MAUVI.AM) <;i;()l.()(;iCAL SIHVKY 53 



ten 111 iKUtiiiiis (.r ihc iii-fii shows lliiil the laiid-dcrivcd clcnifiits of llie 

 deposits arc maiiily (|iiait/.n-,'. ijiiart/, -rraiiis prciloniinatiii^'. I''raginentrt 

 of crvstalliiic rocks occur, wliilc iiiiiin'roiis coiistit iiciil and accessory 

 luiiierals derived from tliciii are found. 



Cliciiiical analyses of several typical specimens, made l)v .Mr. I'eter 

 Fireman, of Colnnildan Cniversity, <:ive the rollowinjj: results: 



AN.\LYSE8 OF M..\HL8. 



Nan.iemoy. AqiiA. 



I. II. III. 

 Woodstock. .Vijuia Creek. Winclicster. 



SiO., 60.87 :il..58 40. OM 



A1„0,, + Fe.jO, a 32 . (iS 7 . 70 41 . 25 



MfrO :>.77 1.0.^) .76 



CaO 1.06 36.78 None. 



Na,0 .2:1 ..59 .43 



K,0 .77 .37 • .39 



H2O at 110° 3.58 0.76 1.31 



CO2 3.17 29 . 79 .55 



Volatile at red heat less CO.^. . 2.84 .21 6.27 



P2O5 None. .09 .13 



98. .t7 ;»>;.'.I2 100.16 



Siliceous matter 73.48 25. oU 52.30 



a Considerable FeoOj in all samples. 



STRIKE AND DIP. 



The strike of the Eocene deposits in Delaware and Maryland is ap- 

 proximately northeast and southwest, while in A'irginia the prevailing 

 trend is more nearh' north and sonth. This change in direction of 

 strike takes jjlace in the area hetween the Patuxent and Rappahannock 

 rivers, chiefly in the Potomac basin. 



Carefnl measurements made at each of the local sections show the 

 dip of the strata to he on the average about 12^ feet to the mile. The 

 Tiirritella bed (Zone 9), which has an elevation of 63 feet at its base iri 

 the Aqnia Creek section, has descended to 25 feet in the Potomac Creek 

 section, 3 miles distant, while the indurated layer (Zone 5), which stands 

 at 24 feet at the western end of the Aquia Creek section, has passed 

 below tide level 2 miles to the southeastward. Similar measurements 

 made at Woodstock and in some of the intervening ravines do not change 

 the average estimate of the dip found at the two points first mentioned. 



