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System	Age	Formation	Average Thickness (ft)	Elevation near Huntsville (ft)	Geologic Description	Exposure Siting in Huntsville - Madison County Area
Quaternary	Recent	Alluvium Deposits	0-30	1560-1580	Unconsolidated sand, clay, and gravel	Some evidence found in northeast Madison County atop Bingham Mountain
Pennsylvanian		Pottsville Formation	85-90	1480	Sandstone, brown and gray-brown, medium to coarse grained, massive and thin bedded, contains some shale and a thin seam of coal near base. Well rounded grains. Iron containing.	Top of Cumberland Plateau including Monte Sano, Green, Keel, and Wallace Mountain
Mississippian	Chester	Pennington Formation	80-100	1400	Shale, red, gray, and green with sand and some shaly limeston beds	Thin seam found near base of sandstone caprock along Monte Sano bike trails running below the bluffs
		Bangor Limestone	350-400	1000	Limestone, blue-gray, dark gray, crystalline, oolitic and partly fossiliferous, dolomitic	Numerous outcroppings found at surface. Exposed in upper rock cuts along Governors Drive/Highway 431 across Monte Sano heading into Big Cove
		Hartselle Sandstone	0-90	910	Sandstone, tan to brownish gray, medium to coarse grained, hard, sharp edged grains	Found all across the upper crest of Chapman Mountain, Weatherly Mountain, King Mountain, and Garth Mountain
		Gasper Formation	40-90	820	Limestone, light-gray to gray, argillaceous, crystalline, abundantly fossiliferous, partly oolitic, some shale layers.	Large exposure all across mountainous slopes
	Meremac	St. Genevieve Limestone	180+/-	640	Limestone, light gray, oolitic, thick-bedded, fossiliferous	Exposure along lower base of mountains
		Tuscumbian Limestone	150-200	below median ground level	Limestone, dark to light gray, crystalline, massive bedded, fossiliferous, some chert near base of layer	Outcroppigs all across Huntsville including Big Springs Park below banks and the courthouse. Thick layers below surface all across metro area. Red Clay Forming.
	Osage	Fort Payne Chert	95-160	below median ground level	Limestone, gray and yellow, abundant chert, highly porous	Heavily Saturated Ground water bearing formation. Tapped into at Dallas Wells.
Devonian		Chattanooga Shale	0.5-10	below median ground level	Shale, black, hard, fissile, contains bitumen and pyrite, some sand, partly radioactive	Thin seams found along Flint River Basin in Northeast and North Central Madison County near Riverton Area.
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