DETAILED RECORDS. 233. 
Patapsco: Feet. 
Dark-blue clay 510-516 
Very tough red or pink clay (crust of iron ore at 524 and 545 feet) 516-548 
Yellow sand; lower portion coarse and water bearing 548-583 
Pink clay 583-587 
Coarse sand and gravel, pebbles one-half inch in diameter; large flow of water. 587-601 
Very hard rock 601 
Rig used, rotary to 250 feet, hollow-rod jumper below. Casing used, 250 feet of 12-inch, 
170 feet of 10-inch, 181 feet of 8-inch. Length of strainer, 15 feet, Well flows 75 gallons 
per minute at elevation of 8 feet above tide. Supply from 587 to 601 feet, Water contains 
iron, but is of excellent quality when filtered. 
687. Well at Chaptico, St. Mary County. 
[Well begun January 9, 1905; completed February 2, 1905. Authority, L. Rude, driller. Geologic 
correlations by W. B. Clark.] 
This well, starting in deposits of Columbia (early Pleistocene) age, penetrates clays, sands, 
and greensands of the Calvert formation of the Chesapeake (Micoene) group and Nanjemoy 
and Aquia formations of the Pamunkey (Eocene) group. A detailed account of the under- 
ground-water resources of that section of the Coastal plain in which this well is situated is 
given in the Nomini folio (No. 23) of the Geologic Atlas of the United States. 
Record of well at Chaptico. 
Columbia: Feet. 
Coarse yellow sand and gravel 1- 20 
Calvert: 
Hard dark sandy clay 20- 70 
Hard, coarse grayish-brown sand containing shell fragments 70- 80 
Hard dark sand and limy clay 80-100 
Hard dark coarse sand 100-120 
Nanjemoy: 
Hard dark coarse sand with glauconite 120-250 
Aquia: 
Soft light-brown sandy clay 250-270 
Hard dark sand containing glauconite; water-bearing 270-295 
Rig used, jet, Diameter of well, 1^ inches. Main water supply at 270 to 291 feet. 
Well flows 7 gallons per minute; static head, 4-22 feet. 
689. Well near Tilghman, Talbot County. 
[Well begun March 10, 1905; completed March 21, 1905. Authority, L. Rude, contractor. Samples 
preserved. Geologic correlations by W. B. Clark.] 
The water-bearing stratum of dark sand in this well possibly belongs to the top of the 
upper (marine) division of the Cretaceous and is part of the Matawan formation; according 
to Mr. Rude, it is about 60 feet thick. The formations penetrated, from top to bottom, are 
Columbia formation (Pleistocene); Calvert formation of the Chesapeake group (Miocene): 
Pamunkey group (Eocene); and Matawan formation (Cretaceous). 
Record of well one-half mile north of Tilghman post-office. 
Columbia: Feet. 
Hard buff clay 0- 12 
Calvert : 
Soft micaceous gray sand with a little glauconite 12- 18 
Soft dark brownish-gray micaceous sand 18- 40 
Gray sand containing shell fragments 40- 50 
Hard dark-gray sandy micaceous clay 50-130 
