PROGRESSIVE OVERLAP 595 



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Where the one-foot bed below the Louisiana limestone retains its sandy 

 character throughout, the change from it to the underlying black 

 shale is abrupt in color and texture, but there is no indication of 

 discontinuity of deposition ; the Black shale and the overlying beds 

 represent one depositional series. 



Below the Black shale, and apparently conformable with it, is a brown, 



much decomposed limestone of arenaceous texture % 



This passes downward conformably into a fine grained buff siliceous 

 limestone. The thickness of this bed varies in different sections 

 from 4 to 10 



Underlying this with a somewhat irregular contact is a fossiliferous lime 

 rock with corals and Stromatoporoids indicating its Siluric age. 



Although the contact between the brown fine grained limestone and 

 the coarse coral limestone is somewhat irregular, there is no direct evi- 

 dence of a stratigraphic break here. The irregularity is not more striking 

 than that often found between successive tiers of limestones, where solu- 

 tion along the contact lines will necessarily produce minor irregularities. 

 Moreover, the lower limestone retains its thickness and character in all 

 the sections examined, while the upper brown limestone varies in thick- 

 ness from place to place. No bedding planes are visible in this brown 

 limestone, and the bedding planes of the overlying shale are apparently 

 conformable with its surface. Nevertheless, it seems as if the line of 

 stratigraphic unconformity (disconformity) is to be sought at the base 

 of or within the Black shale. This deposit is entirely unfossiliferous, 

 but passed upward into a bed with Kinderhook fossils. 



At Burlington the Louisiana limestone is underlain by 25 feet of the 

 Chonopectus sandstone, and about 120 feet of a similar but more argilla- 

 ceous rock, which probably rests upon the Devonic limestones. There is 

 nothing at Louisiana to represent this series, except the 1 foot of rock 

 of the Chonopectus sandstone type and the Black shale. It is true that 

 the Louisiana limestone and the overlying Hannibal and Choteau beds 

 form a greater thickness of rock below the Burlington formation at 

 Louisiana than at Burlington, but it is also true that the fauna of the 

 Louisiana limestone, as far as it is known, is a higher fauna than that 

 of the Chonopectus and lower beds. While the base of the Louisiana 

 limestone may not be and probably is not synchronous in the two locali- 

 ties, yet it seems nevertheless to be the fact that deposition of the Kinder- 

 hook began in the Burlington region before it reached the Louisiana 

 region. Thus there appears to have begun a southward transgression 

 of the sea in lower Kinderhook time, and the Black shale of the Louisiana 

 section seems to be the basal bed of the series in that locality. 



