Also at... https://doi.org/10.5194/esurf-8-221-2020 Tectonic from topography Tectonic from topography Active vs passive tectonic geomorphology Tectonic from topography Active vs passive tectonic geomorphology Hillslope gradient response I Potentially very high spatial density of information I But hillslope gradient response limited by threshold angle Sc Tectonics from fluvial and hillslope processes River profile response Figure 1 from Whittaker, A. C. (2012) How do landscapes record tectonics and climate? Lithosphere, 4, 160–164. I Scales with uplift rate over large range I Limitation from erodibility variations, knickpoints, structure of river networks Tectonics from fluvial and hillslope processes River profile response Hillslope gradient response Figure 2 from Ouimet et al. (2009) Beyond threshold hillslopes: Channel adjustment to base-level fall in tectonically active mountain ranges. Geology, 37(7), 579–5821 Figure 1 from Whittaker, A. C. (2012) How do landscapes record tectonics and climate? Lithosphere, 4, 160–164. Figure 5 from Burbank et al. (1996) Bedrock incision, rock uplift and threshold hillslopes in the northwestern Himalayas. Nature, 379(6565) I Potentially very high spatial density of I Scales with uplift rate over large range information I Limitation from erodibility variations, I But hillslope gradient response limited by knickpoints, structure of river networks threshold angle Sc Hillslope processes and response Insights from High-Resolution topographic analysis Hillslope topographic profile 0 0 1 1 2 s 2 s 2 Figure 6 from Hurst et al. (2012) KSc 1 2βEx 1 2βEx Using hilltop curvature to derive z(x) = @ln @ 1 + + A − 1 + + 1A the spatial distribution of erosion rates 2βE 2 KSc 2 KSc Journal of Geophysical Research, 117(F2), F02017 Non-dimensional form R 2CHT LH R∗ = E ∗ = Sc LH Sc 1 q 1 q R∗ = 1 + (E ∗)2 − ln 1 + 1 + (E ∗)2 − 1 : E ∗ 2 KCHT I Hilltop curvature CHT ) proxy for erosion rate : E = β I Possibility to retrieve tectonic information from hillslope morphology I Limited number of case studies so far Settings Alps and Provence Miocene and Pliocene sedimentary series Provence and SW Alps detrital sediments Digne Quaternary Aiglun Mirabeau Neogene Slow deformation Paleogene I Thrust France Cretaceous e SignificantAnticline axis seismic hazardon Jurassic I Les Mées Blé Triassic Gap Alpine units I e.g. 1909 Lambesc Earthquake External crystalline massifs Internal domain Puimichel Lambruissier Hercynian basement Plateau Sisteron Next slide e Oraison Ass Middle Durance Fault e Valensole Manosque c n Plateau a r u D Aix-en-Provence Croix Lake te Specific challenges for the identificationS of slow faultsVerdon under temperate climate Sea Mediterranean Settings Alps and Provence Miocene and Pliocene sedimentary series detrital sediments Digne Quaternary Aiglun Mirabeau Neogene Paleogene Thrust France Cretaceous e Anticline axis on Jurassic Les Mées Blé Triassic Gap Alpine units External crystalline massifs Internal domain Puimichel Lambruissier Hercynian basement Plateau Sisteron Next slide e Oraison Ass Middle Durance Fault e Valensole Manosque c n Plateau a r u D Aix-en-Provence Croix Lake te S Verdon Sea Mediterranean Settings N D l u Cana ra nce R an cu Puimichel Plateau re I Bléone • Uplifted Mio-Pliocene mollassic deposits 700 • Major depocenter of 800 the SW Alps A I Mées structure s s • Csup-Eocene basement e TWT to top of Oxfordian deformation (Pyrenean orogeny) • Possible Alpine reactivation Settings Puimichel Plateau ENE Pliocene N D l u Miocene Cana ra nce Upper Jurassic 1000 m Dogger - Lias Mées Structure Basement R an cu Puimichel Plateau re I Bléone • Uplifted Mio-Pliocene mollassic deposits 700 • Major depocenter of 800 the SW Alps A I Mées structure s s • Csup-Eocene basement e TWT to top of Oxfordian deformation (Pyrenean orogeny) • Possible Alpine reactivation Settings Sampling site Summit surface D ura nce Cross section Easily erodible R I anc conglomerates ure Pliocene relict I summit surface Major warping of the I surface (LiDAR data) Settings Viewing Sampling site direction Summit surface D ura nce Cross section R Easily erodible anc I ure conglomerates I Pliocene relict summit surface N S I Major warping of the Puimichel Plateau surface (LiDAR data) Les Mées Durance River Settings Sampling site Summit surface D ura nce Cross section Easily erodible R I anc conglomerates ure Pliocene relict I summit surface Major warping of the I surface (LiDAR data) FluvialI Channel parameters profiles ) θ and ksn (θref = 0:25) I Perron and Royden (2012) I Hilltops and flowlines ) R, LH and CHT I Hurst et al. (2012), Grieve et al. (2016), Clubb et al. (2017) Methods Hillslope parameters FluvialI Channel parameters profiles ) θ and ksn (θref = 0:25) I Perron and Royden (2012) I Hilltops and flowlines ) R, LH and CHT I Hurst et al. (2012), Grieve et al. (2016), Clubb et al. (2017) Methods Hillslope parameters FluvialI Channel parameters profiles ) θ and ksn (θref = 0:25) I Perron and Royden (2012) I