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Geology

Linn Park has an amazing geological history, as has been recognised by many organiasations, least of the Linn Park Gentlemen's Walking Club: who else goes home with a piece of coal ?

The Geological Society of Glasgow comments:

Linn Park is one of Glasgow’s hidden gems – a deep rocky gorge and an impressive waterfall tucked away in the busy southside suburbs. The rocks tell a story of Glasgow’s long distant past, many millions of years ago, when volcanoes and tropical coal-swamps dominated the landscape. The gorge was carved through the tough rocks by the White Cart river (merely thousands of years ago!) when it was swollen by melt water from the Ice Age glaciers. Water and coal have since powered Glasgow’s industrial revolution and if you look carefully you can still find traces of it in the woods and river banks, slowly being reclaimed by Nature.

Another comment from the British Geological Survey in 2013 reads:

Along the picturesque river in Linn Park, sedimentary rocks of the Carboniferous age Limestone Coal Formation can be seen.

At Linn Waterfall, the sedimentary rocks have been intruded by a resistant microgabbro sill which forms the waterfall that gives the park its name. Hexagonal columns can be seen in the sill at the falls, similar to the columns at the Giant’s Causeway in Northern Ireland.

Downstream of the waterfall the river runs in a deep gorge. Landslips along the gorge walls indicate that the steep gorge is unstable but also produce good exposures of the sandstones and siltstones that were once deposited by ancient rivers - rock fall at Millholm.

The British Geological Survey Report for Glasgow has three reference points in Linn Park, namely

  • Court Knowe [Ref Point: 17]
  • The Waterfall [Ref Point: 9]
  • White Cart Water, Holmwood House [Ref Point: 8]

An overview by Stuart Nisbet:

The landscape of the area has been shaped by the most recent glaciation which ended 12,000 years ago. The underlying rocks date from the Carboniferous age (310 – 350 Million years old). They have been exposed through the erosive power of the White Cart and its contributing burns. Some have also been exposed by man (by quarrying and mining).

In Linn Park and Netherton Braes, we can see rocks from three main stages of the Carboniferous period [oldest first]:

  • Viséan (Lower Carboniferous), c.350 to 330 Ma. These occur later, when lavas were intruded into the local strata, notably forming Linn Waterfall.
  • Namurian (Upper Carboniferous), c.330 and 310 Ma. Almost all of the rocks in the area are from this period (Limestone Coal Formation and Upper Limestone Formation).
  • Westphalian (Upper Carboniferous to Early Permian), c.310 to 300 Million years ago. These outcrop in the valley of the Kittoch Water, at the upper end of Netherton Braes, near where the Kittoch meets the White Cart, opposite Overlee Park.

Index Limestone

Within the Namurian period, the Index Limestone forms the boundary between the Limestone Coal Group and Upper Limestone Group. This limestone was formed from the shells of billions of marine creatures which settled out of a shallow sea. The shells of these creatures can still be found today, fossilised in the limestone. The Index limestone outcrops generally down the west side of the Cart, thus rocks to the west of the Cart are from the Upper Limestone Group and to the east, from the Limestone Coal Group.

Limestone Coal Formation

When the Limestone Coal Group was laid down, Britain lay much further to the south than today, approximately on the equator. The area which now comprises Central Scotland was part of a large tropical delta, similar to the Amazon delta today. Most of the time the area was flooded by the river and sediments were laid down which formed sandstones and shales.

Over long periods of time the level of the land gradually rose and fell in a cyclic fashion. When the land rose high enough in the estuary for plants to grow, tropical forests developed. The decay and subsequent burial of these forests resulted in the formation of the coal seams in this area.

Upper Limestone Formation

In the Upper Limestone Group, flooding by the sea was a more common event and limestones are more frequent than coals. The periods which formed these economic minerals were relatively infrequent events. Thus the limestones and coals represent only a small percentage of the strata in the area. The bulk of the rocks are sandstone and shale.

Secrets of the River Bed

Introduction

Thanks to Stuart Nisbet for this article and its accompanying photographs.

The White Cart is a highlight of the park and is a natural feature. However, over the centuries, it has been heavily managed by man.

