Les bassins d'avant-chaîne s'édifient au front des chaînes à la suite d'une flexion d... more Les bassins d'avant-chaîne s'édifient au front des chaînes à la suite d'une flexion de la lithosphère continentale. L'étude comparée de différents bassins permet de mettre en évidence les paramètres qui influent très étroitement sur leur évolution et leur géométri
Résumé/Abstract In the Plio-Pleistocene foreland basin of western Taiwan, synorogenic formations ... more Résumé/Abstract In the Plio-Pleistocene foreland basin of western Taiwan, synorogenic formations accumulated due to the uplift of the Central Range. Lithofacies and depositional environments vary from North to South along the western Foothills. To the North, shallow ...
Sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithol... more Sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithology make
them appropriate to isolate the influence of uplift on drainage morphology. Along the northern coast of Sumba
Island, Indonesia, we investigated the correlations between landscape morphology and uplift rates, which
range from 0.02 to 0.6 mm·yr−1
. We studied eight morphometric indices at two scales: whole island
(~11,000 km2
) and within sequences of reefal terraces (~3000 km2
). At the latter scale, we extracted morphometric
indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific
ranges of uplift rates draining only the reefal terraces. Indices extracted from digital elevation models include
residual relief, incision, stream gradient indices (SL and ksn), the hypsometric integral, drainage area, mean relief,
and the shape factor. We find that SL, the hypsometric integral, mean relief and the shape factor of catchments
positively correlate with uplift rates, whereas incision, residual relief, and ksn do not. More precisely, we find
that only the areas that are uplifting at a rate faster than 0.3 mm·yr−1 can yield the extreme values for these indices,
implying that these extreme values are indicative of fast uplifting areas. However, the relationship is not
bivalent because any uplift rate can be associated with low values of the same indices. For all indices, the transient
conditions of the drainage influence the correlation with Pleistocene mean uplift rates, illustrating the necessity
to extract morphometric indices with an appropriate choice of catchment scale. This type of analysis helps to
identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift, allowing
for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates
in unstudied coastal zones.
Dans les régions à vitesses de déformations faibles à moyennes, l'évaluation des tendances évolut... more Dans les régions à vitesses de déformations faibles à moyennes, l'évaluation des tendances évolutives des reliefs passe par l'identification des failles actives et leur expression géomorphologique. L'utilisation d'indicateurs morphologiques et sédimentaires permet de reconstituer les stades de croissance et de dégradation des reliefs. Le segment nord de la faille de la Têt (F.T.N.) est un accident à forte signature morphologique s'exprimant par un escarpement orienté N080 o à N050 o E et long de 30 kilomètres. Les outils morphométriques adaptés à la détection des mouvements verticaux et le signal sédimentaire sont appliqués à la F.T.N. entre Prades et Ille-sur-Têt (Pyrénées-Orientales). Les marqueurs caractéristiques de son évolution sont la morphométrie des facettes triangulaires, des bassins versants et du réseau hydrographique ainsi que la stratigraphie des dépôts détritiques pliocènes. L'étude des lithofaciès et des séquences élémentaires pliocènes montre que la sédimentation est en étroite relation avec l'activité de la faille. La géométrie actuelle de la surface de remblaiement pliocène supérieur du bassin du Conflent, la position altitudinale des paléotalwegs et des ruptures sur le profil en long des cours d'eau montrent clairement que l'activité de faille s'estompe dès le Pliocène supérieur. L'approche multicritère (sédimentologie, structure et géomorphologie) montre que la F.T.N. n'est plus active au Pléistocène. L'escarpement de faille actuel est une ancienne structure exhumée révélée par l'érosion différentielle. Au Quaternaire, l'exhumation de l'escarpement et du remplissage pliocène est en relation avec le basculement de la marge du golfe du Lion.
