The thinning of subcontinental lithosphere: The roles of plume impact and metasomatic weakening

Geologically rapid (tens of Myr) partial removal of thick continental lithosphere is evident beneath Precambrian terranes, such as North China Craton, southern Africa, and the North Atlantic Craton,and has been linked with thermomechanical erosion by mantle plumes. We performed numerical experiments with realistic viscosities to test this hypothesis and constrain the most important parameters that influence cratonic lithosphere erosion. Our models indicate that the thermomechanical erosion by a plume impact on typical Archean lithospheric mantle is unlikely to be more effective than long-term erosion from normal plate-mantle interaction. Therefore, unmodified cratonic roots that have been stable for billions of years will not be significantly disrupted by the erosion of a plume event. However, the buoyancy and strength of highly depleted continental roots can be modified by fluid-melt metasomatism, and our models show that this is essential for the thinning of originally stable continental roots. The long-term but punctuated history of metasomatic enrichment beneath ancient continents makes this mode of weakening very likely. The effect of the plume impact is to speed up the erosion significantly and help the removal of the lithospheric root to occur within tens of Myr if affected by metasomatic weakening

Constraining Deformation, Uplift, and Activity Along the Tuz Golu Fault Zone, Central Anatolia, Turkey

We use a combination of paleostress analysis, tectonic geomorphology, and 40Ar/39Ar geochronology along the Tuz Golu fault zone to constrain deformation and uplift in the Central Anatolian Plateau (CAP) interior. Paleostress analysis shows at least two principal phases of deformation - pre-upper Miocene compression and post-Miocene extension, suggesting a changeover from compression to extension in Anatolia that broadly coincides with the onset of regional uplift. Morphometric analysis provide evidence of a southeastward increase in footwall uplift rate that could be the result of a regional uplift gradient, block rotations, or a combination of these processes. Morphometrics suggest north-northwest tilting of catchments, which may be linked to regional tilting related to uplift of the CAP. We utilize 40Ar/39Ar dating of offset lava flows in the southeastern Tuz Golu fault zone to constrain strike-slip deformation, and derive dextral slip rates that range from 0.58 to 3.53 mm/yr since ~2 Ma.M.A.S.2019-11-10 00:00:0

Tectonic geomorphology and Plio-Quaternary structural evolution of the Tuzgolu fault zone, Turkey: Implications for deformation in the interior of the Central Anatolian Plateau

Situated within the interior of the Central Anatolian Plateau (Turkey), the 200-km-long Tuzgolu extensional fault zone offers first-order constraints on the timing and pattern of regional deformation and uplift. In this study, we analyze the morphometrics of catchments along the Tuzgolti range-front fault and the parallel, basinward Hamzali fault using a variety of measured morphometric indicators coupled with regional geomorphic observations and longitudinal profile analysis. In addition, we use field and remote mapping to constrain the geometry of two key marker beds, the Pliocene Kizilkaya ignimbrite and Kisladag limestone, in order to investigate deformation in the footwall of the Tuzgolu fault zone. The marker beds form a broad arch along the footwall of the fault, with greatest cumulative displacement along the central part of the fault zone, suggesting early Pliocene extensional reactivation of the Tuzgolu fault with a typical fault-displacement profile. However, a change in deformation pattern is marked by transient knick-points along river channels; morphometric indicators sensitive to shorter (1-3 Ma) time scales, including river steepness, basin elongation, and mountain front sinuosity, indicate an overall southeastward increase in footwall uplift rate of the Tuzgolu fault zone, which could reflect block rotation or interaction with the Hasan Dag volcano. Basin asymmetry and basin-fault azimuth measurements indicate north-northwest tilting of footwall catchments, which may be linked to regional tilting across the Central Anatolian Plateau interior. Varying patterns of spatial and temporal deformation along the length of the Tuzgolu fault zone are likely due to the interference of crustal- and lithospheric-scale processes, such as rotation of crustal blocks, extrusion of the Anatolian microplate, crustal heating, gravitational collapse associated with plateau uplift, and mantle-driven vertical displacements

Oblique Deformation in Central Turkey: Fault Interaction and River Incision at the Intersection of the Tuz Gölü and Central Anatolian Fault Zones

Although much of the deformation associated with Arabia-Eurasia collision and Aegean extension is expressed by westward translation of Central Anatolia along the North Anatolian and East Anatolian fault zones, important deformation also takes place in the interior. Major interior faults include the NE-SW striking, left-lateral Central Anatolian fault zone (CAFZ), which splays from the NAFZ, and the NW-SE striking, right-lateral Tuz Gölü fault zone (TGFZ). We examine fault kinematics and river incision in the triangular region bound by the TGFZ to the SW, the CAFZ to the E and the Salanda graben to the N, in order to document fault interaction and landscape development where these fault systems intersect. We document deformation in the footwall of the Tuz Gölü fault, recorded by the warping of ignimbrite and lacustrine units. We investigate the Salanda fault, which displaces a 1.23 Ma basalt flow by 40 m. Paleostress analysis indicates two deformation phases with maximum strain nearly parallel (191 for extension; 183 for shortening).The Salanda fault reactivates older mylonite near the town of Karaburna. We map faults in the interior of this region, including the N-S striking Derinkuyu fault and the newly identified Derbentbaşi fault. The Derinkuyu fault has been inactive since emplacement of a lava dome at its north end. The Derbentbaşi fault offsets lacustrine limestones and older ignimbrites in a right-lateral, west-side down sense prior to regional river incision. Pliocene lacustrine carbonates are largely confined to the hanging walls and footwalls of the TGFZ and the Yeşilhisar strand of the CAFZ; these deposits are deeply incised and can be used to constrain the pattern and timing of river incision. Along the Salanda graben, the Kızılırmak River has incised the surrounding region to a depth of 350 m. Our data suggest a complicated interaction between the TGFZ and CAFZ, with faulting distributed on multiple, obliquely striking structures, few of which remain active today. We also identify an important role for pre-existing weaknesses in governing the location and orientation of faults in this system. We find structural control on the location and/or preservation of lacustrine sedimentation, and evidence for significant recent incision due to regional uplift and local disruption along fault systems