As it flows through Linn Park, the river traditionally passed over three natural or man-made mill dams: Linn Falls, Millholm Dam, and Cathcart Mill Dam.

These obstructions controlled the flow through the park. When the dams were intact, the river was effectively three long, flat, stretches of water, interrupted by the roar of water at the falls.

The story of the Mills is covered elsewhere on this web site, but in this artcile we look at the dam's effects on the river bed.

Cathcart Mill Dam

 

The first dam to fall into disuse was Cathcart Mill Dam, at the upstream corner of the converted Suff Mill mill buildings. Old postcards and OS maps show the dam intact into the 1940s (pic). However the dam had not been maintained since the mills were abandoned c.1900. Although built of very large blocks of sandstone, the dam was gradually breached and washed away, when the river was in spate. The only part remaining is a short stretch on the left bank of the river.


 

Millholm Dam

This dam was three times higher than Cathcart Mill Dam. When it was intact, the river was flat and calm most of the way back from the dam to the foot of Linn Falls.

Millholm Dam was breached in 1984. The dam didn't burst, instead the river worked its way into softer strata in the right bank of the river, and worked its way round the edge of the dam (pic).

Over the centuries, the river bed behind the dam had silted up to the dam's crest. The deposits stored behind the dam built up an archaeological record of what had been brought down by the river, over hundreds of years. Each winter since the dam burst, the river has cut deeper into this material, exposing the river's secrets.

Secrets of the White Cart

The White Cart rises on Corse Hill, above Eaglesham. In its first 14km from Corse Hill to Busby, the river cuts through igneous rock. Then in the next 3km from Overlee to Linn, it passes through sandstones and shales. The debris in the river bed includes samples of all these rocks. The further the rocks have been carried, the rounder are their edges.

Other material brought down by the river is man-made, including bottles, pieces of fireclay, and a host of much smaller debris.

Easiest to identify are hundreds of red bricks. Many are from the demolition of mills and buildings on the riverside further upstream, especially Netherlee Printworks.

Most bricks bear names of the numerous local brickmakers in the northern part of Cathcart Parish .

Cliff Collapse at Millhom

In the park, opposite the site of Millholm Paper Mill is a high cliff, at a bend in the White Cart. The main path to the East through the park passes along the top of the cliff. Nowadays the path is fenced off from the cliff by a high fence.

Since the 1960s, this cliff had become more and more unstable. The river had gradually undercut the mudstones and other softer sediments in the lower part of the cliff. This left a large overhang of sandstone bedrock, protruding several metres over the river. This instability affected two paths: the main path through the park, and particularly lower path which cut across the upper part of the cliff, running down to the grassy area beneath the castle. This lower path was undercut by the overhang.

Over the years Glasgow Corporation, and their successors, posted danger notices, and sometimes closed the lower path. But gradually the hazard was forgotten.

In March 1997 the Parks Department were clearing vegetation from the lower path. A tractor and shredder had driven down the overhanging path. The noise and vibration from the shredding of trees and rhodedendrons echoed down the river valley.

The following day, the cliff collapsed, bringing down hundreds of tons of rock, partially blocking the river. The debris reached the far bank and partly damaged the industrial building on the paper mill site, which was still used as a commercial garage.

A section of the lower park path disappeared, leaving a very dangerous section leading nowhere.

 

The Council closed both paths and hired excavators to clear the worst of the rockfall from the river.

 

The cliff collapse exposed a freshly broken face of the local geological strata. Much of the upper part of the cliff is composed of sandstone, which, when freshly broken was almost white. Many of the collapsed sandstone beds contained Carboniferous fossils, some several metres long.

 

 

 

At least two thin coal seams were exposed, near the top of the cliff (probably the local 'Smithy' and 'Main' coals). Former coal workings contributed to the collapse, including one of several old adits (entry points to workings) which had been visible for many years in the side of the path.

After a few weeks, the upper path was re-opened, with the current high fence installed to keep the public away. Since then, the cliff has gradually become overgrown, and the rock face weathered and darkened.

