Dahlia Shoals
 

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).