Multistage lithospheric drips control active basin formation within an uplifting orogenic plateau

Domain: earth_science
Published: 2024-09-13
Editorial outcome: major_revision

Abstract
According to GNSS/INSAR measurements, the Konya Basin in Central Anatolia is undergoing rapid subsidence within an uplifting orogenic plateau. Further, geophysical studies reveal thickened crust under the basin and a fast seismic wave speed anomaly in the underlying mantle, in addition to a localised depression in calculated residual topography (down to 280 m) over the Konya Basin, based on gravity-topography considerations. Using scaled laboratory (analogue) experiments we show that the active formation of the Konya Basin may be accounted for by the descent of a mantle lithospheric drip causing local circular-shaped surface subsidence. We interpret that the Konya Basin is developing through a secondary drip pulse that is contemporaneous with broad plateau uplift caused by a larger-scale lithospheric drip since the Miocene. The research reveals that basin evolution and plateau uplift may be linked in a multistage process of lithospheric removal during episodic development of orogenic systems.

Introduction
The geodynamic mechanisms of plateau evolution—such as in Tibet, Altiplano-Puna, and Anatolia—are tectonically complex, occurring in the hinterland of convergent orogenic systems. These plateaus have topographic, thermal, and geological characteristics that reflect an interplay of plate shortening and mantle dynamics1–5. Internally drained (deep) sedimentary basins of various scales have been described within the interior of these orogenic plateaus worldwide. However, the origin of such basins amidst an evolving orogeny and topographic rise of the plateau is not well resolved. Here, we explore the geodynamic origin of the Konya Basin, located in the interior of the Central Anatolian Plateau, as one such example of a closed basin-forming event within large-scale plateau uplift (Fig. 1a, b).

The Central Anatolian orogenic plateau is characterised by ~1.5–2 km average elevation with low relief and lower topography in the plateau interior, and high relief mountain ranges at its northern (Pontides) and southern (Taurides) margins (swath profile in Supp. Figure 1a). Cosmogenic dating of river terraces (Kızılırmak) in the plateau interior suggests surface uplift since ~2 Ma, although at much lower rates compared to the Pontides and Taurides6,7. Stratigraphic and geomorphological evidence determines an earlier onset for plateau uplift in the interior. For example, palaeontological evidence (e.g., mollusc bearing sections) from the Karaman Basin of the south-central plateau interior indicates that this region emerged from below sea level by at least ~11 Ma7,8. Furthermore, paleo-elevation estimates derived from incised valleys across basalt terraces in the Cappadocia Volcanic Province indicate surface uplift of up to ~1000 m since 8 Ma9. Meijers et al.10 interprets10 that gradual diminishing of (δ18O) oxygen stable isotope ratios from Miocene lacustrine carbonate deposits of continental basins within the plateau interior was caused by surface uplift (~11–5 Ma). Göǧüş et al. suggests3 that folding of the Kırşehir arc during the Eocene-Miocene led to lithospheric “dripping” and subsequently uplift of the Central Anatolian plateau.

While the eastern and western domains of Anatolia are affected by plate boundary activities, Central Anatolia is essentially tectonically inert. There are no known active crustal scale fault systems11 or associated seismic activity12 in the plateau interior except the NW-SE trending Tuz Gölü fault (Fig. 1b). Based on geodetic measurements and geological interpretations, Özbey et al. interpreted13 this fault system to operate primarily as a strike-slip shear zone, although it is encompassed within an overall region of low magnitude strain14. Fault plane solutions associated with the Bala earthquake sequences (2005–2008), ~50 km north of the Tuz Gölü fault, agree with the strike-slip characteristics of the seismically active shear zone with a complex multiphase evolution15,16. In addition, structural, stratigraphic, and sedimentological data from the Tuz Gölü fault have been used to interpret major motion of this fault system as initially strike-slip with a normal fault component between the post Paleogene to Pliocene17, but this transitioned to a thrust fault during the Late Miocene to Early Pliocene18 (Fig. 1b).

The Konya Basin is a circular shaped, intra-continental, closed (endorheic), sedimentary basin (Fig. 1c) that initially formed as a forearc basin in Central Anatolia following orogenic events between the Late Cretaceous and the Miocene epochs19. The basin preserves a record of long-term sedimentation owing to the lack of external drainage that would otherwise disperse sediments10,20. These sediments are lacustrine, and deposition continued until the Pleistocene based on a well-defined paleoshoreline of the paleolake Konya (Fig. 1b)21–23. Weiss et al. combined24 Sentinel-1 InSAR and Global Navigation Satellite System (GNSS) measurements to map the present-day surface velocity and strain rate across the entire Anatolian plate. These data show a distinct bulls-eye pattern of active subsidence at the Konya Basin with vertical velocity rates approaching ≥20 mm/year (Fig. 1c).

However, as is consistent with the geological evidence described above, the measured internal deformation of the basin is minimal with low shear strain rates and lack of folding and/or active faulting11,24. These data from Weiss et al. present24 a geodynamic puzzle: why is the Konya Basin rapidly subsiding amidst an overall uplifting, and tectonically quiet plateau?

Here, we combine scaled laboratory (analogue) experiments and analyses of geophysical and geological data to explore the dynamics of basin evolution within the Central Anatolian plateau interior. The topographic evolution of a 3D analogue model is measured to quantify the surface expression of lithospheric removal that may account for basin tectonics within the Alpine-Himalayan orogenic plateau system. Model results are interpreted within the framework of the geological evolution of the Central Anatolian plateau over the last ca. 10 My, and compared against the active subsidence of the Konya Basin, an enigmatic region of subdued seismic activity and muted crustal deformation. This research underscores what might be an overlooked multistage process of lithospheric removal within a large-scale orogenic system.

Results
Geophysical constraints on the evolution of the Konya Basin
In addition to the InSAR and GNSS measurements revealing active vertical displacement of the Konya Basin24, there are several geophysical anomalies localised around the basin region (Fig. 2). Seismic studies by Vinnik et al. and Kind et al. suggest25,26 a thin lithosphere beneath Central Anatolia with the lithosphere asthenosphere boundary (LAB) at 60–100 km depth. There is a fast seismic wave speed anomaly (the isotropic S-wave anomaly – Vs) beneath the Kırşehir arc (Fig. 2a, Fichtner et al., 27) that has been interpreted as a remnant of a large-scale drip event that uplifted the Central Anatolian plateau3. Furthermore, Fig. 2a shows that there is another fast seismic wave speed anomaly (Vs ≥ 4.4 km/s27) between 50 km and 80 km depth, located directly beneath the Konya Basin indicating the presence of colder/denser lithosphere. This Konya anomaly is located north of the Cyprus slab and extends into the underlying mantle.

The Konya Basin lithosphere is characterised by a thick crust of ~40 km28,29 with local thickening in the crust (up to 44 km) on the periphery of the basin (Fig. 2b) (ref. 28–32). Crustal thickness variations obtained from Vanacore et al.32 are shown along a 1° swath profile (shaded areas) centred at 33° E (solid lines) in Supp. Fig. 1b.

