Incised Pleistocene valleys in the Western Belgium coastal plain: Age, origins and implications for the evolution of the Southern North Sea Basin

The Belgian coastal plain occupies a key position as it is located at the transition between the Southern North Sea Basin and the Strait of Dover. It is characterized by thick sequences (> 20 m) of Pleistocene terrestrial and littoral sediments. Yet the wider stratigraphical and palaeo-environmental significance of these sediments received little attention. In this paper we draw on the results of a recent sedimentological study based on > 100 drillings that spans the Pleistocene sequence, and present new biostratigraphical (pollen, foraminifera, ostracods) data, all revealing a complex history of deposition. The record includes evidence of the development of incised-valley systems that were initiated in the late Middle and Late Pleistocene. Five phases of fluvial incision can be identified. The majority of the infills are deposited in an estuarine environment that passes into a fluvial environment land inward, except the Weichselian infill which has a predominant fluvial origin. The greatest part of the most seaward located zone of the western coastal plain was free of valley incisions, there, shallow marine sediments built up the record. Local biostratigraphical investigations provide a timeframe. The result is placed in a regional context.

Aquisição, processamento e análise de dados de sísmica de alta resolução na plataforma continental norte do Rio Grande do Norte: Vale inciso do rio açu

On the modern Continental Shelf to the north of Rio Grande do Norte state (NE Brazil) is located a paleo-valley, submerged during the last glacial sea-level lowstand, that marks continuation of the most important river of this area (Açu River). Despite the high level of exploration activity of oil industry, there is few information about shallow stratigraphy. Aiming to fill this gap, situated on the Neogene, was worked a marine seismic investigation, the development of a processing flow for high resolution data seismic, and the recognition of the main feature morphology of the study area: the incised valley of the River Açu. The acquisition of shallow seismic data was undertaken in conjunction with the laboratory of Marine Geology/Geophysics and Environmental Monitoring - GGEMMA of Federal University of Rio Grande do Norte UFRN, in SISPLAT project, where the geomorphological structure of the Rio paleovale Açu was the target of the investigation survey. The acquisition of geophysical data has been over the longitudinal and transverse sections, which were subsequently submitted to the processing, hitherto little-used and / or few addressed in the literature, which provided a much higher quality result with the raw data. Once proposed for the flow data was developed and applied to the data of X-Star (acoustic sensor), using available resources of the program ReflexW 4.5 A surface fluvial architecture has been constructed from the bathymetric data and remote sensing image fused and draped over Digital Elevation Models to create three-dimensional (3D) perspective views that are used to analyze the 3D geometry geological features and provide the mapping morphologically defined. The results are expressed in the analysis of seismic sections that extend over the region of the continental shelf and upper slope from mouth of the Açu River to the shelf edge, providing the identification / quantification of geometrical features such as depth, thickness, horizons and units seismic stratigraphyc area, with emphasis has been placed on the palaeoenvironmental interpretation of discordance limit and fill sediment of the incised valley, control by structural elements, and marked by the influence of changes in the sea level. The interpretation of the evolution of this river is worth can bring information to enable more precise descriptions and interpretations, which describes the palaeoenvironmental controls influencing incised valley evolution and preservation to provide a better comprehensive understanding of this reservoir analog system

Caracterização e análise do talude continental adjacente à bacia potiguar, NE Brasil

