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Journal ofthe Geological Society, London, Vol. 144, 1987, pp. 179-185, 8 figs., 2 tables. Printed in Northern Ireland

Sediment exchanges along the coastal margin of the Moray , Eastern Scotland

G. REID' & J. McMANUS Department of Geology, The University, Dundee, Scotland 1 Present address: Department of Oceanography, University College of North Wales, Menai Bridge, Gwynedd LL.59 5EY, UK Abstrart: The Moray Firthis the largest of only three major coastal embayments on the East Coastof Scotland. The relationships between the offshore, coastal margin and fluvial sediments are examined in terms of processes and deposits. These suggest that the large post-glacial accretions of sediment infilling the inner are in part attributable to transport of material from the offshore zone. Since the fluvial input to the area appears tobe relatively small and much is retained on estuarine tidal flats itis likely that the offshore contribution is the most important constituent of the deposits of the coastal margin. The other major source is glacial and fluvioglacial material now being reworked by marine activity.

Basis of Moray Firth study post-glacial sediments in such areas mayexceed 80 m in Incontrast tothe strongly dissected WestCoast, major thickness. Inthe outer MorayFirth seismicevidence coastal indentations along the East of Scotland are suggests thinner post-and late-glacial accumulations locally limited to the three major embayments of the Forth, the withpatchy distributions resting upona moraine strewn Tay and the largerMoray Firth. Since the rocky stretches of surface (Chesher & Lawson 1983). coastline are sedimentologically relatively inactive,an understanding of the sedimentaryregimes of themajor provides a key to understanding sediment exchanges Hydrographic regime across most of the coast of Eastern Scotland. Investigation The regime of most of the Moray Firth is typically of the Firths of Forth and Tayhave been reported elsewhere that of a low energy diurnal tide environment. Maps of the (AI-Jabbari et al. 1980; Ferentinos & McManus 1981; J. maximum tidal current velocity for mean spring and mean McManus in preparation). This paper provides an interim neap tides (Lee & Ramster 1981) show that most of the area report on studya of the largest of theEast Coast is subject to a peak current of less than 0.5 m S-'. On the embayments, the Moray Firth with its associated inner firths outer edges of the area andin the entrancesto the innerfirths of Dornoch, Cromarty, Inverness and Beady (Fig. 1). The speeds rise to greater than 1 m S-'. In the outer firth S and basis of the work is an analysis of British Geological Survey SE flood tides reverse to yield N flowing ebb tidal currents. (BGS)offshore sediment samples and geophysical records In the inner firths the tidal components are more notably coupled with calculation of fluvial sediment discharges using E-trending. ratingand flow durationdata. Other information used One of the most notablefeatures of the tidal current includes current meter, waverider and meteorological data pattern is the existence of a flow with virtually no N-S or derived from several sources. westerly component whichoccurs off the Buchan coast (Dooley 1971). This feature is a product of shelter from the ebbcomponent of the tidal flowafforded by the Regional setting configuration of thecoast. Some of theolder models of The coastlines of the MorayFirth area can be loosely circulation in thearea feature major eddies(Payne 1963; classified into two types: outer 'hard' coastlines and inner Bohnecke 1922) andthe current anomaly may bethe 'soft' coastlines.These coincidewith the division of the result of such eddyformation (J. Hardistypers. comm.). offshore zone into the Inner Moray Firth and Outer Moray However, the validity of the methods used for these studies Firth (Probert & Mitchell 1980). is uncertainand no definitive circulation patternhas yet The outer coastlines are generally -girt androcky, been published. those of Caithness consisting of OldRed Sandstoneand In an area such as the Moray Firth, characterized by low those of Banffshireconsisting principally of Dalradian tidal currentenergy, winds and waves are critical energy metamorphicrocks, in Banffshire inparticular there is input sources. Where tidal currents are insufficient to erode strongstructural control over the morphology of the sedimentthey may beable to transportmaterial if wave coastline, characteristically producing small pocket . energyhas initiated movement. The importance of such The inner coastline is characterized by large post-glacial processes in areasadjacent to the study area has been accumulations of sediment of a wide particle size range but highlighted by other workers (Owens 1981; Allen 1983). principally of and mud. Thefine sand material is found For this area of theNorth Seathere is a statistical typically in large wind blown deposits such as Culbin 50-yearhighest single wave height of 25-28m (Draper and Momch More. Muddy sediments commonly accumulate 1977). Although this value is a useful guide to the extremes in the middleand upper reaches of theinner firths. which can be expected on a wider time scale, it is not very Boreholeand seismicsurveys havedemonstrated that representative of the wave conditions likely to effect 179

