MARYLAND GEOLOGICAL SURVEY 107
the latter part of June a reconnaissance was made in portions of the
Eastern Shore of Maryland.
In December, 1890, Mr. Darton presented to the Geological
Society of America a resume of the results of his observations in the
Coastal Plain region in a paper entitled " Mesozoic and Cenozoic
Formations of Eastern Virginia and Maryland. "1 In this paper there
were defined the Pamunkey formation, of Eocene age, the Severn
formation, comprising portions of the marine Cretaceous deposits, and
the Chesapeake formation, of Miocene age. An account was given
of the distribution and relations of these formations, and of the Poto-
mac, Appomattox (Lafayette) and Columbia formations.
In the spring of 1891 Mr. Darton completed mapping the sedi-
mentary formations of the Washington quadrangle, and during the
summer of that year there was issued by the survey a preliminary
edition of the sheet, with the geology of the crystalline rocks by Dr.
Williams. There was also prepared by Mr. Darton an account of
the sedimentary formations in the vicinity of Washington for the
" Guide to Washington and its Scientific Institutions, " printed for
the Fifth Session of the International Congress of Geologists.
During 1891-92 Mr. Darton mapped in a preliminary way the
greater part of the Western Shore of Maryland embraced in the
Nomini, Patuxent and Patapsco quadrangles, together with a strip
extending along the eastern side of this area along Chesapeake Bay.
As a result of this work there was published in 1895 the Nomini
folio, No. 23, Geologic Atlas of the United States.
During the summer of 1891 Professor Clark was detailed to
work in the northern Atlantic Coastal Plain, embracing New Jersey,
Delaware and the Eastern Shore of Maryland, and began investiga-
tions upon the Cretaceous formations in the northern portion of the
district.
In February, 1892, as has been said, there was published for the
American Institute of Mining Engineers a guide-book to Baltimore,
to which Mr. Darton contributed a description of the geology of the
sedimentary rocks, and which was accompanied by a preliminary geo-
1 Bull. Geol. Soc. America, vol. ii, pp. 431-450.
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