THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE V. VOL. VIII. 



No. X— OCTOBER, 1911. 



OTiTG-TT<T j^JL, AETICLES. 



I. — Some Notes on the Geology of the Bermuda Islands. 

 By E. Ashington Bullen, B.A. (Lond.), F.L.S., F.G.S. 

 (PLATES XXI-III.) 

 (Concluded from the September Number, p. 395.) 



(4) Recent JEolian Sands. — On the south shore the sand has made 

 .or is making some encroachments on the land, in others on the sea. 

 The ' live ' sand-dunes are principally to be found at Tuckerstown, 

 hut there are some movements at Elbow (or Middleton) Bay and at 

 Warwick Long Bay. The shell-sand is mostly made up of the broken 

 shells of various marine species, some few being entire, with which 

 are mingled the broken tubes of serpulas, fragments of nullipores and 

 corallines, and the red shells of a Vermetus, viz. Teganodus (Siliquaria) 

 ruber, Schum. This latter is so plentiful as to give a distinctly red 

 appearance to the sand of some beaches. 



The coarsest sand on the islands (according to Mr. Richard Kempe, 

 who has lived in the islands since 1848) occurs at Astwood's Bay, in 

 Warwick parish. In other bays the sand varies in size of grain, and 

 a great deal of the finer material is no doubt derived from the 

 degradation of the former coast and cliffs. The present cliffs on the 

 south shore are from 30 to 50 feet high. The former shore extended 

 seaward to a distance of a little over 300 to rather over 700 yards 

 from the present shore-line. The erosion of this coast must have 

 commenced before the deposition of the Devonshire formation, which 

 Verrill places in the Champlain or Post-Glacial Period. 1 The Devon- 

 shire Beds at Hungry Bay abut on the eroded Walsingham rocks. 



The blown sands act as protectors of the present cliffs, as at 

 Warwick Long Bay, where a chain of sand-dunes, ' anchored' by such 

 plants as sea-lavender {Tournefortia gnaphaloides, R. B.), indigo-berry 

 (Randia aculeata, L.), and crab-grass (Stenotaphrum Americanum, 

 Schr.)., are a distinct advanced guard, and, by keeping together the 

 sand, prevent the further inroads of the sea (see Plate XIX). At the 

 same time there are occasional extensive falls of the higher cliffs, as at 

 Kempe's Bay (PI. XX, Fig. 1), where at the time of my visit some 

 100 tons or so of the loosely compacted Paget Beds had fallen to the 

 present beach. It is such falls that account for the land shells 

 {Pcecilozonites Bermudensis, var. zonatus, Yerrill) which occur on the 

 marine beach (Text-fig. 4). 



1 Verrill, "The Bermuda Islands: Geology": Trans. Conn. Acad. Arts 

 Sci., vol. xii, p. 75. 



decade v. — VOL. viii. — no. x. 28 