This work presents the results of the first imaging of continental slope adjacent to Potiguar Basin, in the equatorial Brazilian margin (NE Brazil). Swath bathymetry provided a complete coverage of seafloor between the upper and middle slope (100-1,300 m). Fifteen submarine canyons were mapped. The shape of the slope reflects in distinct spatial distribution of the canyons. The western area displays convex profiles which implied a greater amount of incisions by canyons. Some of them have gradient walls higher than 35°. They were classified according to location and morphology. The canyons with heads indenting shelf edge, association with a incised valley and a large fluvial system, high sinuosities, V shape, terraces along margins, further erosive features such as landslide and gullies allow to deduce a sandy-gravelly sedimentation. These canyons are associated with deposition of submarine fan systems that have been considered permeable hydrocarbon reservoirs. The presence of gullies, furrows and dunes demonstrates the role of bottom currents in the shaping of the slope. The enlargement of canyons and the change in the course when they cross the border fault imply that tectonic has also influenced in the morphology of deep waters environments of Potiguar Basin. The current sedimentation of continental slope is considered mixed because the sediments are composed of siliciclastics and bioclasts. Predominant siliciclastics are calcite, dolomite, quartz, and clay minerals. The presence of stable minerals (zircon, tourmaline and rutile), and fragmented bioclasts implies the contributions of Rivers Açu and Apodi

Caracterização geomorfológica e paleogeográfica da plataforma continental adjacente a foz do Rio Apodi-Mossoró, RN/Brasil

The brazilian marginal basins have a huge potential to generate and accumulate petroleum. Incised valleys which are eroded in response to a fall of relative sea level are related to potential reservoir as well, modern drowned-valley estuaries serve as harbors to petroleum and salt industries, fisheries, waste-disposal sites and recreational areas for a significant fraction of the world s population. The combined influence of these factors has produced a dramatic increase in research on modern and ancient incised-valley systems. This research is one expression of this interest. The integrated use of satellites images and high resolution seismic (bathymetry, sides scan sonar) was used on the Apodi River mouth-RN to characterizes the continental shelf This area is located at the Potiguar Basin in the NE Brazilian Equatorial Atlantic margin. Through bathymetric and side scan sonar data processing, a digital Terrain Model was developed, and a detailed geomorphologic analysis was performed. In this way was possible to recognize the geomorphologic framework and differents sismofacies, which may influence this area. A channel extending from the ApodiMossoró river mouth to the shelf edge dominates the investigated area. This structure can be correlated with the former river valley developed during the late Pleistocene sea level fall. This channel has two main directions (NW-SE and NE-SW) probably controlled by the Potiguar Basin structures. The western margin of the channel is relatively steep and pronounced whereas the eastern margin consists only of a gentle slope. Longitudinal bedforms and massive ridges also occur. The first are formed doe to the shelf sediment rework and the reef-like structures probably are relics of submerged beachrock-lines indicating past shoreline positions during the deglacial sea-level rise. The sub-bottom seismic data allow the identification of different sismic patterns and a marcant discontinuity, interpreted as the Upper

O rio Paraguai no megaleque do Nabileque, sudoeste do Pantanal mato-grossense, MS

The Nabileque fluvial fan is a Quaternary depositional system located along the southwestern border of the Pantanal, covering an area of approximately 9,100 km 2. It is a peculiar alluvial system because it is not associated with inflow from adjacent plateaus. The Nabileque megafan is formed by the Paraguay River at the exit of the Pantanal wetland, coalescing with the Pilcomayo megafan of the Chaco basin. A geomorphological zonation analysis was performed making use of remote sensing data with field verification. Most of the area is a vast alluvial plain made of Pleistocene deposits, whose surface is marked by the presence of an intricate network of distributary paleochannels. Areas blanketed by Pleistocene deposits are dissected by erosional streams and subject to frequent flooding events. The Paraguay River flows in a meander belt constrained by NE fractures associated with the Transbrasiliano Lineament, but deflects towards the SSE after the Negro River confluence composing the system's peripheral drainage. An abandoned meander belt is preserved within a remarkable N-S incised-valley that is interpreted as the ancient Paraguay River course. Processes of avulsion and river capture are suggested to explain the observed changes of the river course. The Nabileque River is an underfit stream within the incised-valley, cutting paleomeanders and point bars of the previous Paraguay River course.

