1] Relatively little research has been undertaken on the use of digital elevation models to recognize the spatially variable glacial imprint of a landscape. Using theoretical topographies and a landscape evolution model, we investigate to what extent the hypsometric analysis of digital elevation models may be used to recognize the glacial signature of mountain ranges. A new morphometric parameter, which we term the hypsokyrtome (from the Greek: ipsos = elevation, kyrtoma = curvature), is derived from the gradient of the hypsometric curve. The efficacy of the hypsometric integral and hypsokyrtome is tested through the study of the Ben Ohau Range, New Zealand, whose glacial imprint has been described previously. With a numerical model we further test the geomorphic parameters in describing the morphologies of regions subject to diverse climatic and tectonic conditions. The hypsokyrtome is highly sensitive to glacial erosion, and the maps produced provide insights into the spatial distribution of glacial erosion. We use SRTM data and focus on two alternative geomorphic settings: the European Alps and the Apennines. The former has been affected by both fluvial and glacial erosion while the latter mainly exhibits a fluvially dominated morphology. The correlation between elevations with increased glacial erosion and Last Glacial Maximum (LGM) equilibrium line altitudes (ELAs) suggests the prevalence of a "glacial buzz saw" in the Alps, indicating that climate may put a limit on alpine topography.

The aim of this paper is to quantify the evolution in time and space of the accommodation (space available for sedimentation) in the case of a growth fault structure resulting from gravity-induced extension comprising a listric fault/raft system located along the West African margin.To achieve this, use was made of an original approach combining two complementary techniques (accommodation variation measurements and 3-D restoration) in order to quantify vertical and horizontal displacement related to deformation, using a data set made up of a 3-D seismic survey and well logs. We applied sequence stratigraphic principles to (i) de¢ne a detailed stratigraphic framework for the Albo -Cenomanian and (ii) measure subsidence rates from accommodation variations. 3-D restoration was used to (iii) reconstruct the evolution of the 3-D geometry of the fault system.The rates of horizontal displacement of structural units were measured and linked to successive stages in the growth of the fault system.

The Pyrenees results from the collision between Spain and Europe and developed between the upper Cretaceous (Santonian) and the Miocene. Its foreland basins are characterised by a thick fill of detrital and carbonate sediments. The diversity of Eocene deposits in the southern Pyrenean foreland basin is of particular use in facies sedimentology due to their exceptional outcropping quality and well established stratigraphic framework and has been taken as type examples of many different sedimentary environments. Most studies have concerned facies sedimentology of detrital series in turbiditic environments, meandering and braided rivers, alluvial fans, and deltas. In contrast, the Eocene carbonate series have attracted less attention. The marine Guara limestones are a formation of lower to middle Eocene age deposited on the southern border of the western Pyrenean foreland basin (Jaca basin). They were deposited as a retrogradational carbonate platform dominated by large benthic foraminifers near or at the flexural forebulge of the foreland basin as the Pyrenean orogen developed. This formation represents the last episode of carbonate platform in the Pyrenees and remains poorly studied. In the present work our aim is to provide a detailed facies analysis and physiographic reconstructions of the Guara carbonate platform. This is crucial to unravel the respective influences of tectonics, climate and rheology of the lithosphere on the foreland basin tectonic and stratigraphic development, and it brings new constraints on the paleoenvironments and paleogeography during the Lutetian, i.e. at the beginning of the major phase of activity of the Pyrenean orogenesis. Two outcrops were studied in the Sierras Marginales at the localities of Arguis and Lusera. The Lusera section once restored in its initial position is located to the North of the Arguis section in a basinward direction such that comparing time-equivalent facies between these two sections helps us reconstructing the paleobathymetric gradient on this side of the foreland basin. The sedimentological and paleontological content show that the Guara formation was deposited in shallow water environments (less than 80 m) and can be classified as a carbonate ramp. The evolution of paleobathymetries with time on these two sections allows us to identify three complete progradational - retrogradational cycles. Those cycles do not match global eustatic variations, perhaps indicating the dominating influence of tectonics in this area. The precise study of foraminifera allowed us to date our sections with respect to the SBZ time scale of Serra-Kiel et al. (1). The bottom of the Guara formation, in the Arguis section is dated from the lower Lutetian (SBZ 13) and the top corresponds to the upper Lutetian (SBZ 16). An important hiatus is recorded between the base of the carbonates and the lower Paleocene subjacent continental deposits. Moreover, the base of the formation is older at Lusera i.e. to the centre of the basin. This hiatus could thus represent the foreland flexural forebulge unconformity (2). By restoring the relative position of the two sections during the Lutetian, we have calculated the possible slope of the Guara ramp during this period for each MFS, with values always lower than 0.5°. Extrapolating this slope to the centre of the basin allows us to estimate the paleodepth of the coeval Eocene turbidites and address the important issue of the depth of deposition of submarine fan systems in foreland settings. Within the limits of our approach we propose that these clastic fan systems have been deposited under water depths of 400 to 200 metres. This is partly in agreement with the upper bound of other estimations based on foraminiferal assemblages and trace fossils, and thus favours a relatively "shallow" view of the Middle Eocene Ainsa-Jaca deep marine basin. 1. J. Serra-Kiel et al., Bulletin De La Societe Geologique De France 169, 281 (March 1, 1998, 1998). 2. S. L. Crampton, P. A. Allen, Aapg Bulletin 79, 1495 (October 1, 1995, 1995).

