TY - JOUR A1 - Ballato, Paolo A1 - Brune, Sascha A1 - Strecker, Manfred T1 - Sedimentary loading–unloading cycles and faulting in intermontane basins BT - Insights from numerical modeling and field observations in the NW Argentine Andes JF - Earth & planetary science letters N2 - The removal, redistribution, and transient storage of sediments in tectonically active mountain belts is thought to exert a first-order control on shallow crustal stresses, fault activity, and hence on the spatiotemporal pattern of regional deformation processes. Accordingly, sediment loading and unloading cycles in intermontane sedimentary basins may inhibit or promote intrabasinal faulting, respectively, but unambiguous evidence for this potential link has been elusive so far. Here we combine 2D numerical experiments that simulate contractional deformation in a broken-foreland setting (i.e., a foreland where shortening is diachronously absorbed by spatially disparate, reverse faults uplifting basement blocks) with field data from intermontane basins in the NW Argentine Andes. Our modeling results suggest that thicker sedimentary fills (>0.7-1.0 km) may suppress basinal faulting processes, while thinner fills (<0.7 km) tend to delay faulting. Conversely, the removal of sedimentary loads via fluvial incision and basin excavation promotes renewed intrabasinal faulting. These results help to better understand the tectono-sedimentary history of intermontane basins that straddle the eastern border of the Andean Plateau in northwestern Argentina. For example, the Santa Maria and the Humahuaca basins record intrabasinal deformation during or after sediment unloading, while the Quebrada del Toro Basin reflects the suppression of intrabasinal faulting due to loading by coarse conglomerates. We conclude that sedimentary loading and unloading cycles may exert a fundamental control on spatiotemporal deformation patterns in intermontane basins of tectonically active broken forelands. (C) 2018 Elsevier B.V. All rights reserved. KW - sedimentary loading and unloading cycles KW - intermontane basins KW - intrabasinal faulting KW - Argentinean broken foreland KW - 2D numerical experiments KW - Andes Y1 - 2019 U6 - https://doi.org/10.1016/j.epsl.2018.10.043 SN - 0012-821X SN - 1385-013X VL - 506 SP - 388 EP - 396 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Cifelli, Francesca A1 - Heidarzadeh, Ghasem A1 - Ghassemi, Mohammad R. A1 - Wickert, Andrew D. A1 - Hassanzadeh, Jamshid A1 - Dupont-Nivet, Guillaume A1 - Balling, Philipp A1 - Sudo, Masafumi A1 - Zeilinger, Gerold A1 - Schmitt, Axel K. A1 - Mattei, Massimo A1 - Strecker, Manfred T1 - Tectono-sedimentary evolution of the northern Iranian Plateau: insights from middle-late Miocene foreland-basin deposits JF - Basin research N2 - Sedimentary basins in the interior of orogenic plateaus can provide unique insights into the early history of plateau evolution and related geodynamic processes. The northern sectors of the Iranian Plateau of the Arabia-Eurasia collision zone offer the unique possibility to study middle-late Miocene terrestrial clastic and volcaniclastic sediments that allow assessing the nascent stages of collisional plateau formation. In particular, these sedimentary archives allow investigating several debated and poorly understood issues associated with the long-term evolution of the Iranian Plateau, including the regional spatio-temporal characteristics of sedimentation and deformation and the mechanisms of plateau growth. We document that middle-late Miocene crustal shortening and thickening processes led to the growth of a basement-cored range (Takab Range Complex) in the interior of the plateau. This triggered the development of a foreland-basin (Great Pari Basin) to the east between 16.5 and 10.7Ma. By 10.7Ma, a fast progradation of conglomerates over the foreland strata occurred, most likely during a decrease in flexural subsidence triggered by rock uplift along an intraforeland basement-cored range (Mahneshan Range Complex). This was in turn followed by the final incorporation of the foreland deposits into the orogenic system and ensuing compartmentalization of the formerly contiguous foreland into several intermontane basins. Overall, our data suggest that shortening and thickening processes led to the outward and vertical growth of the northern sectors of the Iranian Plateau starting from the middle Miocene. This implies that mantle-flow processes may have had a limited contribution toward building the Iranian Plateau in NW Iran. Y1 - 2017 U6 - https://doi.org/10.1111/bre.12180 SN - 0950-091X SN - 1365-2117 VL - 29 SP - 417 EP - 446 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Ballato, Paolo A1 - Cruciani, G. A1 - Dalconi, M. C. A1 - Fabbri, B. A1 - Macchiarola, M. T1 - Mineralogical study of historical bricks from the Great Palace of the Byzantine Emperors in Istanbul based on powder X-ray diffraction data N2 - This study concerns the Quantitative Phase Analysis (QPA) of historical bricks coming from the complex of the Great Palace of the Byzantine Emperors in Istanbul. The studied samples are characterised by different chemical compositions (low and high calcium content), variable firing