. La geologia del distretto di Oamaru, North Otago orientale (divisione di Otago). r grigio-azzurro flaggy arenaria silicea, che in luoghi mostra minuto ma distinctcurrent-biancheria da letto. Esso contiene diatomee e radiolari. Vi è una qualche evidenza di theoccurrence di due letti di arenaria silicea separati da tufi, ma questo non è quitecertain, come la scarpata-faccia è oscurata da un deposito di pendenza in cui blocchi di Oamarustone, terra di diatomacee, arenaria silicea e tufo sono mescolate. La sabbia.stoneseems a consistono di fini quartzose sabbia cementata da infiltrazioni di acque siliceo.it contai

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. The geology of the Oamaru district, North Otago (Eastern Otago division). r bluish-grey flaggy siliceous sandstone, which in places shows minute but distinctcurrent-bedding. It contains diatoms and radiolarians. There is some evidence of theoccurrence of two beds of siliceous sandstone separated by tuffs, but this is not quitecertain, as the scarp-face is obscured by a slope deposit in which blocks of Oamarustone, diatomaceous earth, siliceous sandstone, and tuff are intermingled. The sand.stoneseems to consist of fine quartzose sand cemented by the infiltration of siliceous waters.It contains many peculiar tube-like markings that may possibly be fucoid stems. Below the .sandstone there is a flow of coluirmar basalt, which extends westwardto the bank of the Waiareka Stream. CONFIRMATORY SECTIONS. Section at old Quarry a Mile South of Round Hill (Trig. K).At the old stone-quarry the Waiareka tuffs lying below the Oamaru stone areintercalated with a thin irregular lens of impure diatomaceous earth. The sectionexposed in the quarry-face is shown in Fig. 16. 48. a20 ycvrcis Fig. 16.—Section at old Quarry a Mile South of Rouxd Hill. a. Hard massive dark-grey tuffs formerly quarried for road-metal. b. Lens of diatomaceous earth, varying from 0 to 4 ft. thick. c. Coarse well-bedded tuffs, tachylitic. Section at Cormacks Siding.Beginning at a point about 100 yards west of the railway-siding there is exposedin the north bank of the railway-cutting a deposit of siliceous diatomaceous earth fora distance of 115 yards. The greatest visible thickness of the deposit is 12 ft. Theearth is intruded by a sill of basalt; and it lies about 180 ft. below the base of theOamaru stone. The portion of the deposit richest in diatoms is a light pale-yellowish-grey chalky-like material. In places the diatomaceous material is hard and heavy.Dr. H. A. de Lautour, who devoted much attention to the study of the Miocenediatomaceous earth-deposits of the Oamaru district, considers that the hard

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1910
• booksubjectgeology
• bookyear1918