geology of little killary killary thesis
Excerpt via Thesis:
Some of the grains weather to a pale green colour. In thin section, quartz may be the major wheat type (~50%) with some microcline (~5%) and several rock broken phrases (~1%) all in a fine matrix which includes quartz and/or feldspar, mica and some calcite cement. The vast majority of grains include a red-brown altered casing. The mountain fragments are possibly reworked sediments” (p. 13).
Lettergesh
Analysis simply by Farrell indicates that this development is generally comprised of quartz-rich sandstones, mudstones and siltstones. This specialist adds that, “The sandstone should better be known as greywacke and it is the most common rocktype. The formation has a total thickness of about 1096m including the density of the two microgranodiorite physiques which intrude it. On the base in the formation (L754 610 and surrounds) there is also a body of conglomerate which can be part of the Gowlaun member identified by Laird and McKerrow (1970). This cobble conglomerate is found towards the top of Altnagaighera (L7540 6100) and across the pit on the slopes south of Lough Fee (L7760 6117)” (p. 13). According to Farrell, the spot is minimize by a one major wrong doing known as the Lough Fee wrong doing in the field which has an ENE trend which will offsets the majority of the other significant lithologies with the area (i. e., the metagabbro and Dalradian, the Lettergesh as well as the diorite). Farrell adds that, “It is visible best in the valley only on the SW side of Lough Payment (L7750 6150 and surrounds). The mistake runs through this large sided area and near to the top of Garraun (L7685 6140) there exists a small slim vertical dip in topography that markings the fault” (p. 18). Farrell interprets these findings as suggesting a vertical fault; while there is an average pattern of 040, the trend curves. According to Farrell, “The apparent balance is about 1 ) 4km yet there is almost certainly some dip-slip movement provided the different thicknesses of the formations on either side. Some of the lithologies apparently have a bit of drag plus the diorite nearest the shore is quite sheared and recrystallised, probably because of movement of the fault” (p. 18). The Lough Fee fault is most probably associated with the problems in the Silurian sediments considering the fact that many of them work parallel in a leftward counter such as evinced in the Lough Fee mistake (Farrell, 2003). In sum, Farrell proves that, “The smaller problems are mostly viewed offsetting the diorite by small amounts (usually only a few meters)” (2003, s. 18). Additionally , Farrell information that, “The conglomerate is mainly clast-supported having a matrix of coarse sandstone. It is interbedded with beds of coarse- or medium-grained sandstone. The boundaries between the conglomerate and sandstones are often sharp. From time to time there are a few cobble clasts suspended in sandstone beds, and often there are mattresses of conglomerate which are only one clast heavy. The clasts are mostly quartz arenite (white, pink and white and pink), as well as some volcanic clasts, some sandstone, a lot of jasper, some granitoid clasts, and a couple of clasts of schist. The clast size ranges from 2cm up to 50cm having a modal scale about 10cm. The clasts are all very well rounded. There is certainly some limited evidence of engrenage but quite often the clasts seem to be quite randomly directed. On Altnagaighera (L7555 6070) the outcrops are sharp sided as they have broken along joint faces. Listed below them the steep mountains are full of clasts. These kinds of clasts are simply in different amounts to those in the conglomerate – there are few on the scree slopes other than the either white or pink quartz arenite, probably because of the differences in power and resistance from weathering” (p. 13). Finally, Farrell provides that, “On the coastline (L7310 6280) above the Lough Mask development is a series of thinly bedded green-grey siltstones and mudstones with some bedrooms of sandstone. The beds will be from 1-2cm to 30cm thick. Since the conglomerate lenses out along strike this is the base of the Lettergesh development on the banks. There are fire structures seen in the beds which usually give a approach up to the north and show that the bed frames have not recently been overturned. The flame buildings all indicate the east. Up in the mountains (e. g. L7435 6225) above the conglomerate the Lettergesh also involves thinly bedded siltstones. Above these, within the coast (from L7370 6310) and up inside the mountains (e. g. L7660 6120) will be thick bed frames (9cm about 65cm) of greywacke interbedded with thinner beds of mud and silt. The greywackes are generally graded and therefore are greeny-grey in colour. You will find examples of flame structures in some of the leaner beds and convoluted bed linen. ” (p. 16). Other researchers have got investigated this area as well. For example, according to Williams and Harper’s (1988) assessment of the formation, “The Silurian transmission of the north part happen to be marked by a diachronous overdue Llandovery (early-middle Telychian) transgressive episode which is common to a large number of successions. The transgression triggered the development of comparable sedimentary facies and fossil assemblages” (p. 741). These kinds of authorities add that, “The clast compositions of Llandovery and Wenlock conglomerates suggest erosion of a common provenance of volcanic rocks founded on a metaquartzite basement. Areas of effective volcanism seem to have migrated in a north-westerly direction eventually. It is suggested that the common popular features of the Irish successions might be accommodated within a unified basin model intended for Silurian sedimentation and volcanism. Such a basin might have created in an intra-arc environment and been controlled by oblique-slip fault mechanisms although data for the existence of a Silurian arc is usually equivocal” (Williams Harper, 1988, p. 741).
