assessment study of lichenometric methods for dating surfaces in this paper we discuss the advantages and drawbacks of the most classical approaches used in lichenometry in particular we perform a detailed comparison among methods based on the statistical analysis of either the largest lichen diameters recorded on geomorphic features or the frequency of all lichens to assess the performance of each method a careful comparison design with well defined criteria is proposed and applied to two distinct data sets first we study 350 tombstones this represents an ideal test bed because tombstone dates are known and therefore the quality of the estimated lichen growth curve can be easily tested for the different techniques secondly 37 moraines from two tropical glaciers are investigated this analysis corresponds to our real case study for both data sets we apply our list of criteria that reflects precision error measurements and their theoretical foundations when proposing estimated ages and their associated confidence intervals from this comparison it clearly appears that two methods the mean of the n largest lichen diameters and the recent bayesian method based on extreme value theory offer the most reliable estimates of moraine and tombstones dates concerning the spread of the error the latter approach provides the smallest uncertainty and it is the only one that takes advantage of the statistical nature of the observations by fitting an extreme value distribution to the largest diameters

historical glacier fluctuations of jostedalsbreen and folgefonna southern norway reassessed by new pictorial and written evidence glaciers are sensitive indicators of past climate and thus valuable sources of climate history unfortunately direct determinations of glacier changes variations in length and mass balance did not start with increasing accuracy before the end of the nineteenth century therefore historical and geomorphological evidence has to be used to reconstruct glacier variability for preceding time periods here we present new glacier length reconstructions for selected outlet glaciers of jostedalsbreen and folgefonna two ice caps in southern norway a wealth of different historical sources drawings paintings prints photographs maps written accounts about 400 documents allows reconstruction of glacier length variations for the last 300 jostedalsbreen and 200 years folgefonna respectively we present historical material newly collected for briksdalsbreen boyabreen store supphellebreen bergsetbreen nigardsbreen lodalsbreen all jostedalsbreen and bondhusbrea buerbreen both southern folgefon

subsidence analyses from the north sea triple junction when compared with theoretical subsidence curves calculated from the uniform stretching model water loaded subsidence data from the triple junction region of the north sea suggest that the jurassic cretaceous rifting event caused lithospheric thinning by a factor of c 2 0 although somewhat larger than the stretching factors found elsewhere in the north sea this amount of thinning is anticipated from the overall geometry of the three graben system and is consistent with the observed volume and elemental and isotopic composition of the jurassic forties volcanic province apart from in the southern north sea permo triassic extension is thought to have been relatively minor in comparison to the later jurassic cretaceous phase the anomalously small amount of late jurassic syn rift subsidence in those wells where local fault controlled effects are minimal supports the well known idea of localized relative uplift or doming in the triple junction area c 10 4 km 2 prior to and during the early stages of the jurassic cretaceous rift phase a time dependent differential stretching model in which the lithospheric mantle is initially stretched by a greater amount than the crust is stretched might provide an explanation such a model would require the total amount of stretching integrated over space and time to be the same for the lithospheric mantle and for the crust in order to avoid space problems alternatively the same data could be explained by invoking a small transient thermal anomaly in the asthenosphere

tephrochronology lichenometry and radiocarbon dating at gulkana glacier central alaska range usa multiple geochronologic techniques when used in an integrated approach provide a powerful means of deciphering the stratigraphy of holocene moraine sequences the jarvis creek ash deposited across central alaska at 3650 125 bp underlies a mid holocene lateral moraine of the gulkana glacier this tephrochronological datum provides new control on long term rhizocarpon geographicum growth rates in central alaska and suggests that this species grows at approximately 4mm per century in the central alaska range lichenometry together with tephrochronology and radiocarbon dates from buried organic horizons indicate holocene advances of the gulkana glacier occurred c 5700 260 bp 4100 800 bp 3600 700 bp 800 125 bp and 150 200 years ago

