Depwtment of Agriculture md Technical Instruction for Irelmd. THE CKEOLOGY OF CLAISE ISLANl~, COUNTY MAYO. ,., ,i",_. .--1 BP I _ G.A. J. COLE, F.G.S. ; J. R. KILROE, A.R.C.Sc.1. ; ; T. HALLISSY, B.A. ; AND E. A. NEWELL ARBER,’ M.A. 1 ‘i 4 DUBLIN : PRINTED FOR HIS MAJESTY’S STATIONERY OFFICE, BY BROWNE & NOLAN, LTD., NASSAU STREET. _ _-_-_ ____ - -___. And to be purchased from E. STANFORD, 12,13in nd 14 LONG ACRE, LONDON ; W. & A. K. JOHNSTON, LTD., 2 ST. ANDKEW SQIJARE,TWINBURGH ; HODGES, FIGGIS &. CO., LTD., G~amo~ ST., DUBLIN, from e,ny Agent for the sale of Ordnance Survey Maps, or through any Bookseller, from , T. FISHER UN WIN, 1 ADF:TZHTTRRKACIC, LONDON, W.C., who is sole Agent to the Trade outside the County of London. 1* r % \ 1914. Prfqe *Two Shillings and Sixpence. \ GEOLOGICAL SURVEY OF IRELAND -- DIRECTOR-PROF. GRENVILLE A. J. COLE, M.R.I.A., F.G.S. SENIOR GEOLOGIST-S. Ts. WILKINSON. GEOLOGISTS-W. B. WRIGHT, B.A., F.G.S. ; T. HALLTSSY, B.A. (O&er in charge of t&e Collections) ; H. T. KENNEDY, B.A. SUPERINTENDENT OB MAPS-R. CLARK. DRAUGHTSMAN-M. GAVIN. 1. I ._ I23 124 I IiS -I---I2 Boundaries of the Sheets of the Geological Map on the scale of one inch to one * mile. Various prices. Thick lines mark the boundaries of the colour-printed _ sheets showing superficial deposits, , in addition to the underlying rocks prig+- __* le. 8d. each. _ - -+_ I) _r. / _.__ - ---_-__ --- . -7 - . &_ _ _ _ __ ..-. -- - \f @- I’ f Departrkien t of Agricul hre and Technical , Inst,ruclion for Ireland. b MEMOIRS OF THE GEOLOGICAL )5 SURVEY OF IRELAND. THE GEOLOGY OF CLARE ISLAND, COUNTY MAYO. ‘G. A. J. COLE, F.G.S.; J. R. KILROE, A.R.C.Sc.1.; T. HALLISSY, B.A. ; AND E. A. NEWELL ARBER, M.A. $3uSIis~eb52 @h%craf the illarlw 4hmtissioners af j.Qis #lHajtst~~‘sEreasurg. ____- DUBLIN : PRINTED FOR HIS MAJESTY’S STATIONERY OFFI()E, BY BROWNE & NOLAN, LTD., NASSAU STREET. __- ________ And to be purchased from E. STANFORD, 12,13and 14 LONO ACRE, LONDON ; w. & A. K. JOHNSTON, LTD., 9II ST. ANDREW SQUARE, EDINBUROH ; HODGES, FIGGIS & CO., LTD., GRAFTON ST., DUBIJN, from any Agent for the sale of Ordnance Survey Maps, or through any Bookseller, from T. FISHER UN WIN, 1 ADICLPHITERRACE, LONDON, W.C., who is sole Agent to the Trade outside the County of London. 1914i. Price Two Shillings and S&pence. PREFACE. THE original description of Clare Island by the Geological Survey is contained in a few paragraphs by the late Mr. R. G. Symes, in the Memoir to Sheets 73, 74, 83, and 84, published in 1876. The remarkable work by Messrs. Kinahan and Close on “ The General Glaciation of Iar-Connaught,” which was issued as a separate pamphlet in 1872, prepared the way for detailed studies in the glacial geology of western Mayo ; but it was not until 1909 that the Geological Survey could continue its observations in this interesting district. A natural history and archaeological survey of Glare Island was undertaken in 1908, under the auspices of the British Association for the Advance- ment of Science ; Mr. R. Lloyd Praeger acted as general organiser and editor, and the results are in course of publication by the Royal Irish Academy. We are indebted to Mr. Praeger for the use of several photographs taken by Mr. R. Welch. Sanction was obtained from the Department of Agriculture and Technical Instruction for the utilisation of the Geological Survey in connexion with this series of researches. The present Memoir is the outcome of a survey of the drift-deposits and soils of the island by Mr. T. Hallissy, and of a revision of the history of the older rocks in the light of observations made by Mr. J. R. Kilroe in the county of Mayo in recent years. I have had the opportunity of going over the ground, and have added certain notes and comments in the Memoir. Mr. E. A. Newell Arber has reported on the Carboniferous beds, and the Survey is much indebted to Dr. Wheelton Hind for examining the molluscs found. It is believed that the work will prove serviceable as a description of a typical western islahd, forming a veritable outpost on the Atlantic edge of Europe. GRENVILLE A. J. COLE, Director. Geological Survey Office, 14 Hume Street, Dublin. .Nc;rwmber, 1912. 111. TABLE OF CONTENTS. -- ?Ac+E PREFACE . ii CHAPTER I. Historical References . 1 General Description . 2 Areas and Townlands . 2 Rock Formations and Table of Formations 6 Ballytoohy Series . 7 Knockmore Series . 9 Crushed Zone . 11 Age of Crushed R&s . 13 Harbour Series. Old Red Sandstone 15 Maum Series. Upper Old Red Sand&& 17 Capnagower Series. Lower Carboniferous Sandstone . 18 CHAPTER II. Carboniferous Rocks . .19 * The Molluscav The Plant-rerdaias : . 20 Obscure Markings on Sandstone . 