Hilltops and flowlines ) R, LH and CHT I Hurst et al. (2012), Grieve et al. (2016), Clubb et al. (2017) Methods Hillslope parameters FluvialI Channel parameters profiles ) θ and ksn (θref = 0:25) I Perron and Royden (2012) Methods Hillslope parameters I Hilltops and flowlines ) R, LH and CHT I Hurst et al. (2012), Grieve et al. (2016), Clubb et al. (2017) I Channel profiles ) θ and ksn (θref = 0:25) I Perron and Royden (2012) Methods Hillslope parameters Fluvial parameters I Hilltops and flowlines ) R, LH and CHT I Hurst et al. (2012), Grieve et al. (2016), Clubb et al. (2017) Methods Hillslope parameters Fluvial parameters I Hilltops and flowlines ) R, LH and CHT I Channel profiles ) θ and ksn (θref = 0:25) Hurst et al. (2012), Grieve et al. (2016), I I Perron and Royden (2012) Clubb et al. (2017) ∗ I Same pattern for E (= 2CHT LH =Sc ) I 2-fold increase in hilltop curvature (CHT ) I Slight increase in relief (R), length (LH ) ∼ stable Results Spatial distribution of hillslope morphological properties I A lot of scatter fluvial metrics (slight ksn increase) Channel properties South North ∗ I Same pattern for E (= 2CHT LH =Sc ) I 2-fold increase in hilltop curvature (CHT ) Results Spatial distribution of hillslope morphological properties I Slight increase in relief (R), length (LH ) ∼ stable Hillslope dimensions I A lot of scatter fluvial metrics (slight ksn increase) Channel properties South North ∗ I Same pattern for E (= 2CHT LH =Sc ) Results Spatial distribution of hillslope morphological properties I 2-fold increase in hilltop curvature (CHT ) Hilltop curvature I Slight increase in relief (R), length (LH ) ∼ stable Hillslope dimensions I A lot of scatter fluvial metrics (slight ksn increase) Channel properties South North Results Spatial distribution of hillslope morphological properties ∗ I Same pattern for E (= 2CHT LH =Sc ) Non-dimensional erosion rate I 2-fold increase in hilltop curvature (CHT ) Hilltop curvature I Slight increase in relief (R), length (LH ) ∼ stable Hillslope dimensions I A lot of scatter fluvial metrics (slight ksn increase) Channel properties South North I Globally consistent with available geological data I Steep structure reactivated inside the basement I Slip rate? Results Inversion of Non-Dimensional Erosion rate (E ∗) pattern to constrain fault geometry ● ● I Single planar dislocation into a ) − ● ● ● E* ( ● semi-infinite elastic half-space ● ● ● ● ● ● MCMC inversion to retrieve dislocation I 0 4 8 12 parameters I Horizontal position I Depth 700 800 I Dip angle (m) Elevation Top of Oxfordian black marls Twt (s) Twt 1.1 1.0 0.9 0.8 0.7 Pliocene Miocene Jurassic Depth (km) Basement 4 2 0 0 2 4 6 8 10 12 Horizontal distance (km) Results Inversion of Non-Dimensional Erosion rate (E ∗) pattern to constrain fault geometry ● ● I Single planar dislocation into a ) Tip position (km) − ● ● ● E* ( ● semi-infinite elastic half-space ● ● ● ● ● ● MCMC inversion to retrieve dislocation best fit model I 0 4 8 12 parameters 0 5 10 15 20 I Horizontal position I Depth 700 800 Elevation (m) Elevation I Dip angle Tip depth (km) 0 2 4 6 8 10 Top of Oxfordian black marls I Globally consistent with available geological data Twt (s) Twt I Steep structure reactivated inside the Dip angle (°) 0 20 40 60 80 basement 1.1 1.0 0.9 0.8 0.7 Pliocene Miocene Slip rate? Jurassic I ● Fault length (km) Depth (km) Basement 0 2 4 6 8 10 4 2 0 0 2 4 6 8 10 12 Horizontal distance (km) I No apparent inheritance from pre-deposition history I Consistent denudation signal from 10Be and 26Al Denudation rates 10Be and 26Al concentrations at hilltop sites I No apparent inheritance from pre-deposition history I Consistent denudation signal from 10Be and 26Al Denudation rates 10Be and 26Al concentrations at hilltop sites Denudation rates 10Be and 26Al concentrations at hilltop sites 1:1 Steady state denudation Constant exposure I No apparent inheritance from pre-deposition history I Consistent denudation signal from 10Be and 26Al Denudation rates vs hillslope properties Converting CHT into denudation rates A B C 2 /a 2 /a K Anthropogenic H disturbance 100 0.01 m 0.006 m H K P O M M H 2 /a O K 0.004 m G M O 80 100 120 140 I F I 60 80 G N R I F N 2 /a F R 0.002 m R Denudation rate (mm/ka) Denudation rate Denudation rate (mm/ka) Denudation rate N ~20 mm/ka 20 40 60 G 20 40 0.010 0.015 0.020 0.025 0.030 0.035 0.040 0.000 0.002 0.004 0.006 0.008 0.010 0 2 4 6 8 10 12 2 Hilltop curvature CHT (1/m) Diffusion coefficient (m /a) Horizontal distance (km) KCHT I At shallow slopes near hilltops : E = β I ∼20 mm/ka differential denudation across the transect I Similar amplitude for differential uplift and fault slip rate? Conclusions I HR hillslope morphology analysis allows to decipher denudation and uplift patterns (Hurst et al., 2013, Grieve et al., 2016) I High potential in slow deformation areas I Higher spatial resolving power than approaches based on river profiles analysis I Blind thrust rooted in the basement, folding the Cenozoic cover of the N.