temperatures and different amounts of soluble salts as damage products. In the low-Ca samples, the decrease of the phyllosilicate content (from 23.4 to 6.9 wt%) is associated to the increase of the amorphous fraction (from 24 to 48%). This clear negative correlation between the phyllosilicate content and the amorphous fraction indicates that in low-Ca systems vitrification processes are overwhelming with respect to nucleation and recrystallisation processes. By contrast, high-Ca samples present newly formed Ca(Mg) silicates (diopside from 5.7 to 27.2%; anorthite from 1.4 to 8.7%) and aluminium silicates (gehlenite only in two samples, 6.2 and 7.7%) associated to the decrease of quartz (from 27.7 to 11.5%), phyllosilicate (from 6.5% until complete break down) and amorphous (from 30 to 14%) phase fractions. These findings support the role played by the CaO(MgO) content deriving from carbonates decomposition which reacts with Al2O3 and SiO2 oxides from dehydroxylated clay minerals and quartz grains. The above results have been obtained by X-ray powder diffraction data using the combined Rietveld refinement - internal standard method in order to estimate both the crystalline and the amorphous phase fractions. In addition, the coexistence of two distinct plagioclases in high-Ca samples was modelled as follows: a primary albite, which tends to incorporate Ca during the firing process as demonstrated by the increasing of gamma crystallographic angle, and a newly formed anorthite. Finally, by difference between the X-ray fluorescence data and the chemical compositions inferred by QPA, it proved possible to roughly estimate the residual chemical composition attributable to the amorphous fraction. On the basis of our data, we believe that Rietveld refinement combined with the internal standard method represent a powerful tool to better characterise complex polycrystalline and amorphous mixture as in the case of historical bricks Y1 - 2005 SN - 0935-1221 ER - TY - JOUR A1 - Ballato, Paolo A1 - Landgraf, Angela A1 - Schildgen, Taylor F. A1 - Stockli, Daniel F. A1 - Fox, Matthew A1 - Ghassemi, Mohammad R. A1 - Kirby, Eric A1 - Strecker, Manfred T1 - The growth of a mountain belt forced by base-level fall: Tectonics and surface processes during the evolution of the Alborz Mountains, N Iran JF - Earth & planetary science letters N2 - The idea that climatically modulated erosion may impact orogenic processes has challenged geoscientists for decades. Although modeling studies and physical calculations have provided a solid theoretical basis supporting this interaction, to date, field-based work has produced inconclusive results. The central-western Alborz Mountains in the northern sectors of the Arabia-Eurasia collision zone constitute a promising area to explore these potential feedbacks. This region is characterized by asymmetric precipitation superimposed on an orogen with a history of spatiotemporal changes in exhumation rates, deformation patterns, and prolonged, km-scale base-level changes. Our analysis suggests that despite the existence of a strong climatic gradient at least since 17.5 Ma, the early orogenic evolution (from similar to 36 to 9-6 Ma) was characterized by decoupled orographic precipitation and tectonics. In particular, faster exhumation and sedimentation along the more arid southern orogenic flank point to a north-directed accretionary flux and underthrusting of Central Iran. Conversely, from 6 to 3 Ma, erosion rates along the northern orogenic flank became higher than those in the south, where they dropped to minimum values. This change occurred during a similar to 3-Myr-long, km-scale base-level lowering event in the Caspian Sea. We speculate that mass redistribution processes along the northern flank of the Alborz and presumably across all mountain belts adjacent to the South Caspian Basin and more stable areas of the Eurasian plate increased the sediment load in the basin and ultimately led to the underthrusting of the Caspian Basin beneath the Alborz Mountains. This underthrusting in turn triggered a new phase of northward orogenic expansion, transformed the wetter northern flank into a new pro-wedge, and led to the establishment of apparent steady-state conditions along the northern orogenic flank (i.e., rock uplift equal to erosion rates). Conversely, the southern mountain front became the retro-wedge and experienced limited tectonic activity. These observations overall raise the possibility that mass-distribution processes during a pronounced erosion phase driven by base-level changes may have contributed to the inferred regional plate-tectonic reorganization of the northern Arabia-Eurasia collision during the last similar to 5 Ma. (C) 2015 Elsevier B.V. All rights reserved. KW - orogenic processes KW - surface processes KW - base-level fall KW - erosion KW - rock uplift KW - knickpoints Y1 - 2015 U6 - https://doi.org/10.1016/j.epsl.2015.05.051 SN - 0012-821X SN - 1385-013X VL - 425 SP - 204 EP - 218 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ballato, Paolo A1 - Parra, Mauricio A1 - Schildgen, Taylor F. A1 - Dunkl, I. A1 - Yildirim, C. A1 - Özsayin, Erman A1 - Sobel, Edward A1 - Echtler, H. A1 - Strecker, Manfred T1 - Multiple