Neolithic and Bronze Age Landscapes of North Mayo: Report 2011

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The southern two thirds of the Mullet peninsula are part of the Erris complex, mainly gneisses with a small area of more recent rocks to the extreme south. The Erris complex rocks are amongst the oldest in Ireland, with some of those on the Mullet dating back to 1,900 million years ago (mya). Other rocks in this complex range from 1,900 through to 900 – 650 mya. These rocks, which have been significantly transformed by later metamorphism and deformation formed part of an ancient North American continent which was later sundered from comparable rocks in Greenland and NE America by the formation of the Atlantic ocean approximately 200 mya. From the north of the Mullet peninsula eastwards, through Broad Haven Bay and to Glenlassra the underlying rock is Dalradian in age, from the Grampian and Appin groups. Most of the Dalradian rocks were deposited in a shallow sea following c. 750 mya, and they contain evidence for tropical and glacial climates at different times. Following c 590 mya the Dalradian rocks were uplifted into substantial mountains and eroded as the continental plates converged and moved apart. The Grampian group includes the quartzite and psammitic schists that form the spectacular cliffs of this part of the North Mayo Coast, whilst the northern slopes of the arc of mountains from Ben More to Slieve Fyagh immediately to the south of Belderrig and extending west are mainly part of the Appin group of quartzites and psammitic schists (Dalradian), with Carboniferous sandstones forming the southern slopes and the summit of Slieve Fyagh. The complex of archaeological features in Belderrig is associated with the Broadhaven group of quartzites and psammites. Dalradian pelitic schists of the Inver Schist formation are the core of the area studied by Noel Dunne, including the hills of Knocknalower and Dooncarton. The Dalradian rocks also include intrusive Caledonian metadolerites associated with the opening and closing of the Atlantic (c400 mya). These are significant in the Belderrig area, where they are visible through the psammites and quartzites and are associated with massive quartz veins. Metadolerites to the south and south east of Belderrig form a significant part of the Ben More range. East of Glenlassra the region is dominated by Carboniferous sandstones and limestones deposited from c 360 – 325 mya. Sandstones run from Glenlassra to the west of Killala Bay, which is underlain by Carboniferous limestones (the Upper and Lower Ballina Limestone Formation). Some of the Carboniferous sandstones were deposited on a coastal plain by rivers, but the Downpatrick formation provides evidence of the encroaching Lower Carboniferous sea. The Ballina Limestones indicate the deepening of this sea and fully marine conditions. North of Inishcrone, on the Eastern side of Killala Bay these limestones include fossil corals. The Carboniferous limestones include cherts and silicified limestones. These generally soft sedimentary rocks underlie the coastal lowlands and low hills of the Ballycastle – Killala area, including Maumakeogh and form the dramatic Céide cliffs outside the Céide Fields Centre and, most strikingly, at Downpatrick Head. This base geology underlies the main Céide Fields complex and the complexes of field walls and associated structures discovered by Gretta Byrne’s survey work between Ballycastle and Killala Bay. Deglaciation and sea level change The geological background provides the skeleton, but the surface of the North Mayo landscape has been extensively reworked by the actions of ice and other associated processes during millennia of glaciations and deglaciation. The last Ice Age culminated in Ireland being completely covered in an extensive Ice Sheet at about 28-22,000 years ago. As this ice sheet retreated it left a series of 100
distinctive deposits and landscape features in North Mayo. So distinctive are these, that in fact, the retreat of the ice at the end of the last Ice Age in the area has been the subject of long standing research (for example Symes 1881). Hinch (1913) argued that the ‘shelly drift’ exposed at Belderg and Glenulra was deposited by floating ice although later opinion suggests that this was an active ice margin (see below). Models of the late Glacial history of ice in the region vary (Greenwood and Clark 2009a, Greenwood and Clark 2009b, McCabe 2008) but McCabe suggests that the area was last glaciated c. 26,000 cal BC with evidence at Glenulra and Belderrig for ice moving in a NW direction. The ice then retreated and appears to have been followed by a period of significant isostatic depression (depression of the earth’s crust through the weight of the ice) associated with (very) high relative sea level and deposition of a variety of glaciomarine and marine muds, sands and gravels. Glenulra Valley contains a sequence of glaciomarine/marine muds deposited under water at a period of isostatic depression (25-24,000 cal BC). These are found at c. 80m above today’s sea level, implying that the land was 80m below relative sea level at this time. Given that global sea level was c. 130m below present day sea levels because of the very substantial bodies of water caught up in ice sheets in the Late Glacial, this implies an isostatic depression of c. 210m. Following this period of massive isostatic depression and hence local relative high sea levels, there is evidence for the readvance of the ice. The Belderg shelly drift is now argued to be derived from ice proximal sedimentation from tide water glaciers, followed by ice berg zone mud (McCabe 2008, McCabe, Clark, and Clark 2005): i.e. the area was underwater at the margins of an ice sheet. This dates to approximately 17,000 BC and again indicates considerable isostatic depression, with relative sea level being hypothesised as c 20-30m above present (McCabe 2008, 250). Ice may then have retreated again, and the last major advance of ice in the region was the Killard Point Stadial (c 13,500 cal BC). At this time McCabe reconstructs the Ice Sheet margin as lying at or just beyond the western edge of Killala Bay or Lacken Strand, oriented approximately NNE/SSW, and therefore lying immediately to the east of our primary study areas. The story of deglaciation is important for our region. The ice shaped the hills and valleys of this region over millennia, depositing tills and moving materials across the landscape – some of which were to be important resources following colonisation by people. The area has been ice free for a considerable period of time, although parts of the region were inundated by the sea at different points in this sequence. The deposition of marine muds and gravels in specific parts of the landscape is significant, and creates small pockets of variable resources and soils. Sea level Sea level changes continued long after the immediate retreat of Ice from the Belderrig area, reflecting global sea level change due to ice melt (glacio-eustacy) and local rebound following the removal of Ice masses. The interplay of these processes is complex, and unfortunately, there is no radiocarbon data available on Holocene (post-glacial) sea level in the North Mayo area (Brooks and Edwards 2006), but general models (Brooks et al. 2008) suggest that relative sea levels have consistently risen in the region due. These models suggest that early in the Holocene (which began 9,700 cal BC) sea levels in the region were about 20 metres below present day, and these have since 101
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Neolithic and Bronze Age Landscapes
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Table of Contents Introduction ....
