Mass Movement Phenomena Research Articles

Exploring the Application of a Debris Flow Likelihood Regression Model in Mediterranean Post-Fire Environments, Using Field Observations-Based Validation

Post-fire geomorphic processes and associated risks are an important threat in Mediterranean environments. Currently, post-fire mass movement prediction has limited applications across the Mediterranean despite the abundance of both forest fires and landslide/debris flow disasters. This work applies a debris flow generation likelihood model to evaluate the probability of mass movement phenomena in different catchments of a burnt area, after a catastrophic fire near Schinos (Attica, Greece) in 2021. Then, it uses field observations from the area, recording mass movement phenomena after high-intensity rainfall events, to validate the results. The findings show that the model is successful in determining the probability of debris flow generation in the 21 basins of the study area, ranging from 0.05 to 0.893. The probability values show a statistically significant correlation (sig. = 0.001) with the actual debris flow occurrences in the area, and satisfactory results in terms of the model’s predictive ability, functioning well within the particular geo-environmental characteristics of the Mediterranean environment. The results establish the reliability of the approach as a tool to assess mass movement risks in a region with an abundance of post-fire related hazards and disastrous events.

Composite landslide in the dynamic alpine conditions: a case study of Urbas landslide

The alpine environment is characterized by complex geology, high-energy terrain, deeply incised river valleys with high erosional potential, extreme weather conditions and dynamic geomorphic processes. Such settings provide favourable conditions for the formation of composite landslides rather than individual slope mass movement phenomena. As an example, we present the kinematics of the composite landslide Urbas in the North of Slovenia which developed in the complex geological and morphological settings characteristic of the alpine environment. The research combines several monitoring techniques and involves the integration of both surface and subsurface displacements measured in the landslide area. The results indicate that the composite sliding process consists of several simultaneous and interrelated types of movements occurring in different segments of the unstable mass that are governed by different mechanisms of displacements, such as rockfall, sliding and debris flow. The kinematic characteristics of a deep-seated landslide that formed in such conditions vary spatially, but is rather homogenuous vertically, indicating translational type of movement. Spatial kinematic heterogeneity is primarily related to the diverse terrain topography, reflecting in different displacement trends. Based on the revealed kinematic proprieties of the sliding material, the sediment discharge illustrates the sliding material balance which estimates the volume of the retaining material that represents the potential for slope mass movement events of larger scales.

Snow Avalanche Assessment in Mass Movement-Prone Areas: Results from Climate Extremization in Relationship with Environmental Risk Reduction in the Prati di Tivo Area (Gran Sasso Massif, Central Italy)

Mass movements processes (i.e., landslides and snow avalanches) play an important role in landscape evolution and largely affect high mountain environments worldwide and in Italy. The increase in temperatures, the irregularity of intense weather events, and several heavy snowfall events increased mass movements’ occurrence, especially in mountain regions with a high impact on settlements, infrastructures, and well-developed tourist facilities. In detail, the Prati di Tivo area, located on the northern slope of the Gran Sasso Massif (Central Italy), has been widely affected by mass movement phenomena. Following some recent damaging snow avalanches, a risk mitigation protocol has been activated to develop mitigation activities and land use policies. The main goal was to perform a multidisciplinary analysis of detailed climatic and geomorphological analysis, integrated with Geographic Information System (GIS) processing, to advance snow avalanche hazard assessment methodologies in mass movement-prone areas. Furthermore, this work could represent an operative tool for any geomorphological hazard studies in high mountainous environments, readily available to interested stakeholders. It could also provide a scientific basis for implementing sustainable territorial planning, emergency management, and loss-reduction measures.