Compartimentação geomorfológica e processos deposicionais no megaleque fluvial do rio São Lourenço, Pantanal mato-grossense

The Pantanal wetland is an extensive depositional tract characterized by the presence of fluvial megafans, from which that of the Taquari River is the most extensive and well known. Located on the northern border of the Pantanal, the São Lourenço megafan is a large distributary fluvial system with an area of 16,000 km2, but poorly known regarding its geomorphological and geological features. The Sao Lourenço and the Taquari are coalescent megafans, having the Piquiri interfan meander river in between them. Based on the interpretation of satellite images and field validation, it was possible to identify channel patterns, to interpret depositional and erosional processes, to recognize the phenomena of river avulsion and to map depositional lobes. Three geomorphological zones were recognized on the São Lourenço megafan: 1) abandoned depositional lobes located in the upper/intermediate fan, composed of Pleistocene fluvial deposits and exhibiting distributary paleochannels on their surfaces, which are currently being dissected by tributary channels; 2) an active Holocene confined meander belt formed by fluvial aggradation in a N65E incised-valley; 3) active depositional lobes placed on the distal part of the system, which are the main site of sedimentation and are characterized by frequent avulsion events, channel bifurcation, distributary drainage pattern and the presence of depositional lobated landforms. The active depositional lobes were formed due to an important event of river avulsion that caused the lower portion of the meander belt to be abandoned.

Compartimentação geomorfológica e processos deposicionais no megaleque fluvial do rio São Lourenço, Pantanal mato-grossense

A planície sedimentar do Pantanal é um extenso trato deposicional moderno, no qual megaleques fluviais são as feições que mais se destacam, sendo o do rio Taquari o maior e mais conhecido. Também notável é o megaleque do rio São Lourenço, que, apesar de possuir área de cerca de 16.000 km², é ainda pouco conhecido nos seus aspectos geológicos e geomorfológicos. Situado na borda noroeste do Pantanal, o megaleque do São Lourenço coalesce com o do Taquari, sendo dele separado pela planície fluvial interleque do rio Piquiri. Com base na interpretação de dados orbitais e na sua validação em campo, foi possível identificar padrões de canais, interpretar processos sedimentares, reconhecer fenômenos de avulsão fluvial e delinear lobos deposicionais. Foram reconhecidos três compartimentos geomorfológicos no megaleque do São Lourenço: 1) lobos deposicionais abandonados indiferenciados, situados na porção proximal/média do megaleque e constituídos por sedimentos pleistocênicos depositados por paleocanais distributários, atualmente em dissecação por canais tributários; 2) cinturão de meandros de idade holocênica, limitado por terraços marginais e resultado de agradação fluvial em vale inciso, cuja direção está condicionada por estruturas N65E; 3) lobos deposicionais ativos, situados na porção distal do megaleque e principal área de sedimentação do sistema deposicional, caracterizados por frequentes eventos de avulsão, bifurcações do canal, padrão de drenagem distributária e presença de lóbulos deposicionais. Os lobos deposicionais ativos foram formados a partir de importante evento de avulsão fluvial, que culminou com o abandono da porção inferior do cinturão de meandros.

Channel arrangements and depositional styles in the Sao Lourenco fluvial megafan, Brazilian Pantanal wetland

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evidenze micropaleontologiche e sedimentologiche di cicli deposizionali e climatici circa millenari nei Depositi Tardoquaternari della Piana dell'Arno e del Delta del Po

