This well weathered outcrop consists of tuff (formed from volcanic ash) - associated with volcanism that was active from around 38 million years in the Oamaru area.  This outcrop shows some weakly bedding planes in places, but in the main is massive.  Of significance are two jointed limestone dikes of the Ototara Limestone (Oamaru Stone) that run near vertically through the tuff.  Typically dikes are igneous in origin and intrude existing rock.  The dikes exposed here at Chelmer Street are in fact the reverse of this - where a sedimentary unit is seen to intrude igneous material.  

Please be aware the following hazards include: Falling debris (rock and plants) from overhead and traffic.