Page:VCH Worcestershire 1.djvu/51

GEOLOGY lo feet thick, fossils as a rule are well preserved. Here Rhynchonella acuta, R. tetrahedra and Gryphcea cymbium occur. Springs are thrown out by clayey beds which often occur at the base of the marlstone rock bed, and again at lower levels when sandy beds rest on loams or clays. The waters are usually somewhat ferru- ginous. The rock bed is much quarried in some localities for road- metal, and the loams and clays are serviceable for brick-making. The soil is generally fertile, and is well suited for orchards. The Upper Lias is for the most part a clay formation, having occasional nodules of limestone. A few more persistent bands of lime- stone occur at the base, and these are associated with about 20 feet of paper shales which are slightly bituminous. The Upper Lias occurs above the marlstone in Bredon Hill and in the Cotteswold Hills, but is seldom well exposed. Its thickness varies from 100 to 120 feet, and it is characterized by Ammonites serpentinus, A. bifrons and A. communis. The lower beds of the Upper Lias have attracted much attention on the borders of Worcestershire, especially at Alderton (Dumbleton), and our knowledge is largely due to the researches of the Rev. P. B. Brodie, ^ Mr. R. F. Tomes,^ and others. The beds have yielded sau- rians, also fishes, such as Leptolepis, Pachycormus and Tetragonolepsis, insects including forms allied to Libellula, corals, and cephalopods with the ink-bag preserved. That the lower beds of the Lower Lias were formed in com- paratively shallow water is indicated by the presence of insects and plant remains, as well as large saurians. Mr. Tomes has noted rain-spots on some of the limestone layers, and in one instance he discovered the large wing of a dragon-fly which had been broken through by a spot of rain when lying on an exposed surface of soft calcareous mud. He has also observed distinct evidence of dust having been blown on to these ancient mud-flats. The clayey beds indicate a deeper sea, but this became shallower during the deposition of the Middle Lias and the basement portions of the Upper Lias, and again deeper when the main mass of the Upper Lias clay was spread out. The dark shales of the Lias sometimes led in old times to fruit- less trials for coal as was the case at Hasler Hill, near Evesham, and at Bretforton.' The Inferior Oolite series which forms great part of Bredon Hill, and of the northern Cotteswolds, as at Broadway, Cutsdean and Blockley, comprises at its base a group of sandy and ferruginous beds with con- cretions of calcareous sandstone. These lower strata form the passage- beds between the Upper Lias and Inferior Oolite, they include the zones oi Ammonites jurensis and A. opalinus, and are known as the Midford Sands, or locally in the Cotteswold Hills as the Cotteswold Sand and Cephalopoda bed. Rhynchonella cynocephala is a characteristic fossil. ' Fosiil Insects, p. 55 ; Quart. Journ. Geol. Soc, vol. v. p. 32. « Geol. Mag., 1886, p. 108. 3 Memoirs of H. E. Strickland, pp. 83, 88.