neoglaciation and an early little ice age in western norway lichenometric evidence from the sandane area moraine sequences protalus ramparts rock glaciers and various slope deposits in seven separate glacier basins provide lichenometric ages for glacier retreat in an upland area of sogn og fjordane southern norway geomorphological mapping relative dating based on section rhizocarpon size frequency distributions observations on vegetation cover and numeric dating based on a regional lichen dating curve for section rhizocarpon place moraines into three groups stage 1 moraines of likely preboreal or younger dryas age stage 2 moraines of pre or early little ice age but post preboreal age thirteenth fourteenth centuries and stage 3 moraines of fifteenth century age and younger the occurrence of thirteenth sixteenth century pre or early little ice age moraines at low altitudes in the sandane area is thought to relate to greater availability of moisture and to the capture of wind drifted snow these moraines are some of the oldest little ice age moraines dated by lichenometry in southern n

anoxic events during sedimentation of a palaeogene diatomite in denmark a diatomite about 60 m thick of late palaeocene early eocene age crops out in northern jutland denmark the diatomite is locally termed moler frustules of marine diatoms constitute c 65 by weight of the diatomite and clay minerals chiefly montmorillonite make up the remainder slight variations in the relative supply of diatom frustules and clay minerals are preserved undisturbed in laminated diatomite while lamination is partly destroyed by burrowing organisms in weakly laminated diatomite and obliterated by total bioturbation in structureless diatomite these three facies alternate throughout the sequence the presence or absence of infaunal burrowing organisms is interpreted as a record of the content of dissolved oxygen in the water above the sediment water interface and hence of the position of the redox potential discontinuity interspaced in the diatomite are 179 identifiable layers of volcanic ash these ash layers provide a means of precise lateral correlation they show that levels of laminated diatomite may be followed throughout the basin and therefore that changes between anoxic and oxic conditions occurred simultaneously across the area the laminated diatomites may consequently be interpreted as representing short term anoxic events of which twelve have been recognized

schmidt hammer exposure age dating shd of snow avalanche impact ramparts in southern norway approaches results and implications for landform age dynamics and development schmidt hammer exposure age dating shd was applied to the problem of dating the diachronous surfaces of five distal river bank boulder ramparts deposited by snow avalanches plunging into the jostedola and sprongdola rivers in the jostedalsbreen region of southern norway approaches to local high precision linear age calibration which controlled in different ways for boulder roundness were developed the mean age shdmean and the maximum age shdmax of surface boulders were estimated for whole ramparts crests and distal fringes interpretation was further assisted by reference to r value distributions shdmean ages with 95 confidence intervals ranged from 520 270 years to 5375 965 years whereas shdmax ages expected to be exceeded by 5 of surface boulders ranged from 675 to 9065 years shd ages from the jostedola ramparts tended to be older than those associated with the sprongdola rampart crests were younger than the respective distal fringes and use of relatively rounded boulders yielded more consistent shd ages than angular boulders the shdmean ages indicate differences in recent levels of snow avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and in smaller numbers on the distal fringes shdmax ages provide minimum age estimates of rampart age i e the time elapsed since the ramparts began to form and suggest that at least some of the ramparts have been developing since the early holocene copyright 2015 john wiley sons ltd

origin of anomalous tertiary subsidence adjacent to north atlantic continental margins abstract at the beginning of the tertiary the northern north atlantic continental margins were characterized by voluminous igneous activity caused by continental rifting in the presence of the iceland hot spot many of the mesozoic sedimentary basins close to these margins have been permanently uplifted by igneous underplating and remain close to or above sea level at the present day however a significant number of other basins underwent rapid subsidence at the same time sometimes by as much as 3 km of sediment loaded subsidence in 15 20 ma several hypotheses attempting to explain the cause of this tertiary subsidence have been proposed the observational data are summarized here and then each hypothesis is considered in turn it is argued that many of these are implausible one possible alternative explanation links early tertiary subsidence uplift and magmatism if basaltic melts are trapped within the lithosphere it is possible to produce either uplift or subsidence depending on the density of the trapped melt at depths greater than 50 km melts will solidify rapidly in the garnet stability field to form primary eclogite which is dense enough to cause subsidence while satisfying the constraints of long wavelength airy isostasy unfortunately such an hypothesis is difficult to test the simplest explanation for tertiary subsidence is still a minor episode of lithospheric stretching although to date there is only limited evidence for sufficient tertiary normal faulting further work must be carried out before this simple and testable hypothesis can be confidently rejected

