v1. Three ECHAM5-wiso model experiments for European region. For the first experiment (Europe_PI.nc), boundary conditions are set as pre-industrial and are identical to those in Botsyun et al., 2020. We also conducted two experiments with Middle Miocene boundary conditions reflecting two pCO2 settings (278 ppm and 450 ppm; Europe_Mio_278.nc and Europe_Mio_450.nc experiments) within current estimates of the Middle Miocene pCO2. v2. Global ECHAM5-wiso model experiments. geosp_simulations.nc contains surface geopotential for PI and Miocene experiments with modified Alpine topography and paleogeography.
v1. Three ECHAM5-wiso model experiments for European region. For the first experiment (Europe_PI.nc), boundary conditions are set as pre-industrial and are identical to those in Botsyun et al., 2020. We also conducted two experiments with Middle Miocene boundary conditions reflecting two pCO2 settings (278 ppm and 450 ppm; Europe_Mio_278.nc and Europe_Mio_450.nc experiments) within current estimates of the Middle Miocene pCO2. v2. Global ECHAM5-wiso model experiments. geosp_simulations.nc contains surface geopotential for PI and Miocene experiments with modified Alpine topography and paleogeography.
<p>Erosion and sediment transport in river catchments depend significantly on tectonics, climate and associated vegetation-cover. In this study, we used a numerical modelling approach to quantify the effects of temporal variations in precipitation rates and vegetation-cover over different uplift rates (0.05 mm a<sup>-1</sup>, 0.1 mm a<sup>-1</sup>, 0.2 mm a<sup>-1</sup>) and periodicities (23 kyr, 41 kyr and 100 kyr) of climate and associated vegetation-cover oscillations on erosion, sediment transport and deposition at catchment scale. Landlab, a landscape evolution modelling toolkit was modified to incorporate surface vegetation-cover dependent hillslope and coupled detachment-transport limited fluvial processes, weathering and soil production. The model was applied to (two) sites in the Coastal Chilean Cordillera namely Pan de Acuzar (~26), and La Campana (~33). These sites show a steep gradient in climate and vegetation density from arid climate and sparse vegetation density in northern latitudes to wetter temperate climate and abundant vegetation in the south, with granitic bedrock. The model simulations were run for 15 Myr to create steady-state topographies for both model domains. The sensitivity of these landscapes to changing climate and surface vegetation-cover was analyzed for 3 Myr for five transient model scenarios: (1) oscillating precipitation and constant vegetation cover, (2) constant precipitation and oscillating vegetation cover, (3) coupled oscillations in precipitation and vegetation cover, (4) coupled oscillations in precipitation and vegetation cover with variable periodicities, (5) coupled oscillations in precipitation and vegetation cover with variable rock uplift rates. The results suggest that erosion and sediment transport in densely vegetated landscapes are dominated by changes in precipitation, rather than vegetation-cover change in the southern study area (La Campana), as a result of higher amplitude of precipitation change i.e., 460 mm. Arid (northern) and sparsely vegetated landscapes are dominated by changes in vegetation density rather than precipitation, explained by higher erosion rates in periods with no surface vegetation-cover. Coupled oscillations in climate and vegetation cover suggested dampened influence of transient forcing on climate or vegetation-cover. The influence of periodicity of climate oscillations is significantly pronounced for shorter period (23 kyr oscillations) in terms of erosion rates. Results from different uplift rates suggested a positive linear relationship of topographic elevation and slope, erosion and sediment transport. However, sediment thickness decreases with increasing uplift rates, attributed to higher sediment flux on hillslopes due to linear dependence of slope on rock uplift rates. &#160;These results broadly demonstrate the implications of long term climate change with associated vegetation density on geomorphic processes shaping the topography.</p>
Abstract. Reconstructing Oligocene–Miocene paleoelevation contributes to our understanding of the evolutionary history of the European Alps and sheds light on geodynamic and Earth surface processes involved in the development of Alpine topography. Despite being one of the most intensively explored mountain ranges worldwide, constraints on the elevation history of the European Alps remain scarce. Here we present stable and clumped isotope measurements to provide a new paleoelevation estimate for the mid-Miocene (∼14.5 Ma) European Central Alps. We apply stable isotope δ–δ paleoaltimetry to near-sea-level pedogenic carbonate oxygen isotope (δ18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate hydrogen isotope (δD) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable (δ18O, δ13C) and clumped (Δ47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate δ18O values and Δ47 temperatures (30±5 ∘C) yield a near-sea-level precipitation δ18Ow value of -5.8±1.2 ‰ and, in conjunction with the high-Alpine phyllosilicate δD value of -14.6±0.3 ‰, suggest that the region surrounding the Simplon Fault Zone attained surface elevations of >4000 m no later than the mid-Miocene. Our near-sea-level δ18Ow estimate is supported by paleoclimate (iGCM ECHAM5-wiso) modeled δ18O values, which vary between −4.2 ‰ and −7.6 ‰ for the Northern Alpine Foreland Basin.
