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conformable and the general succession is very similar to 

 that in the cliffs along the river above Stony creek, 12 miles 

 (19 km.) to the north. The absence of the limestone and 

 gypsum in the cliffs of Hopewell cape and their presence 

 elsewhere intervening between the red conglomerate and the 

 grey strata of the Millstone Grit, is presumptive evidence 

 of the existence of an erosion plane beneath the Millstone 

 Grit. Elsewhere in the general district there is evidence 

 that this erosion was of a very pronounced character; that 

 prior to Millstone Grit time, the older Carboniferous 

 strata were carved into pronounced valleys and during 

 the Millstone Grit period these valleys were filled with 

 reddish sandstones and shales, while over all was laid a 

 mantle of the grey quartzose conglomerates and sandstones. 

 On both sides of the valley of Quarry creek, along which 

 runs the road leading to the gypsum quarries, are exposures 

 of red conglorfierate. The conglomerate strata of the 

 ridge on the south side dip gently to the south and are 

 overlain by grey limestone. The red conglomerate and 

 the limestone beds are exposed on the side of the creek at 

 the northern entrance to the gypsum quarries. Similar 

 limestones outcrop to the west on the northern and western 

 sides of the area of gypsum, and in general fashion, the 

 dips indicate that the gypsum occurs towards the centre 

 of a very shallow syncline probably traversed by a north 

 and south fault situated toward the western edge of the 

 area. On the south the gypsum area is bounded by a high 

 ridge over whose summit the grey Millstone Grit strata 

 outcrop, while between these and the gypsum beds, inter- 

 vene red sandstones and conglomerates with a maximum 

 thickness of probably not more than 100 feet (30 m.). 



THE HILLSBOROUGH GYPSUM DEPOSIT. 



(h. E. KRAMM.) 



The limestone upon which the gypsum and anhydrite 

 beds rest, have a thickness of approximately 40 feet (12 m.). 

 The gypsum and anhydrite beds have a thickness of about 

 250 feet (76 m.). The gypsum is the massive crystalline 

 variety. It is usually slightly coloured by some impurities 

 such as oxide of iron, calcium carbonate and organic matter, 

 but absolutely pure gypsum, the variety alabaster, is also 

 found at Hillsborough and mined. Crystals of selenite 