two stage rifting in the north viking graben area north sea inferences from a new three dimensional subsidence analysis abstract backstripping software from the ifp subtec was used to realize a three dimensional subsidence analysis of the norwegian part of the north viking graben for each considered epoch the software produces restored depth maps of the selected stratigraphic horizons as well as tectonic subsidence maps that allows in addition to classical subsidence curve analysis an overview of the spatial evolution of the studied basin the three dimensional data set consists of maps representing the present day geometry of the graben for this study these maps have been established on the basis of a new interpretation of available seismic lines taking into account new information on the time depth conversion and on the age of the different seismic markers data from wells give detailed information on lateral lithological variations sedimentological information and analysis of the geometry of the seismic markers have allowed palaeobathymetry and eroded thickness maps to be established and discussed with a reasonable confidence computed tectonic subsidence maps define three major events and allow discussion of their origin the lower jurassic thermal subsidence in relation to the previous triassic rifting event the jurassic rifting phase and the subsequent cretaceous post rift thermal subsidence and finally a rapid subsidence event at the beginning of the palaeocene thermal modelling provides theoretical subsidence curves the comparison with the observed curves allows testing of and discrimination between several hypotheses about two parameters the age of the first rifting event permo triassic and its relative amplitude with regard to the jurassic event the corresponding stretching factors were compared with the crustal stretching values observed along the nsdp1 seismic profile it appears that the first extensional phase is clearly triassic beginning about 240 ma and that it is characterized by higher stretching factors than the following jurassic phase the ability of different geological processes to produce both the palaeocene subsidence observed in the graben and the contemporaneous uplift of the basin margins is discussed the preferred interpretation involves buckling of the lithosphere in response to the onset of a compressional stress regime at the end of the cretaceous a simple method assuming uniform stretching is proposed for computing maps of stretching factors for both the jurassic and triassic events

modelling late holocene snow avalanche activity incorporating a new approach to lichenometry where snow avalanches descend steeply into large rivers displacing bedload avalanche boulder ramparts may accumulate retaining a record of late holocene snow avalanche frequency the age frequency of surface boulders on 12 such features in upper jostedalen southern norway was investigated using the size frequency distribution of lichens a model was constructed to simulate the influence of variations in avalanche frequency since ad 1325 on lichen size frequency distributions using this modelling approach it is not possible to define a unique pattern of avalanche activity to account for the observed lichen size frequency distributions but it is possible to place strict limits on the range of scenarios that are acceptable the results suggest that maximum avalanche activity occurred during the 19th century after the peak of the little ice age this conflicts with historical records of avalanche damage to property at lower altitude in nearby valleys which may reflect avalanche activity only during a short period of extreme climatic conditions close agreement between the records of snow avalanches and debris flows suggests that both reflect periods of high winter snowfall and rapid spring melting rather than low temperature future greenhouse warming may therefore result in increased avalanche activity in southern norway

classic and new dating methods for assessing the temporal occurrence of mass movements abstract establishing landslide chronologies is essential both for understanding causes of mass movements as part of fundamental geomorphological research and for the assessment of landslide hazards as part of applied geomorphology we discuss the applicability of different methods for determining landslide chronologies frequencies and dynamics in relation to the type of material being dated sampling location and type of mass movement the emphasis is on the possibilities and limitations of the different dating methods established methods such as radiocarbon dating lichenometry and dendrochronology are briefly discussed the paper focuses however on 1 new analytical techniques like accelerator mass spectrometry ams thermally ionising mass spectrometry tims and laser fusion which have led to significant improvements of established dating methods and on 2 new dating methods like optically stimulated luminescence osl dating and alpha recoil track art dating