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5 4 3 2w Pentland Firth Duncansbv

Twi::CAITHNESS

Smith's

MORAY FIRTH 58N

Fig- 1. Map of the Moray Firth showing sites of localities referred to in the text. BF, Beady Firth.

sediment transport on a time scale comparable with other water. Local winds are not generally of suacient strength to shelf processes. Analternative approach is based on the be of importance in the offshore zone. Onshore migration of significant wave heightand period values reported from coastaldune systems, as at Culbin, is sedimentologically wave-rider data,and alsoderived from the Hydraulics significant. ResearchStation (HRS) NORSWAM (North Sea Wave Model) wave climate model for the North Sea. These data sources (HRS, BRITOIL, 10s) demonstrate Sediments of the Moray Firth the complexities of wave height and direction distribution of both locally generated waves and swellwaves generated outside the Moray Firth. Values of significant wave height, Previous work periodand the dominant source direction change from When the Institute of Geological Sciences (now the British location to location across the Firth. Numerical models have Geological Survey) began its survey of the offshore zone of beenconstructed to indicate patterns of shallowing and the UK in the early 197Os, the Moray Firth was one of the refraction.These produce wave height losses and wave first areas to be surveyed and sampled. Theaim of the work length reductions, whilst the configuration of the coastlines was prepareto geological maps of thearea. The produces losses of waves from certain source directions. For investigations involved shallow seismic profiling, sidescan example,the southern coast is generally subject to swell sonarsurveys, Shipek grab sampling, gravity coring, waves from between the N and E, the NW coast is subject vibrocoringand limited underwater photography. The to swell from the NE to E, whilst the Inner Firth is subject surface sediment distribution map of the area based on the to swell from only a very limited direction around northeast. Folk classification (Chesher & Lawson 1983) shows several Local wind conditions vary considerably throughout the area discernable trends. The first of these is a close correlation and reflect changes in the regional topography (Plant 1968). betweenincreasing depth and decreasing , Much of thearea is protectedfrom the prevailing reflecting therelative importance of wave energyto south-westerlies by themountains inland. However, this sedimenttransport processes. This is illustrated by the protection is broken in the Inner Firth where the winds can occurrence of muds in the Deeps off the southern coast (the pass along the Great Glen unhindered. Even as far east as deepest ofwhich reachesa maximum depth of around theFindhorn (RAF Kinloss) the SW winds dominate. 230 m). In contrast the sedimentsof the Smith bank (230'W Towards theextreme east and north of thearea wind and 58"lO'N) and similar areas of high ground consist of exposure increases. Along the Caithness coast onshore S or relativelycoarse sands. However, contrary to this general SE winds are dominant in occurrence and magnitude. trend, there are considerable areas of fine sediment in the On site observation has confirmed the r61eof regional inner Moray Firth where the waters are shallow. winds in controlling directions,breaker paths and Second,there is amajor input of detritalcarbonate breaker types. All of these are sedimentologically important materialinto the area from the north. The sands of the fortogether theydetermine orientation of thelongshore northern Moray Firthcontain upto 99% carbonate driftand the initiation of sedimentmovement in shallow material. The influence of the detrital carbonate population

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isreflected in the distinction between themajor sandy gravel and gravel populations of the area. The gravels of the northwestern area are largely of detrital shelly material derivedfrom themajor shelly facies of theOrkneys and 58 Pentland Firth (Allen 1983; Farrow et al. 1984). Those off thesouthern coast are lithic andare derivedfrom the gravels of the Mouth of the Spey. Chesher & Lawson (1983) distinguished five sedimentary facies in the MorayFirth offshore area: (1) gravelly, (2) sandy, (3) muddysand, (4) muddyand (5) shelly (organic carbonate exceeds 50%). The variations in the distributions of facies (3) and (5) 58 are of particular interest and are discussed in greater detail below.