ABSTRACT Sequences of Plio-Quaternary shorelines generated by sea-level cyclicity and tectonics m... more ABSTRACT Sequences of Plio-Quaternary shorelines generated by sea-level cyclicity and tectonics massively shape the coasts worldwide. Here, we compile a worldwide synthesis of sea-level changes for the following highstands : MIS 1, MIS 3, MIS5e, and MIS 11 and explore the relationships to regional geodynamics. We identified 896 sequences including the MIS 5e benchmark, out of which 177 also feature the highest Holocene shorelines, 6 where the elevation of the MIS 3 shorelines are known, and 40 including that of MIS 11 shorelines. We considered 8 main geodynamical contexts for a statistical analysis: passive margin (337 sites, 14 domains, U=0.06 ± 0.01 mm/a), hot spot chains (45 sites, 14 domains, U=0.02 ± 0.02 mm/a), rifts (45 sites, 2 domains, U=0.12 ± 0.02 mm/a), ridges (3 sites, 1 domain, U=0.14 ± 0.02 mm/a), transform plate boundaries (119 sites, 7 domains, U=0.25 ± 0.03 mm/a), intra-oceanic subductions (131 sites, 4 domains, U=0.43 ± 0.04 mm/a), continental subductions underneath oceanic plates (12 sites, 1 domain, U=0.54+/- 0.04 mm/a), oceanic subductions underneath continental plates (166 sites, 7 domains, U=0.06 ± 0.01 mm/a), intra-continental convergence (10 sites, 2 domains, U=1.47 ± 0.08 mm/a). Counter-intuitive is the fact that passive margin are ubiquitously uplifting, while tectonic segmentation is more important on active margins. Additionally, 511 sites document the elevation of the highest shoreline of the sequence, from which we extrapolate a minimum age of onset for the sequence (based on MIS 5e uplift rates). 99% (511 sites) were formed at least during Pliocene and/or Quaternary, showing that potentially more ancient records are either eroded or non-existent.
Abstract: The aim of this contribution is to show the styles of growing anticlines and the ways i... more Abstract: The aim of this contribution is to show the styles of growing anticlines and the ways in which they accommodate oblique convergence through proximal foreland basins and intramontane basins. The four natural examples of individual fault-related-folds are: the ...
1] At the NW corner of the Pacific region, just south of the Kamchatsky Peninsula, the northern t... more 1] At the NW corner of the Pacific region, just south of the Kamchatsky Peninsula, the northern tip of the Pacific plate subduction and associated volcanic arc interacts with the western end of the Aleutian-Komandorsky dextral transform plate boundary and associated arc. Study of both Holocene and Pleistocene sequences of uplifted marine terraces and also of fluvial drainage patterns on the Kamchatsky Peninsula allows us to highlight active tectonics produced by complex plate interaction. Our results show that the central eastern coast of the peninsula is currently divided into four different zones consisting in uplifted blocks associated with various uplift rates in front of a fold-and-thrust zone to the west. Our main tectonic benchmark-the altitude of the shoreline correlated to the Last Interglacial Maximum (Marine Isotopic Stage 5e)-yields late Pleistocene uplift rates ranging from 0.2 to 2.74 mm/yr. One of the main active faults bounding the coastal blocks is dextral and is interpreted as a prolongation of an offshore fault of the Aleutian-Komandorsky dextral transform plate boundary. We suggest that structures on the Kamchatsky Peninsula accommodate a part of the transform motion, but that mainly, the arc-continent collision of the Aleutian arc against Kamchatka produces a "bulldozer" effect on the Kamchatsky Peninsula. Citation: Pedoja, K., C. Authemayou, T. Pinegina, J. Bourgeois, M. Nexer, B. Delcaillau, and V. Regard (2013), "Arccontinent collision" of the Aleutian-Komandorsky arc into Kamchatka: Insight into Quaternary tectonic segmentation through Pleistocene marine terraces and morphometric analysis of fluvial drainage, Tectonics, 32, 827-842,
AbstractÐNumerous studies have shown that development of a forward breaking sequence in a thrust ... more AbstractÐNumerous studies have shown that development of a forward breaking sequence in a thrust belt is accompanied by reactivation of inner faults and development of break-back thrusts. The partitioning of shortening in the Outer and Lesser Himalayan thrust belt follows these rules. Tectonic and sedimentary relationships in this thrust belt exemplify out-of-sequence thrusts in the Lesser Himalayas and break-back imbricate fans close to the MBT (Main Boundary Thrust) and MDT (Main Dun Thrust) which are transported during their development above the Himalayan basal detachment. The displacement along a single splay of the imbricate fan of the MDT was >40 m, before abandonment and nucleation of a new inner splay. The development of the break-back imbricate fan is discontinuous in time. Furthermore, superimposition of ultracataclasite, pressure-solution cleavage, extensional crenulation cleavage and tension gashes in the fault zones suggests that the 40 m displacement occurred by discrete slip events, or most probably by a succession of several seismic/ aseismic deformations. These data require several scales of sequential displacement in the Outer and Lesser Himalayas consisting of forward propagation of the thrust system, out-of-sequence reactivation, break-back nucleation of thrust splays, and seismic/aseismic fault slip. Our ®ndings require an intermediate period of tectonism between the <1000 y earthquake cycle and the >500 Ka deformation of the accretionary sediments of the Himalayas. #
