The other side of the range is to the north east of the Shag River valley that contains the lower part of The Pigroot.

[3]: 173–175  A layer in some of the Horse Range Formation is a ignimbrite rhyolitic deposit from what must have been a surface eruption at about 112 million years ago.

[4] Underneath this is the basement of metamorphosed quartzofeldpathic semischist sedimentary rocks of the Rakaia Terrane.

[2]: 330  This marble has also been mapped at Conical Hill in the middle of the Horse Range, 15 km (9.3 mi) to the north west of the main Blue Mountain Formation.

[2]: 329 The highest point in the Horse Range is Conical Peak, at 945 metres (3,100 ft).