Sediment size patterns Fromalmost 1OOOBGS sedimentstations a subset of 312 (Fig. 2) was selected to provideas near as possible a ~~ uniformdensity of sampling points. In practice the 3 50W 3 oow 2 low availability of adequate material following preliminary e.3. Mean particle size of sand fraction of the bottom sediments analysis by BGS was also important. From many sites there (to the nearest wholephi unit). was insufficient material formore detailed grain size analysis. Preliminary results of seiving the sand fractions at 4 phi (70% of samples)and f phi (30% of samples) The deeper watersin the south and centre of the intervals give confirmation of directionaltrends suggested outer Moray Firth are dominated by very fine sands. by other survey methods. Plots of mean and mode rounded The size modes, which are generally finer than the up to the nearest whole phi both show similar patterns of means, yieldsimilar distributionpatterns. In variation (Fig. 3). additionthey highlight atongue of medium-fine The principal features recognized inthis map may be sands extending S from Helmsdale across an area of summarized: finer bed materials and towards the isolate patch of Coarsesands and fine gravels borderthe northern coarse materials off Tarbat Ness. coast from Duncansby Head to the Dornoch Firth, Discontinuouspatches of coarse glacial detritusin the southern east of the Spey and dominate parts of the Outer Moray Firth yield grain size data theentrance to the Inner MorayFirth between notrelated topresent dynamics and which are Tarbat Ness and Culbin. anomalous. In such areasthe resulting contour Finesands dominate most of theoffshore seabed anomalies are indicated on Fig. 3 by an oblique line down to a depth of about 50 m. between phi values.

Carbonate fraction of sandr and muds From the full BGS data set available on working maps it has been possible to demonstrate further directional trends in thesediment distribution. Detrital carbonate sediments, principallymollusc or shellfragments derived from the north, are major contributions to the deposits of the Moray Firtharea, and they provide a useful markerpopulation. The proportion of carbonate material varies greatly with size fraction of the sediment (Table 1). Contours of the percentage of carbonatein sand size particles (Fig. 4) reveal high concentrationsin the north, withprogressively lower values furthersouth. Localized tongues enter the Dornoch Firth and the Inner Moray Firth and there is an intervening area of high concentration off Tarbat Ness. Further east a third tongue of carbonate muds points towards the mouth of the Findhorn. These patterns confirm trends discussed above, but are in conflict with photographicevidence from the sea bed whichshows that localized coarsesediment transport is occurring in the contrary direction, NNE out of the Inner Firth(Chesher & Lawson 1983). The detailedpatterns of 3 sow 3 ;)ON 2 low motion are therefore complex and despite onshore transport trends being demonstratedfrom the mapped sediment Fig. 2. Location of sediment sample sitesin the Moray Firth. distributions for the area as a whole, there is the likelihood

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Table 1. Percentage of carbonatein mu& atsites indicated in Fig. 5.

% of % of Fig. 5 Station no. mudfraction total sample 57 A MF 132 11.0 9.0 B MF 592 22.7 17.0 C MF 577 33.8 1.0 D MF 597 35.1 2.0 E MF466 14.0 4.8 57 F MF 22 22.0 8.6 G MF 19 22.5 2.8 H MF604 46.2 2.7 32.6 1.4 I MF 553 3 50 W 3 oow J MF 335 49.0 2.4 K MF 138 46.7 8.6 Fig. 5. The carbonate percentageof the mud fraction of bottom L MF 51 46.8 21.0 sediments from the inner partof the Moray Firth. A-N are sites of M MF 52 45.2 17.0 samples referredto in Table 1. N MF 662 41.9 22.0

