The Canadian provinces of New Brunswick and mainly Nova Scotia show large areas and masses of gypsum and anhydrite. These are evaporates of the late lower carboniferous Windsor-Series, developed in a shallow epicontinental sea under tropical and aride climate near the former equator line. Since than plate tectonical movements shifted these areas into the nowadays position at the eastern rim of North America, the same latitude as middle to southern Europe, with which area it was joined during sedimentation (Pangaia).
The sulfatic series of locally several hundreds of meters are mostly covered by a blanket of ground moraines of the latest or Wisconsin glaciation. These mostly impermeable glacial sediments offer an acidic soil milieu with a vegetation not adapted to gypsum and prevent the hydraulic contact, i.e. the precipitation from percolating through the soluble gypsum layers. So the majority of the near to surface gypsum does not show many signs of karstification.
There are smaller areas, where the ground moraine is thin or of merely sandy texture and more permeable, or where the erosion from seashore, lakeshore or rivers have produced white cliffs (similar to the steep slopes of quarries), there mostly linear denudation of gypsum and karstification occurs, rarely in larger areas, with development of typical gypsum karst structures as caves, springs and swallets, dolines, sinkholes, and long cliffs with nets of so called “Schlottenkarren”. Only here we find a vegetation, typical for sulfatic soils, bearing orchids, for example the Yellow Ladyslipper; the pink variety is adapted to the more acidic soils on granite or greywacke.
Research and documentation of the eastern Canadian gypsum karst landscapes just began few decades ago. There are thorough investigation on gypsum resources for the mining industry and water resource management by the Nova Scotian Geological Survey (Adams, 1991, or Baechler&Boehner, 2014) and some documentations of the natural history department of the Nova Scotian Museum regarding the Hayes Cave Site and some glacial mammal findings in gypsum sinkholes, opened by quarrying.
The surface of Nova Scotian gypsum areas is covered not with the former primordial, but with forests of second or third clearcutting generation, dominated by softwood. The older quarries show no or only few activities of recultivation.
Quarrying of gypsum (locally called plaster) seized 1956 in the Dingwall area at the north eastern tip of the Cape Breton (pen)insula of Nova Scotia. There was no rehabilitation or were there any other changes on the surface. The quarry startet in 1933 with an esteamed resource of 35 mio. tons of gypsum by the Atlantic Gypsum Company. It is situated in the middle of the Aspy River estuary. This river spills granitic detritus from the highland of the Cape Breton national park eastbound into the Atlantic, crossing or running alongside the Aspy fault, a former plate boundary and running steep down into the outcrop area of the late lower carboniferous Windsor series with its evaporates.
Transport of raw material from the quarry was at first by ox or horse carts, later with trucks for few hundred meters down to the Dingwall fishing harbor at the Atlantic shore. With a maximum exploitation of 100.000 tons each year the total spoil was 15-20 mio. tons gypsum. The production ended 1956 with the rising financial burden of keeping the fishing harbor free of sediments for oceangoing freight ships; all these information come from the tiny Cape North museum and archive (thanks to them!).
The former quarry consist of several areas, all together ca. 36 hectares of sulfatic surface. Before only small parts were open gypsum karst, mainly cliffs, due to shore or river erosion. The larger part was covered by moraine, the boulder of which you can find scattered around. Up to three floors of 5 to 20 meters of the better qualities of hydrated evaporate rock were quarried down unto the rather irregular anhydrite surface. Only smaller “islands” with thicker moraine cover were left untouched.
The evaporates are nearly horizontal and the layers thickness is about meters. The hydration of anhydrite to gypsum is irregular, partly spherical or of woolsack type, what can be seen impressively on the old quarry surface. The gypsum is mostly pure white.
The nearly horizontal anhydrite floor is opposed at least since 60, partly up to 80 years to the precipitation of ca. 1.500 mm/ year. Salty sea spray from easterly storms may not be excluded as an accelerator for the hydration process, which is the transition from anhydrite to gypsum and leads to an enlargement of the rock volume for about 20 % by incorporating 2 water molecules into 1 anhydrite molecule or in chemical words: CaSO4 + 2 H2O = CaSO4 . 2 H2O.
