'96 



J. BARRELL MEASUREMENTS OF GEOLOGIC TIME 



and dissected. Then submergence took place to a maximum of 220 feet 

 above present sealevel and the early Pleistocene Sunderland was deposited. 

 Uplift caused dissection as before, and then another submergence to 100 

 feet led to the deposition of the middle Pleistocene Wicomico. This in 

 turn was uplifted and dissected. Finally, the late Pleistocene Talbot 

 formation was laid down up to 40 feet above present sealevel. In these 

 Pleistocene deposits the aggregate progressive movement of baselevel was 



Columnar 

 secMon 





D - 



D - 

 D~ 



A 









* /. *^' • ■.-.'. ■ 





'''/.'• '' •'•'•'} '• 





•'*." ••■.■'••.'•■.'• 





/.''.V'.';'.: {•*■ 









':::■■'■'. '■'■'■'.'■ 





:-;MM 



! /V/ 





— J-^^^^^V) 









r 



:/:.: ::: '.w: 



/ 



Time intervals recorded by sedimenhaHon 



Figure 5. — Sedimentary Record made hy harmonic Oscillations in Baselevel 



A-A. Primary curve of rising baselevel. 

 B-B. Diastrophic oscillations, giving disconformities D-D. 



C-C. Minor oscillations, exaggerated and simplified, due largely to climatic rhythms. 

 Equation of curve C-C : y = sin x — .25 cos 8 x — .05 cos 64 x. 



in a contrary direction to that which leads to the permanent preservation 

 of sediments. They have, furthermore, been geologically rapid, but the 

 nature of the oscillations is nevertheless illustrative of the habit of diastro- 

 phism, clear to us because of the recency in time. 



In times of slow movements of baselevel the numerous smaller rhythms, 

 some of which are climatic in their origin, are able to take effect in the 

 planation of unconsolidated sediments. These frequent smaller oscilla- 

 tions give a crenulation to that sinusoidal curve which measures the 

 progress of diastrophism. In figure 5 the curve C-C shows the summa- 