The Pakuashan anticline is uniquely suited for study of the forward and lateral growth of fault-r... more The Pakuashan anticline is uniquely suited for study of the forward and lateral growth of fault-related folds. The Pakuashan ridge development arises from the late Quaternary uplift of the most external thrust zone of the western foothills of Taiwan. From Kaoshiung to Taichung, recent and active westward thrusting occurs at the front of the foothills. The Pakuashan anticline, trending N 1508E in the northern part to N 0008 in the southern part, has been active throughout the Quaternary period. This activity is marked by geological structures, tectonic geomorphology and seismicity. A multisource and multiscale approach to study of the continental collision setting has been undertaken to combine tectonics, sedimentology and geomorphology. Studies of fracture patterns allow identification of two main features of stress orientations: a WNWrESE compression direction, and E-W and N-S extension directions. Quantitative geomorphic parameters have been used to define the morphotectonic evolution and to infer tectonic style along the mountain front. Geomorphic evidence provides significant information on the processes that govern lateral propagation of an active anticline. Quaternary terraces are uplifted, tilted and folded over the Pakuashan ridge. Drainage systems in areas of active compression give information on the thrust zone structures and their development. Steep drainage and high local relief indicate that the Pakuashan anticline forms a well-defined zone of high uplift, especially in the southern part. The two main controls on drainage in that area are rock strength in the hanging wall and propagation of the deformation towards the south. q 1998 Elsevier Science B.V. All rights reserved.
Comparison between numerical models and structural data is used for a better understanding of the... more Comparison between numerical models and structural data is used for a better understanding of the evolution of the Siwalik thrust belt of western Nepal. The numerical model involves discontinuities within a critical wedge model, a kinematic forward model of serial cross sections, and a linear diusion algorithm to simulate erosion and sedimentation. In western Nepal, large Piggy-back basins (Duns) are located above thick thrust sheets that involve more than 5500 m of the Neogene Siwalik Group, whereas Piggy-back basin sedimentation is less developed above thinner thrust sheets (4300 m thick). Numerical model results suggest that thrust sheet thickness and extension of wedge-top basins are both related to an increase of the basal de collement dip beneath the duns. The West Dang Transfer zone (WDTZ) is a N±NE trending tectonic lineament that limits the westward extent of the large Piggy-back basins of mid-western Nepal and is linked to a thickening of the Himalayan wedge eastward. The WDTZ also aects the seismotectonics pattern, the geometry of the thrust front, the lateral extent of Lesser Himalayan thrust sheets, and the subsidence of the foreland basin during middle Siwalik sedimentation. Numerical models suggest that the individualisation of the Piggy-back basins at the transition between the middle Siwalik and upper Siwaliks followed the deposition of the middle Siwaliks that induced a geometry of the foreland basin close to the critical taper. As WDTZ induces an E±W thickning of the Himalayan wedge, it could also induce a northward shift of the leading edge of the ductile deformation above the basal detachment in Greater Himalayas of far-western Nepal. Field data locally suggest episodic out-o-sequence thrusting in the frontal thrust belt of western Nepal, whereas numerical results suggests that episodic out-o sequence reactivation could be a general characteristic of the Himalayan wedge evolution often hidden by erosion. #
Les bassins d'avant-chaîne s'édifient au front des chaînes à la suite d'une flexion d... more Les bassins d'avant-chaîne s'édifient au front des chaînes à la suite d'une flexion de la lithosphère continentale. L'étude comparée de différents bassins permet de mettre en évidence les paramètres qui influent très étroitement sur leur évolution et leur géométri
Résumé/Abstract In the Plio-Pleistocene foreland basin of western Taiwan, synorogenic formations ... more Résumé/Abstract In the Plio-Pleistocene foreland basin of western Taiwan, synorogenic formations accumulated due to the uplift of the Central Range. Lithofacies and depositional environments vary from North to South along the western Foothills. To the North, shallow ...
Sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithol... more Sequences of coral reef terraces characterized by staircase morphologies and a homogeneous lithology make
them appropriate to isolate the influence of uplift on drainage morphology. Along the northern coast of Sumba
Island, Indonesia, we investigated the correlations between landscape morphology and uplift rates, which
range from 0.02 to 0.6 mm·yr−1
. We studied eight morphometric indices at two scales: whole island
(~11,000 km2
) and within sequences of reefal terraces (~3000 km2
). At the latter scale, we extracted morphometric
indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific
ranges of uplift rates draining only the reefal terraces. Indices extracted from digital elevation models include
residual relief, incision, stream gradient indices (SL and ksn), the hypsometric integral, drainage area, mean relief,
and the shape factor. We find that SL, the hypsometric integral, mean relief and the shape factor of catchments
positively correlate with uplift rates, whereas incision, residual relief, and ksn do not. More precisely, we find
that only the areas that are uplifting at a rate faster than 0.3 mm·yr−1 can yield the extreme values for these indices,
implying that these extreme values are indicative of fast uplifting areas. However, the relationship is not
bivalent because any uplift rate can be associated with low values of the same indices. For all indices, the transient
conditions of the drainage influence the correlation with Pleistocene mean uplift rates, illustrating the necessity
to extract morphometric indices with an appropriate choice of catchment scale. This type of analysis helps to
identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift, allowing
for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates
in unstudied coastal zones.
Dans les régions à vitesses de déformations faibles à moyennes, l'évaluation des tendances évolut... more Dans les régions à vitesses de déformations faibles à moyennes, l'évaluation des tendances évolutives des reliefs passe par l'identification des failles actives et leur expression géomorphologique. L'utilisation d'indicateurs morphologiques et sédimentaires permet de reconstituer les stades de croissance et de dégradation des reliefs. Le segment nord de la faille de la Têt (F.T.N.) est un accident à forte signature morphologique s'exprimant par un escarpement orienté N080 o à N050 o E et long de 30 kilomètres. Les outils morphométriques adaptés à la détection des mouvements verticaux et le signal sédimentaire sont appliqués à la F.T.N. entre Prades et Ille-sur-Têt (Pyrénées-Orientales). Les marqueurs caractéristiques de son évolution sont la morphométrie des facettes triangulaires, des bassins versants et du réseau hydrographique ainsi que la stratigraphie des dépôts détritiques pliocènes. L'étude des lithofaciès et des séquences élémentaires pliocènes montre que la sédimentation est en étroite relation avec l'activité de la faille. La géométrie actuelle de la surface de remblaiement pliocène supérieur du bassin du Conflent, la position altitudinale des paléotalwegs et des ruptures sur le profil en long des cours d'eau montrent clairement que l'activité de faille s'estompe dès le Pliocène supérieur. L'approche multicritère (sédimentologie, structure et géomorphologie) montre que la F.T.N. n'est plus active au Pléistocène. L'escarpement de faille actuel est une ancienne structure exhumée révélée par l'érosion différentielle. Au Quaternaire, l'exhumation de l'escarpement et du remplissage pliocène est en relation avec le basculement de la marge du golfe du Lion.