exhumation phases in the Central Pontides (N Turkey) BT - new temporal constraints on Major geodynamic changes associated with the closure of the Neo-Tethys Ocean JF - Tectonics N2 - The Central Pontides of N Turkey represents a mobile orogenic belt of the southern Eurasian margin that experienced several phases of exhumation associated with the consumption of different branches of the Neo-Tethys Ocean and the amalgamation of continental domains. Our new low-temperature thermochronology data help to constrain the timing of these episodes, providing new insights into associated geodynamic processes. In particular, our data suggest that exhumation occurred at (1) similar to 110 to 90Ma, most likely during tectonic accretion and exhumation of metamorphic rocks from the subduction zone; (2) from similar to 60 to 40Ma, during the collision of the Kirehir and Anatolide-Tauride microcontinental domains with the Eurasian margin; (3) from similar to 0 to 25Ma, either during the early stages of the Arabia-Eurasia collision (soft collision) when the Arabian passive margin reached the trench, implying 70 to 530km of subduction of the Arabian passive margin, or during a phase of trench advance predating hard collision at similar to 20Ma; and (4) similar to 11Ma to the present, during transpression associated with the westward motion of Anatolia. Our findings document the punctuated nature of fault-related exhumation, with episodes of fast cooling followed by periods of slow cooling or subsidence, the role of inverted normal faults in controlling the Paleogene exhumation pattern, and of the North Anatolian Fault in dictating the most recent pattern of exhumation. KW - thermal modeling KW - Central Pontides KW - Arabia-Eurasia collision KW - trench advance KW - Anatolia westward motion KW - inversion tectonics Y1 - 2018 U6 - https://doi.org/10.1029/2017TC004808 SN - 0278-7407 SN - 1944-9194 VL - 37 IS - 6 SP - 1831 EP - 1857 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ballato, Paolo A1 - Stockli, Daniel F. A1 - Ghassemi, Mohammad R. A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Hassanzadeh, Jamshid A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Accommodation of transpressional strain in the Arabia-Eurasia collision zone new constraints from (U-Th)/He thermochronology in the Alborz mountains, north Iran JF - Tectonics N2 - The Alborz range of N Iran provides key information on the spatiotemporal evolution and characteristics of the Arabia-Eurasia continental collision zone. The southwestern Alborz range constitutes a transpressional duplex, which accommodates oblique shortening between Central Iran and the South Caspian Basin. The duplex comprises NW-striking frontal ramps that are kinematically linked to inherited E-W-striking, right-stepping lateral to obliquely oriented ramps. New zircon and apatite (U-Th)/He data provide a high-resolution framework to unravel the evolution of collisional tectonics in this region. Our data record two pulses of fast cooling associated with SW-directed thrusting across the frontal ramps at similar to 18-14 and 9.5-7.5 Ma, resulting in the tectonic repetition of a fossil zircon partial retention zone and a cooling pattern with a half U-shaped geometry. Uniform cooling ages of similar to 7-6 Ma along the southernmost E-W striking oblique ramp and across its associated NW-striking frontal ramps suggests that the ramp was reactivated as a master throughgoing, N-dipping thrust. We interpret this major change in fault kinematics and deformation style to be related to a change in the shortening direction from NE to N/NNE. The reduction in the obliquity of thrusting may indicate the termination of strike-slip faulting (and possibly thrusting) across the Iranian Plateau, which could have been triggered by an increase in elevation. Furthermore, we suggest that similar to 7-6-m.y.-old S-directed thrusting predated inception of the westward motion of the South Caspian Basin. Citation: Ballato, P., D. F. Stockli, M. R. Ghassemi, A. Landgraf, M. R. Strecker, J. Hassanzadeh, A. Friedrich, and S. H. Tabatabaei (2012), Accommodation of transpressional strain in the Arabia-Eurasia collision zone: new constraints from (U-Th)/He thermochronology in the Alborz mountains. Y1 - 2013 U6 - https://doi.org/10.1029/2012TC003159 SN - 0278-7407 VL - 32 IS - 1 SP - 1 EP - 18 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Ballato, Paolo A1 - Strecker, Manfred T1 - Assessing tectonic and climatic causal mechanisms in foreland-basin stratal architecture: insights from the Alborz Mountains, northern Iran JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - The southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3-km-thick sequence of Miocene sedimentary rocks, constituting three basin-wde coarsening-upward units spanning a period of 10(6)years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment-provenance data to characterize the relationships between tectonically-generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S>1, typical of each basal unit (17.5-16.0, 13.8-13.1 and 10.3-9.6Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S<1 (13.8 and 