From geomorphology to shape-fabric: The interplay of geomorphological controls and their spatial variability in the Teteltzingo lahar deposit, Citlaltépetl volcano (Mexico)

The distribution and characteristics of volcaniclastic deposits are the result of the interplay among numerous factors acting at different and multileveled scales of space and time. Such complexity requires multiple techniques for the study of volcanic regions. This approach provides a strong basis for understanding volcanic processes and their relationship with the resulting landforms or deposits and for reconstructing dynamic properties of flows. The aim of this paper is thus to understand the interplay between the geomorphologic environment and the origin and transport of large-magnitude debris flows. For this reason, we selected the eastern sector of the Citlaltépetl volcano and the Teteltzingo lahar event (Veracruz, Mexico). Information from geomorphological and morphometric analysis (including the linear features) was linked with field and shape-fabric data on selected outcrops. The study area was divided into three morphometric zones based on their elevation, slope, drainage network, and the trend in linear features. These zones are volcanic mountain zone, minor folded ranges and cumulative volcaniclastic plain. The geomorphological map enabled us to understand the origin of the landforms observed in each of the three morphometric zones. The characteristics of the Teteltzingo lahar deposit (i.e., geographic distribution, thickness and components) are associated with the morphologic and morphometric characteristics of the landscape. The particle shape-fabric analysis gave evidence that particle iso-orientation is consistent with the flow direction and orientation of some regional linear features, especially in the medial and distal zones. Moreover, the degree of iso-orientation was shown to be dependent on travel distance and particle diameter. The highest degree of iso-orientation was found in the coarse particles (gravel grain-size) throughout the entire deposit, being more developed in the distal zone. The evidence presented here suggests an interplay between geomorphological–structural controls and their spatial variability with the distribution of large-magnitude lahars. This highlights the importance of a multi-scale vision of mass movement phenomena that show how morphological and sedimentological characteristics are linked and could affect the generation and dynamics of future flows.

‘Onesimus to Philemon’: Runaway Slaves and Religious Conversion in Colonial ‘Kerala’, India, 1816–1855

Abstract Several theories emerged, based on the Christian conversion of lower caste communities in colonial India. The social and economic aspects predominate the study of religious conversion among the lower castes in Kerala. Most of these studies only explored the lower caste conversion after the legal abolition of slavery in Kerala (1855). The existing literature followed the mass movement phenomena. These studies ignore the slave lifeworld and conversion history before the abolition period, and they argued, through religious conversion, the former slave castes began breaking social and caste hierarchy with the help of Protestant Christianity. The dominant Dalit Christian historiography does not open the complexity of slave Christian past. Against this background, this paper explores the history of slave caste conversion before the abolition period. From the colonial period, the missionary writings bear out that the slaves were hostile to and suspicious of new religions. They accepted Christianity only cautiously. It was a conscious choice, even as many Dalits refused Christian teachings.

Landslide investigation using electrical resistivity tomography (ERT) technique at the location of water channel PLTM Lambangan, Pagimana, Central Sulawesi

Mass movement phenomena that occur in the research area affect the destruction of water channel in the area of PLTM Lambangan that located at the location. This research aimed to investigate soil movement phenomena in order to determine control factors that causing soil prone to move, especially in the surface geological aspect and underground lithology condition in the research area. Investigation method applied is by underground geologic and geophysical surveys using electrical method, that is Electrical Resistivity Tomography (ERT) with Wenner Configuration. Results of investigation show that geological factors are quite related to the soil movement. Movement phenomena occur in the surface with hilly to steep cut topography (21-55%) with material sourced from alluviation of clastic sediment dan carbonatic rocks. The damaged area is people farming area where fibre root of plant adds water absorption capacity of the soil. Also, sliding materials show water seepage that indicates that the moving slope has been saturated. This condition supported by information from geoelectric survey which indicates that in general the under surface material potent to slide or move because of unconsolidated material with its resistivity values in the order of 16 – 43 m that estimated related to alluvial or saturated residual soil.