Mantle convective support of topography can be analysed from elastically uncompensated long-wavelength gravity anomalies33–36. Based on the relationship between gravity and topography, it is generally suggested that the ratio associated with convective support at long-wavelengths (≥~300 km) is 50 mGal/km for continents and 30 mGal/km for ocean bathymetry (Howell et al., 34 and references therein). By subtracting the isostatically supported topography based on crustal thickness29 from observed topography, one can obtain the non-isostatic component of the topography (i.e., the residual topography, Fig. 2c37). Our calculations show a residual topography variation with a local depression (~280 m) across the Konya Basin (Fig. 2c, Supp. Fig. 1a). These findings are in concordance with residual topography anomaly estimates in the eastern Mediterranean from satellite gravity-topography (GOCE) data (Fig. 2d; Fig. 13c in Howell et al., 34). Figure 2e demonstrates that the surface topography of the Konya Basin is flat in comparison to the region surrounding the basin.

Based on geophysical anomalies in the region, we hypothesise that lithospheric dynamics account for active subsidence of the Konya Basin. Namely, the presence of a fast seismic wave speed anomaly (Fig. 2a) indicates a colder/denser lithospheric body sinking into the underlying sub-lithospheric mantle beneath the basin. Negative residual topography indicates that the topography in the region is non-isostatic, and dynamic topography is causing the surface to be substantially (~280 m) lower than it should be according to gravity-topography isostatic considerations. Together, these geophysical data may indicate the presence of a lithospheric drip actively pulling the crust downward. The geophysical anomalies are consistent with documented observables for lithospheric removal interpreted in other regions around the globe, such as the Tulare Lake basin of the southern Sierra Nevada38, Lake Titicaca of the Altiplano plateau39, and the Arizaro Basin of the Puna plateau40.

We note that this hypothesis of active lithospheric dripping beneath the Konya Basin may present a complicated geodynamic framework in the context of the broad evolution of plateau uplift over the past ~10 My. If we consider that the Central Anatolian Plateau overall has been uplifting owing to a primary stage of lithospheric dripping3,10,41, interpretation of the geophysical and geological data prompts the question whether it is possible to have a secondary, or late-stage dripping event causing active basin subsidence simultaneously? To reconcile these findings with the subsidence observed by Weiss et al.24, we conducted 3D analogue modelling of lithosphere-mantle dynamics for the region. The geodynamic modelling investigates how a secondary event of lithospheric removal via dripping can cause basin subsidence within a regime of large-scale plateau evolution.

Dynamics and the surface response to late stage dripping lithosphere
A physical scaled analogue model was set up (see Methods) to explore how gravitationally unstable lithosphere drips into the underlying mantle. An initial perturbation develops into a primary drip (Fig. 3a–c) that results in removal of mantle lithosphere as well as plateau uplift over the first ca. 40 h. Side-view images of the experiments show the primary drip pulse at 10 h (Fig. 3a) when the drip has started to descend, and by 25 h (Fig. 3b) the drip is sinking more rapidly and approaching the bottom of the tank. There is no visible deformation of the crust on the surface area directly above the drip (or elsewhere; Fig. 3c). We provide more detailed information of topographic evolution of the surface due to the primary drip in Supp. Fig. 3.

Notably, a secondary drip event (Fig. 3d–h) develops following the primary drip (similar to the phenomenon observed in Pysklywec & Cruden, (2004)). At 50.6 h after the primary drip reaches the bottom of the box and a period of low activity in the model, a secondary pulse of downwelling starts to develop within the stretching lithosphere (“drip tail”) as indicated by the distribution of green velocity vectors (Fig. 3d). Note that the drip tail is thinned and elongated, but an exception is in the middle where the secondary drip begins to grow. Figure 3e zooms into a top view 3 × 5 cm area above the drip and shows an elevation contour map of the surface. This was created using data obtained from digital photogrammetry calculated using high-resolution oblique camera images (sensitive to ±0.1 mm changes; ±0.5 km scaled; see Methods section). Subsidence of the surface scaled to ~1.25 ± 0.5 km is shown in the surface elevation contour map.

In Fig. 3f, by 57.1 h, the secondary drip pulse has travelled ~1 cm deeper into the tank compared to the previous frame. The green vectors show that the descent rate has increased. The digital photogrammetry data (Fig. 3g) show that this causes an increase in surface subsidence, deepening the basin to a scaled depth of ~1.5 km ± 0.5 km at its deepest point. This pulse of a secondary drip is interpreted to be causing renewed active subsidence at the surface and forming an oval shaped basin (see Supp. Fig. 3).

Figure 3h shows the model surface at the end of the experiment where there is still no significant deformation recorded across the crust associated with the drip (i.e., an asympomatic drip; Suppl. Fig. 2). Figure 3i shows a contour map of the scaled vertical surface displacement, calculated by subtracting Fig. 3e from Fig. 3g. The resulting displacement field shows regions with positive vertical displacement (pink-yellow) that indicates surface uplift and regions with a negative vertical displacement (blue-black) that denotes subsidence. Notably, surface subsidence is recorded corresponding to displacement of the deepest point of the basin, outlined in the black dashed square. In summary, the active local subsidence and uplift is driven by late stage (secondary) dripping following the main lithospheric removal episode.

Methods
Materials
An analogue model is a simplified, 3D model created in the laboratory using selected materials as scaled analogues for the Earth’s sub-lithospheric mantle, mantle lithosphere (upper mantle) and the upper crust. The analogue model in this study was constructed using methods from58,59. The sub-lithospheric mantle in the model was a viscous silicone polymer - polydimethylsiloxane (PDMS). The mantle lithosphere was created using a viscous, homogeneous mixture of 70% PDMS and 30% Plasticine™ modelling clay59. The modelling clay was added to increase the density and viscosity of the mantle lithosphere in relation to the underlying sub-lithospheric mantle. A brittle upper crust was created using a combination of well sorted, fine-grained (500 µm, dry, solid) silica sand and (300 μm, dry, hollow) ceramic e-spheres (Envirospheres®)59,60. The density, viscosity and thickness of these materials are outlined in Table 1. As previously described in ref. 59, the upper crust material was estimated to have negligible cohesion61, but the angle of internal friction (φ) of the crust was ~35° (Table 1). This angle was determined by equating the angle of repose of the upper crust material in a conical pile to the angle of internal friction62. Such an approach for measuring the strength of granular materials is feasible given that the sand and e-spheres are particles of uniform size, density, and moisture content63.

The sub-lithospheric mantle (PDMS) and mantle lithosphere (PDMS+modelling clay) materials are the same as used in ref. 59 (i.e. both viscous, non-Newtonian materials) and are defined by the power law:

σn = ηϵ_ (1)

where σ is stress, ϵ_ is strain rate, η is consistency/viscosity, and n a stress exponent58,64. A strain-controlled rheometer (Discovery HR-3 Hybrid) was used to measure the n value (Table 1) and effective dynamic viscosity (ηeff) of all viscous materials used in the model. The rheology values in Table 1 were recorded at a strain rate of 10−5 s−1, an approximate rate of deformation in the experiment59.