that these transports are only part of a more complicated overall pattern. enclosedFirth of Clydesuggest that biogenic of Plots of the percentage of carbonate mud (Fig. 5 and shell material may be asimportant in the production of Table arel) particularly useful in highlighting the calcareousmuds as physical abrasion(Farrow I% Clokie complexities of transport of fine material in the Inner Moray 1979). Firth.Carbonates commonly form 40-60% of the fine sediments of the entire Moray Firth area, but they decrease in proportioninto the Inner Firths and in thearea Sediments of the Inner Moray Firth immediately off themouth of the Spey. Insuch sites TheInner MorayFirth area istypified by inshorerather temgenous fluvially transported lithic muds enter the sea than open sea conditions (Craig 1959). The oceanographic and provide a masking effect on the carbonate content. If regime is that of a coastal embayment rather than that of an thecarbonate mud is considered as aproportion of the although the upper reaches of the individual firths whole sediment, (Table 1) rather than as a proportionof the are clearly estuarine with associated extensive intertidal flats mud fraction alone it appears that, despite the influence of and salt marshes. the lithic muds, large amounts of carbonate mud are being Severalsites of majorsediment accumulationoccur carried into the area from offshore (e.g. Sites A, B, Table along the coastal margin of the area, including Nigg and 1). This assumption is made on the basis of the dominant Udale Bay in theCromarty Firth, Loch Fleet, Munlochy influence of the detritalcarbonate sediments and their Bay,Beauly Firth and Findhorn Bay.Post-glacial (after known transportdown into the Moray Firth from the N. 10 000 BP) sediment accumulation of up to 60 m of marine Although nodetailed studyhas yet beenmade of the silt and silty sand has been demonstrated in the Cromarty constituents of thecarbonate mud preliminary visual Firth (Peacock 1976). inspection suggests that the high carbonate levels are less However, these sediments do not represent a straight- due to thepresence of micro-organisms than to comminuted forward accumulation of marine material sincelarge scale shelldebris. The mechanismfor the formation of the reworking of glacial sediments is a major influence on the carbonatemuds is notknown but reports from themore coastal margin e.g. at Findhorn Bay the pattern of accretion is complicated by the influence of the massivewindblown deposits of Culbin Sands, which have only relatively recently been stabilized by afforestation (Steers 1937). Perhapsas much as 40% of theouter coastline of the Inner Moray Firth area is of soft sediment (Smith & Mather 1973). The response of thesedeposits to longshoredrift, 57 wind and wave activity indicates a long term nett migration of material into the inner firths. and bar developments along the southern shores of the Moray Firth show both westward andshoreward migrationfollowing thegeneral I trend of longshoredrift. This activity is not always 57 accumulativesince distal growth appears to occur atthe expense of proximal erosion.In addition to along- /i km migration patternsthere appears to be local netonshore 8d R FlNDHORN t i_~~v- l migration. The extensivedeposits which constitutethe 3 50W 3 00 W Momch More at the mouth of the Dornoch Firth are still Fig. 4. The percentage of the sand fraction of the bottom sediments extending at their seaward extremity (Nature Conservancy formed by carbonate materials. Council 1978).