A multidisciplinary study was carried out on the Late Quaternary-Holocene subsurface deposits of two Mediterranean coastal areas: Arno coastal plain (Northern Tyrrhenian Sea) and Modern Po Delta (Northern Adriatic Sea). Detailed facies analyses, including sedimentological and micropalaeontological (benthic foraminifers and ostracods) investigations, were performed on nine continuously-cored boreholes of variable depth (ca. from 30 meters to100 meters). Six cores were located in the Arno coastal plain and three cores in the Modern Po Delta. To provide an accurate chronological framework, twenty-four organic-rich samples were collected along the fossil successions for radiocarbon dating (AMS 14C). In order to reconstruct the depositional and palaeoenvironmental evolution of the study areas, core data were combined with selected well logs, provided by local companies, along several stratigraphic sections. These sections revealed the presence of a transgressive-regressive (T-R) sequence, composing of continental, coastal and shallow-marine deposits dated to the Late Pleistocene-Holocene period, beneath the Arno coastal plain and the Modern Po Delta. Above the alluvial deposits attributed to the last glacial period, the post-glacial transgressive succession (TST) consists of back-barrier, transgressive barrier and inner shelf deposits. Peak of transgression (MFS) took place around the Late-Middle Holocene transition and was identified by subtle micropalaeontological indicators within undifferentiated fine-grained deposits. Upward a thick prograding succession (HST) records the turnaround to regressive conditions that led to a rapid delta progradation in both study areas. Particularly, the outbuilding of modern-age Po Delta coincides with mud-belt formation during the late HST (ca. 600 cal yr BP), as evidenced by a fossil microfauna similar to the foraminiferal assemblage observed in the present Northern Adriatic mud-belt. A complex interaction between allocyclic and autocyclic factors controlled facies evolution during the highstand period. The presence of local parameters and the absence of a predominant factor prevent from discerning or quantifying consequences of the complex relationships between climate and deltaic evolution. On the contrary transgressive sedimentation seems to be mainly controlled by two allocyclic key factors, sea-level rise and climate variability, that minimized the effects of local parameters on coastal palaeoenvironments. TST depositional architecture recorded in both study areas reflects a well-known millennial-scale variability of sea-level rising trend and climate during the Late glacial-Holocene period. Repeated phases of backswamp development and infilling by crevasse processes (parasequences) were recorded in the subsurface of Modern Po Delta during the early stages of transgression (ca. 11,000-9,500 cal yr BP). In the Arno coastal plain the presence of a deep-incised valley system, probably formed at OSI 3/2 transition, led to the development of a thick (ca. 35-40 m) transgressive succession composed of coastal plain, bay-head delta and estuarine deposits dated to the Last glacial-Early Holocene period. Within the transgressive valley fill sequence, high-resolution facies analyses allowed the identification and lateral tracing of three parasequences of millennial duration. The parasequences, ca. 8-12 meters thick, are bounded by flooding surfaces and show a typical internal shallowing-upward trend evidenced by subtle micropalaeontological investigations. The vertical stacking pattern of parasequences shows a close affinity with the step-like sea-level rising trend occurred between 14,000-8,000 cal years BP. Episodes of rapid sea-level rise and subsequent stillstand phases were paralleled by changes in climatic conditions, as suggested by pollen analyses performed on a core drilled in the proximal section of the Arno palaeovalley (pollen analyses performed by Dr. Marianna Ricci Lucchi). Rapid shifts to warmer climate conditions accompanied episodes of rapid sea-level rise, in contrast stillstand phases occurred during temporary colder climate conditions. For the first time the palaeoclimatic signature of high frequency depositional cycles is clearly documented. Moreover, two of the three "regressive" pulsations, recorded at the top of parasequences by episodes of partial estuary infilling in the proximal and central portions of Arno palaeovalley, may be correlated with the most important cold events of the post-glacial period: Younger Dryas and 8,200 cal yr BP event. The stratigraphic and palaeoclimatic data of Arno coastal plain and Po Delta were compared with those reported for the most important deltaic and coastal systems in the worldwide literature. The depositional architecture of transgressive successions reflects the strong influence of millennial-scale eustatic and climatic variability on worldwide coastal sedimentation during the Late glacial-Holocene period (ca. 14,000-7,000 cal yr BP). The most complete and accurate record of high-frequency eustatic and climatic events are usually found within the transgressive succession of very high accommodation settings, such as incised-valley systems where exceptionally thick packages of Late glacial-Early Holocene deposits are preserved.