Experimental setup
The analogue experiment was conducted in the Tectonophysics lab at the University of Toronto, using the experimental setup methods described by Andersen et al.59. The model was scaled for length, density, dynamic viscosity, time, and gravity. A 25 × 25 × 20 cm Plexiglass box was filled with recycled PDMS (containing some clay impurities) to serve as the analogue sub-lithospheric mantle and was left for ~14 days until all air bubbles had been removed, which is essential to reduce noise in the images taken during the experiment59. The contrast in density between the model’s mantle lithosphere and sub-lithospheric mantle, creates an instability (Rayleigh-Taylor instability) between these layers, thus drips could initiate naturally during the experiment59,65,66. However, to ensure the position of the primary drip, a 2.5 cm hemispherical perturbation of the same material as the mantle lithosphere was inserted into the centre of the PDMS mantle until a flat surface reformed, akin to the method described in ref. 58 and Method 2 in ref. 59. After the perturbation was inserted, a 2 cm thick viscous mantle lithosphere was then placed on top of the PDMS (and perturbation) ensuring there was minimal trapped air to reduce noise and again left until a flat surface formed59. Viscous drag at the box boundaries was mitigated during this step by lubricating the inside of the Plexiglass box with Petroleum Jelly. Further, the box was of sufficient volume that any drag from the edges of the box did not hinder the descent of the drip or associated flow in the centre, thus an additional lubricant such as a mixture of petroleum jelly and paraffin oil was not required67. To simplify the dynamics of the model, the viscous lower crust was assumed to be part of the upper mantle lithosphere59. The brittle upper crust was sieved in an even 2 mm thick layer on top of the mantle lithosphere. Scattered black sand particles on the surface of the model served as tracers, which are required for the image correlation techniques used in the image analysis59. This model had a free surface at the upper crust as the plexiglass box was open at the top.

The kinematics of the experiment were recorded by two digital cameras (CCD, 11MPx, 16bit) (Imager ProX by LaVision GMbH, Göttingen, Germany) from above, which took images at oblique angles to the model surface and one digital camera from the side (CCD, 11MPx, 16bit) (Imager Pro by LaVision GMbH, Göttingen, Germany), which captured images normal to the front plane of the box (Fig. 3 demonstrates this angle)59. The model was illuminated from above and from the side against a black background. This created a strong contrast, so the camera only recorded motion from the model59. The LaVision GMbH software recorded the evolution of the model at an interval of one image every 58 s.

For the mantle material, recycled PDMS was used which included small, dispersed particles of clay. These served as tracer particles for the imaging system where relative displacement was calculated between consecutive images, and subsequently used to calculate velocity vectors in the analogue mantle59. The DaVis software uses 2-dimensional Particle Imaging Velocimetry, which tracks changes in the pattern of the marker particles in consecutive images using a cross-correlation technique, from which the velocity field is calculated68. This was the same method employed in ref. 59, and other previous studies have also used this technique or similar imaging techniques to compute mantle flow and crustal velocity fields59,68–73. The contrast between the black background and the instability allowed us to track the motion of the drip and the flow in the mantle, however, this means that the results show flow velocities through the volume of the entire box projected onto the front plane of the image59.

The StrainMaster tool in the DaVis software uses digital photogrammetry to compute surface height and vertical displacement, which requires the cameras to take two images at oblique angles to the model surface. The two top cameras were calibrated so the relationship between the raw oblique images and real-world space was known through a calibration model. This calibration model was used together with matching the pattern between the two cameras above the model to compute a single corrected image required for the digital photogrammetry calculations of surface elevation to a precision of ±0.0945 mm (scaling to ~±0.47 km in nature)59.

Scaling
To compare the analogue experiments with nature, scaling relationships were established for time, length, gravity, density, and dynamic viscosity58,59. The length scale (L) was calculated based on the mantle lithosphere thickness (denoted by subscript m) of lm = 20 mm in the model. As mentioned previously, the lithosphere beneath Central Anatolia is thin, with the LAB located at ~60–100 km depth25,26, therefore, we chose to scale the length of the mantle lithosphere to a natural value of 100 km. The upper crust in this model was thin and corresponds in nature to only the brittle portion of the upper crust, where geophysical studies have determined a thin, below average effective elastic thickness of 6 km in Western Anatolia74,75. A regional Bouguer gravity anomaly map shows high gravity anomalies in Konya (Central Anatolia)76. The authors of this work interpret the cause of this high anomaly to be a mass of high density oceanic (ophiolitic) crust that was obducted during the closure of the Tethys ocean and subsequently covered by a layer of sediments. Our model upper crust has a high density to approximate this condition. It has a high density (1100 kg/m3) in comparison to PDMS (1010 kg/m3). However, analogue models are limited by the materials available, especially when selecting a granular material to mimic brittle behaviour that maintains a reasonable angle of internal friction so that it does not behave like a powder with high internal friction59,77. Seismic tomography and modelling studies suggest that the Central Anatolian Plateau has undergone lithospheric removal and mantle uplift that is supported by slow seismic wave speed anomalies beneath a thinned lithosphere3,27. This interpretation is in accord with our model where the dense mantle lithosphere (and lower crust) has undergone an initial phase of dripping and removal before the secondary drip. Petrological studies argue that basaltic melts in Central Anatolia contain high-density pyroxenite, which may be responsible for the growth of the instability and subsequent drip process in Central Anatolia78.