In these long decades about the half of the quarry surface has developed a pattern of buckles with hundreds of swellling caves. You can find all stages of growth and decay or collapse, partly generations of these phenomenon are to discern one over the other. The sizes vary as well as the longitudinal directions. Some caves on the lowest floor are partly inundated, but there is no difference to non-inundated caves, which means that this is not a factor for the hydration process.
The surface of the bubbles or caves, mostly about half meter in hight, is pure gypsum or half anhydrite, partly solid rock, partly made up of millions of fragments of sugar cube size, both types often with sharp boundaries. The reason for these patterns are not yet examined.
About one out of ten bubbles is open, so to be determined as caves. The majority can be checked by the noises of your steps on them, but please avoid this as not do destroy these young structures! You need some walking around and looking inside the open ones to notice the fascinating all around phenomenon of hydration buckles of 2-8 meters in median size. Don’t forget, that the last years of quarrying is done by machines or caterpillars, leaving a really flat surface.
Fig. 10 Maruhn-Cave - Surface of a young, but second largest bubble cave of the former Dingwall quarry: left partly caved in in 2017, middle in 2003. All other white buckles in the background are swelling caves as well. Those not yet open gave sounds by stepping on them. Right: Inside Maruhn Cave, 2003. The yardstick is 2 meters.
In 2003 the largest open swelling cave (or in German: Zwergenhöhle) was Maruhn-Cave with a floor space of ca. 9,5 x 4,5 meters with a smooth roof bank and a maximum height of 1 meter. Below the roof several older banks have separated and collapsed, each of 5-12 cm of thickness. So, this cave is actually growing and collapsing. Indeed, in October 2017 the roof is partly caved in and it was dangerous to slip in the ruins.
In 2006 another large buckle opened, now the largest dwarf cave ever seen over there or in the world! Called it Ramesh Cave it has a ground space of about 12,1 x 7,9 m and 1,15 m high. The cave is a remarkably uniform developed vault. Until October 2017 it shrinked laterally to 9,95 x 4,50 m, the latter due to a further incasion of the “entrance”. It was now 1,32 m high, which resembles a growth of 1,5 cm/a. The length datas a rather uncertain due to the smaller and smaller fissures, from where the roof or bubble starts to lift off.
The process speed must be fast, in close neighborhood you find starting flat bubbles, mature caves, caves of high and steep asymmetric roof and finally decayed caves, last one very similar to the famous “Waldschmiede” on Sachsenstein/Walkenried (South Harz, Germany).
As it happens within about 5 decades, the speed should be around >100 cm in 50 years or >2 cm/a. The author started a measurement program with iron bolts in 4 caves, checking it every three years since then. The results are not far from the estimated dimensions and not far from the results, taken from the German South Harz swelling caves on the Sachsenstein. E.g. Maruhn-Cave: the height was rising 20 cm/10 years, the vault was shrinking 23 cm/10 years.
The Dingwall area is an attractive goal for all friends of gypsum karst, touristic and scientific. In the brackish waters of the Aspy River estuary (North Harbour, South Harbour) there are several longer gypsum cliffs with breeding bald eagles on treetops and pure gypsum islands. It is a marvellous landscape for hiking and paddling. Especially from the sea kayak one can study the different forms of erosion and corrosion effects of sea- and brackwater on gypsum. Hiking on cliff tops, though difficult due to the uncleared and dense forest, unveil the nets of honeycombed so called “Schlottenkarren”.
Dingwall and neighbouring Cape North are suitable starting points for ecological and geological excursions into the Cape Breton National Park, which covers with the Aspy fault the welded seam of former or Paleozoic terranes.
To log this earthcache, if you like, you may send a photo from the entrance of Ramesh Cave per eMail; just if you like, you may optional send a selfie with Ramesh Cave in the background. Further on please give answers to these three questions (by eMail to the author):
1. Within a 5 minutes stroll around Ramesh Cave: how many open other caves you can find? Give a rough number.
2. Why the rock swelles up? Give an explanation with your own and with simple words.
3. Nova Scotia gypsum or plaster is mainly used for: ....
Happy holidays in Cape Breton!