ABSTRACT Sequences of Plio-Quaternary shorelines generated by sea-level cyclicity and tectonics m... more ABSTRACT Sequences of Plio-Quaternary shorelines generated by sea-level cyclicity and tectonics massively shape the coasts worldwide. Here, we compile a worldwide synthesis of sea-level changes for the following highstands : MIS 1, MIS 3, MIS5e, and MIS 11 and explore the relationships to regional geodynamics. We identified 896 sequences including the MIS 5e benchmark, out of which 177 also feature the highest Holocene shorelines, 6 where the elevation of the MIS 3 shorelines are known, and 40 including that of MIS 11 shorelines. We considered 8 main geodynamical contexts for a statistical analysis: passive margin (337 sites, 14 domains, U=0.06 ± 0.01 mm/a), hot spot chains (45 sites, 14 domains, U=0.02 ± 0.02 mm/a), rifts (45 sites, 2 domains, U=0.12 ± 0.02 mm/a), ridges (3 sites, 1 domain, U=0.14 ± 0.02 mm/a), transform plate boundaries (119 sites, 7 domains, U=0.25 ± 0.03 mm/a), intra-oceanic subductions (131 sites, 4 domains, U=0.43 ± 0.04 mm/a), continental subductions underneath oceanic plates (12 sites, 1 domain, U=0.54+/- 0.04 mm/a), oceanic subductions underneath continental plates (166 sites, 7 domains, U=0.06 ± 0.01 mm/a), intra-continental convergence (10 sites, 2 domains, U=1.47 ± 0.08 mm/a). Counter-intuitive is the fact that passive margin are ubiquitously uplifting, while tectonic segmentation is more important on active margins. Additionally, 511 sites document the elevation of the highest shoreline of the sequence, from which we extrapolate a minimum age of onset for the sequence (based on MIS 5e uplift rates). 99% (511 sites) were formed at least during Pliocene and/or Quaternary, showing that potentially more ancient records are either eroded or non-existent.
Abstract: The aim of this contribution is to show the styles of growing anticlines and the ways i... more Abstract: The aim of this contribution is to show the styles of growing anticlines and the ways in which they accommodate oblique convergence through proximal foreland basins and intramontane basins. The four natural examples of individual fault-related-folds are: the ...
1] At the NW corner of the Pacific region, just south of the Kamchatsky Peninsula, the northern t... more 1] At the NW corner of the Pacific region, just south of the Kamchatsky Peninsula, the northern tip of the Pacific plate subduction and associated volcanic arc interacts with the western end of the Aleutian-Komandorsky dextral transform plate boundary and associated arc. Study of both Holocene and Pleistocene sequences of uplifted marine terraces and also of fluvial drainage patterns on the Kamchatsky Peninsula allows us to highlight active tectonics produced by complex plate interaction. Our results show that the central eastern coast of the peninsula is currently divided into four different zones consisting in uplifted blocks associated with various uplift rates in front of a fold-and-thrust zone to the west. Our main tectonic benchmark-the altitude of the shoreline correlated to the Last Interglacial Maximum (Marine Isotopic Stage 5e)-yields late Pleistocene uplift rates ranging from 0.2 to 2.74 mm/yr. One of the main active faults bounding the coastal blocks is dextral and is interpreted as a prolongation of an offshore fault of the Aleutian-Komandorsky dextral transform plate boundary. We suggest that structures on the Kamchatsky Peninsula accommodate a part of the transform motion, but that mainly, the arc-continent collision of the Aleutian arc against Kamchatka produces a "bulldozer" effect on the Kamchatsky Peninsula. Citation: Pedoja, K., C. Authemayou, T. Pinegina, J. Bourgeois, M. Nexer, B. Delcaillau, and V. Regard (2013), "Arccontinent collision" of the Aleutian-Komandorsky arc into Kamchatka: Insight into Quaternary tectonic segmentation through Pleistocene marine terraces and morphometric analysis of fluvial drainage, Tectonics, 32, 827-842,
