Pirada Shale Fm
Period:
Cambrian
Age Interval:
Province:
Senegal Basin
Type Locality and Naming
Synonym: Pirada Shale, Pirada Fm
References: Brownfield and Charpentier, 2003
[Fig. 1. Generalized map of the central and southern parts of the Senegal Basin showing part of the Senegal Province, the Mauritania, Northern, and Casamance subbasins, the Mesozoic carbonate platform edge, the northern and southern salt basins, the Mauritanide Mountains, the Bové Basin, Deep Sea Drilling Project sites 367 and 368, the 2-second sediment isopach, and the onshore depth to basement isopachs (Brownfield and Charpentier, 2003)]
[Fig. 2: Generalized stratigraphic column for the Northern subbasin and the southern part of the Mauritania subbasins (Brownfield and Charpentier, 2003).]
Lithology and Thickness
The Pirada Shale is one of the pre-rift sections, and is made up entirely of shale and is estimated to be about 350m thick (fig. 4 of Brownfield and Charpentier, 2003). The Cambrian sedimentary section is as much as 1,250 m thick and contains three units: the Pirada Shale, the Cantari Shale, and the Caium Sandstone.
Lithology Pattern:
Claystone
Relationships and Distribution
Lower contact
Non-conformably overlies the undifferentiated Precambrian metamorphic rocks (Brownfield and Charpentier, 2003).
Upper contact
Cantari Shale Fm (conformable)
Regional extent
Senegal Province, Mauritania, Senegal, The Gambia, and Guinea-Bissau, Northwest Africa
GeoJSON
{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[-17.78,22.85],[-17.27,22.83],[-16.61,22.77],[-16.26,22.7],[-16.51,21.78],[-16.1,21.53],[-16.08,20.98],[-15.36,20.16],[-14.12,18.91],[-13.34,17.94],[-13.71,17.32],[-13.18,16.63],[-13.28,15.95],[-12.62,14.69],[-12.62,13.65],[-13.04,12.95],[-13.55,12.66],[-14.54,12.5],[-15.05,12.07],[-15.15,11.59],[-14.9,11.26],[-14.97,10.14],[-15.32,9],[-16.36,9.09],[-17.58,9.35],[-17.88,9.5],[-17.58,10.73],[-17.8,12.09],[-17.97,14.06],[-18.09,14.74],[-17.86,15.58],[-17.47,15.8],[-17.35,16.21],[-17.18,17.8],[-17.72,18.86],[-18.64,20.42],[-18.33,21.18],[-17.78,22.85]]]]}}
Fossils
Age
lower Cambrian
Age Span:
Beginning stage:
Fortunian
Fraction up in beginning stage:
0
Beginning date (Ma):
538.80
Ending stage:
Cambrian Stage 2
Fraction up in the ending stage:
1.0
Ending date (Ma):
521.00
Depositional setting
Depositional pattern:
Additional Information
Compiler:
Enam O. Obiosio, Solomon Joshua Avong, Henry Nasir Suleiman, Rebecca Bobick (and Wen Du), modified from Brownfield, M.E. and Charpentier, R.R., 2003. "Assessment of the Undiscovered Oil and Gas of the Senegal Province, Mauritania, Senegal, The Gambia, and Guinea-Bissau, Northwest Africa", U.S. Geological Survey Bulletin 2207-A, 1-26.