14c dating and palaeoenvironment of the historic little ice age glacier advance of nigardsbreen southwest norway moss and grass remains associated with a well developed in situ palaeosol buried beneath a moraine ridge in front of nigardsbreen jostedalsbreen ice cap southern norway have been 14c dated pollen preserved with the plant remains suggests the existence of an agricultural landscape prior to the deposition of the moraine the calibrated dates and the pollen spectra are in close accord with historically documented evidence for the timing and palaeoenvironment of the little ice age advance of the glacier considerable potential is indicated for estimating the maximum ages of moraine ridges and for palaeoenvironmental reconstruction where such documentary evidence does not exist

a rhizocarpon geographicum growth curve for the cascade range of washington and northern oregon usa lichen thallus measurements from 22 surfaces of known age on mount baker mount hood and mount rainier are used to construct a regional rhizocarpon geographicum growth curve for the cascade range of washington and northern oregon growth rates determined by measuring the largest thallus diameters on the same surfaces at mount rainier in 1976 and 2002 are used for comparison with lichenometric data from mount baker and mount hood similar lichen thallus diameter vs age relationships identified in the data from the three mountains suggest the presence of uniform growth rates over the 400 km range a regional growth curve developed during our study shows three growth phases of successively slower growth a rapid phase from 8 to 20 yr a linear phase from 20 to 145 yr and a slow phase of unknown duration beyond ca 145 yr uncertainty in lichen growth rates beyond 145 yr limits projection of the curve beyond that age however the age range of the constrained growth curve covers an important period of recent climate variability when applied in appropriate settings our growth curve can be used to determine numeric ages to 10 yr for surfaces between 20 and 145 years old in areas where other techniques are not applicable or do not provide unique or well constrained ages

lichenometric dating of the little ice age maximum in mt cook national park southern alps new zealand lichenometric dating studies using the yellow green rhizocarpon subgenus at the eugenie hooker mueller and tasman glaciers in mt cook national park southern alps new zealand reveal a little i

on the accuracy of lichenometric dates an assessment based on the little ice age moraine sequence of nigardsbreen southern norway families of lichenometric dating curves are constructed using four historically dated moraine ridges on the glacier foreland of nigardsbreen jostedalsbreen ice cap southern norway a further 20 little ice age moraine ridges are dated in terms of median predicted dates derived from the families of curves four approaches are used to assess the accuracy of the median predicted dates 1 the extent to which the dates form a temporal sequence 2 the extent to which they agree with local independent evidence of glacier variations 3 the extent to which dates agree when the moraine sequences on the two sides of the glacier foreland are dated separately and 4 the extent to which they agree when section rhizocarpon is differentiated from lichens of the rhizocarpon subgenus as a whole it is concluded that under conditions favourable for lichenometric dating median predicted dates have attained an accuracy of 10 on the little ice age timescale realistic error limits are considered to be of the o

glacial geomorphological mapping a review of approaches and frameworks for best practice geomorphological mapping is a well established method for examining earth surface processes and landscape evolution in a range of environmental contexts in glacial research it provides crucial data for a wide range of process oriented studies and palaeoglaciological reconstructions in the latter case providing an essential geomorphological framework for establishing glacial chronologies in recent decades there have been significant developments in remote sensing and geographical information systems gis with a plethora of high quality remotely sensed datasets now often freely available most recently the emergence of unmanned aerial vehicle uav technology has allowed sub decimetre scale aerial images and digital elevation models dems to be obtained traditional field mapping methods still have an important role in glacial geomorphology particularly in cirque glacier valley glacier and icefield ice cap outlet settings field mapping is also used in ice sheet settings but often takes the form of necessarily highly selective ground truthing of remote mapping given the increasing abundance of datasets and methods available for mapping effective approaches are necessary to enable assimilation of data and ensure robustness this paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available with a focus on their applicability in particular glacial settings we distinguish two overarching work streams that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes i mapping of ice sheet geomorphological imprints using a combined remote sensing approach with some field checking where feasible and ii mapping of alpine and plateau style ice mass cirque glacier valley glacier icefield and ice cap geomorphological imprints using remote sensing and considerable field mapping key challenges to accurate and robust geomorphological mapping are highlighted often necessitating compromises and pragmatic solutions the importance of combining multiple datasets and or mapping approaches is emphasised akin to multi proxy approaches used in many earth science disciplines based on our review we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment comparison and integration of geomorphological data these will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions finally we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and or sedimentological evidence and that such data should ideally be collected as part of a holistic assessment of the overall glacier system

