L. Hatch — Marine Terraces in S.E. Connecticut. 323 



Where the 200-foot level abuts against the 400-foot level 

 the difference is easier to see. 



Relation of the Terraces to the Geology of the Region. 



There would be little value in a study of this kind, however, 

 unless we might eliminate the hypothesis that such terraces 

 may be due to differences in rock structure or hardness. For- 

 tunately the geology has been worked ouf^ over the larger 

 part of the area so that this hypothesis may be tested. This 

 part includes most of the better-defined terrace levels, and a 

 number of each, w^hich may be compared. 



The best profile (showing all the terraces) is undoubtedly 

 that of the long divide extending south from Wintechog Hill, 

 and which may be continued northward to Bay Mountain in 



Fig. 3. 



Pw in W- ^ ' 



Tdugwank 



PCPsTon 

 Oiabbro 



[7777-1 Horn blender 

 schisb 



flt^ ^Alask.W [773S ^D^-^>-^^ 

 Jneiss 



iSVonirgroni, , vi Stonin^fon 

 liiijectionlil^ qneiis 



Fig. 3. Geology along divide extending south from Wintechog Hill and 

 continued north to Bay Mt. (Moosup Quad.). Geology by G. F. Loughlin, 

 U. S. Geol. Surv., Bull. 492, 1910, and by writer, Conn. Geol. and Nat. His. 

 Surv., Bulletin in preparation. 



the next quadrangle. The geology along this line is shown in 

 fig. 3. Four distinct terraces are seen, and except for the gen- 

 tle rise between the 200- and 300-foot levels, the ten-ace levels 

 show no relation whatever to the rock structure. This rise 

 occurs at the contact of normal Sterling granite and an injec- 

 tion gneiss. This position, however, does not seem significant, 

 for the rocks are not notably different in hardness and the con- 

 tact elsewhere has no topographic expression. The 300-foot 

 level is distinctly shown in fig. 1 E, covering considerable area, 

 and there is probably no error in considering it a separate ter- 

 race. 



The best terraces are found on the hard rock, but are not 

 due to differences in hardness, for the same rock, such as alask- 



* The northwest corner of Stonington quadrangle was mapped by G. F. 

 Loughlin, U. S. Geol. Surv., Bull. 493, 1910. The southeast part was map- 

 ped by the writer, Conn. Geol. and Natl. Hist. Survey Bulletin in prepara- 

 tion. 