The early Cenozoic (Paleocene and Eocene) is known as the warmest period of the last 100 My, with little or no ice at the poles. This period shows an important transition between greenhouse climate to the present icehouse period. Geochemical and sedimentological data have shown that the first permanent ice cap was established on Antarctica at the Eocene/Oligocene boundary (˜34 Ma). However, some authors proposed that ephemeral ice sheets may have grown on Antarctica during the previously assumed ice-free late Cretaceous to middle Eocene world (Lear et al., 2000; Miller et al., 2005; Tripati et al, 2005) and the ages proposed for the first glaciation of the Cenozoic range from ~100 to 33.8 Ma. The sedimentation in the southern border of the Pyrenean foreland basin is characterized by the coexistence of carbonate and siliciclastic systems from the Paleocene to the Middle Eocene. In particular, the Guara ramp system, or Alveolina limestones, developed diachronously from the Lower Eocene onwards on the southward propagating foreland basin as the Pyrenean orogen developed. However, we remark the complete disappearance of the Guara ramp and of all carbonate systems in this basin from the beginning of the Bartonian (41.3 Ma) onwards. We propose to examine this disappearance as to be the consequence of a rapid cooling associated with the possible occurrence of ephemeral ice-sheets on Antarctica. This assumption was tested through two approaches. First, we have studied the sedimentological record from the Lutetian carbonates to the Bartonian clastics in order to constrain the evolution of the amplitude of the high-frequency (Milankovitch scale, <1My) sea level variations. Our results show that the sea level variations during the Lutetian were of relatively low amplitude of +/-10m, whereas the sea level variations recorded during the Bartonian seem to approximate up to +/- 50 m of amplitude, suggesting a possible stronger influence of glacioeustasy. We have also performed geochemical analyses on oyster shells to estimate the paleo-temperatures during this interval. Our record is not continuous but allows us to document a succession of 1) relatively warm temperatures during the Lutetian (˜30°C), 2) an increase of the temperatures during the early Bartonian (˜33°C) corresponding to the Middle Eocene Climatic Optimum (Bohaty and Zachos, 2003), followed by 3) a strong decrease during the upper Bartonian (˜25°C). The sedimentological evidence, along with its record of isotopic and sea level variations all suggest a significant climate change at the transition from the Lutetian to the Bartonian. This climate shift could be a possible explanation for the definitive disappearance of the carbonate platform in the south Pyrenean foreland basin, and it adds to the growing evidence of ice on Antarctica prior to the Eocene-Oligocene boundary.

The present study reports a sedimentological analysis of the Guara Limestone Formation deposited during the Lutetian in the Sierras Exteriores, in the South-Pyrenean foreland basin. We provide a detailed facies analysis of the carbonates to precise the paleoenvironmental context during their deposition. We show that those limestones are mainly composed of shallow-water foraminifers and were deposited in relative shallow-water environments (b120 m) during the whole Lutetian (SBZ 13 to SBZ 16). The Guara Limestone Formation represents the last occurrence of carbonate platform in the South-Pyrenean foreland basin and disappeared definitely at the Lutetian to Bartonian transition. The demise of carbonate producers at the end of the Lutetian could be related to an increase of continental erosion, due to tectonic and/or climatic forcing. We illustrate that in the Jaca basin, this event correlates with a marked increase in subsidence rate. However, this deformation event is local and the carbonate systems in the Pyrenean foreland resisted to many deformation events during the whole basin history before. Paleobathymetric reconstructions in the Jaca basin, where shallow marine sections outcrop, suggest an increase of the amplitude of high-frequency sea-level cycles. This increase is contemporaneous with several climatic evidences, which suggest the appearance of early ice-sheets near the Lutetian-Bartonian boundary. The demise of carbonate producers seems, therefore, to be the result of a major environmental shift in the basin accompanying increased subsidence rates, switching from low nutrient oligotrophic conditionsfavourable for shallow water benthic foraminifersto eutrophic conditions due to the increase of erosion and terrigenous nutrient input associated with higher-frequency sea-level changes and river destabilization.

