The history of the Styx River is closely related to the formation of the Canterbury Plains. In earlier times the flow of the Styx River would have been provided by a combination of spring water and channels connecting with the Waimakariri River. There is a strip of very young soils along the middle reaches of the Styx River and Smacks Creek that suggest a recent connection between the two river systems.
Today the Styx River consists of a low-gradient, narrow, meandering, single-thread channel that is incised into a fan surface largely formed by sedimentation from the Waimakariri River. The springs that feed the Styx River ecosystem mainly occur along a line that is close to the western limit of the surface confining layer of fine-grained sediment overlying gravel, and probably indicate the presence of gravel channels within the Springston or Christchurch Formation.