204 (;. II. (■iiADM'H'K — r()ST-()i;i»()\'i(!.\N di-J'CIjm a'i kin 



Tn the (liaoi-;nns (figures 7, 8. and 9) tlic AcrticMl scale is exagsierated 

 tliree times and the amoTint of compression is also oAcrdra'WTi for the 

 sake of ])ers[)ieuity, but dips as liigli as ;;o deiirees were measured licre 

 iu tlie Potsdam, and at least four u'ood sviidiiies can be nuide out in less 

 than a (piai'ter of a ndle, liaving always the steeper dips toward the south- 

 east as i\n tlie ervstallines. In figure li tliere is n(» exaggeration and the 

 di|)s are siiowii as actually meas;ired, reaeliing 4.i degrees at one point on 

 the east kiioll. The amplitude of tliese folds is (iuite the same (al)out 

 300 feet) as of those on Harrison Ch-eek, luit tlie jaAVS of the pre-Cam- 

 brian vise are not so \'isible here, the conditions being probably more as 

 in figure !'. At other near-by outcrops the Potsdam has suffered crush- 

 ing and mierofaulting or brecciation. and just north of Dekalb village 

 ("Old Dekalb""), on the south margin of the Ogdensburg quadrangle, is 

 the fine examijle of crumpling figured long ago by Emmons.^ 



Time and Cause of thi-: FoLUJXd 



These observations, which can be duplicatt'd at many other points in 

 the Saint Lawrence Valley, indicate that we ai'e dealing here with a true 

 deformation superimposed on the original stratification and invoking 

 rocks as young at least as the Beekmantowii. Ciishing" believes that these 

 movements were under Avay even earlier, and in favor of this view the 

 Avriter would urge the much greater disturbance of the Potsdam, and 

 particularly the red Potsdam, in the Canton region, the difference being 

 so marke(l as to lead to a search for an unconformity at the summit of 

 the latter — a search that failed l)ecause no contact could be located. The 

 most suggesti\(> locality is tlie knoll JTist south of old Dekall). on the 

 ( Joii\-erneui- (|uadrangle. 



In easting about for an exjilanat ion of this deformat i<in. which is wide- 

 spread o\('i- the district between the Adii'ondacks and the Ivaurentide 

 hills, beyonil the Ottawa Eiver (see key ma|) ) . if is most natural to tui'n 

 to the former as the seat of disturbance, since they have been repeatedly 

 domed upward, besides block-faulted. The comparatively thin veneer of 

 Paleozoics in the continually deepening trough (d' the Saint Lawrence 

 could hardly fail to experience some crowding during such domings of 

 the Adirondack massif, and all the facts seem to accord well with this 

 inference. 



Dr. E. Emmon.s : Geol()j;.v of the Socoiicl Disiricl. .New Yoik. p. 104. 

 Op. dt., p. 114. 