21 CHAPTER III. Igneous Rocks . 22 The Rocks of the Zone ‘of Movement and Intrusion . 26 CHAPTER IV. Faulting and Present Structure of Glare Island . 27 CHAPTER V. c . Superficial Deposits . 29 Superficial Deposits. -Detailed Description 34 Evidence of Glaciation . 35 Boulder-clay . 37 Local Drift . 38 Moraines . 38 aolian Deposits . 39 Storm-beach . : . 39 Peat and Alluv& . 39 Land Connection . 40 CHAPTER VI. Soils . l . 44 Soils-Capillirity bf , . 46 Chemical Characteristics . 47 Tables of Analyses . 49 . I, I. ._ 1 i PLATES. PLA!LQ I.-General View of North Part of Glare Island, Knock- more in the. distance. Frorttie@x. ,, XL-Model of Glare Island on the same vertical and PAUB horizontal scale. Photo. from cast . 3 , ,, III.-Cliffs of the Knockmore, Series, West Coast, Glare Island . 10 9, IV.-Scarp produced by weathering down of the Fault Plane, north side of Knocknaveen . 1 26 PLATB V. Fig. A.-&!~a~ Moraine, Loughaunaphuca, Glare Island 38 ,, B.-Glaciated Rock-surface, Ooghtiska . FIGURES IN TEXT. Fig. 1 .-Sketch section through Croagh Patrick and Glare Island 27 ?? 2.-Map showing direction of Ice-movement and Orientation, of Drumlins in West Connaught . ‘. 31 es 3.-Map of Ireland showing the Localities at which Submerged Peat has been found . 42 #? 4.-Diagrams showing the rise of water by Capillarityin Soils ofClareIsland . s . 47 TH& GEOLOGY OF‘ C&ARE ISLAND, CO. MAYO. CHAPTER 1. BY J. R. KILROE. HISTORICAL REFERENCES, Clare Island is well known historically as a chief resort of the celebrated Grace O’Malley, Queen of the West, in the stirring times when English rule was being established in Ireland under Queen Elizabeth. Grania Uaile, as her western majesty was best known, is reputed to have held sway over large areas of Mayo and Galway, and to have rigorously main- tained her inherited rights by means of a strong fleet. The “Anthologia Hibernica ” * refers to “ the O’Malley principality, extending from the lake called Lough Corrib, in the County , Galway, to Croagh Patrick, in the County Mayo ; and from thence to the city of Sligo.” According to Roderic O’Flaherty,? the dominions of the O’Malleys seem to have been less extensive. He gives them as “ the Owles,” Latinized from “ of Umhall ” (or Ui Mhaille), comprising the .present baronies of Murrisk and Burrishoole ; and the latter barony seems to have been the centre of the O’Malley principality ; the “ queen ” was known to O’Flaherty as Grace O’Malley of Burrishoole. Ac- cording to G. B. O’Connor& Grace O’Malley, the Queen of the West, the last representative of Irish independent naval strength, “ ravaged and plundered the maritime towns and districts, both native and ‘Enghsh.” The deeply indented coast line of Mayo and Galway, with its many safe harbours and sheltered roadsteads, facilitated the manceuvres by which the Queen of the West maintained hek rule, or extended her sway as the case might be ; and in shelter of Glare’ Island her fleet could ride in safety from the strong western storms. Above the small bay in the south-east corner, which is the only safe haven in the island, stands Grania Uaile’s Castle, a well built but unhandsome square structure, and a substantial monument. of her rule. The island was taken over by the Congested Districts Board the 15th March, 1895, having been purchased from the Misses McDonnell, who inherited from J. C. McDonnell.(I The Board * Vol. iii. p. 340. t “ A Chronological Description of West, or E-iar Connaught ” ( 1684, pub: 1846), 140% $ “! kizabethan Ireland,” by G. B. O’Connor, pp. 64-276. On Grania Uaile and the history gf Glare Island generally, see T. J. Westropp, “ Glare Island Survey, History ‘&‘Archaeology,” Proc. R. Irxsh Acad., vol. xxxi (1911), Part 2. 11Information supplied by the Secretary of the C~ngestod Dis@icts Board, who g@~ ;t$e nameq; of the original proprietors &B Sir Edward HalA ,. II, A&wBo~, James wrn: Far&n, and .GeoFgeI;&, ?-- 2 re-apportioned the island into “ seventy-four holdings, ex- clusive of commonage, upon which the tenants have the rights of grazing,” and, after expending large sums upon Improvement Works, re-sold to the tenants, who contracted to pay in in&al- ments at 8$ per cent. for SS& years. The improvements con- sisted in the erection of substantial stone fences, development of roads, etc., which greatly ameliorated the condition of existence on the island. The alteration of the boundaries of the fields and holdings were associated with changes in the townland boundaries, and hence the Ordnance Map of 1899 greatly differs from that of 188% The names and areas of the townlands as taken from the latest Ordnance Maps are as follows, viz.