Observational evidence on the effects of mega-fires on the frequency of hydrogeomorphic hazards. The case of the Peloponnese fires of 2007 in Greece

Even though rare, mega-fires raging during very dry and windy conditions, record catastrophic impacts on infrastructure, the environment and human life, as well as extremely high suppression and rehabilitation costs. Apart from the direct consequences, mega-fires induce long-term effects in the geomorphological and hydrological processes, influencing environmental factors that in turn can affect the occurrence of other natural hazards, such as floods and mass movement phenomena. This work focuses on the forest fire of 2007 in Peloponnese, Greece that to date corresponds to the largest fire in the country's record that burnt 1773km2, causing 78 fatalities and very significant damages in property and infrastructure. Specifically, this work examines the occurrence of flood and mass movement phenomena, before and after this mega-fire and analyses different influencing factors to investigate the degree to which the 2007 fire and/or other parameters have affected their frequency.Observational evidence based on several data sources collected during the period 1989–2016 show that the 2007 fire has contributed to an increase of average flood and mass movement events frequency by approximately 3.3 and 5.6 times respectively. Fire affected areas record a substantial increase in the occurrence of both phenomena, presenting a noticeably stronger increase compared to neighbouring areas that have not been affected. Examination of the monthly occurrence of events showed an increase even in months of the year were rainfall intensity presented decreasing trends. Although no major land use changes has been identified and chlorophyll is shown to recover 2years after the fire incident, differences on the type of vegetation as tall forest has been substituted with lower vegetation are considered significant drivers for the observed increase in flood and mass movement frequency in the fire affected areas.

Geotechnical and landslide aspects in weathered granitoid rock masses (Serre Massif, southern Calabria, Italy)

The weathering processes produce important chemical and physical transformations in rock masses producing a decay of their strength and then stability. In this study different methodologies were employed to define the physical-mechanical properties and the minero-petrographical changes at each grade of weathering, useful to determine a geological model of the weathered granitoids involved in mass movements. The paper focuses on a multidisciplinary research on the weathering profiles of the Paleozoic granitoid rocks surrounding the village of Fabrizia located in the Serre Massif (southern Calabria, Italy). Fabrizia lies on an old erosion surface composed of basement rocks made up of weathered granitoids, belonging to the Serre Massif granitoid complex, and overlain by thin eluvial-colluvial deposits.The tectonic uplift of the area combined with Mediterranean climatic conditions, both active at least since the Quaternary, are the main causes of the deep weathering of the plutonic rocks. The weathered profiles of the granitoid complex have been studied through field observations, borehole explorations with geotechnical tests and seismic surveys coupled to minero-petrographical analysis and laboratory tests. Weathered profiles are mainly composed by rock masses varying from completely weathered and residual soil (classes V–VI) to moderately weathered rocks (class III), characterized by a progressive increase of geotechnical properties (e.g., seismic wave velocity, rock quality designation, internal friction angle, uniaxial compressive strength) with a decrease of weathering. The weathered rocks display a wide variety of mass movement. Landslide types are rockfalls for the fresher rocks (class III); translational slides occur between different weathering degrees (classes IV and V) and rotational slides dominate at the top of the slopes and generally involve the weathering grades from class IV to classes V–VI. The shallow horizons are composed of thin eluvial-colluvial deposits and more weathered granitoids (classes V–VI) that may generate dangerous debris flows or debris avalanches during intense and prolonged rainfall. The landslide surface is usually at a depth lower than 2m in the debris flow type, while deeper landslides (depth>2m) are rotational and translational types with sliding surfaces occurring mainly in the transition between the classes IV and V.The field survey coupled to geotechnical, geophysical and minero-petrographical data allowed the recognition of the different weathered horizons and relative geotechnical properties useful to the reconstruction of the reliable geological model. The model represents an important support for the study of the landslide processes and for a sustainable management of the territory. The used approach provided results to set a general reference framework for establishing more precise correlations between mass movement phenomena and weathering processes.

Kinematic behaviour of a large earthflow defined by surface displacement monitoring, DEM differencing, and ERT imaging