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Offshore sediment transport pathway Over the last decademuch work has been carried outby the Institute of Oceanographic Sciences (10s) and workers in British universities relating to the transport of sediments on the aroundthe UK (Stride 1982). A principal source of information is bedformdata from sidescan sonarrecords. Maps constructed following these studies show theapparent directions of offshore sand transportbut not of finer sediments.Generally these pathways trend parallel to large sections of the UK coastline indicatingthat for sand sized material atleast, offshore sediment transport occurs along pathways closely aligned to the direction of the maximum tidal currentvector. Major points of interest in the vicinity of the Moray Firth are the positions of a zone of bedload convergence off the coast of Fraserburgh (Owens 1981) and a zone of bedload parting in the PentlandFirth (Allen 1983). These, together with the apparent sediment transport paths within the Moray Firth (Stride 1982) imply that material is travelling into the Firth from the N, passing along the Caithness coast and into the area of the Inner Moray Firth. Material also seems to be migrating out of the Firth in the SE. In order to examine these trends in more detail a study of the orientation and morphology of bedforms in the area from BGS sidescan data has been carried out. Results from this workshow that welldefined bedforms are generally absentas would be expected in such a low energyzone. Sand ribbons do occur on the outer edges of the area and areoriented parallel with the coast of Caithnessand the direction of tidal flow. These pass into sand waves to the RIVER DISCHARGE m3/5 southas the tidalcurrent energy drops off suggesting Fig. 6. Suspended sediment concentration variationwith river transport along the Caithness coast in the direction of the discharge at thelowest gauging station on theRiver Nairn. Inner Firth. Sand patches, both transverse and longitudinal appear to be the predominant bedform of the centre of the sections of the Highland River Purification Board and the Outer Moray Firth. These features have a low relief. North East River Purification Board. It has been suggested that isolated patches of shell sand As in all catchments, the suspended sediment concentra- and gravel mapped off the Fraserburgh and Peterhead coast tions vary as the river discharges change through the year. and in thecentral MorayFirth may representstarved Plotting the sparse and unevenlycollected information on carbonatesand patches and sand wave fields moving suspended concentrations against water discharge for each southward across the area (Chesher & Lawson 1983). This individual river yields distributions in which the suggestion is to some degree supportedby the recognition of concentration-dischargerelationship usuallyis diffuse the patchy and subdued bedforms (above) as recorded on during low flows but assumes a distinct linear pattern during the sidescan records. Theorientation of thesebedforms high river discharges, as in the example of the River Nairn indicates eastward transport along the southern coast east of (Fig. 6). A meanlinear relationship on log-log scales the Spey.Further west in the coastalzone westward between concentration and water discharge as plotted on the transport dominates, but offshore the patternis complex and solid line in the figure, is obtained from such a plot. Using there is no clearly defined zone of partition. the long-term (20 years) flow durationcurve, which indicates the proportion of the average year in which river flows at the lowermost gauging stationsexceeded given Fluvial sediment input rates,in combination with the aboverelationship a crude The Scottish mainland, which provides the westernand estimate of the long-term mean annual suspended sediment southernboundaries of the MorayFirth, exhibits con- load may be calculated. The loadsestimated for each siderablevariety of geological structure.Underlying the river probably give a minimal figure for sediment transport hinterland of most river catchments are Moinian or in the system concerned. In the catchments of the Forth and Dalradianmetamorphic rockswith substantial largely Tay basins similar processing yields estimate about 30% of graniticintrusions, whereas many parts of the coast are thoseobtained from weekly observationsover twoyear formed of sandstones of Devonian and Permian ages. periods. Inthe absence of systematic data of our own on In most river systems the bedload is considered to be up suspensions in the rivers,estimation of the sediment to 10% of the quantity of the suspended load (Parker et al. transport from the mainland to the sea has been attempted 1964). There is no confirmation that such a figure is using the central data base of information on suspensions appropriatefor application inthe rivers of Northern from 1975 to 1983,held by the Scottish Development Scotland, although Al-Ansari & McManus (1979) demonstr- Department, Edinburgh. This has been used in conjunction atedthat bedload was 3-5% of the estimatedsuspended withflow durationcurves obtained from the hydrological sediment load of the River Earn (Tayside Region). To all

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Table 2. Mean annual sediment discharge from rivers draining into the Moray Firth

Suspended TotalSuspended Area solids load solids lead Yield t km-' Riveryear-' km2 year-' year-'

955 9500 10450 10.9 10450 Deveron9500 955 SPeY 2861 30800 33880 30800 2861 SPeY 11.8 Lossie900 216 990 4.4 Findhorn34400 782 27840 48.4 313 8800 313 9680 31.1 Nairn - Supply to southernshores: 92840 t

Ness 1839 2oooo 22000 12.0 Conon 962 5500 6050 6.3 Shin 575 4700 5170 9.1 Supply to innerFirths: -33220 t

Total from non-gauged rivers-l4 000 t year-' approx. Total fluvial sediment discharge-l40 000 t year-' approx.

