| Popis: |
Nearly forty years ago Mr. Bowman drew attention to “a small patch of Silurians west of Abergele,” in which he described the following subdivisions in descending order:— f. A conglomerate of pebbles of greenish micaceous sandstone in a light loamy earth resting on a similar sandstone. c. Thick red marl with numerous pebbles of red sandstone, micaceous, with many bivalves. d. A hard compact conglomerate of green sandstone and quartzose rock. c. Compact red limestone. b. Fine blue loamy clay. a. Clay-slate. He makes the observation that the red-sandstone pebbles in bed e resemble Ludlow rock, and names four Ludlow species as occurring in them. Our attention was directed to these beds by numerous excavations made in them at the time of the recent activity in the iron trade. The only good exposure is in Ffernant Dingle, a deep ravine running from the Pen-y-Cefn lane southward past Cefn-y-Fran, about one mile south of Llysfaen. The southern or lower end of this dingle is occupied by Wenlock shale, a pale blue slaty clay, with occasional sandy beds. The beds are much jointed, and sometimes cleaved so as to weather into pencil-like fragments. At the south end of the dingle they are nearly horizontal, but dip gently to the north higher up, near Cefn-y-Fran. At this point the Wenlock shale is unconformably overlain by hard, mottled, red and green brecciated limestone, containing beds of green sandstone pebbles in a sandy matrix. The limestone and the conglomerates dip to the N.N.E. at 28°. |