Large earthflow-type landslides are destructive mass movement phenomena with highly unpredictable behaviour. Knowledge of earthflow kinematics is essential for understanding the mechanisms that control its movements. The present paper characterises the kinematic behaviour of a large earthflow near the village of Ľubietová in Central Slovakia over a period of 35years following its most recent reactivation in 1977. For this purpose, multi-temporal spatial data acquired by point-based in-situ monitoring and optical remote sensing methods have been used. Quantitative data analyses including strain modelling and DEM differencing techniques have enabled us to: (i) calculate the annual landslide movement rates; (ii) detect the trend of surface displacements; (iii) characterise spatial variability of movement rates; (iv) measure changes in the surface topography on a decadal scale; and (v) define areas with distinct kinematic behaviour. The results also integrate the qualitative characteristics of surface topography, in particular the distribution of surface structures as defined by a high-resolution DEM, and the landslide subsurface structure, as revealed by 2D resistivity imaging. Then, the ground surface kinematics of the landslide is evaluated with respect to the specific conditions encountered in the study area including slope morphology, landslide subsurface structure, and local geological and hydrometeorological conditions. Finally, the broader implications of the presented research are discussed with particular focus on the role that strain-related structures play in landslide kinematic behaviour.

Geochemical characteristics and genesis of Mačje Jame and Vranjski Potok As-Cu-bearing iron occurrences west and southwest of the town of Busovača, Mid-Bosnian Schist Mountains

Investigated landslide is the largest active mass movement along the Croatian coast, situated on the north-eastern slope in the central part of the Rjecina Valley (north-eastern coastal part of Adriatic Sea, Croatia). Slopes in this valley are formed in siliciclastic rocks - flysch, while limestone rock mass is visible on the cliffs around the top of the river valley. The slopes are at the limit of a stable equilibrium state, and mass movement phenomena have been recorded since 19th century. Samples for laboratory testing were taken from the flysch bedrock, weathered zone and slope formations, and were recovered to provide specimens for data on their mineralogical, physical and geotechnical properties. Correlation between mineralogical and geotechnical properties and their influence on sliding processes are presented in this paper. Clay fraction in samples ranges from 17 % to 38 %. Clay activity of the tested samples is from 0.45 to 0.89, and the residual friction angle varies from 13.0° to 17.7°. These results correspond to the presence of kaolinite and illite groups of clay mineral. Mineral composition and decrease in strength of fine-grained soil materials, due to the increase of pore water pressures, contributes to the slope movements.

Meandering of Tributaries of the Tigris River Due to Mass Movements within Iraq

Tigris and Euphrates are the main rivers in Iraq. The former has 5 main tributaries while the latter has no tributaries within Iraq. All these rivers exhibit meandering and/or shifting of their courses due to many reasons; such as mass movements and alluvial fan's development. The meandering and shifting of river courses due to mass movements is dealt with in this study. Many examples are given from different parts of Iraq within different rivers and streams. In each case, the geology of the involved area is described; the reasons of the shifting and/or meandering of the river course are given. GIS technique was used to determine the coverage of the involved area. Landsat, Google Earth and DEM images were used to indicate the suffered areas from shifting and meandering of the rivers and streams. When possible, age of the shifting and/or meandering of the river and stream courses was estimated; using exposure age determination; mainly depending on the presence of river terraces, erosional forms, vegetation cover and the maturity of the involved area. Some of the given examples of shifting of river courses were found to be still active; others are inactive. In many cases, indications for very large mass movement phenomena were seen. Moreover, some of the large involved areas are highly populated, others includes few houses and/ or farms. The majority of the meanders are developed due to mass movement phenomena; others are caused by alluvial fans and/or tectonic features, lime plunging of anticlines.

The relationship between geology and rock weathering on the rock instability along Mugling–Narayanghat road corridor, Central Nepal Himalaya

