Bathymetry and selected perspective views of 6 reef and coastal areas in
Northern Lake Michigan.

Dahlia Shoals
 

Click on the thumbnail images to view Dahlia Shoals perspective images at full size, or use the Location Map at the bottom of the page to navigate to perspective views of other locations.

Figure 7.1- Shaded relief map of Dahlia shoal and southwest side of Ile aux Galets. The outline of the image is marked by numerous smooth amphitheater-like features opening to the southwest and northwest. Their original origin is unknown but at present they appear to be in filling with sediment. The Dahlia shoal portion of the area southwest of the 500 m wide linear trough has rough relief, an arcuate ridge, and radiating ridges to the northest similar to those seen at Gull Island Reef. This area is underlain by carbonates of the Detroit River Group (Mich. DNR). (See full-size JPEG--451 kb)

Thumbnails

Figure 7.2 - Oblique view looking southeast over Ile Aux Gallet with Dahlia Shoal in background. The rougher relief (of cobbles and boulders or outcrop?) occurs in water depths less than 12-15m. Limestone outcrops are reported from Ile Aux Gallet underwater observations (Somers, 1968). In deeper water patches and re-entrants of smoother morphology indicate depositional sites (sand?). Distance across the bottom of image is about 2.1 km. (JPEG 293 kb)

Figure 7.3- Oblique Perspective of Dahlia Shoal looking west . Two lobe like troughs at the left and shallow portion of the reef terminate eastward in rough relief and meter-high ridges similar to Boulder and Gull Island Reefs (Fig. 2 and 3). Sediment sand drapes the deeper slopes to the south and east, but less so to the west and south suggesting sediment transport from those directions. Distance across the bottom of perspective is about 3.9 km. (JPEG 244 kb)

Location Map
Click on the boxes within the Location Map below to view the mapview and perspective images of those locations.

http://geopubs.wr.usgs.gov/open-file/of03-120/gl-dahlia.html
for more information contact Peter Barnes
maintained by Carolyn Donlin
last modified 7 February 2003 (kml)
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Department of the Interior   U.S. Geological Survey   Geologic Division   Western Region Coastal & Marine Geology