41-1 CHIRP Seismic Imagery from West Okoboji Lake, an Emerging Terrestrial Archive of Late Quaternary Environmental Change in Northwest Iowa

Session: Paleontology, Stratigraphy, Sediments, and Soils (Posters)

Poster Booth No.: 22

Presenting Author:

John Dilworth

Authors:

Dilworth, John¹, Spanbauer, Trisha Lyn², Woolery, Edward W.³, McGlue, Michael M.⁴

(1) Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY, USA, (2) Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY, USA, (3) Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY, USA, (4) Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY, USA,

Abstract:

Here, we document the first compressed high-intensity radiated pulse (CHIRP) seismic images of West Okoboji Lake, one of the Iowa Great Lakes and an emerging source of Late Pleistocene and Holocene sedimentary records of environmental and ecological change in America’s heartland. CHIRP seismic data were collected with an Edgetech 3200-XS subbottom profiling system and a 512i tow vehicle; the system was deployed from a vessel of opportunity and operated over a range of frequencies (~0.5–10 kHz). A grid of seismic profiles totaling ~56 line km were collected from West Okoboji Lake, and these data were integrated with existing geological maps from Dickinson County (northwest Iowa) and lake floor sediments to provide new insights on patterns and processes of deposition. CHIRP image quality varied widely owing to acquisition challenges (waves, boat traffic) and shallow gas curtains, but the images illustrate patterns of lake floor relief and in the best instances, clear zones of sediment accumulation. Low amplitude, semicontinuous reflections organized as lenses and bidirectionally down-lapping pods are conspicuous in West Okoboji Lake, particularly between ~23 and 27 ms TWTT below the lake surface, whereas at shallower depths, this acoustic facies tends to exhibit draping geometries. Internal seiche activity has been documented at West Okoboji Lake in the summer months, when the long axis of the lake is aligned with the prevailing wind direction; this process may influence the observed accumulation geometries. Though mostly obscured by gas, mixed-amplitude, semicontinuous reflections characterize deeper deposits in West Okoboji Lake, providing a glimpse of the expanded stratigraphic record archived in the basin. Future percussion piston coring efforts will target both shallow and deep accumulations delimited by the CHIRP data.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

doi: 10.1130/abs/2026SE-11555

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