TiiOMSOX. — Fliiif-btd.s (issociafcd in'fh Jmi/ri Ln/iesfoiie. 53 



tlie flint-beds are estimated by McKay (1886) as over 500 ft. in thickness.- 

 In Sawpit Gully, a tributary of the Nidd Stream, at Coverham,'the junction 

 between the flint-beds and the underlying sandy mudstones is sharp, and 

 not gradual. The mudstones contain numerous pyritic concretions in their 

 topmost 20 ft., and at the junction itself there is a strong yellow efflorescence. 

 The lowest flint lenticules are light -coloured on the exterior, but do not 

 show the carbonate rhombohedra that are so ch.aracteristic of the lenticulai- 

 flint-beds in general. In the valley of the Nidd Stream, above the junction 

 of Sawpit Gully there is a thick band of dark, but not black, flint or chert 

 within the Cretaceous mudstones, over 1.000 ft. below the base of the main 

 flint-beds. This band of flint is not lenticular in character, and does not 

 exhibit the flint-carbonate rock associated with the flints at the base of the 

 limestone series. 



Between Coverham and the Dee Kiver. still farther to the south-west, 

 the flint-beds at the base of the limestone, as well as the limestone itself, 

 attain their maximum thickness. In the Mead Gorge there are massive 

 beds of flint at the base of the limestone series, and then alternations of 

 limestone and flint -beds for some distance higher up. By measuring the 

 dip and pacing the width of the outcrops I made the following rough 

 estimate. of the thickness at this point, neglecting some small faults which 

 reduce the apparent thickness : — 



Top. Grey marls (fossiliferous Oamaruian mudstone). 



, Hard argillaceous limestone (Weka Pass stone of Ft. 



McKay) .. .. .. .. .. 150 



Marly limestone . . . . . . . . 400 



Hard chalky limestone . . . . . . . . 280 



Marly limestone . . . . . . . . 420 



Hard chalky limestone. . .. .. .. 90 



Flint-beds with limestone intercalations .. .. 1.410 



2.750 



To the south-west of the Dee River the flint-beds again decrease in thick- 

 ness, and, according to McKay (1886), they disappear altogether before 

 the limestone reaches the Dart Eiver.- In the Upper Awatere Valley the 

 Amuri limestone is much thinner than in the Clarence Valley, and the 

 flint-beds are mentioned by McKay (1890) as occurring at its base. Finally, 

 a considerable development of these beds with the Amuri limestone is 

 reported by McKay (1877) near the mouth of the Flaxbourne River, in the 

 Cape Campbell district. 



III. Character of the Flikts. 



"What have been termed '"flint-beds" in the above account are layers 

 composed either wholly of black flint or of large lenticules of flint surrounded 

 by a semi-crystalline material. The layers are distinct from one another 

 above and below, and are in close contact alone surfaces resemblina; beddins- 

 planes. Where the layers are composed of flint they are generally about 

 6 in. to 8 in. in thickness, and the surfaces of contact are apjiroximately 

 parallel. Where the layers consist of dark flint only in certain lenticules, 

 the bounding surfaces are more irregular, as the layers exhibit numerous 

 swellings following in a reduced degree the shape of the lenticules, and 

 reaching in some cases a thickness of 18 in. or more. Plates II and III 

 will give a better idea of the phenomena tlian any lengthy description. It 

 seems' reasonable to suppose that the surfaces of separation of the layers 