River drainage patterns sculpt terrestrial landscapes. Whether these patterns contain fingerprints of past tectonic events is debated. On the one hand, elaborate dendritic river networks always retain an invariant structure, implying that rivers will simply reorganize in response to tectonic perturbations, without long-term trace of the tectonic event. On the other hand, many rivers in active mountain belts seem to be passive features and may record long-term crustal deformation. Here we use numerical simulations, constrained by drainage patterns observed in the Southern Alps of New Zealand, to analyse the response of river basins to distributed plate tectonic strain. We find that both dynamically reorganized and passively deformed rivers coexist in the Southern Alps. Rivers on the western side of the mountain range reorganize and rapidly evolve in response to tectonic deformation. In contrast, rivers on the eastern side resist reorganization and record large-scale plate tectonic influence over timescales of tens of millions of years. We conclude that both types of river drainage pattern in the Southern Alps are primarily controlled by plate tectonic strain, implying that landscape topography can be used to reconstruct the distribution of tectonic strain within zones of continental deformation around the world.

The last two decades have been marked by a large amount of studies on the relative influences of climate and tectonics on landscape evolution. Coevally, considerable advances have been achieved in numerical modelling of landscape evolution. These have been particularly useful in testing hypotheses and scenarios of the potential controls and feedbacks between climate, tectonics and landscape evolution. However, our current knowledge of the physical processes of erosion in nature remains incomplete. Indeed, although the predictions of landscape evolution models are often insightful, they are also sometimes overlooked due to their lack of physical basis. In parallel with current field and experimental investigations on erosion processes, one way to tackle this problem is to compare simulated and natural landscapes. Then, this allows us to know how can one assess whether a simulated landscape is realistic in a long-standing problem in geomorphology. The scaling between stream length and upstream drainage area, a relation known as Hack's law provides a constrain on the geometry of natural landscapes. It is however notoriously difficult to use this law to assess the goodness of a landscape evolution model since it must be regarded over a logarithmic range of scales (stream orders), which is usually not possible in landscape evolution models because of their resolution. The convergence angle, a measure of a basin's elongation ) is a similar metrics of drainage basin shape. It is controlled by the slope and roughness of the undissected surface on which a new basin develops. This relation arises from analytical predictions of water flow over simple topography and is supported by data on median to large-scale natural networks. In the present study we investigate the influence of slope and surface roughness on the shape of river basins using the CASCADE code . Results show that the rules used to route water in CASCADE (similar to those used in other landscape evolution models) are sufficient to produce a range of basin forms that correspond to the sample of natural basins used in this study. As expected, the convergence angle depends on the global slope and on the roughness. A new unexpected result is that it remains constant through time in the case of simple block uplift and is affected neither by the fluvial erosion coefficient nor by the diffusion coefficient used.

Drainage networks in linear mountain ranges always display a particular geometrical organisation whereby the spacing between the major drainage basins is on average equal to half the mountain width (distance from the mountain front to the main drainage divide), independent of climate and tectonics. This relationship is valid for mountains having di¡erent widths and is thus usually thought to be maintained by drainage reorganisation during mountain belt widening. However, such large-scale systematic drainage reorganisation has never been evidenced. In this paper, we suggest an alternative explanation, namely that the observed drainage basin relationships are an inherent property of dendritic river networks and that these relationships are established on the undissected, lowland margins outside mountain ranges and are progressively incorporated and quenched into uplifted topography during range widening.Thus, we suggest that the large-scale geometry of drainage networks in mountain ranges is mainly antecedent to erosion.We propose a model in which the largescale drainage geometry is controlled mainly by the geometrical properties of the undissected surfaces (in particular, the ratio of the regional slope to the local slope related to roughness) over which rivers are £owing before uplift, and is therefore independent of climate and tectonics.