The geological configuration of the study area in Central Anatolia yields the following scaling relationships. Based on an average natural mantle lithosphere thickness (denoted by subscript n) of ln = 100 km in Central Anatolia, the length scale ratio was L = lm / ln = 2.00 × 10−7. The density of the model PDMS sub-lithospheric mantle was ρm = 1010 kg m−3. Assuming an average density of the asthenospheric mantle in nature of ρn = 3060 kg m−3, this yields a density scaling factor of P = ρm / ρn = 0.3359. The experiments are gravity driven and the scaling ratio for gravity is G = gm / gn = 1. The measured effective dynamic viscosity of the PDMS (ηm) was 1.9 × 104 Pas, and scaling with an approximate viscosity of the asthenosphere (ηn) of 1021 Pas gives a viscosity scale ratio M = ηm / ηn = 1.50 × 10−1759. A dimensional analysis of M, P, L, and G shows the time scaling factor (T) can be defined as T = M / PLG = tm / tn = 1.82 × 10−1042,59. Using this scaling factor, 1.59 h in the model is 1 My in nature. Table 1 list the scaling factors for the model and natural Earth values.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this manuscript, Anderson and colleagues describe the geological setting and geophysical characteristics of the actively subsiding Konya basin in the south central part of the Anatolian plateau. Based on these characteristics they argue that the basin is a dynamic topographic feature that is forming due the the pull of a gravitationally unstable drip at the base of the mantle lithosphere. This drip is interpreted to be secondary to a, presumably larger, primary drip which formed ca. 10 Ma ago, which led to (isostatic?) uplift of the broader Anatolian plateau. The authors evaluate their hypothesis by the use of a simple 3D analogue drip experiment, which does a reasonable job of replicating the size and subsidence rate of the Koyna basin.\n\nI found the idea that a small, actively subsiding, closed basin could be forming due to the action of a secondary gravitational instability within a still uplifting orogenic plateau to be particularly noteworthy and original. The idea is tested by a novel experimental setup capable of measuring both flow in the asthenospheric mantle and surface topography in response to the dripping instability. For these reasons I think the work is worthy of publication after fairly major revisions, which are recommended to make the communication of results and their interpretation more robust. I have provided an annotated PDF, which the authors should use for their revisions and only summarise the major points in my review below.\n\n1. The manuscript is generally well written and the figures are mostly of good quality. However, there are some sections of text that have rather awkward phrasing or odd or unsuitable word choices, which are indicated in the PDF. Likewise, the figure captions could be clearer and include more detailed explanation of the figure contents, which are quite complicated in places.\n\n2. I struggled a bit with what is known about the current state of the Anatolian lithosphere and its tectonic evolution. It is not clear until one reads the Methods section what the current thickness of the lithosphere is (i.e., it is quite thin with a thick crust and a thinned mantle lithosphere). This and how so much lithosphere came to be removed needs to be more clearly explained early on in the manuscript, particularly in the context of the broad-scale plateau uplift that started ca 10 Ma ago. It needs to be spelled out more clearly that this initial lithosphere removal event is attributed to a (presumably much larger) primary drip (of the Kursehir magmatic arc root?) and the the current high velocity feature in the lithosphere below the Konya basin and the associated surface subsidence are relatively late features attributed to a smaller, secondary drip.\n\n3. In a similar manner, the early history/behaviour in the drip experiment is not presented so the context of what happens between 50.6 and 57.1 hours is rather unclear. It would be very beneficial to the reader to know what happened in the first 50.6 hours of the experiment. When did the primary drip form? How large was it? How fast did it descend? How large was the associated surface basin? Did uplift occur after the primary drip stopped being active? How did the timing of these events and their scales match up with Anatolian tectonics? There seems to be a missed opportunity here.\n\n4. Following on from this, I found the rational for the setup of the experiment a bit confusing. The lithospheric thickness appears to have been chosen based on modern day constraints from geophysics, which is after removal of a lot of lithosphere by the primary drip, which drove regional plateau uplift around 10 Ma and thereafter. Surely, a more appropriate starting condition should have the original crust and mantle lithosphere in place so the experiment can evolve to form a primary drip, have lithosphere removed, and then develop a secondary drip? The thickness of the lithosphere in the experiment at 57.1 hours could then be compared to present-day values in Anatolia as another check.\n\n5. I had a few questions and suggested improvements in the Methods section. For example, the density of the upper crust reported in Table 1 seems implausibly high and if correct will have significantly unrealistic body force effects. The explanations of the PIV and digital photogrammetry techniques could be clearer and improved. There is important geological/geophysical background information hiding in the Methods section that needs to be front and centre in the main body of the text.\n\n6. Lastly, why did the secondary drip form in the first place? Do secondary drips form in all of these types of experiments or was the one presented here special in some way? Some information/discussion along these lines would help to broaden the impact/relevance of the contribution.", "reviewer_2": "This paper starts with an interesting idea, that a basin formed on the Central Anatolian Plateau owes its existence to downward motion in the mantle underneath the crust. The idea is appealing, but the question perhaps is whether the authors have done enough to make the idea convincing. The paper begins with a description of the relevant observations, in particular the evidence from recently published InSAR measurements which apparently show the surface of the Konya Basin in the Central Anatolian Plateau subsiding, from a seismic tomography model in which a relatively high-velocity volume in the uppermost mantle beneath the basin is evident, and from a model of residual topography that depends on gravity and crustal thickness estimates. The authors support their idea with a description of a fluid dynamical experiment in which they observe downward flows in a tank of material called PDMS.\n\nThe tank observations relate to the period following an initial Rayleigh-Taylor instability in which an upper dense layer forms a central blob which sinks through the mantle. However the authors do not relate the basin formation to the initial instability of the layer, but rather to a “late-stage” event in which a secondary drip forms and downward motion is accelerated. What exactly causes this late-stage event is not explained. It appears to be a relatively minor perturbation in the diameter of the vertical column of dense material, perhaps consequent on the prior slowing of the flow when the initial blob hit the floor of the tank. I am wondering why, if this small perturbation in the flow can have such a significant effect on the surface, what would have been the effect of the initial instability ? And why not attempt to explain the basin formation in terms of a more recent primary blob formation event?\n\nWhat the authors have to say about velocity is a bit hard to pin down. The experimental observations seem to relate primarily to the velocity of the drip in the mantle at a scaled depth of about twice the thickness of the mantle. They actually say that the flow velocities are integrated throughout the volume of the box, but surely they don’t mean the entire volume of the box. So where exactly is the velocity measured ? At some depth, or depth range ? There are also estimates of surface subsidence velocity from the InSAR and these can be related to surface measurements from the experiments for which they infer deflections of about +/- 1.5 km, and claim a precision of 95 microns (0.5 km scaled). In Fig 3 we see plots of surface deflection (made complicated and essentially unusable by using colour and 3D projection at the same time) and in Fig 3e of the subsidence rate distribution at a time that is late in the experiment. I find it difficult to know what to take away from this experiment when we are given only snippets of information about it, but lack for example a clear understanding of how the experiment is proceeding in time. We are also shown in Fig 3 grey rectangles that purport to be raw PIV camera images. Why ? They show nothing useful to the reader, but obscure the surface deflection plots, which should be shown without distortion on a 2D plot.