GRAHAME CHAMPNESS

Introduction

The proposed  (May 1987)  Paparoa National  Park is in an area of  approximately 30,000  ha  situated  between  the coast and  the crest  of the  Paparoa Range  in the north west of the South Island of New Zealand.  It reaches from the coastline  to the crest of the Paparoa Range at Mount Lodge (1,447 metres).

Two  major  features  give  character  to  the  area  and dominate the  theme of  the Park.   These are the lowland bush and  the limestone landscapes.  The scenic coastline already  plays  an  important  role  for  recreation  and tourism with  features like  the Pancake Rocks and Truman Track.

Within the boundary of the new Park there is an extensive area  (approximately   40%)  containing  karst  features. Until recent  years the general public’s knowledge of the karst in  the area  was limited  to the  karren field  at Dolomite Point.   Although  this area is small it is very accessible and  is known  internationally as  the Pancake Rocks.   Cavers were  also aware  of some cave systems in the Bullock  Creek, Fox  River 4  Mile and  Ananui  Creek areas, however, there still remains much unexplored karst terrain.

The Karst  in General

The major  geological feature  is the  limestone syncline running down  the western  side of  the Paparoa Range. On the western  side of the syncline the karst plateau rises to 472  metres with  an average height of 370 metres. The abrupt edge  on this  side of the limestone ends with the massive limestone  cliffs running 20 kilometres along the coastline. It  is these  cliffs which give the region its distinctive karst scenery. The karst plateau is dissected by rivers  flowing from  the Paparoas  and there  are six major  limestone  gorges  within  the  new  Park.  Scenic qualities of  these gorges  are heightened by steep walls of white  limestone contrasting  with the  rich greens of the bush.   The syncline gently dips to the south and the bed of the syncline lies only 40 metres above sea level.

The eastern  side of  the  syncline  is  not  visibly  as spectacular as  the west  though the  limestone has  been pushed up  steeply to  659 metres  at Waikori.  Along the eastern edge it is also dominated by the foothills of the Paparoas.

There are  six distinct  beds which  make up the tertiary rocks found  in the  syncline.  These  are  -  Mawheranui Group; Brunner Coal Measures found in the north and south  and the  deepest the Rapahoe Group; the Kaiata Formation, a         massive  formation of  impervious marine  mudstone  and sandstone which  is impervious  to water;  and  the  Nile Group  of   limestone  and   highly  calcareous   clastic sediments.   This group  has two  divisions which are the major rock  where the  karst  development  has  occurred.
These  are  the  Tiropahi  Limestone  and  the  Potikohua Limestone which  are both very rich in calcium. Overlying this is  the Blue  Bottom group,  the Welsh formation and the  O’Keefe   formation,  marine  mudstones,  and  muddy sandstones with minor limestone near the base.

Speleogenisis

Most of  the cave  systems in the area have been found to the west  or in the bed of the syncline.  The majority of these caves  have developed down in the 5o to  10o dip of the syncline. They usually follow the bedding planes of the Tiropahi or Potikohua Limestones.

Work in  the Metro cave by Williams (1970) shows that sea level  fluctuations  during  the  Pleistocene  had  major effects on  the cave during its development.  No work has been done  to relate  this to other caves in the area but it is  likely that  they were  affected in  the same way. There is  growing evidence  of the  presence of an inland sea behind  Punakaiki in recent geological time.  Some of the caves  are high  and dry  along  cliff  faces  whilst others are  still  affected  by  rainstorms  along  creek margins i.e.  Xanadu in  Bullock Creek.  There is a range present of  caves from  those in  a state of collapse and decay  to  others  still  below  the  phreatic  zone  and therefore still developing.

Sub Fossils and Fossils

There are  many rich  deposits of sub-fossils.  These are mainly  of   avian  remains  but  there  are  reports  of reptilian, mammalian  and molluscan remains.  The extinct Moa features  in most  deposits ranging  from the  larger species   to the  small bush  Moa; their smaller relation the Kiwi  (one species  of Kiwi  is still  present in the region) has  also been  found.  These deposits indicate a rich avifauna was present at some stage in the past.

Fossils  found   in  the  caves  are  from  the  Tertiary limestones or  the Upper  Miocene.  The  fossils  so  far recorded range from whale bones and part whale skeletons, shark’s teeth  from many  species, fossilised  crab claws and several species of sea shells.

Biological Values

The Punakaiki  Karst is  important because it is the only extensive area  of lowland  karst in New Zealand with its bush cover  almost intact.   For  this reason most of the biological processes  which have developed over thousands of years are still in place and operating naturally.

Many of  the  cave  systems  in  the  area  receive  high food/energy inputs  from flooding.  Food for  glow worms, spiders, carabid  beetles etc  is carried  in by  regular flooding. Wetas are also present in most of the caves and recently an unusual wasp which is a parasite on weta eggs has been recorded in the Metro Cave system.
In general  very little is known about the biology of the Punakaiki Karst. 

Caves and the Public

The Fox River Cave was discovered about 1903 and has been visited by  the  general  public  ever  since.    It  was regarded as  a tourist  cave for many years with a locked gate and caretaker, however, for reasons unknown the gate was removed  and not  replaced.   Recently the  cave  has received renewed interest with many visitors on a regular basis, no  control has  lead to a steady deterioration of the speleothems  and  cave  environment.    It  is  still attractive and  often the  first experience  the  general public have of a cave in this area.

Unfortunately no  accessible and  highly decorated  cave, which would  be ideal  for tourist  development, has been found.   The Metro  Cave would be suitable as a show cave with a  different type  of experience.  Its 8 km of tubes and passages  could provide adventure type tourist caving experience.

There is  a recognised need for the development of a cave in the  area which  would provide  the public with a cave experience.   There are  several littoral caves along the coast which  the public have had access to for many years these  are  not  limestone  caves  but  are  in  granite, granitic breccia, sandstone and mudstone.

The Future

Karst management  in  New  Zealand  is  only  just  being recognised as  a very important part of our heritage. The new Department of Conservation now has the responsibility to  ensure   a  National   Karst  Resource   is   managed appropriately.  The   delicate  nature   of   the   karst environment makes  this  a  task  without  precedent  and managers of the Paparoa area must now cater for the needs and judgements of future generations.