ACKMA Journal #2 – December, 1988

Introduction

All caves, whatever their type of origin, generally exhibit some variety of speleothems, which they can occur in a large range of materials.  One substance that does result in a major range of speleothems is mud As mud implies something that is unclean or foul very little regard has been shown for this feature of a cave on the past. Historically, mud features have suffered more damage than any other, as a result of the almost total disregard for it as cave decoration.

Origin

Speleothems is a generic term used to describe secondary mineral deposits - mainly of calcite, aragonite, and gypsum - which develop in limestone caves.  However, the term also has wide meanings.  The origins of mud and its mineral composition are important factors in determining the shape and size of speleothems that may develop. Specific gravity and water content play major roles Mud can be defined as wet earth and it is generally carried into caves by stream action or man movement from the surrounding countryside. Therefore, its composition is controlled by the rock and soil types in the catchment area.  Other sources of mud are areolian materials, and the insoluble residue of the solution process - which can be the source of particularly fine muds.

Mud stalagmites are usually structureless, but some show concentric layering, particle size stratification or colour differentiation between lighter calcarious or siliceous cores outside clay coverings (Deal, 1966; Hill & Forti, 1986). While calcite and silica may be the major mineral constituent of the muds, there seems to be a separation of the clay minerals into different mud layers.  Organic materials play a role too.  Some of the very sticky muds within caves contain large amounts of organic matter.

Development

Development of different mud formations come about through a number of processes. Water dripping into caves forms glop holes (Spider Cave, Jenolan). Glop holes are often lined with calcite, and excellent examples can be  viewed in Spider Cave at Jenolan and Eagles Nest Cave at Yarrangobilly. Water running down the walls of caves is possibly the main contributor to the development of a large range in the shapes and sizes of mud speleothems, known as vermiculation. These can be seen in Wiburds Lake Cave, Jenolan, Eagles Nest Cave, Yarrangobilly, and in the Colong Caves.

The ebb and flow of water in caves plays a role in the development of these mud formations.  Gravity helps develop this type of decoration on undercut walls in caves, leaving pendular - type features.  Good examples are seen in the Bouverie Cave, at Wombeyan. There is also evidence in Wiburd’s Lake Cave and Mammoth Cave, Jenolan. that a depositional process takes place, with drops of water carrying mud particles creating a stalagmite type of deposit as a feature.

Mud or sediment banks in caves can contain evidence of geomorphological processes over very long periods. Mud deposits may provide evidence of outside environmental effects, and the filling of pool areas such as in Narrengullen Cave, near Burrinjuck Darm, may be indicators of denudation processes in European times. Carol Hill’s and Paulo Forti’s valuable new book: Cave Minerals of the World shows photos of mud mushrooms where, due to ponding, mud has been deposited on existing formations, and later become calcified.  These are seen in Lausinas Cave, France (Cabrot 1975).

A range of formations, possibly the pendular type because they are all on overhanging walls, can be seen in the first section of Imperial Cave at Jenolan. The formations here have had the mud replaced by calcite. Another process of mud formations or shapes can be seen in a cave where wind and sea spray seem to be the primary sculpturing agents. Examples have been noted on Kangaroo Island, South Australia.

Management

The problem with mud in caves is people, and its consequent unnatural reworking and removal If you have ever washed caving gear after a caving trip, it is apparent that immense amounts of mud have been removed on it from caves, over time. One artificial mud formation that is frequently seen in caves is "splots" - these being the result of irresponsible mud fights, or simple carelessness when moving things around. Drawing in nice smooth mud is a form of grafitti causing damage to surfaces that could give clues to flow rates. 

Be it removal on gear (boots, etc) or by throwing, some areas of caves have experienced total mud removal (Wiburd’s Lake Cave, Jenolan, for example). Yet if one were to remove all crystalline deposits from an equivalent area, much hue and cry would result. From management environmental and scientific viewpoints mud formations and deposits should be afforded the same consideration and protection as any other type of formation.

REFERENCES
Deal, 1966; cited in Hill, C. A, & Forti, P. Cave Minerals of the World. Abode Press, Albuquerque, 1986.

Cabrot, 1975.  Ibid.

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