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Scientific Research associated with
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Introduction This report reviews th
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- A summary of the radiocarbon dati
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Creating Digital Archaeological Lan
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Figure 2: Data Model for NBNM GIS R
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Figure 4: example of outputs at Cé
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Rathlackan As a result of a lack of
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Radiocarbon Dating A further tranch
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RATHLACKAN Lab Number F no S. No Co
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GLENULRA ENCLOSURE Notes Cal BC (95
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Lab Code Cutting Sample Material AR
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Charcoal analysis from Neolithic an
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Results Overall charcoal 83 samples
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Glenulra Scatter 92E140 Middle Neol
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Oak and birch were recorded from Cu
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35 30 no of samples 25 20 15 10 5 0
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Area A A long length of Neolithic f
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piece was 17 years old when cut, ba
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elating to midden B2P and from five
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1% 6% Corylus 1% 14% 25% 0% 2% 4% 4
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posts burnt in situ. Rather the pos
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When the charcoal is examined throu
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at Glenulra scatter. Alder was iden
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een freely available in the area. T
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References Byrne, G., Warren, G., W
Page 55 and 56: Verrill, L. and Tipping, R. 2010. U
Page 57 and 58: Table 3 Charcoal identifications fr
Page 59 and 60: Sample Date Ctg Context Description
Page 61 and 62: Sample Date Ctg Context Description
Page 63 and 64: Sample Trench Time period Descripti
Page 79 and 80: Table 7 Wood identification details
Page 81 and 82: Table 8 Charcoal identifications fr
Page 83 and 84: Cutting Sample Date Feature Descrip
Page 89 and 90: Table 8 Sample assessment Rathlacka
Page 91 and 92: Phase F. S. Trench Deposit type Loc
Page 93 and 94: Behy-Glenulra: Céide Fields visito
Page 95 and 96: A possible midden (B2P) contained a
Page 97 and 98: Wild remains Hazelnut shell fragmen
Page 99 and 100: References Beijerinck, W. 1947. Zad
Page 101 and 102: Verrill, L. and Tipping, R. 2010. A
Page 103 and 104: Soils and Geology Graeme Warren Thi
Page 105: Figure 3: overview of geological fe
Page 109 and 110: Figure 4: major landuse categories.
Page 111 and 112: References ?? Soil Map of West Mayo
Page 113 and 114: The first scientific paper on late
Page 115 and 116: Also in the summer of 1963, fifty k
Page 117 and 118: the earth for the bank coming from
Page 119 and 120: dates from the macrofossil remains
Page 121 and 122: New Research and Researchers Over t
Page 123 and 124: Probed Surveys: Erris, Céide Field
Page 125 and 126: Iron probes of varying lengths had
Page 127 and 128: Céide hill twenty five years earli
Page 129 and 130: Survey on the Glenamoy - Bartnatra
Page 131 and 132: Bungurra River drains the Knocknalo
Page 133 and 134: The elevation of the tombs, all sit
Page 135 and 136: In 1936, 2 sub-rectangular cists, C
Page 137 and 138: Dooncarton Southwest slope 3.15 km
Page 139 and 140: The cross-section area occupied by
Page 141 and 142: No upper boundary was located on Kn
Page 143 and 144: The third house site, H3, on Gortme
Page 145 and 146: The 2 court tombs, Ma38 and Ma23, l
Page 147 and 148: This void is substantiated by exami
Page 149 and 150: Survey from Ballinglen to Rathfran
Page 151 and 152: Lissadrone basin. The peat cover is
Page 153 and 154: Two similar large round cairns are
Page 155 and 156: Wall Gaps Because of concealment an
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supported by an orthostat visible u
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and with different building techniq
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Survey Illustrations: Figure 1: Ove
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Figure 4: Seefin walls with associa
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Figure 7: Walls from the study area
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Figure 8: Cabintown Site A. 161
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Figure 11: Rathlackan sites H12 Fig
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Figure 15: Creevagh H5, Figure 16:
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Figure 19: Carrowkibbock Upper H20.
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Neolithic and Bronze Age Landscapes of North Mayo: Report 2011

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