\n\nThe authors also make a simplifying assumption of using a relatively dense crustal layer in the experiment. This can have a significant dynamical effect, especially when it comes to computing surface deflection and deflection rate. This is a major difference from the actual geophysical problem where crustal buoyancy is more significant, sufficient to cast in doubt any kind of quantitative scaling of the surface deflection inferred from the tank experiments.\n\nIn summary, I like the geological concept and the tank experiments are interesting but could be explained in more detail. However, the use of a relatively high density, thin crust in the experiments, seems like a problem in that it minimizes crustal buoyancy compared to the Earth. Consequently I don’t find that the authors are making a convincing case for how to quantitatively apply the results from the tank experiments to the geological problem. I feel that these problems need to be addressed in more detail before the paper would be acceptable.", "reviewer_3": "Dear Editor,\n\nI have read the manuscript entitled Multistage lithospheric drips control active basin formation within an uplifting orogenic plateau submitted by Andersen et al. The paper strives to elucidate the formation of the Konya Basin within the Central Anatolian Plateau. They suggest that the ongoing 5 cm/yr subsidence rate based on InSAR and GNSS analysis is a consequence of deep-rooted geophysical phenomena such as the descent of a lithospheric drip based on fast seismic wave anomaly beneath the basin. This manuscript is not ready to publish in your journal and needs to be more elaborated with local geology and geomorphology. I am a geomorphologist; therefore, I will particularly emphasize a few critical geomorphic points that authors must consider.\n\n1. The time span that InSAR and GNSS analysis covers is very short from a geological point of view; however, lithospheric dripping takes millions of years. If you combine these two data, there is a considerable time gap between them and it would be better if authors look at local geology and geomorphology to fill this gap. For instance, did they check the inclination of bedding of sedimentary rocks? Do they tilt to the Konya Basin or not? If we consider 5 cm/yr subsidence, there must be significant tilting, although it is an asymptomatic drip.\n\n2. Similarly, local geomorphology. In our paper (Melnick et al., 2017), we studied paleolake shorelines in Tuz Gölü and Konya Basin. These are the shorelines belonging to LGM (20 ka) Lake. As you know, the shorelines are the best geomorphic markers to quantify vertical deformations. It would be really useful for the authors if they checked these data and correlated them with their model. If we consider 5 cm/yr subsidence, all these paleo shorelines need to be strongly deformed, which is not the case.\n\n3. Authors suggest there is no crustal deformation within the Konya Basin. Still, in our paper (Melnick et al., 2017), we showed the 12 m vertical displacement along the Sultanhanı Fault and a surface rupture that might be produced by an earthquake magnitude 6.5 or higher. Additionally, an earthquake ML 5.1 occurred on August 1 2023, in Konya within the subsidence circle of the paper, indicating obvious crustal deformation. It is rare but exists.\n\n4. I think this comment is the most critical because the authors did not consider the Konya Basin's karstic characteristics and the human effect. If you look at the subsidence pattern, the centre of the Konya Basin is stable and not subsiding. This area corresponds to Bozdağ Mountain National Park, with no agriculture. All the rapidly subsiding areas overlap with karstic plains that are intensively cultivated. Since the area is semiarid, the farmers pump more underground water every year, and this extraction of groundwater gives rise to subsidence of the land surface, like in San Joaquin Valley, California, in the 1950-60s. This is a well-known process in the region, and every year we have news about the formation of sinkholes within the Konya basin because of the drop in underground water level.\n\nI recommend that the Authors consider these issues.\n\nFor these reasons, I found the manuscript not ready the publish in Nature Communications."}, "author_response": "Response to Reviewer Comments\nLine numbers correspond to the original document that was submitted for review, not the newly\nrevised manuscript.\n\nResponse to Reviewer 1\nIn this manuscript, Andersen and colleagues describe the geological setting and\ngeophysical characteristics of the actively subsiding Konya basin in the south central part\nof the Anatolian plateau. Based on these characteristics they argue that the basin is a\ndynamic topographic feature that is forming due the the pull of a gravitationally unstable\ndrip at the base of the mantle lithosphere. This drip is interpreted to be secondary to a,\npresumably larger, primary drip which formed ca. 10 Ma ago, which led to (isostatic?)\nuplift of the broader Anatolian plateau. The authors evaluate their hypothesis by the use\nof a simple 3D analogue drip experiment, which does a reasonable job of replicating the\nsize and subsidence rate of the Koyna basin.\n\n1) I found the idea that a small, actively subsiding, closed basin could be forming due to the\naction of a secondary gravitational instability within a still uplifting orogenic plateau to\nbe particularly noteworthy and original. The idea is tested by a novel experimental setup\ncapable of measuring both flow in the asthenospheric mantle and surface topography in\nresponse to the dripping instability. For these reasons I think the work is worthy of\npublication after fairly major revisions, which are recommended to make the\ncommunication of results and their interpretation more robust. I have provided an\nannotated PDF, which the authors should use for their revisions and only summarise the\nmajor points in my review below.\n\n2) I struggled a bit with what is known about the current state of the Anatolian lithosphere\nand its tectonic evolution. It is not clear until one reads the Methods section what the\ncurrent thickness of the lithosphere is (i.e., it is quite thin with a thick crust and a thinned\nmantle lithosphere). This and how so much lithosphere came to be removed needs to be\nmore clearly explained early on in the manuscript, particularly in the context of the\nbroad-scale plateau uplift that started ca 10 Ma ago. It needs to be spelled out more\nclearly that this initial lithosphere removal event is attributed to a (presumably much\nlarger) primary drip (of the Kursehir magmatic arc root?) and the the current high\nvelocity feature in the lithosphere below the Konya basin and the associated surface\nsubsidence are relatively late features attributed to a smaller, secondary drip.\nResponse: In the revised manuscript we elaborate on the tectonic evolution of the two-stage\nlithospheric dripping process at central Anatolia where the initial event produces plateau\nuplift, and the later process causes active subsidence of the Konya basin. Specifically, we\nhave added in the Introduction and Geophysical Constraints sections passages of several\nsentences (with appropriate references) that explain how the folded Kırşehir arc formed an\narc root and mantle lithosphere removal causing plateau uplift. We further clarify that the\ndrip that produced plateau uplift is a primary drip. In addition, we completely redrafted\nFigure 4—the schematic diagram that illustrates how the two-stage dripping process works\nand revised the associated text in the Discussion to explain more clearly.\n\nTo address the reviewer’s other comment, we added a profile in figure 2 that shows the\ncurrent crustal thickness. We also added a sentence to the ‘Geophysical constraints on the\nevolution of the Konya basin’ section that explains that the lithospheric thickness beneath the\nplateau is in the range of 60 km – 100 km (Vinnik et al., 2014; Kind et al, 2015).\n\n3) 3. In a similar manner, the early history/behaviour in the drip experiment is not presented\nso the context of what happens between 50.6 and 57.1 hours is rather unclear. It would be\nvery beneficial to the reader to know what happened in the first 50.6 hours of the experiment.\nWhen did the primary drip form? How large was it? How fast did it descend?\nHow large was the associated surface basin? Did uplift occur after the primary drip\nstopped being active? How did the timing of these events and their scales match up with\nAnatolian tectonics? There seems to be a missed opportunity here.\nResponse: In the revised manuscript we added new photos in Figure 3 and explanations that\ndescribe the early behavior in the drip experiments—i.e., in the first 50.6 hours (with images\nat 10h and 25h after initiation of the experiment). This illustrates the early-stage development\nof lithospheric drip where large -scale removal caused plateau uplift. We emphasize that the\npurpose of this work is not to focus on the plateau formation in the early stage; rather it aims\nto explain anomalous active subsidence in the Konya basin (secondary drip). Due to the\nnature of geodynamic experimental work, a given experiment cannot explain the geological\nevolution of a region in terms of complete events while matching their scales.