The present study was conducted along the Mugling–Narayanghat road section and its surrounding region that is most affected by landslide and related mass-movement phenomena. The main rock types in the study area are limestone, dolomite, slate, phyllite, quartzite and amphibolites of Lesser Himalaya, sandstone, mudstone and conglomerates of Siwaliks and Holocene Deposits. Due to the important role of geology and rock weathering in the instabilities, an attempt has been made to understand the relationship between these phenomena. Consequently, landslides of the road section and its surrounding region have been assessed using remote sensing, Geographical information systems and multiple field visits. A landslide inventory map was prepared and comprising 275 landslides. Nine landslides representing the whole area were selected for detailed studies. Field surveys, integrated with laboratory tests, were used as the main criteria for determining the weathering zones in the landslide area. From the overall study, it is seen that large and complex landslides are related to deep rock weathering followed by the intervention of geological structures as faults, joints and fractures. Rotational types of landslides are observed in highly weathered rocks, where the dip direction of the foliation plane together with the rock weathering plays a principle role. Shallow landslides are developed in the slope covered by residual soil or colluviums. The rock is rather fresh below these covers. Some shallow landslides (rock topples) are related to the attitude of the foliation plane and are generally observed in fresh rocks. Debris slides and debris flows occur in colluviums or residual soil-covered slopes. In few instances, they are also related to the rock fall occurring at higher slopes. The materials from the rock fall are mixed with the colluviums and other materials lying on the slope downhill and flow as debris flow. Rock falls are mainly related to the joint pattern and the slope angle. They are found in less-weathered rocks. From all these, it is concluded that the rock weathering followed by geological structures has prominent role in the rock slope instability along Mugling–Narayanghat road section and its surrounding regions.

Rockfall detachment susceptibility map in El Hierro Island, Canary Islands, Spain

A semi-quantitative heuristic methodology is developed to map a rockfall detachment susceptibility zonation of El Hierro Island (Canary Archipelago). The rationalized procedure, which we called non-weighted bounded indicators, is based on overlapping thematic maps of conditioning factors to mass movement, which are appropriately and individually rescaled and then composed by addition to obtain a susceptibility numerical index through a GIS. As the consistency of the geomorphological analysis depends on the expert subjective criteria and the appropriate interpretation of the landscape, the use of this methodology reduces subjectivity and quantifies the degree of susceptibility. The main factors affecting the mass movement phenomena (rockfalls events), also recognized in the field and, therefore, considered in the presented GIS arrangement, are slope, profile curvature, lithology, vegetation cover and dykes density. To calculate the slope threshold or minimum angle characteristic of rockfall source areas, mixed Gaussian slope frequency decomposition is used. The curvature index reveals stepwise areas. Qualitative geomechanical characteristics are linked to a quantitative index according to a volcanic lithological-complexes classification. Both destabilization (root-wedging) and stabilization effects are considered into the vegetation cover index. The dyke density index incorporates the bearing rock capacity decrease produced in the halo around a dyke network intrusion. Slope, curvature and vegetation indexes thresholds have been fitted following field observations. A rockfall detachment susceptibility map is obtained and classified based on the histogram maxima. The rockfall inventory, based on rockfall events reported within the island, was used for the model validation. A 12 % of the whole island shows medium to very high susceptibility.

Slope-failure Analysis and Classification: Review of a Century of Effort

The geoscience literature is replete with bewildering descriptions and classifications resulting from a century of analysis of gravitative transfer of materials downslope. The complexity of mass-movement phenomena has led to a profusion of confusing terminology that this paper attempts to clarify. International recognition of the hazard to life and property posed by slope failure highlights the need for increased precision in its description in a quest for prediction, control, and remediation of the diverse phenomena. The most useful classifications are those that employ as their primary criteria the type of movement (e.g., fall, topple, slide, spread, flow) and the type of material (e.g., rock, debris, earth) involved, with secondary considerations of velocity and the amount and phase of H2O. Recently, interest has focused on the massive, subaqueous failures that can generate huge tsunamis, as well as the massive, dangerous collapses of volcanoes. Future slopefailure research is expected to incorporate quantitative and geotechnical assessments of process mechanics, including remote sensing, numerical indices and modeling, and advanced assessments of flow rheology.

Mass movements related to tectonics in the Aspromonte massif (southern Italy)

Geomorphic and structural studies have been carried out on the headwaters of Vallone Colella Torrent, in an area intensely affected by mass-movement phenomena on the Aspromonte massif of southern Italy. Rock types outcropping in the area are mostly gneiss and granitoids, with subordinate presence of metarenites, phyllites, and biotite schists; all lithologies experienced low-grade metamorphism, as indicated by petrographic analysis. Structural surveys, performed at macroscopic and mesoscopic scale, allowed recognition of several sets of discontinuities related to different deformation events. The upper reaches of Vallone Colella Torrent present a large, active landslide zone, the debris materials of which feed the debris flows along the drainage system towards the main valley. Mass-movement phenomena are both shallow and deep-seated; the latter are limited to a sector of the study area, while shallow processes are present throughout the landslide zone. Some considerations of the relationship between tectonics and mass movement are presented, with particular reference to the presence of a large-scale downthrown wedge (bounded by structural surfaces on both sides of the valley), located in the same area affected by deep-seated phenomena.