Many fold-and-thrust belts are dominated by crustal scale folding that exhibit fairly regular fold spacing. Such is the case of the southern Fars region in the Zagros Mountains, where fold spacing shows a normal distribution around a dominant wavelength of 14 Km ± 3Km, while having a wide variability of length to wavelength ratio . So far it is not fully clear to which extend this is consistent with a crustal-scale folding instability.

Thin-skinned fold-and-thrust belts are generally considered as the result of contractional deformation of a sedimentary succession over a weak décollement layer. The resulting surface expression frequently consists of anticlines and synclines spaced in a fairly regular manner. It is thus tempting to use this spacing along with other geological constraints to obtain insights into the dynamics and rheology of the crust on geological time scales. Here we use the Zagros Mountains of Iran as a case study, as it is one of the most spectacular, well-studied thin-skinned fold-andthrust belts in the world. Both analytical and numerical models are employed to study what controls fold spacing and under what conditions folding dominates over thrusting. The models show that if only a single basal décollement layer is present underneath a brittle sedimentary cover, deformation is dominated by thrusting, which is inconsistent with the data of the Zagros fold belt. If we instead take into account additional décollement layers that have been documented in the fi eld, a switch in deformation mode occurs and crustal-scale folding is obtained with the correct spacing and time scales. We show that fold spacing can be used to constrain the friction angle of the crust, which is ~5°° in the Zagros fold belt. This implies that on geological time scales, the upper crust is signifi cantly weaker than previously thought, possibly due to the effect of fl uids.

We investigate the influence of initial conditions of slope and surface roughness on the shape 15 (length to width aspect ratio) of incipient drainage basins in numerical experiments of simple 16 tilted surfaces using the CASCADE code of landscape evolution. Comparison with data on the 17 shape of river basins in nature show that simple rules of the steepest descent routing of water 18 are sufficient to account for a natural range of incipient drainage basin shape, independently of 19 the erosion processes at work. To produce numerical basins that respect the main aspect ratio 20 of natural drainage basins, one must use very low initial regional surface slopes of less than 1° 21 at the scale of the entire drainage basins, and a local roughness slope of less than 3° at the scale 22 of local surface irregularities. Numerical studies addressing real study cases may take advantage 23 Castelltort_Manuscript_R3.docx Click here to view linked References of the relation between local roughness and regional slope in order to produce catchment 24 aspect ratios similar to the natural studied cases. 25 26

The connection of the Ebro basin via the Ebro River to the Mediterranean Sea is supposed to have played a major role in the rejuvenation of relief of northern Spain and especially of the South Pyrenees from the Neogene by lowering the initial base level of the Ebro internal drainage area down to sea level. However, the timing and causes of this connection are still debated. A fundamental issue is whether the Ebro basin became connected to the Mediterranean before or after the Messinian salinity crisis? Morphological analysis and numerical modeling of landscape evolution show that this connection did not exist before the Messinian salinity crisis but is effective from the Pliocene because of progressive regressive erosion.

This work presents sedimentological observations and interpretations on three detailed sections of the Pliocene Yutengping/Ailiaochiao formations, deposited in the early stages of collision in Taiwan. Seven facies associations record paleoenvironments of deposition ranging from nearshore to lower offshore with a strong influence of tidal reworking, even in shelfal sub-tidal environments, and a pro-delta setting characterized by mass-flows. The association of shallow facies of the upper offshore to lower shoreface with pro-delta turbidite facies sourced in the orogen to the east suggests a peculiar setting in which turbidite deposition occurred below wave base but on the shelf, in water depths of probably less than 100 m. This adds to the examples of ''shallow turbidites" increasingly commonly found in foreland basins and challenges the classical view of a ''deep" early underfilled foreland basin. Time series analysis on tidal rhythmites allow us to identify a yearly signal in the form of periodic changes of sand-supply, energy and bioturbation that suggests a marked seasonality possibly affecting precipitation and sediment delivery as well as temperature. The Taiwan foreland basin may also present a potentially high-resolution record in shallow sediments of the early installation of monsoonal circulation patterns in east Asia. We confirm partly the paleogeography during the early stages of collision in Taiwan: the Chinese margin displayed a pronounced non-cylindrical geometry with a large basement promontory to the west in place of the modern Taiwan mountain range. Collision in Taiwan may have happened at once along the whole length of the modern mountain range, instead of progressively from north to south as classically considered.