. The Quarterly journal of the Geological Society of London. : > s : a ^ . S? O ^ CO S :« ^:^^ iIII i o-g 0 a c/5 oj c3 2 2- s fl ^ ?ill o ^ o oi=i S 0 S III ^ C III :^^^;3 . . . J= s r-H cNcoTrio<X)t^GC«JiOr-((M CO •pnBpjoj 1852.] WESTON ON PORTLAND. 117 AVe must now refer to the contemporaneous Purbeck beds in tbeIsle of Portland. Former sections * have shown that the Isle of Portland dips away tothe S., so that the high escarpment on the N. diminishes to a muralcliif, very little elevated above the sea-level, at the Bill. This ex-tremity I examined for the express purpose of determini
. The Quarterly journal of the Geological Society of London. : > s : a ^ . S? O ^ CO S :« ^:^^ iIII i o-g 0 a c/5 oj c3 2 2- s fl ^ ?ill o ^ o oi=i S 0 S III ^ C III :^^^;3 . . . J= s r-H cNcoTrio<X)t^GC«JiOr-((M CO •pnBpjoj 1852.] WESTON ON PORTLAND. 117 AVe must now refer to the contemporaneous Purbeck beds in tbeIsle of Portland. Former sections * have shown that the Isle of Portland dips away tothe S., so that the high escarpment on the N. diminishes to a muralcliif, very little elevated above the sea-level, at the Bill. This ex-tremity I examined for the express purpose of determining whethermy suspicions of the extension of the Purbeck so far South, whichmy hurried visit in 1847 had led me to entertain, were correct orfallacious ; and I now found on its western side an unequivocal sectionof the junction of the marine and freshwater strata, as in the accom-panying sketch. Fig. 10.—Section of part of the Cliff at the Bill of Portland, Shingle-bed ..r Purbeck Second Dirt-bedPurbeckFirst Dirt-bed Purbeck{Valvata and Cyrena.). Portland(Trigonice, Pectines, ^c.) 7. Marine. 6, Alternations of terrestrialand freshwater ? 5. Terrestrial. 4. Freshwater ? 3. Terrestrial. 2. Freshwater. 1. Marine. No. 1 is the Portland formation. It is quarried down to nearlyhigh^water-mark, and abounds, from the lowest portions to within ashort distance from its junction with No. 2, with remains of marinelamellibranchiate molluscs. The beds which are immediately belowthe Purbeck in the northern part of the island, are, on the other hand,equally marked by a profusion of gasteropodous molluscs. No. 2. This stratum is not very decidedly separated from No. 1,and its equivalent in the quarry containing such numerous casts andimpressions of gasteropods is Hthologically a bond fide portion of thesubjacent and unquestionable marine deposit. The strata 1 and 2appear in situ to have been continuous and of common origin. Forbes has, however, in his valuable paper On the successi
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