Abstract Upper crustal extensional structures range from steep normal faults to shallow‐dipping detachments. The relationship between extension and formation of synkinematic hanging wall basins including their relative timing is not well understood. The South Rhodope core complex, Southern Balkans, has experienced extension for >40 Ma leading to a number of extensional structures and Cenozoic sedimentary basins. We present new bedrock and basin detrital zircon and apatite (U‐Th‐Sm)/He ages from the Pirin and Rila Mountains and the Sandanski basin. Results identify three episodes of Cenozoic extension in SW Bulgaria accommodated by (1) the Eocene/Oligocene Mesta detachment; (2) the early to middle Miocene Gorno Spanchevo fault (circa 18–15 Ma), which is the northern prolongation of the Strymon low‐angle detachment; and (3) the late Miocene West Pirin fault (≤10 Ma). Detachment faulting on the Strymon fault accommodated tens of kilometers of ENE‐WSW extension and created ~1500 m topographic relief, but because the resulting hillslopes were gentle (≤10°), extension did not lead to enhanced footwall erosion or formation of a hanging wall basin. In contrast, the West Pirin normal fault resulted in mostly vertical motion of its footwall causing steep topography, rapid erosion, and formation of the synrift Sandanski basin. Digital topographic analysis of river channel profiles identifies the latest episodes of deformation including westward tilting of the Sandanski and Strymon basins and Quaternary N‐S extension. This study demonstrates that basin formation in the South Rhodope core complex is related to normal faulting postdating the main episode of crustal stretching by detachment faulting.
The potential structural controls on exhumation across the southern Peruvian Andes are not well understood, in part due to limited structural studies that co-locate with thermochronometric datasets. We integrate these two datasets and evaluate the relative contribution that fault geometry, magnitude, and shortening rate have on predicted cooling ages. Here we present a balanced cross-section constructed using new structural observations. This section, combined with existing thermochronometer data and a thermokinematic model, investigates the drivers of high exhumation and young canyon thermochronometric ages along the deeply incised Marcapata canyon in southern Peru. Together, these approaches constrain the timing and magnitude of exhumation in this portion of the southern Peruvian Andes and provide a mechanism for documenting how the internal architecture changes along strike. The balanced cross-section (oriented N30E) covers the Subandean Zone to the northeast, the Marcapata canyon on the eastern flank of the southern Peruvian Andes, and the Altiplano-Eastern Cordillera boundary to the southwest (13–18° S). Exhumation is constrained by four low-temperature thermochronometer systems, including apatite and zircon (U-Th)/He (AHe and ZHe, respectively) and fission-track (AFT and ZFT, respectively). The youngest AHe (∼1–3 Ma), AFT (∼3–7 Ma), ZHe (∼4–7 Ma), and ZFT (∼14–17 Ma) ages are located in the center and valley bottom of the Marcapata canyon. The thermokinematically modeled cross-section produces cooling ages determined by fault geometry and kinematics. Reset ZFT ages require burial of Ordovician rocks in excess of 5.5 km above the original 6.5 km depositional depth. We find that the ZFT and ZHe ages in the Eastern Cordillera are sensitive to the history and magnitude of burial, age and location of uplift, and canyon incision. Canyon incision is required to reproduce the youngest canyon thermochronometric ages while slow shortening rates from ∼10 Ma to Present are required to reproduce interfluve thermochronometric ages. Shortening is accommodated by basement faults that feed slip up through three different décollement levels before reaching the surface. The proposed stacked basement geometry sets the first-order cooling signal seen in modeled ages. We determined that the total shortening in this section from the Subandean Zone to the Altiplano is 147.5 km, similar to shortening estimates in an adjacent thermo-kinematically modeled section in the San Gabán canyon 50 km to the southeast. Both the ZHe and ZFT ages in the Marcapata section (4–5 and 14 Ma) are noticeably younger than cooling ages from the San Gabán section (16 and 29 Ma). The Marcapata section's higher magnitude of exhumation is due to a repetition of basement thrusts that continues to elevate the Eastern Cordillera while active deformation occurs in the Subandean Zone. The youngest thermochronometric ages in all four systems are co-located with the overlapping basement thrust geometry. This basement geometry, kinematic sequence of deformation, and canyon incision co-conspire to produce the young cooling ages observed in the Eastern Cordillera.