13.8-11Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra-basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S<1, at 11-10.3Ma and 9-6-7.6Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically-induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. KW - sediment supply KW - climatic and tectonic forcing KW - accommodation-space KW - sediment-supply ratio (A /S) KW - foreland-basin stratigraphy KW - Alborz Mountains Y1 - 2014 U6 - https://doi.org/10.1002/esp.3480 SN - 0197-9337 SN - 1096-9837 VL - 39 IS - 1 SP - 110 EP - 125 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Ballato, Paolo A1 - Uba, Cornelius Eji A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Sudo, Masafumi A1 - Stockli, Daniel F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran JF - Geological Society of America bulletin N2 - A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone. Y1 - 2011 U6 - https://doi.org/10.1130/B30091.1 SN - 0016-7606 VL - 123 IS - 1-2 SP - 106 EP - 131 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Cifelli, Francesca A1 - Ballato, Paolo A1 - Alimohammadian, Habib A1 - Sabouri, Jafar A1 - Mattei, Massimo T1 - Tectonic magnetic lineation and oroclinal bending of the Alborz range: Implications on the Iran-Southern Caspian geodynamics JF - Tectonics N2 - In this study we use the anisotropy of magnetic susceptibility (AMS) and paleomagnetic data for deciphering the origin of magnetic lineation in weakly deformed sedimentary rocks and for evaluating oroclinal processes within the Arabia-Eurasia collision zone. In particular, we have analyzed the Miocene Upper Red Formation (URF) from the outer curved front of the southern Central Alborz Mountains of north Iran, to test for the first time with paleomagnetic data the origin (primary versus secondary) of this orogenic arc. AMS data document the existence of a magnetic lineation parallel to the orientation of the major tectonic structures, which vary along strike from WNW to ENE. These directions are highly oblique to the paleoflow directions and hence suggest that the magnetic lineation in the URF was produced by compressional deformation during layer-parallel shortening. In addition, our paleomagnetic data document clockwise and anticlockwise rotations along vertical axis for the western and eastern sectors of the Central Alborz Mountains, respectively. Combined, our results suggest that the orogen represents an orocline, which formed not earlier than circa 7.6Ma most likely through bending processes caused by the relative motion between the rigid crustal blocks of the collision zone. Moreover, our study provides new insights into the Iran-Southern Caspian Basin kinematic evolution suggesting that the present-day SW motion of the South Caspian Basin with respect to Central Iran postdates oroclinal bending and hence cannot be as old as late Miocene to early Pliocene but a rather recent configuration (i.e., 3 to <1Ma). KW - oroclinal bending KW - magnetic fabric KW - Alborz range KW - Southern Caspian Basin Y1 - 2015 U6 - https://doi.org/10.1002/2014TC003626 SN - 0278-7407 SN - 1944-9194 VL - 34 IS - 1 SP - 116 EP - 132 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Donner, Stefanie A1 - Ghods, Abdolreza A1 - Krüer, Frank A1 - Rößler, Dirk A1 - Landgraf, Angela A1 - Ballato, Paolo T1 - The Ahar-Varzeghan Earthquake Doublet (M-w 6.4 and 6.2) of 11 August 2012: Regional Seismic Moment Tensors JF - Bulletin of the Seismological Society of America N2 - On 11 August 2012 an earthquake doublet (M-w 6.4 and 6.2) occurred near the city of Ahar, northwest Iran. Both events were only 6 km and 11 minutes apart, producing a surface rupture of about 12 km in length. Historical and modern seismicity has so far been sparse in this area. Spatially, the region represents a transitional zone between different tectonic domains, including compression in Iran, westward extrusion of the Anatolian plate, and thrusting beneath the Caucasus. In this study, we inverted the surface waveforms of the two mainshocks and 11 aftershocks (M-w >= 4.3) to obtain regional seismic moment tensors. The earthquakes analyzed can be grouped into pure strike slip (including the first mainshock) and oblique reverse mechanisms (including the second mainshock). The sequence provides information about faulting mechanisms at the spatial scale of the entire rock volume affected by the earthquake doublet, including coinciding deformation on minor faults (sub) parallel to the main fault and Riedel shears. It occurred on a so far unknown fault structure, which we call the Ahar fault. Alongside the seismological data, we used geological maps, satellite images, and digital elevation data to analyze the geomorphology of the region. Our analysis suggests that the adjacent North Tabriz fault, which accomodates up to 7 mm/yr of right-lateral strike-slip faulting, does not compensate the entire lateral shear strain, and that part of it is compensated farther north. Combined, our results suggest a temporally and spatially complex style of deformation (reverse and strike slip) overprinting older reverse deformation. Y1 - 2015 U6 - https://doi.org/10.1785/0120140042 SN - 0037-1106 SN - 1943-3573 VL - 105 IS - 2A SP - 791 EP - 807 PB - Seismological Society of America CY - Albany ER -