MISSISSIPPIAN. 423 



The shales are dark or even black and the dolomites blue or dark and impure. 

 The general association of dolomite and gypsum is like that in the Salina, but the 

 deposits contain more clastic mud in proportion to the lime salts. 



According to Lane the deposition of the Michigan formation went on until " a 

 depression to the west opened connection with the wide ocean at the time of the 

 Maxville limestone of Ohio." Deposition appears to have gone on continuously 

 with change to the formation of limestone. 



The Bayport (Maxville?) limestone succeeds the Michigan formation, the two 

 formations composing the Grand Rapids group. The Bayport is a hard light- 

 colored limestone with chert. It was deeply eroded before the deposition of the 

 overlying Parma sandstone, of Pottsville age. The thickness remaining is usually 

 only 50 to 75 feet, but in the well at Mount Pleasant Lane ^'^^ recognizes as Maxville 

 (Bayport) : 



Feet. 



Shale and red limestone (weathered?) 30 



White limestone 30 



White sandstone, very salt water 120 



White limestone 55 



235 



The erosion of the Bayport limestone was general and at some points is com- 

 plete. The formation is taken as the plane of division between the Mississippian 

 and Pennsylvanian. 



L 20. NOVA SCOTIA AND ADJACENT NEW BRUNSWICK. 



For discussion of this area by Ells and Bailey see Chapter VIII, pages 384-386. 



M 20. BONA VENTURE COUNTY, QUEBEC. 



The "Lower Carboniferous" (Mississippian) is represented by the Bona venture 

 conglomerate along the north shore of Chaleur Bay and the extremity of the Gaspe 

 Peninsula. The Bonaventure, as described by Logan,'^"'' is a basal conglomerate, 

 in places remarkably coarse, composed of pebbles, bowlders, and blocks derived 

 from the underlying Silurian limestones and igneous rocks intrusive in them; all 

 embedded in a red sandstone, which constitutes also an upper and more continuous 

 member. Ells^°^^ distinguishes between the basal conglomerate and the upper red 

 sandstone, more particularly on the south shore, near Restigouche Harbor, where 

 the lower conglomerates are interstratified ' ' with gray beds containing Psilophyton 

 and other Devonian fossils," and are unconformably overlain by the upper beds. 



The relations of the Bonaventure conglomerate in the eastern exposures of 

 Gaspe Peninsula have recently been studied by Clarke,^^^"^ who describes them as 

 follows : 



Over the tops of the broken and decapitated folds of sand, limestone and conglomerate in 

 Gaspe County lies a mantle of coarse clastic material, partly sand but chiefly jasper and hmestone 

 conglomerates. These strata do not appear north of Gaspe Bay and are chiefly confined to the 

 mountains about Perce and to Bonaventure Island. Sandstones and conglomerates together 

 may attain an elevation o( 1,500 feet represented by the Perce Mountain and they have a gentle 

 and apparently uniform dip to the north, not often exceeding 10° and generally less. These con- 

 stitute the Bonaventure formation of Logan and were regarded by him as of early Carbonic age. 