Mass movement and erosion hazard patterns by multivariate analysis of landscape integrated data: the Upper Orcia River Valley (Siena, Italy) case

A landscape integrated survey was carried out on the badlands area in the Upper Orcia River Valley (Siena, Italy). A methodology has been investigated to explain the soil response to dynamic and anthropic factors from an erosion hazard point of view. The Upper Orcia River Valley is one of the many neogenic basins linked to the Pliocene sea ingression, in Tuscany and all over Italy. Sediments are mainly fine silty-clay and the region is characterized by an estensive net of joints, faults and fractures due to the neotectonics in the area. The area is undergoing a fast land degradation characterized by “biancane” (domes), “calanchi” (very steep and deep gullies with a typical dendritic drainage net), gullies, several surficial erosional forms and mass movement phenomena (creeping, landslides, solifluctions and anthropic levelling). Seventeen Land Units and 46 Types were recognized according to the relationships between Elementary Landform and slope (EL), Hydrographic Net Patterns (HNP), River Bed (RB), Geomorphic Dynamics (GD), Erosion Forms (EF), Mass Movements (MM), vegetation and land use (VLU), Cultural Management systems (CM) and Morphological Sequences (MS). Lithology and soils were not taken into account as the former is to be considered almost homogeneous, while the latter are of the Entisols and Inceptisols orders ( Soil Survey Staff, 1975) in the Typic Xerorthent and Xerochrept Subgroups. The soil pattern is mainly linked to geomorphic dynamics and appears extremely leopardized, every landform being characterized by various toposequences. PCA and clustering based on Euclidean distance (similarity measure) were utilized. A normalization of the variables to the standard deviation of the population was used. The previous PCA and Varimax rotation reduced the number of the variables from the original 9 to the 5 more weighing ones (1-2-5-6-7). Clusters were created to verify the Land Types groups as well as the possibility of unifying Land Units with the higher similarity level. The cluster analysis resulted in 15 groups that can well explain different land degradation patterns and which, in some cases, confirmed the Land System Analysis. The Authors came to the conclusion that multivariate analysis of landscape characteristics can only partially substitute the landscape integrated survey but can be considered a helpful means to analyse the distribution in the area of mass movements and erosion phenomena.

Hilislope geomorphology and geotechnique

This review focuses on recent Canadian contributions to hillslope geomorphology, and emphasizes geotechnical studies of mass movement phenomena in the Canadian Cordillera, including debris flows, rock avalanches, talus slopes, rock creep, and slow earthflows. A brief discussion is included of quick-clay flow slides in eastern Canada, and gelifluction phenomena in arctic and alpine areas. Comparisons are made with similar geotechnical work conducted in the Pacific-rim steeplands.

The supply and use of engineering geology information relating to slope instability hazards for planning purposes

Abstract This paper seeks to examine the use of one type of information which engineering geologists can supply to planners, in particular, that relating to slope instability problems. Mass-movement phenomena can provide major obstacles to planning objectives and may require costly measures if they are to be avoided or stabilized. The recent publications of Varnes (1984), Brunsden & Prior (1984) and Crozier (1986) all bear witness to the intense interest and importance attached to slope instability phenomena and their planning impacts. This paper examines how information is supplied by engineering geologists to planners and the role that it may play in producing safer, more cost-effective planning solutions to the risks to both life and property posed by mass-movements. The paper focuses its attention on the methods of supply of hazard information to planners and especially on hazard mapping. A selection of the more widely used slope hazard mapping techniques is examined and critically evaluated in planning terms. In addition, the ways of describing phenomena presently used on the relevant documents is examined for its suitability for, and compatibility with, planning requirements. The second part of the paper focuses attention on the use of hazard information within planning systems basing its discussion on working systems in North America, Australia, and Continental Europe while also making reference to work being produced in the United Kingdom. The potential contribution of engineering geology to hazard avoidance and planning controls in hazardous areas is discussed drawing upon case-study material. The final part of the paper discusses possible areas of incompatibility between earth-science information and planning systems drawing upon practical examples. In particular the differences between the planning and geological timescales are discussed.