recent behaviour of the debeli namet glacier durmitor montenegro a small cirque glacier is present in a north east facing cirque on the mountain of sljeme 2455 m a s l in the durmitor massif montenegro sediment ridges in front of this glacier are interpreted as moraines and can be attributed to recent glacier activity over the past 130 years lichenometry was applied to determine the relative ages of different moraines using aspicilia calcarea agg one set of moraines dates from about 1878 ad whilst another set of inner moraines dates from about 1904 ad the most recent moraines appear to have formed within the last 11 years in front of an active glacier margin copyright 2007 john wiley sons ltd

an improved technique for the reconstruction of former glacier mass balance and dynamics abstract the recognition of past glacier extent and dynamics is a fundamental aspect of investigations of the climatic sensitivity of glaciers especially when examining short lived climate events such as the younger dryas or little ice age existing approaches to the reconstruction of glacier form and dynamics depend on speculative reasoning of key glacier dynamic parameters including the role of basal slip and subglacial deformation in glacier mass transfer this study reviews approaches to glacier reconstruction derivation of former glacier equilibrium line altitudes ela s and estimation of mass balance and dynamics concluding that most reconstructions of glacier mass balance are compromised by a lack of glaciological considerations an alternative approach to glacier reconstruction is presented demonstrated and discussed by which an empirical relationship between ablation gradient and mass loss at the ela is used to derive mass balance mass flux through the ela and average balance velocity at the ela this glaciological approach is applied to four reconstructed glaciers to test previous interpretations that each reflects younger dryas glaciation in the uk the study concludes that this approach provides a more robust technique for reconstructing former glacier dynamics and may be applied to test geomorphological interpretations of former mountain glaciation

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

a new approach to lichenometry dating single age and diachronous surfaces a new approach to lichenometry based on large samples of the single largest lichen on each boulder is presented on surfaces of uniform age lichen sizes measured in this way are near normally distributed so the mean value can be used in constructing lichenometric dating curves by combining mean values from several sites statistically defined confidence limits can be assigned to predicted dates in a pilot study dates obtained for little ice age moraines of two glaciers in southern norway are consistent with those obtained using other approaches unlike standard lichenometry the new approach can be used to investigate the age frequency of boulders on diachronous surfaces formed by continuous or periodic accretion or disturbance it has been used successfully to access the record of late holocene snow avalanche activity retained on avalanche boulder ramparts in upper jostedalen western norway pilot studies are also presented of its use on a talus slope solifluction lobes and periglacial pattern

paraglacial debris cone formation on recently deglaciated terrain western norway five debris cones have formed on terrain deglaciated since ad 1750 75 in bergsetdalen western norway three were surveyed and studied in detail two accumulated over 108 215 years and the third over 57 108 years accumulation on all three appears to have effectively ceased around or slightly before ad 1965 through exhaustion of readily entrainable sediment in source areas upslope the volumes of the three cones range from c 9500 m3 to 403 600 m3 and imply average sediment accumulation rates of 8 44 mm yr 1 sediment erosion at one site was calculated to be 37 93 mm yr 1 averaged over the entire sediment source area paraglacial reworking of glacial drift by debris flows appears to have been the main agent of cone development at two sites but snow avalanches are thought to represent the main process of sediment transport at the largest cone these findings indicate that substantial debris cones may form and become inactive within 100 200 years of deglaciation implying that many late pleistocene parag

