Ground-Penetrating Radar Investigations of Nearshore Sediments

of Eastern Lake Michigan

William A. Sauck, W. R. Laton, D. L. Seng, William A. Sauck, W. R. Laton, D. L. Seng,

and M. A. VanderEideand M. A. VanderEide

Institute for Water SciencesInstitute for Water Sciences

Dept. of GeosciencesDept. of Geosciences

Western Michigan UniversityWestern Michigan University

Kalamazoo, MI 49008Kalamazoo, MI 49008

IAGLR, May, 2000

Acknowledgements

USGS: Woods Hole (1991-93 funding).USGS: Woods Hole (1991-93 funding). US Army Corps of Engineers (1992-93)US Army Corps of Engineers (1992-93) US EPA - Univ. of Mich. (1993-94)US EPA - Univ. of Mich. (1993-94) COE-Toltest Contract (1997-98).COE-Toltest Contract (1997-98). Student helpersStudent helpers

Outline

IntroductionIntroduction Review of Equipment UsedReview of Equipment Used ResultsResults

““Modern or Mobile” Sand Thickness Modern or Mobile” Sand Thickness Channel-forms at River MouthsChannel-forms at River Mouths Glacial Drift LithologiesGlacial Drift Lithologies Discovery of submerged aeolian sand depositDiscovery of submerged aeolian sand deposit

ConclusionsConclusions RecommendationsRecommendations

Introduction

History of GPR Use in Lakes and Rivers.History of GPR Use in Lakes and Rivers. Purpose of these investigations.Purpose of these investigations. Chippewa low stage of L. Michigan.Chippewa low stage of L. Michigan. Relative permittivity controls GPR velocity.Relative permittivity controls GPR velocity. Conductivity controls GPR attenuation.Conductivity controls GPR attenuation. Innovations in this study.Innovations in this study.

Equipment Used

7 m work boat (MonArk) or 6 m Carolina 7 m work boat (MonArk) or 6 m Carolina Skiff.Skiff.

GSSI SIR-10A+ GPR System, with custom GSSI SIR-10A+ GPR System, with custom 35 m Tescorp cable.35 m Tescorp cable.

Custom 55 cm monostatic dipole antenna.Custom 55 cm monostatic dipole antenna. Differential GPS (Magellan ProMark X-CP), Differential GPS (Magellan ProMark X-CP),

using Milwaukee USCG Diff. Beacon using Milwaukee USCG Diff. Beacon Transmitter.Transmitter.

Lowrance X-16 analog sonar (upward-Lowrance X-16 analog sonar (upward-looking, bottom-sled mounted)looking, bottom-sled mounted)

GPR, Sonar, and Differential GPS RadioBeacon Receiver installed in 19’ Carolina Skiff.

The Bottom-towed GPR Antenna

Built to obtain uniform sub-bottom Built to obtain uniform sub-bottom penetration regardless of water depth.penetration regardless of water depth.

55 cm monostatic dipole (145 MHz) with GSSI 55 cm monostatic dipole (145 MHz) with GSSI 769DA transceiver antenna driver card.769DA transceiver antenna driver card.

Enclosed in larger diameter PVC pipe.Enclosed in larger diameter PVC pipe. Strapped to bottom sled made of 2” diam. Strapped to bottom sled made of 2” diam.

PVC pipe filled with concrete ballast.PVC pipe filled with concrete ballast. Upward looking SONAR transducer mounted Upward looking SONAR transducer mounted

on front corner of sled.on front corner of sled.

Underwater GPR antenna mounted on weighted bottom sled, being deployed at shore from Monark work boat.

Results:

Warren Dunes

WNW

Results: St. Joseph-Benton Harbor Channel-forms

Shore-parallel profilesShore-parallel profiles Stacked channels buried below “modern” Stacked channels buried below “modern”

sands; relict from rise of Lake level after sands; relict from rise of Lake level after Chippewa low stage.Chippewa low stage.

Possible location of north wall of large valley Possible location of north wall of large valley excavated during Chippewa low stage.excavated during Chippewa low stage.

St. Joseph-BentonHarborProfiles

Miami ParkGPRProfiles

W

W

Muskegon

W

LittleSablePoint

ManisteeGPRProfiles

Manistee: Lateral change of substrate lithology.

WNW

(1/3)

NNE

(2/3)

NNE

(3/3)

NNE

Manistee: Submerged dune field

Shore-Parallel Line (3 slides)Shore-Parallel Line (3 slides)

Manistee: Aeolian sand lapping onto till (1/3)

NNE

(2/3)

NNE

(3/3)

NNE

Manistee: Submerged dune field.

Shore-perpendicular line (2 slides).Shore-perpendicular line (2 slides).

(1/2)

WNW

(2/2)

WNW

Conclusions

More than 50 line kilometers have been surveyed More than 50 line kilometers have been surveyed in Lake Michigan.in Lake Michigan.

The base of “modern” sands / top of older The base of “modern” sands / top of older substrate is a strong reflector at all sites.substrate is a strong reflector at all sites.

GPR has been very useful for sand thickness GPR has been very useful for sand thickness studies.studies.

Penetration in sands and gravels is 6-10 meters.Penetration in sands and gravels is 6-10 meters. Some lithologies can be identified or inferred.Some lithologies can be identified or inferred. Numerous peri-glacial, lacustrine, aeolian, and Numerous peri-glacial, lacustrine, aeolian, and

fluvial depositional environments can be fluvial depositional environments can be recognized.recognized.

Recommendations

Improve antenna system; minimize top-of-water Improve antenna system; minimize top-of-water reflection.reflection.

Test in more regions and different lake Test in more regions and different lake environments.environments.

Add other sensors to bottom sled.Add other sensors to bottom sled. Longer cable for use in water depths greater than Longer cable for use in water depths greater than

ten meters.ten meters. GPR is best used in sand/gravel environments; GPR is best used in sand/gravel environments;

clays are relatively impenetrable. Thus, GPR and clays are relatively impenetrable. Thus, GPR and seismic methods are complementary.seismic methods are complementary.

Thank You!

GSSI SIR-10A+; Mainframe Below, Control / Readout Console Above.

Map of area justnorth of Manistee(1 km grid)

DGPS boat tracks of GPRsurvey lines; Manistee.

Real time corrections from Milwaukee Coast Guard Transmitter.

(1000 ft grid)