Sedimentology of the Vietnam shelf

On the Vietnam Shelf more than 1000 miles of shallow high-resolution seismics were analyzed to unravel post-glacial evolution in a tropical, siliciclastic environment together with 25 sediment cores from water depths between 21 and 169 m to determine stratigraphy, distribution and style of sedimentation. Fourty-seven samples were dated with the AMS-14C technique. The shelf was grouped into three regions: a southern part, a central part, and a northern part. On the broad Southern Shelf, sedimentation is influenced by the Mekong River, which drains into the SCS in this area. Here, incised valley fills are abundant that were cut into the late Pleistocene land surface by the Paleo-Mekong River during times of sea level lowstand. Those valleys are filled with transgressive deposits. The Holocene sedimentation rate in this low gradient accommodation-dominated depositional system is in the range of 5-10 and 25-40 cm/ky at locations sheltered from currents. The Central Shelf is narrow and the sedimentary strata are conformable. Here, numerous small mountainous rivers reach the SCS and transport large amounts of detrital sediment onto the shelf. Therefore, the Holocene sedimentation rate is high with values of 50-100 cm/ky in this supply-dominated depositional system. The broad Northern Shelf in the vicinity of the Red River Delta shows, as on the Southern Shelf, incised valleys cut into the Pleistocene land surface by paleo river channels. In this accommodation-dominated shelf area, the sedimentation rate is low with values of 5-10 cm/ky. Where applicable, we assigned the sampled deposits to different paleo-facies. The latter are related to certain intervals of water depths at their time of deposition. Comparison with the sea-level curve of (Hanebuth et al., 2000, doi:10.1126/science.288.5468.1033) indicates subsidence on the Central Shelf, which is in agreement with the high sedimentation rates in this area. In contrast, data from the Northern Shelf suggest tectonic uplift that might be related to recent tectonic movements along the Ailao Shan-Red River Fault zone. Data from the Southern Shelf are generally in agreement with the sea-level curve mentioned above.

Caracterização morfológica-sedimentar do vale inciso Apodi-Mossoró e plataforma continental adjacente - Bacia Potiguar Offshore

Systems of incised valleys have been studied in different continental shelves, including the Brazilian continental margin. The interest to characterize this feature is given by the information that it can provide variations on sea level, as well as the ability to host economically significant quantities of hydrocarbons in reservoirs located in deposits filling of the incised valleys. This thesis has the overall objective to characterize the morphology and sedimentary cover of the incised valley Apodi-Mossoró, located in the Northern Continental shelf of Rio Grande do Norte state, adjacent to Areia Branca city. The methodology included the integration of satellite imagery, bathymetric data, sedimentological data, shallow seismic, and the identification of foraminifera. The results indicate that the ApodiMossró incised valley is currently formed by two channels, shallow channel and deep channel, which have distinct morphological and sedimentological characteristics. The deep channel has connection with one of the heads of the Apodi Canyon, located in the slope area. The acquisition, processing and interpretation of shallow seismic data allowed the recognition of the depositional surface, erosional surface, discordance, and sismofaceis. The erosional surface mapped from shallow seismic sections is possibly a indicative of an ancient surface of valley incision, where it would probably be associated with the limit Pleistocene/Holocene. Different sismofaceis were identified and reflect the rise in sea level with standards sometimes agradacional, sometimes progradational. The thickness of sediments on this surface was estimated at a maximum of 22m thick in the central portion of the incised valley. Statistically, there are differences between the adjacent continental shelf and channels, and between these channels, for the content of calcium carbonate, organic matter, sand and mud perceptual, except for the gravel grain size. The analysis of living and dead foraminifera showed the presence of fifty species distributed in regards to morphology, depth and type of sediment. Four type of seismic echocharacteres were identified and mapped, as well as their bedforms, indicating different sedimentary processes along the incised valley. The integration of results suggests an activation of the Apodi-Mossoró incised valley in the Late Pleistocene.

