Transcript
Page 1: Project Poster - Ross of Mull

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(C) Crown copyright/database right 2012. An Ordnance Survey/Edina supplied service. FOR EDUCATIONAL USE ONLY.

GESP

TBSP

LMSP

TSP

GESP

GESP

TSP

TSP

SymbologyObserved boundary

Inferred boundaryObserved fault

Inferred fault

Synform

Antiform

Drift boundary U

16

75 Bedding (S0)& dip value Z S

Z S

63

81

Cleavage (S2)

Cleavage (S3)

Cleavage (S1)77

Minor Z fold axis

Minor S fold axis

Hinge line (S3)

Hinge line (S2)Minor Z fold axis

Minor S fold axisVertical

bedding (S0)

Overturnedbedding (S0)

Majorfold axisYounging

direction

Dip & strike of dolerite sheet

Downthrow tick & relativedisplacementMinor W

fold axis

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140000 141000 142000 143000 144000

140000 141000 142000 143000 144000

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A B C DHorizontal Distance, 100 metre Intervals Horizontal Distance, 100 metre Intervals

Re-folding of F2 structurescontrolled by competency changes in psammite andlocal strain

Relic cross-beddingpreserved in psammite.

Scale: 500 metres

A B C D139550, 719120 141550, 718450 142020, 718850 143710, 718105

WNW ESEAssapol Syncline coreassociated with F3 w-folds

Boudinaged quartzite beds show extensional distortion and fragmentation

Transitional boundarydivided by quartzite marker bed

Boudinagedcalc-silicate lensesdecrease in abundance tothe west

TBSP

LMSP

TSP

GESP

Gneissose banding ingarnetiferous pelitesimprints a penetrativeS1 cleavage

Unknown trendof dolerite sillcontinuing west

Camptonite dykesTight parasiticF3 z-folds

Parasitic F3 s-folds younginto core

F3 average axialplane 80E/028

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DESCRIPTION CHRONOSTRATIGRAPHY*LITHOSTRATIGRAPHY

BASE NOT SEEN

TOP NOT SEEN

FORMATION

Marine beach depositsPeatTill / Boulder clay

Quartzofeldspathic psammitewith numerous local gritty and micaceous bands.Sedimentary structures present, including cross-bedding andconvolute bedding.

Gneissose semi-pelite interbedded by north-south boudinagedquartzite. Subordinate calc-silicatelenses and fissile pelite beds.

Coarsely crystalline garnetiferouspelitic gneiss with subordinant semi-pelitic banding and local calc-silicate lenses.

Quartz dominated bandedpsammite with semi-pelitic and pelitic interbeds, both locally garnetiferous.

AGE (Ma.) LITHOLOGY

Drift Quaternary (2.588 - 0 Ma.)

Neoproterozoic Era (1000 - 542 Ma.)

InterbeddedPsammite (IPSM)GarnetiferousPsammite (GPSM)Calc-Silicate (CS)

GarnetiferousPelitic Gneiss (GPG)GarnetiferousPelitic Schist (GPS)

Semi-Pelite (SP)Quartzite (QTZ)Calc-Silicate (CS)Fissile Pelite (FP)

Psammite (PSM)MicaceousPsammite (MPSM)

Garb Eilean StripedPsammite Formation 2402 m

Lagan Mor Semi-Pelite Formation 176 m

Torr Stallachdach Psammite Formation 1597 m

Traigh Bhan Sgurra Pelite Formation 316 m

T T T

T = Transitional boundary

*(Holdsworth & Harris, 1987)

Undifferentiated Basaltic Dykes

Brown Dolerite Sheet

Granitic Pegmatite

Ultramafic Camptonite Dykes

IGNEOUS INTRUSIONS

PEG

CMPT

BSLT

B-DOL Paleogene (66 - 23 Ma.)

Paleogene (66 - 23 Ma.)

Paleogene [Paleocene Epoch] (66 - 56 Ma.)

Ordovician - Devonian (488 - 359 Ma.)

GESP

TBSP

LMSP

TSP

Figure 3 - (above) Generalised Vertical Section of SE coast of the Ross-of-Mull.

Holdsworth R. E., Harris A. L. & Roberts A. M., 1987.The stratigraphy, structure and regional significance of the marine rocks of Mull, Argyllshire, west Scotland, Geological Journal, v. 22, p. 83-107.

Figure 1 - (below) Fair copy map, showing full extent ofmapping area including solid geology, drift, structural data and line of cross-section.

Figure 2 - (right) A WNW - ESE cross-sectionfrom GR 139550, 719120 to GR 143710, 718105.

Figure 4 - (right)A location map with insert of field area.(modified from Google Earth 2014)

Figure 5 - (right) D3 stereonetshowing average axial plane of the Assapol Synclineand evidence for acurvilinear hinge.

Mendum J.R., Barber A.J., Butler R.W.H., Flinn D., Goodenough K.M., Krabbendam M., Park R.G. & Stewart A.D, 2009. Lewisian, Torridonian and Moine Rocks of Scotland: an introduction, Geological Conservation Review Series, v. 34, p 8-16.

References:

Figure 4: Google Earth 8.0 2014, Imagery date 7/1/2006, south-east of the Ross-of-Mull, Satellite image

Figure 1: Ordinance Survey (GB), Using EDINA Digimaps Ordinance Survey Service 2014

The Ross-of-Mull is located in the Inner Hebrides, NW Scotland. Mapping a section of south-east coast revealed rocks to be of the Neoproterozoic Moine Supergroup. Rocks in this area have undergone polyphase deformation associated with the Caledonian Orogeny and closure of the Iapetus Ocean. In addition the rocks underwent mid-amphibolite facies metamor-phism. Three phases of deformation were observed during mapping; a sequence D1-D3. The dominate compressional phase is D3, this event has produced a tight upright synform, termed the Assapol Syncline. Subsequently, structures associated with D1-D2 are often observed in zones of relatively low strain. A general vertical section of the area has also been pro-duced; the Torr Stallachdach Psammite Formation forms the base of this succession, and displays preservation of relic cross-bedding and de-watering structures. Overlying this is the Lagan Mor Formation made up of semi-pelites interbedded quartzites. The upper boundary is transitional with the Traigh Bhan Sgurra Formation, this formation is characterised by a distinctive gneissose fabric. The Garb Eilean Striped Psammite Formation is located at the top of the succession and ex-hibits large scale F2 and F3 folding.

Candidate Number: 129015856

Traigh Bhan Na Sgurra

Scoor House

2000 metres

10 kilometres

N

Iona Fionnphort

Bunessan

Lochaline

Tobermory

Isle of Mull

A’ ChlèitGarbh Eilean

Port Bheathain

N

The Neoproterozoic rocks of the south-east coast of the Ross-of-Mull, NW ScotlandN

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W

Poles to S0 around F3 folds

Poles to S3 axial plane

Poles to S3 cleavage

F3 hinge line

S0 average (SE limb)

S0 average (NW limb)

Average axial plane

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