1884.] NATURAL SCIENCES OP PHILADELPHIA. 23t 



PRELIMINAKY NOTES ON THE GEOLOGY OF DELAWARE— LAURENTI AN, 

 PAL2:0Z0IC AND CRETACEOUS AREAS. 



by frederick d. chester. 



Introduction. 



During the years 1837 and 1838, Professor James C. Booth, in 

 accordance with an act of the State Legislature, made a geolog- 

 ical surA'^ey of Delaware, the results of which were published in 

 a report that appeared in 1841. This old memoir is of great 

 value, both from the accuracy of the author's observations and his 

 minute attention to detail ; I cannot, therefore, expect to supplant 

 it, my aim being an entirely different one, i. e., to so completely 

 reconstruct our geology as to bring it into sympathy with the 

 results of adjacent States. Professor Booth's great and only 

 fault as a geologist lay in his entire indifference to stratigraphical 

 order ; and his classification of deposits according to mineralog- 

 ical and physical characters, leaves one in utter confusion. 



My main object, therefore, is to endeavor to undo the tangles 

 which Professor Booth has unconsciously made, by stating the 

 facts in the briefest and clearest manner possible. 



The results, as embodied in the following paper, are preliminary 

 to what is hoped will be a full report upon the State. 



Geological Outline. 

 The formations represented within the bounds of the State 

 are Laurentian (?), Cambro-Silurian, Silurian-Devonian (?), Creta- 

 ceous, Tertiary and Quarternary. The relations and positions 

 of the several divisions of the chronological scale can be best 

 represented by the accompanying table (I), also the thickness of 

 each formation. Column 2, with which the Delaware series is 

 compared, is constructed according to what seem the best results, 

 combining home and foreign equivalents. The accompanying 

 map (PL V) is drawn upon a scale of four miles to the inch, 

 and is sufficiently large to show all necessary details. A word 

 is here necessary in regard to the boundaries as shown by 

 the map. The lenticular areas which indicate the magnesian 

 marble, can only serve to represent the position of outcrops. 

 Owing to the fact that these calcareous deposits are entirely 

 covered by the micaceous rocks, surface indications offer no 

 means of determining the entire area covered by the former. 



