(574 E. O. ULRICH REVISION OF THE PALEOZOIC SYSTEMS 



deposits can do it. Further, in view of the facts mentioned in the pre- 

 ceding paragraph, especially in the absence of any evidence to the con- 

 trary, it seems reasonably established that the Canadian extends to the 

 base of the Jonesboro limestone at Jonesboro, Tennessee. 



Regarding the age of the top of the Jonesboro limestone, the position 

 of the Ceratopea zone in other, presumably more complete, sections gives 

 the only competent clue. At Chambersburg, Pennsylvania, the Ceratopea 

 fauna is found 1,100 feet beneath the top of the Beekmantown lime- 

 stone, vhich there has a total thickness of about 2,300 feet. Though 

 the Ceratopea has not been observed at Bellefonte, the only part of this 

 great section that at all suggests its zone is the Axeman limestone, which 

 here lies 2,145 feet beneath the top of the Canadian. In Oklahoma the 

 Ceratopea zone was not exactly located in the measured section, but, ac- 

 cording to the best evidence now available, it lies not less than 3,000 feet 

 beneath the top of the Arbuckle limestone. According to these data, it 

 appears that the Jonesboro limestone represents only the lower half of 

 the Canadian system as now constituted. 



Canadian limestone in Tuckaleechee and Wear coves, Tennessee. — In 

 the Knoxville folio, No. 16, IT. S. Geological Survey Atlas, magnesian 

 and pure limestones are mapped in Tuckaleechee and Wear coves, some 

 20 to 25 miles southeast of Knoxville, as Knox dolomite. These lime- 

 stones have yielded a few fossils of types unquestionably younger than 

 any so far found in the typical Knox. They are overlain by slates and 

 conglomerates of the "Ocoee series," which presumably have been thrust 

 northwestwardly over them. The limestone forms the floor of the coves 

 and is relatively flat-lying, so that the full thickness is not shown. Still, 

 the irregularities of surface erosion and the slight dip of the rocks cause 

 exposures of several hundred feet in Tuckaleechee Cove. 



An incomplete list of the fossils includes the following : Didymograptus 

 cf. hifidus^ Dalmanella cf. electra, Proton- artliia cf. rossi, Helicotoma f 

 sp. Hormotoma cf. arfempiiin. undeterminable fragments of trilobites, 

 and plates of cystidea. Judging from this f annul e, the beds are certainly 

 pdst-Ozarkian. The alliances of the several species strongly suggest 

 middle Canadian zones. 



The shale fades of the Canadian — The Levis shale type of sediments. — 

 The Levis shale type of sediments of this period seems to have been 

 deposited in narrow synclinal troughs or channels on the inner border 

 of Paleozoic land masses which then included what are now marginal . 

 areas of the T^orth American continent. Judging from the present dis- 

 tribution of the peculiar graptolite faunas which are so characteristic 

 of the Canadian shale formations, one of these channels entered the con- 



