The geology of the neighbourhood of Edinburgh : (map 32) / by H.H. Howell and Archibald Geikie ; appendix and lists of fossils by J.W. Salter.

Date:: 1861

Credit: The geology of the neighbourhood of Edinburgh : (map 32) / by H.H. Howell and Archibald Geikie ; appendix and lists of fossils by J.W. Salter. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

26/164 page 16

$In fine, the truly bedded character of all these felstones, their interstratificaoions of sandstone, conglomerate, and ash, and tlien^ undouoted place in the Upper 01 d Red Sandstone, indicate that in the later part o2 the Old Red period volcanic agencies were lono- and acowe'y at wor-k in M'd Lothian. The fact, too, that these rocks are covered by conglomerates and sandstones gradu- atinf upward into those of the Lower Carboniferous series shows that*^ these agencies had become quiescent here before the com- mencement o'the Carboniferous period. The upper conglomerates, forming the gradation into the Carboniferous group, occur on the east side of \^be hdls at Liberton and on the west side at Habbie's Howe; their nature and their passage into the superincumbent strata are detailed in the next chapter. CHAPTER IV. Basement Beds of Lower Carboniferous Group. The long parallel faults by which the Pentlai d Hills are bounded mal^erially retard any atteirpt lo ascertain the thick- ness of the great mass of sandstones and conglomerates forming the passage beds or neutral ground between the Old Red Sand- stone ard the Lower Carboniferous. It is not certain that the who^e of that series now reaches the surface, nor that, if ii. does reach the surface, we have not parts repeated by the faulting. Making d 7e allowance, however, for either alternative, the repe- tition or im])erfection in the series is probably not of any great extent, if the sections be taken north of the Pentlands, since a gradual ascending series can be traced from the Braid Hill fel- stones up through the Upper Old Red Conglomerate of Liberton, into a series of pale calcareous sandstones and pebbly conglo- merates, which form the base of the Lower Carboniferous group, and extending northwards by Craigmillar, re-appear at the Castle Rock of Edinburgh. From this point the series can be traced in ascending order eastward through the central ridge of the Old Town and the rocks of Arthur's Seat. In this section there occurs of course one marked break. One of the larger faults (which, however, is thinning off to the north-east,) intervenes between the Castle Rock of Edinburgh and Craigmillar, so that it is only from their lithobgical aspect, and from the general structure of the district, that we conjoin the higher part o* the Craigmillar beds with the strata at the Castle Rock. In a country so broken and shattered, and so obscured by superficial accumulations, the geologist cannot hope for minute accuracy, and must often con- tent himself that his scattered facts and isolated observations be linked together by what he regards as at best only plausible conjecture.$