CAVE FORMATIONS

GYPSUM AND LIMESTONE

Virtually all of the world's solution caves are formed in either gypsum or limestone.

About 350 Million years ago, large inland seas covered most of what is now New Brunswick.  As the climate grew warmer, more water evaporated than accumulated in the course of a year and the seas shrank.  The warm seas were suited for the growth of marine invertebrates and over millions of years their hard shells formed thick layers of gypsum and limestone.  These minerals, along with other “evaporates” like dolomite, salt and potash were also formed as the minerals precipitated from the ever concentrating sea water.

Gypsum, or calcium sulphate, is one of the softest and most common mineral in the world, and is widely used for wallboard or sheetrock, Plaster of Paris and as a fertilizer or soil conditioner.  High grade gypsum was also used in sculpture and dental work.

Limestone, or calcium carbonate, is also a soft mineral and the one most often associated with cave systems.  It’s most common uses are for agricultural lime, cement and building stone.

 THE CAVES OF SOUTHERN NEW BRUNSWICK

Of the approximate 20 caves that have been discovered in New Brunswick, all but one are in the  Mississippian  limestones and gypsums in the southern portion of the Province. 

The Mississippian period marks the beginning of the Carboniferous or coal age era that existed some 350 million years ago.

In the Hillsborough area there are 7 known caves (5 gypsum and 2 limestone), The North and South White Caves, The Underground Lake, The Lost Brook Cave, The Berryton Cave and two newly discovered and as yet unnamed caves. 

THE HILLSBOROUGH FORMATION

The Hillsborough formation is unique in that it has both gypsum and limestone.  Although the formation varies, there is essentially a bed of gypsum and one of limestone that runs for several Kilometres. This "ice cream bowl" formation has the 20-30 meter thick gypsum tucked into the underlying limestone bowl.

The limestone and gypsum was deposited in thick beds as carbonates and sulfates.  In time, it was covered by the eroded debris from the Caledonia Mountains.  This debris served as a protective cap and over millions of years compressed the thick layers of precipitates and marine invertebrates into rock.

Eventually erosion and the retreat of the massive ice sheets nearly 10,000 years ago, removed the covering layers of shale, sandstone and conglomerate and exposed the underlying limestone and gypsum.  As the glaciers melted, large volumes of surface water filled the low valleys and depressions left by the advancing glaciers.  This water, acidified by carbon dioxide from the air and by decaying plant material, percolated through the surface soils and cracks in the gypsum and limestone.  Over the course of time, the tiny cracks and fissures were deepened and widened to form the caves that we see today.