226 CONFERENCE ON PALEOZOIC PALEOGEOGRAPHY 



tion of it may leave a recognizable impression ; or, again, the greater the 

 influx of terrigenous matter, including vegetal debris, with consequently 

 more rapid sedimentary deposition, the more likely the burial of a part 

 of the plant refuse in recognizable condition. 



It would appear that the areas of most abundant terrigenous muds, 

 with plant ingredients, between Central An^erica and the Cocos or the 

 Galapagos Islands, are regions of deposition of somewhat carbonaceous 

 shales, probably more or less calcareous in certain districts, and possibly 

 comparable to those of the Upper Devonian in portions of Ohio. They 

 contain the raw materials for the petroleum and natural gas of a future 

 geologic age, when portions of partially decayed plant refuse in the region 

 of the western Pacific Islands will be found in calcareous shales or shaly 

 ferriferous or manganiferous limestones. 



If, now, we turn to examine the geological conditions attending the 

 occurrence of well preserved plants in limestones or other clearly marine 

 strata of geologic age, we find that in nearly every case of reasonably 

 good preservation of leaf or fern material there is associated geologic evi- 

 dence of the existence of land not far distant. The best preserved filicoid 

 types of the Ithaca group are associated with contemporaneous channel 

 cutting and other local shoal water phenomena. The relatively well pre- 

 served material in the Portage (Hatch), near Naples, New York, is said 

 to be associated with coaly streaks, which I regard as indicative of prob- 

 able local flats or possibly a partially land-locked or temporarily lagoonal' 

 environment. The splendid Archceopteris fronds of the Catskill and 

 Chemung in southern New York and northeastern Pennsylvania are in 

 most cases stratigraphically associated with contemporaneous erosion 

 planes, truncated mud beds, carbonaceous wedges, breccias or conglomer- 

 ates — all indicative of subaerial exposure or approximate littoral condi- 

 tions. So, also, with the better grade of material from the Burgoon and 

 the lower Pocono. The floras in the Canaan limestones of the Buck- 

 hannon quadrangle in West Virginia, in the Bluefield shale formation at 

 Abbs Valley, in southwest Virginia, and in the Bangor of Alabama, ap- 

 pear in interbedded shales containing thin coals; in sand wedges of 

 littoral, or possibly shoal, origin ; or if in impure limestones, as in West 

 Virginia, at horizons of limestone breccias. In fact, the discovery of 

 thes^ plants is very important, as drawing attention to the occurrence of 

 diastrophic movement during the long period of Mississippian marine 

 sedimentation. The floras and sections have not yet been studied suffi- 

 ciently to show how many uplifts took place in one region or another of 

 the Appalachian trough during Mississippian time. According to the 