\n\nWe thank the reviewer for pointing out this opportunity and we have enhanced explanations\nof the primary and secondary removal events to clarify the full scope of tectonic events in\ncentral Anatolia.\n\n4) Following on from this, I found the rational for the setup of the experiment a bit\nconfusing. The lithospheric thickness appears to have been chosen based on modern day\nconstraints from geophysics, which is after removal of a lot of lithosphere by the primary\ndrip, which drove regional plateau uplift around 10 Ma and thereafter. Surely, a more\nappropriate starting condition should have the original crust and mantle lithosphere in\nplace so the experiment can evolve to form a primary drip, have lithosphere removed, and\nthen develop a secondary drip? The thickness of the lithosphere in the experiment at 57.1\nhours could then be compared to present-day values in Anatolia as another check.\nResponse: In the revised manuscript we clarified that lithospheric thickness estimate is not\nselected based on current geophysical constraints where it is in the range of 60-100 km\n(Vinnik et al 2014; Kind et al., 2015), therefore we chose 110 km for the lithospheric\nthickness as a reasonable approximation for orogenic areas/magmatic arcs. To advance\nfurther our two-stage drip hypothesis we elaborated on the final figure (Figure 4) where a\nrange of geological, geophysical, and petrological constraints are interpreted.\n\n5) I had a few questions and suggested improvements in the Methods section. For example,\nthe density of the upper crust reported in Table 1 seems implausibly high and if correct\nwill have significantly unrealistic body force effects. The explanations of the PIV and\ndigital photogrammetry techniques could be clearer and improved. There is important\ngeological/geophysical background information hiding in the Methods section that needs\nto be front and centre in the main body of the text.\nResponse: In the revised manuscript we explain why our initial crustal density is at the\nhigher end compared to regular densities for the crust. This is because the density of the\ncrust underneath central Anatolia, specifically the Konya basin, is high as inferred from\ngeophysical analyses (i.e., +0.25 kg/m3 Bouguer gravity anomaly) (Aydın & İşseven,\n2018). This estimate is supported by the area being located above a Tethyan suture,\nrepresented by (higher density) ophiolitic rocks. We have explained this condition in the\nrevised manuscript (Methods section) to clarify our setup. Description of the primary\nmodel parameters has also been added to the main text, as recommended by the reviewer.\nWe have improved the explanations of PIV and digital photogrammetry as well.\n\n6) Lastly, why did the secondary drip form in the first place? Do secondary drips form in all\nof these types of experiments or was the one presented here special in some way? Some\ninformation/discussion along these lines would help to broaden the impact/relevance of\nthe contribution.\nResponse: In the Discussion section of the revised manuscript, we expand on this point to\ndescribe that secondary drips can be a natural consequence of ongoing lithospheric\nremoval/dripping processes. Our experience from both numerical and analogue\nexperiments demonstrates that once the lithosphere becomes unstable and the removal is\ninstigated, multistage dripping may occur. Depending on rheological and density\nvariations, the process may be more pronounced and here we relate this in the context of\norogenic cyclicity. In the revised manuscript, we cited other cases where such repetitive\ndripping has been interpreted for various regions around the globe, based on geological\nand geophysical data.\n\nReviewer 1 kindly provided an annotated pdf document with many phrasing, grammar,\nand punctuation corrections. We have implemented those suggested changes to improve\nthe clarity of the work. We have provided responses to the comments on this document in\nthis response letter.\n\n1) Line 50-53: Suggest you break this up into 2 sentences - otherwise it is hard to follow.\nAlso, what do you mean by \"outstanding\" - outstanding in what way?\nResponse: This sentence was broken up into 2 sentences and the word outstanding was\nremoved from the new manuscript.\n\n2) Line 55: Do you need to say \"based on stratigraphic analysis\"?\nResponse: This statement was removed from the manuscript.\n\n3) Line 75: should be \"oxygen stable isotope ratios within.\nResponse: This wording has been changed in the new manuscript\n\n4) Line 88: What does this mean? Structural observations? Normally one would do surface\nmapping and look for features like slickenlines, kinematic indicators and offset markers\nto make such deductions. \"Subsurface data\" implies either data collected underground in\nmines, or by drilling or from geophysics (3D seismic/potential field data, etc).\nResponse: The phrase “subsurface data” now reads as “structural, stratigraphic, and\nsedimentological data” to specify the type of data we are referencing.\n\n5) Line 89: This sounds like the fault is not well understood or that it has a complex\nmultiphase history.\nResponse: The fault does have a complex multiphase history. In the revised manuscript,\nwe have modified this explanation to clarify the main kinematic behaviour of the fault\n(with reference to Cemen et al., 1999; Fernandez-Blanco, 2013).\n\n6) Line 93: Sorry, but this hasn't been defined or described yet, so how are we supposed to\nknow what and where it is? There is something labelled Tuz Gölü in Fig. 1b but there is\nno explanation about what it is.\nResponse: Fig 1b now specifies that there is a Tuz Gölü basin and a Tuz Gölü fault,\nwhich are labelled. We have also modified the explanation in this passage, so that specific\nreference to the Tuz Golu basin is now gone.\n\n7) Line 95: between? How can something begin from the late Cretaceous TO the Miocene?\nResponse: We have changed the wording of this in the updated manuscript and it now\nreads as “between the Late Cretaceous and the Miocene epochs.”\n\n8) Line 96: preserves a record of long-term?\nResponse: This has been changed in the updated manuscript to read as “The basin\npreserves a record of long-term sedimentation”\n\n9) Line 98: This doesn't follow from the first part of the sentence\nResponse: This sentence was broken up into two sentences for clarity.\n\n10) Line 116: Use ca. for time - tilda for things like dimensions, etc\nResponse: We have corrected this in the revised manuscript.\n\n11) Line 117: Do you need to repeat this information here?\nResponse: We have kept this information to emphasize this puzzling phenomenon in the\nKonya Basin. It’s an important part of the observations that we will be returning to, and\nwant to make this clear to readers.\n\n12) Line 118: This sentence doesn't really add much” and “Why recycling? What is being\nrecycled?\nResponse: In the revised manuscript, we modified the term recycling and explain how\nmultistage removal may be an important mechanism for orogenic cycle.\n\n13) Line 125: This and the following text seem to imply that the base of the lithosphere is at\n~50 - 60 km depth, which seems very shallow for an orogenic plateau with a ~40 km\nthick crust.\nResponse: We clarified this lithospheric structure based on geophysical studies with new\nreferences (Vinnik et al. 2014; Kind et al. 2015). These authors estimate that the\nlithosphere beneath Central Anatolia is thin, and the base of the lithosphere is ~60 km –\n100 km. We have elaborated on this more precise information in the geophysical\nconstraints section of the revised manuscript.\n\n14) Line 126: Can you please explain what you mean by \"undulation\" and \"protrude\" here?\nAlso what is the significance of the larger high Vs anomaly north of the Konya basin\nunder the Kirsehir arc?\nResponse: We have modified this entire discussion to clarify the structural geometry of\nthe lithosphere in the region, with reference to Figure 2. To explain the high Vs anomaly\nto the north of the Konya basin, we added a sentence regarding the previous geodynamic\nhistory of the Central Anatolian plateau where folding of the arc formed a thickened\n(higher density) arc root beneath the Kirsehir arc.\n\n15) Line 127: North of? Above? \"In front\" seems like an odd word choice\nResponse: The wording in this sentence has been changed to read as “north of the\ninterpreted Cyprus Slab”.\n\n16) Line 129: What do you mean by anomaly in this context?” “According to Fig. 2, the\nsmall circular region of thicker crust seems to be offset from the centre of the basin.