As Escadarias de Terraços do Ródão à Chamusca (Baixo Tejo) - Caracterização e Interpretação de Dados Sedimentares, Tectónicos, Climáticos e do Paleolítico

As unidades estratigráficas que resultaram da evolução do rio Tejo em Portugal, aqui analisadas em pormenor entre Vila Velha de Ródão e Chamusca, possuem distintas características sedimentares e indústrias líticas: uma unidade culminante do enchimento sedimentar (o ancestral Tejo, antes do início da etapa de incisão fluvial) - SLD13 (+142 a 262 m acima do leito actual; com provável idade 3,6 a 1,8 Ma), sem indústrias identificadas; terraço T1 (+76 a 180 m; ca. 1000? a 900 ka), sem indústrias; terraço T2 (+57 a 150 m; idade estimada em ca. 600 ka), sem indústrias; terraço T3 (+36 a 113 m; ca. 460 a 360? ka), sem indústrias; terraço T4 (+26 a 55 m; ca. 335 a 155 ka), Paleolítico Inferior (Acheulense) em níveis da base e intermédios mas Paleolítico Médio inicial em níveis do topo; terraço T5 (+5 a 34 m; 135 a 73 ka), Paleolítico Médio (com talhe Mustierense, Levallois); terraço T6 (+3 a 14 m; 62 a 32 ka), Paleolítico Médio final (Mustierense final); Areias da Carregueira (areias eólicas) e coluviões (+3 a ca. 100 m; 32 a 12 ka), Paleolítico Superior a Epipaleolítico; enchimento da planície aluvial (+0 a 8 m; ca. 12 ka a actual), Mesolítico e indústrias mais recentes. As diferenças na elevação (a.r.b.) das escadarias de terraços resultam de soerguimento diferencial, devido a falhas ativas. Numa dada escadaria datada, a projeção da elevação da superfície de cada terraço (a.r.b.) versus a sua idade permitiu estimar a idade do topo do terraço T2 (ca. 600 ka) e a provável idade do início da etapa de incisão (ca. 1,8 Ma). Obteve-se a duração da fase de agradação dos terraços baixos e médios: T6 – 30 ka; T5 – 62 ka; T4 – ca. 180 ka; T3 – ca. 100? ka. Conclui-se que durante o Plistocénico médio e final, as fases de incisão e alargamento do vale foram curtas (ca. 11-25 ka) e ocorreram durante períodos de nível do mar muito baixo, alternando com mais longas fases de inundação e agradação do vale durante níveis do mar mais altos. Estas oscilações eustáticas de causa climática estão sobrepostas a um contexto de soerguimento de longo termo, controlando o desenvolvimento das escadarias. Calculou-se que para os últimos ca. 155 ka as taxas de incisão de curto-termo apresentam valores (0,09 a 0,41 m/ka), aproximadamente, duplos dos calculados para o intervalo ca. 155 a 900 ka (0,04 a 0,28 m/ka). Este aumento na taxa de incisão deve estar relacionado com um aumento na taxa de soerguimento por intensificação da compressão devido à convergência entre as placas Africana e Eurasiática. Abstract: The terrace staircases of the Lower Tagus River (Ródão to Chamusca) – characterization and interpretation of the sedimentary, tectonic, climatic and Palaeolithic data The stratigraphic units that record the evolution of the Tagus River in Portugal (study area between Vila Velha de Ródão and Chamusca villages) have different sedimentary characteristics and lithic industries: a culminant sedimentary unit (the ancestral Tagus, before the drainage network entrenchment) – SLD13 (+142 to 262 m above river bed – a.r.b.; with probable age 3.6 to 1.8 Ma), without artefacts; T1 terrace (+76 to 180 m; ca. 1000? to 900 ka), without artefacts; T2 terrace (+57 to 150 m; top deposits with a probable age ca. 600 ka), without artefacts; T3 terrace (+36 to 113 m; ca. 460 to 360? ka), without artefacts; T4 terrace (+26 to 55 m; ca. 335 a 155 ka), Lower Paleolithic (Acheulian) at basal and middle levels but early Middle Paleolithic at top levels; T5 terrace (+5 to 34 m; 135 to 73 ka), Middle Paleolithic (Mousterian; Levallois technique); T6 terrace (+3 to 14 m; 62 to 32 ka), late Middle Paleolithic (late Mousterian); Carregueira Sands (aeolian sands) and colluvium (+3 a ca. 100 m; 32 to 12 ka), Upper Paleolithic to Epipaleolithic; alluvial plain (+0 to 8 m; ca. 12 ka to present), Mesolithic and more recent industries. The differences in elevation (a.r.b.) of the several terrace staircases results from differential uplift due to active faults. The age interval for each aggradation phase of T3 to T6 terraces was obtained: T3 – ca. 100? ka; T4 – ca. 180 ka; T5 – 62 ka; T6 – 30 ka. The intervals of river down-cutting and widening of the valley floor were short (ca. 11-25 ka) and coincided with periods of very low sea-level. The plotting of the elevation (a.r.b.) versus the age of each terrace surface allows to estimate the age of the T2 terrace (ca. 600 ka) and the probable age of the beginning of the incision stage (ca. 1.8 Ma). So, the high amplitude sea-level changes that characterized the Middle and Late Pleistocene strongly determined the episodic down-cutting phases of the river during the low stands sea levels that alternated with the flooding and aggradation phases of the incised valley during highstand sea levels. These climate related eustatic oscillations are superimposed onto a long term uplift pattern, controlling the river terrace staircase development. During the last ca. 155 ka, the short-term incision rates (0.09 a 0.41 m/ka) were twice the values determined for the interval 155 to 900 ka (0.04 to 0.28 m/ka). This increase in incision rate should be related with an increase in uplift rate resulting from an intensification of compression due to the convergence between African - Eurasian plates.