Ancient Submarine Canyons of Tethyan Continental Margins, Czechoslovakia

Two large ancient submarine canyons buried below the Neogene foredeep and the Carpathian flysch belt are recognized within the ancient Tethyan margins. The features, as much as 10 km wide and 1,060 m deep, were cut into crystalline and sedimentary rocks of the Variscan platform and filled with late Eocene and early Oligocene sediments. The axes of both canyons follow the northwest-southeast structural trend of the platform. Farther downslope the two canyons probably join to form a single canyon-fan valley system. The submarine valleys are located within a northwest-southeast-trending tectonic depression which is filled with autochthonous Tethyan strata of Mesozoic and Paleogene ages. In terms of plate tectonics, this long-lived depression on the borderland between the Alps and the Carpathians, extending from the Tethyan seaway far into the platform, has been interpreted as an aulacogen. The sedimentary fill of the canyons is composed of silty mudstone in the upper part of the sequence, whereas sandstones and conglomerates are distributed mainly in the lower axial part of the valleys. Proximal and distal turbidites, grain-flow, and debris-flow deposits and pebbly mudstones have been recognized within the fill. The presence of pebbly mudstones, slump folds, and other mass-movement phenomena indicate relatively steep paleoslopes. The foraminiferal thanatocoenoses comprise: (a) indigenous canyon dwellers, (b) synsedimentary Foraminifera rewashed from estuaries and open-shelf environments, and (c) faunas reworked from older sediments. On the basis of indigenous planktonics, the duration of the canyon filling is estimated at 10 to 12 m.y. The fossil record, however, represents only the final stage of the canyon development; the early erosional stages have left little evidence within the canyons. The Tethyan canyons are considered to be submerged land valleys further developed by submarine processes. Their cutting and filling in late Eocene to early Oligocene time coincided with worldwide cooling of climate and possible eustatic sea-level changes, which also may have affected the canyon development. The Paleogene canyons also coincided with widespread accumulation of subsea-fan deposits in the Tethyan region (e.g., Annot Formation of the Alps, Krosno Formation of the Carpathians). The presence of ancient submarine canyons within the Tethyan continental margins provided means for coarse sediment to bypass the shelf environment. This strongly supports the writer's view that the tectonically fragmented marginal zone of the Variscan platform was much more important as a source of clastic materials than previously was believed. The canyon fill comprises both organic-rich petroleum source rocks and sandstone traps such as the proximal turbidites and grain-flow deposits. The tectonically controlled canyons also may have served as migration paths from the mobile belt to potential reservoirs in the foreland. Fossil submarine canyons can be identified elsewhere within the ancient continental margins; attention to the frontal zones of orogenic belts might thus prove fruitful in the search for petroleum.

Mass-movement phenomena in an upper carboniferous greywacke-argillite sequence in North-Eastern New South Wales

Abstract Thick slump breccias, interbedded with greywackes and argillites, are well exposed in shore platforms and cliffs at Halliday's Point, 230 km north of Sydney. They are unusual in two respects. Firstly, they were formed by submarine slumping of marine sediments initially deposited by turbidity currents and pelagic sedimentation. The slumping was initiated by minor tilting of the sea floor perhaps brought about by faulting or by volcanic activity. Secondly, it was the coarse sandy layers which proved the more unstable lithology and which failed by viscous fluid flow. The finer grained interbedded layers in the slump mass fractured and remained as blocks and slabs, some large in size, in a matrix of coarser sediment. The rocks at Halliday's Point were derived predominantly from a volcanic source. Measurement of slump folds suggests emplacement of the breccias from a north-easterly direction.