\nResponse: In this region within and around Konya, we see a thickened crust ~40-44 km,\nthicker than the surrounding crust in the plateau at ~34 km. There is thick crust at ~40 km\nin the basin with thicker anomalies at the peripheries. We have revised the manuscript to\nstate this.\n\n17) Line 136: ???\nResponse: We have removed the statement “(i.e., down going mantle flow support on\ntopography)” from the revised manuscript. The description of residual topography has been\nre-written and clarified.\n\n18) Line 143 -146: See previous comment on the location/depth of the LAB. I think it is\ncritical here to define where the base of the lithosphere is.\nResponse: As described above, the lithosphere beneath Central Anatolia is 60 – 100 km\nthick based on seismic data from Vinnik et al. (2014) and Kind et al. (2015) (as implicitly\nrecommended by the reviewer, we added explanation/reference of this in the revised\nmanuscript.) The base of the anomaly referred to in this passage is 60 km, consistent with\nthese available data.\n\n19) Line 164-166: But does the modelling also account for simultaneous plateau uplift that\nyou also claim to be driven by a lithospheric drip?\nResponse: Yes, it does, although this primary drip event is not the main focus of this\npaper. We have made substantial revisions to the manuscript to explain this. In the revised\nFigure 3 we now include a depiction of the full drip process evolution. In Figure 3h, we\nshow vertical displacement. The main point we emphasize is that the basin created by the\nsecondary drip is deepening (illustrated by the dashed box). However, surrounding this\narea, the vertical displacement is positive (i.e., the surface is uplifting as a plateau). Over\nthe duration of the initial stages of the experiment, the surface progressively uplifted\n(consistent with the plateau uplift from Gogus et al., 2017).\n\n20) Line 169: Some context is required for the reader to understand what is meant by late\nstage versus early-intermediate stages. It would therefore be useful to describe what\nhappens in this kind of drip experiment over time, particularly since such information is\nnot presented in the methods section either.\nResponse: We agree with the reviewer that this was not well explained in the original\nmanuscript. We have updated Figure 3 to show the first 25h of the experiment where the\nprimary drip has almost touched the bottom of the tank (Figure 3a-c). It emphasizes the\nlarger scale of the drip in comparison to the secondary drip.\n\n21) Line 177: There is no context/explanation provided for what is meant by \"raw\"\ncamera image here, in the methods section or the figure caption, so it just comes across as\njargon. Why not just say what it is, which is an oblique digital image of the model surface?\nResponse: As recommended, we revised the description of the modeling method to be\nclearer about how camera images are used to estimate the surface topography associated\nwith the model.\n\n22) Line 181: Why not just say \"deformation\" here? Also, importantly, was there any\ndeformation observed of the upper crust in the early and intermediate stages of the\nexperiment?\nResponse: For clarity, we have changed “strain localization” to deformation. Figure 3c\nshows an image of the surface of the experiment at 25h where there was no crustal\nshortening or significant deformation earlier in the experiment. We explain this in the\nrevised manuscript.\n\n23) Line 193: It is important to also outine what happened at early and intermediate stages.\nFor example, how do you know what components of subsidence can be attributed to the\ninitial drip verses the secondary drip?\nResponse: In general, the primary drip caused an overall surface uplift, whereas the\nsecondary drip is causing a late-stage subsidence. We have clarified this in the revised\nmanuscript with the modifications to Figure 3 and modified written passages.\n\n24) Line 196: Should be i.e., = that is. Not e.g., = for example\nResponse: Thank you, we have changed this to i.e.,\n\n25) Line 197: How much of this is noise and how much is real? No errors have been\nquantified/presented.\nResponse: This figure has been revised. Rather than vertical velocity, we use vertical\ndisplacement in the updated Figure 3h. The error on the camera measurements is ±0.0945\nmm; this is given in the Methods section of the revised manuscript.\n\n26) Line 203: This was never documented, described or explained\n27) Line 214: These were never adequately explained.\n28) Response (Points 25 and 26): The substantial revisions made to Figure 3 and the text now\ndescribe the primary drip progression. These explanations are distributed through the\nIntroduction and Modelling sections of the revised manuscript. In addition, we refer to\nearlier work (Gogus et al., 2017) that focuses specifically on this type of primary drip\nevent.\n\n29) Line 215-217: This requires some further explanation/clarification. Active dripping\ndoesn't cause surface uplift, so what one can guess here is that the surface uplift is an\nisostatic response to removal of the magmatic arc root by a dripping mechanism.\nResponse: This sentence has been changed in the updated manuscript to read as “It has\nbeen suggested that the rise of Central Anatolia over the past ~10 My occurred due to\ndripping of the Kırşehir magmatic arc root after middle Eocene-Miocene lithospheric\nthickening (Göǧüş et al., 2017; Meijers et al., 2018; McPhee et al., 2022) (Fig. 4a).”. This\nwill clarify how this uplift is occurring.\n\n30) Line 220: This would have been good to know a lot earlier on.\nIn the revised manuscript, we now explain in the Introduction (i.e., much earlier) about\nthese events: seismic evidence for lithospheric thinning (Fichtner et al., 2013) and\ninterpretations for lithospheric removal and plateau uplift.\n\n31) Line 226: towards?\nResponse: we have changed this in the updated manuscript to read “towards the Konya\nBasin”.\n\nComments on Table 1\n32) These thickness values seem to be very different to the Anatolian plateau and Konya\nbasin\nResponse: The brittle upper crust is modeling the purely brittle part of the upper crust\nwhich has a below average thickness of 6 km in Western Anatolia, so we chose 10 km for\nsimplicity. We assumed the viscous lower crust was part of the mantle lithosphere. In\ntotal the lithospheric thickness beneath Anatolia is 60 km – 100 km so we chose the\nhigher end and have a mantle lithospheric thickness of 100 km.\n\n33) This is a very strange density to use for the continental crust. It is even higher that the\nasthenoshere!\nResponse: This is the density of a fine grained, silica sand that we used as the model\nupper crust. We tested two different crust materials (sand and silica spheres/e-spheres) in\na series of experiments, and neither crust seemed to influence the outcome of the\nexperiment but rather the outcome was influenced by how the drip was initiated and the\nrheology of the mantle lithosphere. Aydin & Işseven (2018) report high Bouguer gravity\nvalues in the Konya region of Turkey. They attribute this to a portion of dense oceanic\ncrust (ophiolitic) that was obducted during the closure of the Tethys Ocean and\nsubsequently then covered by sediments burying it to a depth of ~4.8 km. Therefore, we\nbelieve that a dense crust is reasonable for this model.\n\n34) This table reports more than just \"rheology\"\nResponse: The title of the table has been changed in the updated manuscript to “Table 1 |\nRheology, density and thickness of analogue materials with scaling factor (SF).”\n\n35) Line 284: Surely it was also added to change the rheology/viscosity?\nResponse: Thank you for mentioning this. The clay did also increase the viscosity. This\nhas been updated in the manuscript to read “to increase the density and viscosity of the\nmantle lithosphere.”\n\n36) Line 286: Please check that the density reported in Table 1 is correct. It doesn't seem\nlikely for this mix of materials.\nResponse: Thank you for highlighting this error. The density in the table was that of a\nfine-grained silica sand. The experiment shown here had an upper crust of sand rather\nthan silica spheres and e-spheres. We have updated the manuscript so that the correct\nmaterial is listed.\n\n37) Line 287: Not just rheological...\nResponse: We have removed “rheological properties”, and the updated manuscript now\nreads as “The density, viscosity and thickness of these materials are outlined in Table 1.”.\n\n38) Line 308-310: Since you use only 2 layers, this is a pretty extreme approximation!\nResponse: We agree that this is an approximation. This approach is considered to be\nfairly standard in scaled laboratory experiments.\n\n39) Line 356: You've now said this 3 times.\nResponse: We have changed this paragraph in the updated manuscript so as not to repeat\ninformation.\n\n40) Line 357: You could say this more simply. PIV tracks changes in patterns of particles\nusing a cross-correlation technique, from which the velocity field is calculated.\nResponse: We have updated how we explain this in the new manuscript.