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Travelling out of Rishton along the Wilpshire road, you leave the built up area of Hyndburn to countryside which mainly consists of farmland. At first glance the emphasis in the area seems to be related to the effects of the industrial revolution and subsequent 20th century, but look beyond your first impression and what emerges is a record of a time when the area we know today had a tropical climate in a period known as the carboniferous.
Star Delph Quarry (also known as Harper Clough Quarry) lies hidden next to the Wilpshire road. The quarry was first abandoned in 1897. Luckily it has not suffered the fate of landfill like the nearby Close Brow Quarry, as what is hidden in this wooded delph is a record of the carboniferous period. Star Delph is known for a pattern on the rock face, which is the fossilised record of the root pattern (called stigmaria) of a large plant known as a lepidonendron. This pattern on the titled rock face, shows the root pattern on the outside with the trunk in the middle. You can see why it is known as the Star. Lepidodendron, also known as the "Scale tree" is an extinct tree-like plant related to the Lycopsids (club mosses). It was part of the coal forest flora. They sometimes reached heights of over 30 metres (100 ft), and the trunks were often over 1 m (3.3 ft) in diameter, and thrived during the Carboniferous period. Sometimes called "giant club mosses". Lepidodendron had tall, thick trunks that rarely branched and were topped with a crown of bifurcating branches bearing clusters of leaves. These leaves were long and narrow, similar to large blades of grass, and were spirally-arranged. Lepidodendron likely lived in the wettest parts of the coal swamps that existed during the Carboniferous period. They grew in dense stands, likely having as many as 1000 to 2000 giant clubmosses per hectare. This would have been possible because they did not branch until fully grown, and would have spent much of their lives as unbranched poles. In its juvenile stages, the trunk was supported by grass-like leaves that grew straight out of the trunk. Stigmaria are a type of branching tree root fossil found in Carboniferous rocks. They were the roots of coal forest lycopsid trees such as Sigillaria and Lepidodendron. Fossils are the preserved remains or traces of animals plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. Fossils are formed by a variety of processes: (1) Permineralization. This occurs after burial, as an animal or plants empty spaces within an organism (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater and the minerals precipitate from the groundwater, thus occupying the empty spaces. This process can occur in very small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce very detailed fossils. For this to occur , the plant or animal the organism must becovered by sediment soon after death or soon after the initial decaying process. The degree to which the remains are decayed when covered determines the later details of the fossil. Some fossils consist only of skeletal remains or teeth; other fossils contain traces of skin, feathers or even soft tissues. (2) Casts and molds. In some cases the original remains of the organism have been completely dissolved or otherwise destroyed. When all that is left is an organism-shaped hole in the rock, it is called an external mold. If this hole is later filled with other minerals, it is a cast. (3) Authigenic mineralisation. This is a special form of cast and mold formation. If the chemistry is right, the organism (or fragment of organism) can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. If this happens rapidly before significant decay to the organic tissue, very fine three-dimensional morphological detail can be preserved. (4) Replacement and recrystallization. Replacement occurs when the shell, bone or other tissue is replaced with another mineral. In some cases mineral replacement of the original shell occurs so gradually and at such fine scales that microstructural features are preserved despite the total loss of original material. (5) Adpression (compression-impression) fossils. Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state. This chemical change is an expression of diagenesis. Often what remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression. Often, however, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. (6) Bioimmuration, is a type of preservation in which a skeletal organism overgrows or otherwise subsumes another organism, preserving the latter, or an impression of it, within the skeleton. As you can see, the rock is tilted, originally the face you see was horizontal, but millions of years after it was formed , masive earth movments caused it to fold and tilt upwards. The rock is sandstone, part of the millstone grit series of the Carboniferous period. The Carboniferous is a period in our geological history that lasted from 359 million years ago to 299 million years ago. It was preceeded by the Devonian period and followed by the Permian period. The rock that you see was laid down during the Namurian sub division of the Carboniferous period, it lasted between 326 and 313 million years ago. It is during the Namurian that the rocks known as Millstone Grit were laid down. You hear this type of rock mentioned a lot in the Pennines. Millstone grit rocks are part of a group which comprises over 30 differently identified sandstones. Now, how was it laid down? At the time of the carboniferous, Britain had a hot climate. This area formed part of a large river delta system, the rivers carried large volumes of sand and mud, which were deposited in the delta system. At times, the areas between the river channels formed swamps covered in tropical forest. At other times, the sea rose over the delta, and flooded the forests. Sand was deposited in the river channels, and over time sandstone was formed. Its is a sedementary rock, this means that the grains of sand that make up the rock were laid down and then compressed over time to make the rock that we see today. Now there is more to this little disused quarry than the Delph Star, if you walk further along the footpath you will come to an area where there is a small waterfall. This is a waypoint. Here you will notice that there are different layers of rock lying at an angle. The rocks also appear different. Here you see a marine band (where the waterfall is), and then layers of shale and sandstone. Marine band is a geological term for a bed of rock, commonly black or dark grey shale. These strata represent episodes of flooding by seawater and are important in enabling the comparison or correlation of rock sequences in different localities. Shale is from where mud was deposited in the river floodplains or in the sea. As you can see there are different layers, which is known as strata. As layers of sediment accumulate to great thickness, they are compacted and begin to harden into sedimentary rock. Each layer they form is called a bed or stratum, the process by which this occurs is called stratification. The separation between each bed is called a bedding plane and signifies a cessation of deposition at that location for a period of time. Here you can see the bedding planes. To log your find, please answer the following questions and contact Hillgorilla with the answers. (1) What colour is the rock where the Delph Star is? (2) What does the rock feel like where the Delph star is? (3) The information board refers to a part of America, which part? (4) What angle does the rock lie at where the Delph Star is? (5) What type of fossilisation process do you think took place? At the Waypoint. (6) Please describe the stratification, what is the order of the different layers. (7) As an option, please take the following photographs : (i) You or your GPS at the Delph Star. (ii) The tilted rock face. (iii) You or your GPS at the different layers of strata. PLEASE DO NOT INCLUDE THE INFORMATION BOARD IN YOUR PICTURES. PLEASE : Only enter the site at the entrance point. Do not climb on the rocks or damage the site in any way. BE CAREFUL, AND DO NOT CLIMB ON THE ROCKS. PLEASE BE CAREFUL NEAR THE QUARRIED AREAS AS THERE ARE DROPS. KEEP A CLOSE EYE ON CHILDREN. The two parking areas are just about big enough for one car. Please be careful walking along the road. IT IS ROUGH AND SLIPPY UNDERFOOT IN PLACES. Sources of information: Internet search about the geology of the area. Local knowlegde.
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