AbstractÐNumerous studies have shown that development of a forward breaking sequence in a thrust ... more AbstractÐNumerous studies have shown that development of a forward breaking sequence in a thrust belt is accompanied by reactivation of inner faults and development of break-back thrusts. The partitioning of shortening in the Outer and Lesser Himalayan thrust belt follows these rules. Tectonic and sedimentary relationships in this thrust belt exemplify out-of-sequence thrusts in the Lesser Himalayas and break-back imbricate fans close to the MBT (Main Boundary Thrust) and MDT (Main Dun Thrust) which are transported during their development above the Himalayan basal detachment. The displacement along a single splay of the imbricate fan of the MDT was >40 m, before abandonment and nucleation of a new inner splay. The development of the break-back imbricate fan is discontinuous in time. Furthermore, superimposition of ultracataclasite, pressure-solution cleavage, extensional crenulation cleavage and tension gashes in the fault zones suggests that the 40 m displacement occurred by discrete slip events, or most probably by a succession of several seismic/ aseismic deformations. These data require several scales of sequential displacement in the Outer and Lesser Himalayas consisting of forward propagation of the thrust system, out-of-sequence reactivation, break-back nucleation of thrust splays, and seismic/aseismic fault slip. Our ®ndings require an intermediate period of tectonism between the <1000 y earthquake cycle and the >500 Ka deformation of the accretionary sediments of the Himalayas. #
The Pakuashan anticline is uniquely suited for study of the forward and lateral growth of fault-r... more The Pakuashan anticline is uniquely suited for study of the forward and lateral growth of fault-related folds. The Pakuashan ridge development arises from the late Quaternary uplift of the most external thrust zone of the western foothills of Taiwan. From Kaoshiung to Taichung, recent and active westward thrusting occurs at the front of the foothills. The Pakuashan anticline, trending N 1508E in the northern part to N 0008 in the southern part, has been active throughout the Quaternary period. This activity is marked by geological structures, tectonic geomorphology and seismicity. A multisource and multiscale approach to study of the continental collision setting has been undertaken to combine tectonics, sedimentology and geomorphology. Studies of fracture patterns allow identification of two main features of stress orientations: a WNWrESE compression direction, and E-W and N-S extension directions. Quantitative geomorphic parameters have been used to define the morphotectonic evolution and to infer tectonic style along the mountain front. Geomorphic evidence provides significant information on the processes that govern lateral propagation of an active anticline. Quaternary terraces are uplifted, tilted and folded over the Pakuashan ridge. Drainage systems in areas of active compression give information on the thrust zone structures and their development. Steep drainage and high local relief indicate that the Pakuashan anticline forms a well-defined zone of high uplift, especially in the southern part. The two main controls on drainage in that area are rock strength in the hanging wall and propagation of the deformation towards the south. q 1998 Elsevier Science B.V. All rights reserved.
