Figure 20. Close-up of crystalline basement map over Triassic-Jurassic sills and volcanic rocks at the northern border of the Taoudeni Basin (box 20, Fig. 17, Plates 1 and 2). Edges of Triassic-Jurassic sills within the Taoudeni Basin produce characteristic linear anomalies arranged in polygons—often as low-high pairs (Fig. 20). High frequency anomalies (SE corner of map) typically characterize Triassic-Jurassic volcanic rocks whose susceptibilities range from 15-33 x 10-3 SI (dolerites, microgabbros, Excel spreadsheet). Calculated depths to the top of magnetic basement (Fig. 11, Plate 3) range from ~50-1.5 km in the southwest.
