CONCLUSION 275 



erate/^ ^ but the possible relation or confusion locally with edgewise con- 

 glomerate may be at least mentioned here. 



PRESERVATION 



The conglomerate in the Galena is finely preserved. This is evident 

 from association of many perfect fossils, as well as from the pebbles 

 themselves. Fine preservation can, of course, not be claimed as a char- 

 acteristic of conglomerates of any kind. If they occur in undisturbed 

 shaly matrix or associated with many well kept fossils, the condition of 

 the pebbles should at least be good. But the probability that corrosion 

 conglomerates often lie in porous limestone or sandstone where they can 

 be leached and more or less defaced must be considered in addition to 

 the probability, as indicated in the preceding paragraphs, that conglom- 

 erate formed at least in essentially the same way as these may originally 

 bear little that is characteristic. Any limestone conglomerate, therefore, 

 that does not contain pebbles which are characteristic of lag-gravel, 

 river, sea-beach, or other gravel may be suspected of being corrosion con- 

 glomerate. I may add here that the name corrosion conglomerate is 

 used by me not because no mechanical agent is involved in forming them, 

 but merely because corrqsion surface would be the most persisting fea- 

 ture when once developed. 



Conclusion 



As interpreted, the occurrence of conglomerate in the Galena is in 

 itself not of great significance. It represents merely a time of quiet or 

 failure of sedimentary deposition. Times of no deposition were probably 

 common enough while formations of the Cambrian and Ordovician were 

 making — that is why they are thin — in this region. Some of those times 

 are represented by intraformational conglomerates and some are not, if 

 conditions of the Galena-Trenton are typical. Greater significance arises 

 from the example or evidence which the study of this conglomerate af- 

 fords, tending to show that conglomerate can be formed in the sea under 

 diverse conditions; that not all marine conglomerate is made on the 

 shores. 



In conclusion, an estimate is attempted with respect to the agents and 

 to the probable limit of the conditions under which corrosion con- 

 glomerate might have formed. Two probable agents — ^giant sea-weeds 

 and earthquakes — have already been mentioned. Giant sea-weeds an- 

 chored to the bottom, if entangled by rafts of other sea-weeds driven by 



« G. W, Stose : Folio 170, U. S. Geological Survey, , , 