Comparison between numerical models and structural data is used for a better understanding of the... more Comparison between numerical models and structural data is used for a better understanding of the evolution of the Siwalik thrust belt of western Nepal. The numerical model involves discontinuities within a critical wedge model, a kinematic forward model of serial cross sections, and a linear diusion algorithm to simulate erosion and sedimentation. In western Nepal, large Piggy-back basins (Duns) are located above thick thrust sheets that involve more than 5500 m of the Neogene Siwalik Group, whereas Piggy-back basin sedimentation is less developed above thinner thrust sheets (4300 m thick). Numerical model results suggest that thrust sheet thickness and extension of wedge-top basins are both related to an increase of the basal de collement dip beneath the duns. The West Dang Transfer zone (WDTZ) is a N±NE trending tectonic lineament that limits the westward extent of the large Piggy-back basins of mid-western Nepal and is linked to a thickening of the Himalayan wedge eastward. The WDTZ also aects the seismotectonics pattern, the geometry of the thrust front, the lateral extent of Lesser Himalayan thrust sheets, and the subsidence of the foreland basin during middle Siwalik sedimentation. Numerical models suggest that the individualisation of the Piggy-back basins at the transition between the middle Siwalik and upper Siwaliks followed the deposition of the middle Siwaliks that induced a geometry of the foreland basin close to the critical taper. As WDTZ induces an E±W thickning of the Himalayan wedge, it could also induce a northward shift of the leading edge of the ductile deformation above the basal detachment in Greater Himalayas of far-western Nepal. Field data locally suggest episodic out-o-sequence thrusting in the frontal thrust belt of western Nepal, whereas numerical results suggests that episodic out-o sequence reactivation could be a general characteristic of the Himalayan wedge evolution often hidden by erosion. #
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Papers by B. Delcaillau
them appropriate to isolate the influence of uplift on drainage morphology. Along the northern coast of Sumba
Island, Indonesia, we investigated the correlations between landscape morphology and uplift rates, which
range from 0.02 to 0.6 mm·yr−1
. We studied eight morphometric indices at two scales: whole island
(~11,000 km2
) and within sequences of reefal terraces (~3000 km2
). At the latter scale, we extracted morphometric
indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific
ranges of uplift rates draining only the reefal terraces. Indices extracted from digital elevation models include
residual relief, incision, stream gradient indices (SL and ksn), the hypsometric integral, drainage area, mean relief,
and the shape factor. We find that SL, the hypsometric integral, mean relief and the shape factor of catchments
positively correlate with uplift rates, whereas incision, residual relief, and ksn do not. More precisely, we find
that only the areas that are uplifting at a rate faster than 0.3 mm·yr−1 can yield the extreme values for these indices,
implying that these extreme values are indicative of fast uplifting areas. However, the relationship is not
bivalent because any uplift rate can be associated with low values of the same indices. For all indices, the transient
conditions of the drainage influence the correlation with Pleistocene mean uplift rates, illustrating the necessity
to extract morphometric indices with an appropriate choice of catchment scale. This type of analysis helps to
identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift, allowing
for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates
in unstudied coastal zones.
them appropriate to isolate the influence of uplift on drainage morphology. Along the northern coast of Sumba
Island, Indonesia, we investigated the correlations between landscape morphology and uplift rates, which
range from 0.02 to 0.6 mm·yr−1
. We studied eight morphometric indices at two scales: whole island
(~11,000 km2
) and within sequences of reefal terraces (~3000 km2
). At the latter scale, we extracted morphometric
indices for 15 individual catchments draining mostly the reefal terraces and for 30 areas undergoing specific
ranges of uplift rates draining only the reefal terraces. Indices extracted from digital elevation models include
residual relief, incision, stream gradient indices (SL and ksn), the hypsometric integral, drainage area, mean relief,
and the shape factor. We find that SL, the hypsometric integral, mean relief and the shape factor of catchments
positively correlate with uplift rates, whereas incision, residual relief, and ksn do not. More precisely, we find
that only the areas that are uplifting at a rate faster than 0.3 mm·yr−1 can yield the extreme values for these indices,
implying that these extreme values are indicative of fast uplifting areas. However, the relationship is not
bivalent because any uplift rate can be associated with low values of the same indices. For all indices, the transient
conditions of the drainage influence the correlation with Pleistocene mean uplift rates, illustrating the necessity
to extract morphometric indices with an appropriate choice of catchment scale. This type of analysis helps to
identify the morphometric indices that are most useful for tectonic analysis in areas of unknown uplift, allowing
for easy identification of short spatial variations of uplift rate and detection of areas with relatively fast uplift rates
in unstudied coastal zones.