computed suspension loads a figure of 10% has been added of the terrain in thecatchments is peat covered and this may to permit estimation of the total solids load of the rivers. contribute to theorganic material, but indigenous organisms The calculated mean annual solids transportof each river within the rivers are certainly important contributors to the draininginto the MorayFirth is indicatedin Table 2. biogenic fraction of the load. Summing the predicted loads yields a minimal estimate that 140 OOO t year-' forms the fluvial contribution of sediments. Discussion If the differenceobtained between sparse samplings and frequent sampling techniques in the Tay basin is appropriate The main patterns of sediment migration are summarized in to the Moray Firth rivers, the total loads may reach as much Fig. 8. Marinesediments enter the Moray Firthfrom the as 460 OOO t year-'. northand become dispersed along routes parallel tothe Not all of the sedimentin suspension is of mineral matter,for routine ashing of filter residuesreveals that material of organic origin is important. The proportion of organic matter variesthrough the year, being greatest in November-February. The range of variation is also greater t

in the winter. Although individual samples yielded between 0, , , , , 50 Wi 17 & 93% or organic matter,mean monthly values were l generally 50-70%,suggesting thatat least halfof the solids load is of non-mineral, biogenic matter (Fig. 7). Much

'"1 RIVER NAIRN 1976 - 1979

COASTAL TYPE Hard : &$S Sofl : (intermediate) m soft : m OFFSHORE Tidalcurrent General orientation ---- Sediment TransportPath 4 Sediment Transport Path(probable) a Shelly CarbonatePath U 0' Partlng Bedload JFMAMJJASOND * MONTHS ConvergenceBedload H O ffshore Trap Offshore m Fig. 7. Variations of the mean and rangeof the percentage of organic matter in the suspensionsof the River Nairn in different Fig. 8. Summary diagram of transport paths and sediment sinks in months of the year. the Moray Firth area.