A stacked Late Quaternary fluvio-periglacial sequence from the Axe valley, southern England with implications for landscape evolution and Palaeolithic archaeology

The current model of mid-latitude late Quaternary terrace sequences, is that they are uplift-driven but climatically controlled terrace staircases, relating to both regional-scale crustal and tectonic factors, and palaeohydrological variations forced by quasi-cyclic climatic conditions in the 100 K world (post Mid Pleistocene Transition). This model appears to hold for the majority of the river valleys draining into the English Channel which exhibit 8–15 terrace levels over approximately 60–100 m of altitudinal elevation. However, one valley, the Axe, has only one major morphological terrace and has long-been regarded as anomalous. This paper uses both conventional and novel stratigraphical methods (digital granulometry and terrestrial laser scanning) to show that this terrace is a stacked sedimentary sequence of 20–30 m thickness with a quasi-continuous (i.e. with hiatuses) pulsed, record of fluvial and periglacial sedimentation over at least the last 300–400 K yrs as determined principally by OSL dating of the upper two thirds of the sequence. Since uplift has been regional, there is no evidence of anomalous neotectonics, and climatic history must be comparable to the adjacent catchments (both of which have staircase sequences) a catchment-specific mechanism is required. The Axe is the only valley in North West Europe incised entirely into the near-horizontally bedded chert (crypto-crystalline quartz) and sand-rich Lower Cretaceous rocks creating a buried valley. Mapping of the valley slopes has identified many large landslide scars associated with past and present springs. It is proposed that these are thaw-slump scars and represent large hill-slope failures caused by Vauclausian water pressures and hydraulic fracturing of the chert during rapid permafrost melting. A simple 1D model of this thermokarstic process is used to explore this mechanism, and it is proposed that the resultant anomalously high input of chert and sand into the valley during terminations caused pulsed aggradation until the last termination. It is also proposed that interglacial and interstadial incision may have been prevented by the over-sized and interlocking nature of the sub-angular chert clasts until the Lateglacial when confinement of the river overcame this immobility threshold. One result of this hydrogeologically mediated valley evolution was to provide a sequence of proximal Palaeolithic archaeology over two MIS cycles. This study demonstrates that uplift tectonics and climate alone do not fully determine Quaternary valley evolution and that lithological and hydrogeological conditions are a fundamental cause of variation in terrestrial Quaternary records and landform evolution.