FLOUA Ol" ()M)Ki; roTO.MAC. FORMA TU )N. .')53 



the i-('lati()iis of tliosc hods in the Stiilcs of \'ii',<j;iiiia, Mai-ylaiul, Dc^laware, 

 and Xcw Jersey, and altlioujrh it was not then known that the nioiv 

 northeasterly outci-ops repi-esent a hitiliei- phase of the formation, witli an 

 (Mitii'ely different flora, the views here e\pi-(>ss(Ml represent the eominon 

 oi)ini()n prior to the invest ifjations of Pi'ofessoi' Fontain(>, Doctoi' Xcnv- 

 l)(>rry, and myself of the floras yielded by tlies(> beds. He says: 



ill llic l)('h |iarti;illv uccupicil !)y the surface deposit, lieie referretl to lliere is 

 exposed another group of strata with which, at first view, tiie sandy and argillaeeous 

 layers of this formation niijilit reachiy he confounded. These are the siiieions, 

 artrilhieeous. and pel)l)ly l)eds, which, underlying,' the Tertiary in Vir.srinia, and llie 

 w-ell-mai-lxed Cretaceous formation fartlier north, iiave, in the hitter re,u;ion, been 

 reo-arded as helonsink' >"' ''le l)a.sc of tlie Cretaceous s(>ries of the Ahantic States. 

 Jn Vir<;inia the i'onnation consists typically of a rather coarse and sometimes pebbly 

 sandstone, in whicii the fjrains of ([uartz and ftddspar are feel)ly cemented by kaolin, 

 derived from the decomposition of the latter, and of argillaceous and siiieions clays 

 variously colored and more or l(>ss charged with vegetable remains, either silicilied 

 or in the condition of lignite. The.se constitute the group of beds desigmited in 

 the Virginia geologicul reports as the I'pper Secondary Sandstone, and referred 

 bv me long since (1842) to the upi)er part of the -lurassic series, corresponding 

 ])robahly to the Purbeck beds of British geologists. From the Potomac northward 

 this group of deposits, as exposed in the deep railroad cuts between Washington and 

 Baltimore and on to Wilmington, is made up of variegated, soft, argillaceous, and 

 siiieions beds, wliicdi, from the jjreponderance of ferruginous coloring toward the 

 Delaware, haV been called by Professor Booth the red clay formation. At> a few jioints 

 only toward the bottom of the tlejjosit it brings to view a bed of the fclspathic sand, 

 or crumbling sandstone, above referred to. Traced transversely, it is seen to dip 

 beneath the Cretaceous greensand at various points in New Jersey, Delaw are, and 

 Maryland, but in Virginia disappears in its eastward dip beneath the Kocene 

 T( niary. 



How far we may consider this group of sedimiMits in Marylanch Delaware, and 

 New Jersey as merely a contimiation of the Virginia ft)rmation above described 

 can l)e determined only by further investigation. But the discovery in them at 

 Baltimore, by Professor Tyson, of stumps of cycads would seem to biing them 

 into near relation with the formation at Fredericksburg containing similar remains, 

 and to favor their being referred, at least in part, to the horizon of the upper Jurassic 

 rocks. Pos.sibly we may find here a passage group analo on to the Wealden ol 

 Britisli geology. Whatever nuiy be the result- of further ( if jvery, it would seem 

 to be premature at this time to assume the whole of these deposits from the Potomac 

 northward as belonging to the Cretaceous series. 



Where the Tertiary or Cretaceous rocks are present in this belt there is, of 

 coTH-se. no danger of confounding the superficial gravel and cobblestone deposit with 

 Mox xi.vni — 0>5 23 



