Thomson. — Geology of Middle Waipara and Weha Pass Districf. 357 



top of the ridge overlooking the Weka Pass, the greater part of the sky- 

 line between the Weka Creek and the Waipara River, and the summit 

 of Moimt Brown. It contains a rich brachiopod fauna, the commonest 

 species being Magadina hrowni Thomson, Pachymagas jJCirH (Hutton), and 

 species of Rhizothyris. The uppermost limestone, E, forms the cuesta. south- 

 east of the main band, D, at the approach to the Weka Pass, and is 

 characterized by the brachiopods Neothyris novara (von Ihering) and 

 Stethothyris sxiffiata (Tate). 



Middle Waipara, South of Boby's Creek Faidt. — Starting at the westerji 

 end of the district, in the tributary of Boby's Creek rising near Mount Grey, 

 the Weka Pass stone passes up gradually into grey mudstones, the typical 

 "grey marls," which are here apparently 200ft. to 300ft. thick. They 

 yielded Verconella costata, Malletia australis, Limojisis aurita, Pecten hnttoni, 

 and Diplodon zelandica (Gray) ?. Above these the seetion is not clear, but 

 there are sands containing Turritella and Malletia. The watershed between 

 Boby's Creek and the Kowhai River is here occupied by a cuesta of the 

 lowest Mount Brown limestone, A, which is a white polyzoan limestone, 

 about 50 ft. thick. It yielded Pecten hnttoni, fragments of, a ribbed Pecten, 

 and Pachymagas clarkei n. sp. The higher Mount Brown limestones were 

 not here studied. 



In Mount Brown two bands of reddish-brown limestone may be dis- 

 tinguished. The lower, B, is not richly fossiliferous, but has yielded 

 Anomia trigonopsis and Pecten jjaZmi^es. Bed C has not been identified, 

 but the upper band, D, forming the summit, is thicker than usual. Fossils 

 are scarce near the summit on either side, but in the cliffs overlooking the 

 Waipara River, where over 100 ft. of limestone is exposed, there is a very 

 persistent band, formed mainly of Magadina hrowni, near the top. From 

 some holes at the base of the cliff I obtained an abundance of Bouchardia 

 minima Thomson, besides Magadina hrowni, Pachymagas McKayi n. sp., 

 Anomia trigonopsis, Pecten williamsoni Zittel(?), P. zelandiae, and Lima 

 colorata. 



Middle Waipara, North and North-east of Bohy's Creek Fault. — On the 

 northern side of the Boby's Creek fault, in the north branch of Boby's Creek, 

 the Weka Pass stone passes up gradually into grey mudstones, about 60 ft. 

 thick. These are followed bv a considerable thickness of soft sandstones, 

 separated into uppsr and lower divisions by a thin bed of mudstone con- 

 taining Mopsea sp. and Foraminifera. The upper sands are cut off bv 

 the fault. 



The most complete section is that afforded by. the banks of the Waipara 

 River below the limestone gorge, and partially repeated in the lower part 

 of Boby's Creek owing to folding. The section is continued in the higher 

 slopes to the east up to the horizon of the main Mount Brown limestone, 

 and includes the following beds : — „ 



Main Mount Brown limestone (D) . . . . . . 60 



Loose yellow-brown sands . . . . . . . . 80 



Third Mount Brown limestone (C) . . . . . . 30 



Bluish muddy sandstones with concretions, passing down 



into polyzoan shelly beds and a grit at the base . . 200 



Mudstones with thin sandstone intercalations . . 200 



Whitish sandstones with thin mudstone intercalations . . 200 



Glauconitic mudstone . . . . . . . . 25 



795 



