositional architecture, topography and hydrostratigraphy in dissected, pre-Illinoian till sheets is poorly understood. Boreholes alone are inadequate to characterize the complex geology of buried valleys, but airborne electromagnetic surveys have proven useful for this purpose. A key question is whether the sedimentary architecture of buried valleys can be interpreted from airborne electromagnetic profiles. This study employs airborne electromagnetic resistivity profiles to interpret the three-dimensional sedimentary architecture of cross-cutting buried valleys in a ca 400 km2 area along the western margin of Laurentide glaciation in North America. A progenitor bedrock valley is succeeded by at least five generations of tunnel valleys that become progressively younger northward. Tunnel-valley infills are highly variable, reflecting under-filled and over-filled conditions. Under-filled tunnel valleys are expressed on the modern landscape and contain fine sediments that act as hydraulic barriers. Over-filled tunnel valleys are not recognized in the modern landscape, but where they are present they form hydraulic windows between deep aquifer units and the land surface. The interpretation of tunnel-valley genesis herein provides evidence of the relationships between depositional processes and glacial landforms in a dissected, pre-Illinoian till sheet, and contributes to the understanding of the complex physical hydrology of glacial aquifers in general.

Original languageEnglish (US)
Pages (from-to)553-581
Number of pages29
JournalSedimentology
Volume64
Issue number2
DOIs
StatePublished - Feb 1 2017

Keywords

  • Airborne geophysics
  • buried valleys
  • glacial
  • hydrogeology
  • tunnel valleys

ASJC Scopus subject areas

  • Geology
  • Stratigraphy

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