702 



SCIENCE 



[N.S. Vol. XXV. No. 644 



The high standard of investigation and pub- 

 lication reached in the previous reports of the 

 Maryland Geological Survey under the direc- 

 tion of Professor W. B. Clark is maintained 

 in the recent volume on the ' Pleiocene and 

 Pleistocene of the Coastal Plain ' ; the later 

 physical history of the district being treated 

 by G. B. Shattuck, recently of Johns Hopkins 

 University, now professor of geology at Vassar 

 College, while its paleontology is discussed by 

 Clark, Lucas, HoUick and other experts. The 

 chief physical results of this elaborate study, 

 already outlined by Shattuck six years ago 

 ('The Pleistocene Problem of the North At- 

 lantic Coastal Plain/ Johns Hopkins Uni- 

 versity Circulars, No. 152, 1901), concern the 

 marine terraces that have been carved on the 

 slopes of the previously dissected coastal plain, 

 and are presented in the first half of the 

 report under such headings as general strati- 

 graphic relations, physiography of each ter- 

 race, structure of each terrace, method of 

 interpretation, resulting inferences as to geo- 

 logical history, and summary. The chapters 

 on paleontology include a general account of 

 the Pleistocene fauna by Clark, and flora by 

 Hollick ; then a discussion of systematic 

 paleontology under ten headings from mam- 

 malia to spermatophyta by various authors, 

 and a special chapter on the elephants of the 

 Pleistocene by Lucas. So detailed a treatment 

 of Pleistocene paleontology is novel in Amer- 

 ican geological reports. 



The geological history of the region to 

 which this review is directed, may be briefly 

 summarized as follows : The series of marine 

 strata, chiefly Cretaceous and Tertiary, which 

 make up the body of the Maryland portion of 

 the Atlantic coastal plain, was uplifted and 

 perhaps nearly baseleveled by subaerial ero- 

 sion, in time to receive, when again sub- 

 merged, a broad sheet of Lafayette (Pleio- 

 cene) gravels and sands. Another uplift 

 again exposed the coastal plain, thus reno- 

 vated, to prolonged erosion under the leader- 

 ship of the Potomac, Susquehanna (Chesa- 

 peake), and other large rivers, the main val- 

 leys thus gaining an expression of advanced 

 maturity, with depth and breadth perhaps 

 not far short of the dimensions which they 



now possess. Next came a strong depression; 

 the mature valleys were drowned and a well- 

 defined shore-clifE or scarp was cut on their 

 slopes (the stage of development reached by 

 the shore line being inferred by the reviewer 

 to have been advanced youth or early ma- 

 turity). Sunderland is the name given to 

 this scarp and to the associated marine terrace 

 deposits then formed. A series of short-lived 

 partial uplifts and slight depressions followed; 

 each uplift permitting a renewal of dissection 

 on the emerged slopes; each depression suffi- 

 cing to produce a new scarp with a submarine 

 terrace. Three sets of scarps and terraces 

 below the Sunderland were thus formed; the 

 Wicomico, the Talbot and the Eecent; all, like 

 the Sunderland, contouring around the frayed- 

 out slopes of the dissected coastal plain, and 

 now standing at altitudes of (about) 200, 100, 

 40 and zero feet. 



This interpretation has two chief bases. 

 First, a critical study of the features along 

 the present shore line; second, a comparison 

 of these features with similar features at 

 higher levels. The work has every appearance 

 of being carefully done. It will be interest- 

 ing to note how far the conclusions are sup- 

 ported by new studies, either of a more de- 

 tailed character in Maryland, or of a broader 

 character in neighboring states. 



An understanding of the development of the 

 present shore line is evidently of fundamental 

 importance. It is shown to have followed a 

 moderate submergence of the previously dis- 

 sected coastal plain. The very irregular 

 initial shore line thus produced has been sys- 

 tematically modified by the development of 

 long, off-shore sand reefs on the most exposed 

 ocean front, while scarps have been cut on 

 the headlands of the less exposed bays, and 

 short sand reefs have frequently been thrown 

 across the smaller reentrants within which 

 deltas and marshes have accumulated. At the 

 same time a submarine terrace of gravels, 

 sands and clays is believed to have been 

 formed for a certain distance off shore. At 

 various points where the headland scarps are 

 cut back, the neighboring sand reefs have been 

 forced to retreat at about the same rate; and 

 thus the inner border of the stratified terrace 