an inverse approach to the course of the little ice age glacier advance and the following deglaciation at austerdalsisen eastern svartisen northern norway the course of the little ice age lia in scandinavia is characterized by large glacier advances that started at about ad 1300 and culminated at about ad 1750 the end of the lia is marked as an unprecedented and ongoing glacier retreat that accelerated from the early 20th century the course of the lia is here presented based on fluctuations of austerdalsisen the largest valley outlet glacier draining the austre svartisen ostisen ice cap nordland northern norway during the lia glacierization austerdalsisen separated into two branches and relative to the present glacier terminus a western valley glacier advanced more than 4 km whereas a se valley glacier advanced about 3 km at present meltwater from austerdalsisen drains towards se if the glacier obtains a critical magnitude however most of the meltwater is drained westwards across a higher overflow gap based on radiocarbon dated lake sediments distal proglacial glaciolacustrine glaciofluvial sediments and historical observations the c

lower palaeogene stratigraphy of the northern north sea abstract the lower palaeogene stratigraphy of the northern north sea is described using wireline log and biostratigraphic data at group and formation level a close similarity can be shown with the stratigraphy defined in the outer moray firth area of the central north sea a two fold subdivision into the montrose and moray groups is recognized the montrose group consists of the maureen and lista formations while the succeeding moray group contains the sele balder dornoch and beauly formations the maureen and lista formations are dominantly argillaceous units that contain poorly defined sandstones the most laterally extensive of these is the heimdal member developed within the lista formation the dornoch and beauly formations are shelfal sandstone units that pass eastwards and northwards into the age equivalent dominantly argillaceous sele and balder formations the sele formation contains the hermod member while the balder formation contains the odin member these are massively developed sandstone units of very limited extent the lower palaeogene succession contains a number of high gamma log markers that are often associated with influxes of microfossils and microflora these are interpreted as condensed claystone horizons representing pauses in marine sedimentation during episodes of maximum transgression they can be correlated with similar marker horizons described from the outer moray firth area giving further confidence that the stratigraphy forms a regional framework that can be applied over the whole north sea area

little ice age glacier variations in jotunheimen southern norwvay a study in regionally controlled lichenometric dating of recessional moraines with implications for climate and lichen growth rates a new approach to regional lichenometric dating is developed and applied to little ice age moraine ridge sequences on 16 glacier forelands in jotunheimen southern norway lichenometric dating curves based on the rhizocarpon subgenus are constructed independently for west central and east jotunheimen although there are differences between the subregions a composite regional moraine chronology for jotunheimen identifies 12 episodes of moraine formation in ad 1743 1750 the regional little ice age glacier maximum 1762 1771 1782 1790 1796 1802 1811 1818 1833 1838 1845 1854 1860 1868 1871 1879 1886 1898 1915 1922 and 1927 1934 spatial and temporal patterns in glacier behaviour between the subregions and between jotunheimen and the neighbouring jostedalsbreen are explained in terms of the interaction of annual to decadal variations in summer temperature and winter precipitation glacier advances and moraine formation events driven primarily by winter precipitation variations exhibit subregio

revised lower palaeogene lithostratigraphy for the outer moray firth north sea abstract the lower palaeogene lithostratigraphy of the outer moray firth has been revised using wireline log and biostratigraphic data a two fold subdivision into the montrose and moray groups is recognized the montrose group consists of the maureen and lista formations whereas the younger moray group contains the sele balder dornoch and beauly formations the lista formation contains the arenaceous andrew and balmoral members separated by the tuffaceous glamis member the dornoch and beauly formations are prograding shelfal sandstone units that pass basinwards into the age equivalent dominantly argillaceous sele and balder formations the sele formation contains the forties and cromarty members which are locally developed sand rich units stratigraphic analysis has led to the identification of a number of consistently developed high gamma log markers that are interpreted as condensed mudstone horizons these markers are believed to record clastic sediment starvation during periods of maximum marine transgression they often have a strong biostratigraphic fingerprint coinciding with influxes of rich concentrations of microfossils and microflora they are interpreted as the product of synchronous regional transgressive events and have been an important aid to the development of a confident lithostratigraphic framework for the lower palaeogene of the outer moray firth