Glencraff
The research by Farrell indicates which the Glencraff creation is situated conformably on top of the Lettergesh using a total fullness of 68 meters. In respect to Farrell, “The formation consists of thin (on average 5-10cm) laterally continuous mattresses of siltstone and mudstone with some, rarer, sandstone beds. The beds are very highly cleaved in locations. The outcrop is much less good concerning the additional formations, maybe because it is simpler to erode. Within the coast there is certainly one large outcrop in L7408 6403, below Islandlyre, but additional inland (L7440 6395) there exists a grassy low-lying area where most of the Glencraff was likely to be. By Culfin Water (L7560 6325) there is reasonable outcrop to get a short while but heading towards Lough Muck the outcrop goes away into a bog” (p. 20). Besides Farrell (2003), you will discover few other educational sources for this formation but one seminal source, Nealon, advises, “The Silurian, Glencraff Formation of north Galway has previously been construed as a deep-basinal, distal-turbidite series, representing the culmination of the marine criminal offense. It is interpreted here while mid- to outer-shelf thunderstorm deposits, most of which gathered below storm wave base. The formation is divided into five lithofacies ranged A to E; Facies A is comprised of very finely bedded sandstones that show intermittent hummocky cross-stratification (HCS), and considerable low-angle combination lamination and horizontal laminierung. Facies M. consists of parallel-laminated, thin bedded sandstones; Facies C. Of generally substantial siltstones, and Facies G. Of mudstone. Facies A, B, and C. are interpreted as having been deposited by storm activity, primarily below surprise wave base. Facies D. occurs only at the top of the formation and consists of a series of thinly bedded tuffs which contain abounding large-scale hummocky cross-stratification and they are therefore interpreted as previously being deposited in slightly shallower water compared to the rest of the development. A slight steady decrease in normal water depth is usually recorded through most of the creation by an increase in the incident of modest HCS in the Facies A sandstones. inches Finally, Neaton adds that, “The improved shallowing of water depth during deposition of the tuffs is interpreted as being to some extent caused by the rapid inflow of the tuffs themselves. Paleocurrent data and facies relationships indicate that the shoreline lay down to the southwest with a around northeast-southwest orientation” (p. 55). In addition , Farrell (2003) information that, “The Glencraff formation was laterally continuous and thinly bedded suggesting deep-water deposition. No ripples, crossbeds or any different structures were observed. The grain dimensions are, on average, less space-consuming than the Lettergesh sandstones under. The different materials size implies either even more distal deposition or a different sediment source” (p. 13). It is possible that the Glencraff formation represents the highest point in the transgression, and even though no evidence of this was present in the field, previous investigator by Laird and McKerrow (1970) discovered graded bedsheets that construed the Glencraff as turbidites (Farrell, 2003).
Lough Ruin
Found according to; consistently with above the Glencraff formation, the Lough Muck formation is usually 249 yards thick. According to Farrell, “The border between the two was challenging to pinpoint and may even be gradational. The Lough Muck involves grey and green mudstones, siltsones and sandstones. The beds are mostly laterally continuous and are also from 1cm to 20cm thick (on average about 10-15cm). The main factor accustomed to differentiate these from the Glencraff was the existence