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tidal flow paths. The readily identifiablecarbonate sands References penetrate into the central basin, travelling through systems AL-ANSARI,N. A. & MCMANUS,J. 1979. Fluvial sediments entering the Tay of sand waves, ribbons and patches. They are also of great estuary: sediment dischargefrom the River Earn. ScottishJournal importancealong the north western coastal section. With Geology, 15, 203-16. comminutionthe carbonate muds migrate into theinner AL-JABBARI,M. H., MCMANUS,J. & AL-ANSARI,N. A. 1980. Sediment and firth,the site towards which lithic muds fromreworked solute discharge into the Tay estuary from the river system. Proceedings of the Royal Society of Edinburgh, 78, 15-32. glacial deposits or discharged by rivers are also carried. The ALLEN,N. H. 1983. Recenttemperate carbonate deposits on thecontinental estuarine firths and the offshore deeps function as sinks for shelf north and west of Scotland: distribution,sedimentology and reserves. sedimentaccumulation principally in the absence of a PhD thesis, University of Strathclyde. strongenergy input, in sheltered deepembayments or in BOHNECKE,G. 1922. Salzgehalund Stromungen der Norbee. Verkoff Institute Meerest Universitat Berl Neve Fuige A, Geog-naturwiss Reihe deep water below effective wave base. No. 10: 1-34. The estimated fluvial sediment load of 140 000 t year-’ CHESHER,J. H. & LAWSON,D. 1983. The Geology of theMoray Firth. has been derived from sparse data. In order to assess their Reports of the Institute of Geological Sciences Nos 83/5. reliability sediment discharges were calculated fromthe same CRAIG,R. E. 1959. Hydrography of Scottishcoastal waters. ScottishHome Dept Marine Research Service, 2. data base forthe Tay basin, where estimates averaged DOOLEY,H. 1971. Currents off the North east of Scotland. Scottish Fisheries approximately one third of the loads computed from rating Bulletin, No. 39. curves established byweekly sampling(Al-Jabbari et al. DRAPER,L. 1977. OffshoreInstallations: Guidance on Designand 1980). Inconsequence, perhaps 460000 t of terrigenous Construction. Her Majesty’s Stationery Office, London. FARROW,G., ALLEN,N. H. & AKPAN,E. B.1984. Bioclastic Carbonate material enters the sea or the inner firths annually. Of this Sedimentation on a high latitude, Tide dominated shelf: northeast totalabout 24% is dischargedinto theinner firths where , Scotland. Journal of Sedimentary Petrology, 54,373-93. mostisbelieved to becomeentrapped. The remaining FARROW, G.& CLOKIEJ. 1979. Molluscan grazing of sublittoral algal bored 350 OOO t is available for transport towards the Inner Moray shellsand the production of carbonate mudin the Firth of Clyde, Firth, where the lithic mud of the 325 000 t suspension load Scotland. Transactions of the Royal Society of Edinburgh, 70, 139-48. FERENTINOS,G. & MCMANUS,J. 1981. Nearshore processesand shoreline becomesintermixed with the marinecarbonate muds, but development in St Andrews Bay, Scotland, UK. Special Publication of remains dominant (over 70%) in the bed deposits. If all the the International Association of Sedimentologists, 5, 161-74. lithic mud is fluvially derived and accumulates west of a line LEE, A. J. & RAMSTER,J. W. 1981. Atlas of Seas Around the British Isles. from Brora to Burghead the carbonate muds enter the area M.A.F.F. Directorate of Fisheries Research. MCMANUS,J. 1986. Land derived sediment and solute transport to the Forth in a ratio of 3 : 7 or 2 : 8, otherwise they would swamp or be & Tay . Journal of the Geological Society, London, 143,927-34. swamped by the lithic input, i.e. perhaps 80000 t of marine NATURECONSERVANCY COUNCIL,1978. Nature conservation within the Moray carbonate mud settles in the inner firth annually. Firth area. NCC N.W. Scotland Region. It is not possible atpresent to estimaterates of sand OWENS,R. 1981.Holocene sedimentation in the north-western North Sea. Special Publication of the International Association of Sedimentologists, migration along the shores into the inner parts of the Moray 5, 303-22. Firth.Nevertheless, both marine derived and terrestrial PARKER,G. G. HELY, A. G., KEIGHTON,W. B. & OLMSTED,F. H. 1964. materials areseen to contributesubstantially to deposits Water resource of the Delaware river basin. Professional Paper of the US now accumulating on the sea bed of the Inner Moray Firth. Geological Survey, 381, 1-200. Many of the terrestrial lithic mud particles have migrated PAYNE,R. 1963. Bottom currents in the Moray Firth. ScottishFisheries Bulletin, 20, 267. considerabledistances from their source rivers before PEACOCK, J. D. 1976.Subsurface Deposits of Invernessand the Inner becoming deposited. The coastal zones of the Inner Moray Cromarty Firth. In: GILL,G. (ed.) MorayFirth Geological Studies. Firththerefore serve as sinks of sedimentaccumulation, 102-4. PLANT, J. A. 1968. Theclimate of thecoastal region of the Moray Firth. many of the materials being dominantly extraneous to the Climatological Memorandum No. 62, Meterological Office. areas of deposition. F’XOBERT,P. K. & MITCHELL,R. 1980. Natureconservation implications of siting wave energyconverters offthe Moray Firth. N.C.C. report for T.A.G.7 (WaveEnergy Steering Committee), Nature Conservation Theauthors wouldlike to thank the MarineGeology Unit Council. (Edinburgh) of the British Geological Survey for access to the SMITH,J. S. & MATHER,A. S. 1973. Beaches of East Sutherland and Easter geophysical records, sediment samples and other data; Britoil and Ross. Report to the Countryside Commissionfor Scotland by the Conoco for access to wave data; the Scottish Development Department of Geography. University of Aberdeen. STEERS,J. A. 1937. The Culbin Sands andBurghead Bay. Geographical Departmentand the Highland andNorth-East River Purification Journal, 90, 498-528. Boards for river data. The study was supported financially through a STRIDE,A. H. 1982. Offshore Tidal Sands, Processes and Deposits. Chapman NERC CASE Studentship. & Hall. London.

Received 19 April 1985; revised typescript accepted 29 November 1985.

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