The cliff collapse illustrated how natural geological proccesses (erosion by the river) and man-made proccesses (mineral abstraction) can have a major impact on the landscape in a relatively short period of time. The figure shows the riverbank from the cliff upstream to Millholm Dam.

Catchment Areas etc

The river running through Linn park is one of two "Carts": the White Cart and the Black Cart. The rivers meet just before they join the Clyde to the North East of Glasgow Airport. The White Cart drains an area including the Eaglesham Moor. The Black Cart drains the flatter lands around Paisley and Johnstone: read more about them in these documents from SEPA, which describe the catchment areas, the likelihood of flooding, and the flood management plans:

The rivers are distinctively different with the White Cart passing through Linn Park in a steep sided gorge formed presumambly in the Ice Age. And this is what makes Linn Park such an attractive place to visit. The steep fall on the river gives rise to lots of "White water"as it tumbles down - hence its name.

Water flow in the River

The flow of water in [or the gauging of] the river is monitored at the Weir just above the Bailey Bridge which provides access to the Gas Monitoring station. There is a path to it from the edge of the Cemetery - See Walking, and select the walk called: "White Bridge loop to the Netherton Braes".

The records from 1981 to 2018 are held by the National River Flow Archive, and can be viewed here: https://nrfa.ceh.ac.uk/data/station/meanflow/84030. The records for the year are normally transferred in the following Autumn.

The records for the last few days are available from the Scottish Environmental Protection Agency at White Cart Water @ Overlee. It is these records that are then transferred to the National River Flow Archive.

There are two other gauging stations above this one, both on tributaries, namely

Health of the River

The Clyde River Foundation [CRIMP] is one of the best sources of information whether it be research or history.

The Field Studies Council [FSC] provide the basic tool of how to identify wildlife in general. Their specific publication entitled "A key to the major groups of British freshwater invertebrates" is part of their AIDGAP series and is used by CRIMP.

Possibly one of the best publications is River Clyde Fishery Management Plan 2009-15 [pdf format]

Obviously a healthy landscape improves the health of the river. One good site is https://www.buglife.org.uk/ whcih had a project in Glasgow. The report is here: https://www.buglife.org.uk/sites/default/files/Glasgow%20Buzzing%20final%20report_0.pdf. Again it is a report on invertebrates.

How do we judge the River ?

First of all we look at the color of the water: there seem to be three main colors:

  • A good peaty color - nice and clear when the water flow is relatively low.
  • A horrible dirty color - just after a down pour after a dry period. All the muck off roads and pavements, as well as direct drainage off the land. All the dog shit gets and stuff washed away thank heavens. It also includes all the microscopic bites of rubber from car tyres as the wear away, as well as dust from brake pads - which includes asbestos ....
  • A good muddy color - after a period of prolonged rain - just natural erosion. Does a lot of good, and when the water recedes, the banks and islands in the river a refreshed.

Next we look at the river life:

  • Do we see all the normal guys - Ducks, Kingfishers, Dippers, Wagtails, and the Herons - and do we see them regularly ?
  • Are the fish rising ? 
  • In season do we see fish leaping the waterfall - both Salmon and Brown Trout.
  • And in the spring do we see shoals of smalts ?

Conclusions [as at summer 2019]

  • Fish are happy. Salmon haven't been seen recently [a problem in all rivers in Scotland]
  • Ducks are now rare - the hundreds of 20 years ago are down to just a few
  • Other river birds are simply not seen as often as they used to be - when did we last see a Cormorant ?

How do we judge the the Park and environs ?

  • First of we look at the way the park is maintained.
    • Tarmac roads and paths - no drainage means run off straight into the river.
    • Metalled paths, i.e the zigzag and the top wood.
    • Soft paths - their misuse leads to damage
    • Grasslands - over mowing has now ceased
    • Woodlands - not maintained
    • River banks - not maintained
  • Next we see what types of bird are prevalent - are we overdosed with gulls and magpies ?
  • Are the usual small birds still arround - what's the dawn chorus like ?
  • Do we see bats down by the river, and in the hedgerows ?
  • Lastly we ask are we seeing squirrels, rabbits, deer and and foxes etc

Conclusions [as at summer 2019]

  • [under discussion]