\n\n41) Line 360: Specifically the Strainmaster routine within DaVis\nResponse: The updated manuscript now reads as “The Strainmaster routine in the DaVis\nsoftware uses digital photogrammetry to compute surface height and vertical\ndisplacement”.\n\n42) Line 362: This could be said more simply. Also, \"raw\" image has no context because you\ndon't explain that DaVis computes a corrected image from the two oblique raw images.\nYou also need explain the the cameras take images at oblique angles of the model surface,\nwhich is required for the photogrammetry calculations.\nResponse: We have updated this section to describe that the overhead cameras are oblique\nto the model surface and that we use these images with a calibration model to produce a\nsingle corrected image that is required for the photogrammetry calculations.\n\n43) Line 369: Please explain all subscripts\nResponse: We have clarified the manuscript to state the subscript m is for model values\nand subscript n is for natural Earth values\n\n44) Line 369-371: It would have helped to learn this much earlier in the paper\nWe have added description of this and the Fichtner et al. (2013) reference to the\nIntroduction.\n\n45) Line 371: But this is presumably the thickness after the initial removal of mantle\nlithosphere. Surely the model needs to start with the original lithosphere thickness?\nResponse: Thanks for pointing this again. In the revised manuscript we clarified this\ninitial condition in various places.\n\n46) Line 380-382: There is a problem here because you model should really start with the\noriginal crustal and lithospheric thickness before the formation of the primary drip and\nremoval of mantle and crust alluded to here.\nResponse: Thanks for pointing this again. In the revised manuscript we clarified this\ninitial condition in various places.\n\n47) Line 386: I assume you mean asthenospheric mantle. Upper mantle could also mean\nlithospheric mantle.\nResponse: Yes, we have revised it to read as “asthenospheric mantle”.\n\nComments on Figure 1\n48) Line 676: Not clear how these are shown on this map\nResponse: We have removed “Major plate boundaries” from the caption. Figure 1a shows\nTectonic motions of Anatolia.\n\n49) Line 679: Sorry, but isn't this a shaded relief topographic map?\nResponse: The caption now reads as “Shaded relief topographic map of Central\nAnatolia”.\n\n50) Line 681: The faults are actually white lines. Only the half arrows indicating sense of\nshear are yellow.\nResponse: We have changed “yellow” to “white” in the updated manuscript and added\nthat yellow arrows indicate the sense of shear.\n\n51) Line 683: Labelling is confusing because only the inset is labelled (c) - The whole figure\nis (c) and the inset zooms in to the Konya Basin\nResponse: Figure 1c) is meant to be the zoomed inset. We show the entire map to show\nwhere that data came from.\n\n52) Line 684: Define Vup (mm/yr) please.\nResponse: We have updated the caption to read as “vertical velocities (V ) in mm/yr”.\nup\n\nComments on Figure 2\n53) Line 686: What is the dashed white line? LAB??\nResponse: We have changed this figure in the updated manuscript. The new caption\nexplains that the dashed white line is the LAB.\n\nResponse to Reviewer 2\n1) This paper starts with an interesting idea, that a basin formed on the Central Anatolian\nPlateau owes its existence to downward motion in the mantle underneath the crust. The\nidea is appealing, but the question perhaps is whether the authors have done enough to\nmake the idea convincing. The paper begins with a description of the relevant\nobservations, in particular the evidence from recently published InSAR measurements\nwhich apparently show the surface of the Konya Basin in the Central Anatolian Plateau\nsubsiding, from a seismic tomography model in which a relatively high-velocity volume\nin the uppermost mantle beneath the basin is evident, and from a model of residual\ntopography that depends on gravity and crustal thickness estimates. The authors support\ntheir idea with a description of a fluid dynamical experiment in which they observe\ndownward flows in a tank of material called PDMS.\nResponse: Thank you for the positive comments on our manuscript. We have made\nnumerous changes in the manuscript to clarify and strengthen our explanation of this new\nidea. Figure 4 has been revised to a more sophisticated cartoon graphic that clearly\nillustrates our idea that the Konya Basin is subsiding due to a secondary drip. We have\nalso provided references to instances in other locations where researchers also suspect\nthis is occurring in the central Andes, Tibet and Appalachian mountains. Figure 3 was\nupdated to show how the primary drip progression and how a secondary drip developed\nin the model following the initial dripping incident.\n\n2) The tank observations relate to the period following an initial Rayleigh-Taylor instability\nin which an upper dense layer forms a central blob which sinks through the mantle.\nHowever, the authors do not relate the basin formation to the initial instability of the layer,\nbut rather to a “late-stage” event in which a secondary drip forms and downward motion is\naccelerated. What exactly causes this late-stage event is not explained. It appears to be a\nrelatively minor perturbation in the diameter of the vertical column of dense material,\nperhaps consequent on the prior slowing of the flow when the initial blob hit the floor of\nthe tank. I am wondering why, if this small perturbation in the flow can have such a\nsignificant effect on the surface, what would have been the effect of the initial instability ?\nAnd why not attempt to explain the basin formation in terms of a more recent primary blob\nformation event?\nResponse: In the revised manuscript, we expanded on this point with a new Figure 4\nwhere the primary drip produced uplift and formation of the central Anatolian plateau\napproximately 10-8 Ma and the subsequent late-stage blob/drip produced active\nsubsidence of the Konya basin. Most of that connection between the two-stage dripping\nprocess was interpreted in the context of the geodynamic evolution of central Anatolia.\nThe model evolution shows that the primary drip hits the bottom of the tank much earlier\n(25 hours after the initiation of the experiment), therefore, the formation of the late-stage\nevent is not caused by a boundary effect. Please see new Figure 3 for illustration of the\nfull dripping process.\n\nWe hope that with the new figures 3 and 4 we have a more thorough illustration and\ndescription of the process: the first drip with large scale material removal/drip is linked to\nplateau uplift; and the subsequent one with smaller scale dripping is related to active\nbasin formation.\n\n3) What the authors have to say about velocity is a bit hard to pin down. The experimental\nobservations seem to relate primarily to the velocity of the drip in the mantle at a scaled\ndepth of about twice the thickness of the mantle. They actually say that the flow\nvelocities are integrated throughout the volume of the box, but surely they don’t mean the\nentire volume of the box. So where exactly is the velocity measured ? At some depth, or\ndepth range ? There are also estimates of surface subsidence velocity from the InSAR and\nthese can be related to surface measurements from the experiments for which they infer\ndeflections of about +/- 1.5 km, and claim a precision of 95 microns (0.5 km scaled). In\nFig 3 we see plots of surface deflection (made complicated and essentially unusable by\nusing colour and 3D projection at the same time) and in Fig 3e of the subsidence rate\ndistribution at a time that is late in the experiment. I find it difficult to know what to take\naway from this experiment when we are given only snippets of information about it, but\nlack for example a clear understanding of how the experiment is proceeding in time. We\nare also shown in Fig 3 grey rectangles that purport to be raw PIV camera images. Why ?\nThey show nothing useful to the reader, but obscure the surface deflection plots, which\nshould be shown without distortion on a 2D plot.\nResponse: Based on the reviewer’s comments, we made appreciable modifications to\nFigure 3:\n1) We show the entire evolution of the drip experiment, including the earlier stages, so\nthat the full experiment (and cycle of the drip process) may be better understood.\n2) The surface velocities are now omitted because they can not be directly reconciled\nwith INSAR based constraints owing to various uncertainties. We rather show the amount\nof vertical displacements between consecutive time slices to quantify subsidence of a\nKonya-type basin and surrounding uplift.\n3) We also deleted the grey rectangles showing the raw PIV camera images. In the\nrevised figure 3, we demonstrate more thorough analyses of topographic evolution of the\nlithospheric drip process.\n\n4) The authors also make a simplifying assumption of using a relatively dense crustal layer\nin the experiment. This can have a significant dynamical effect, especially when it comes\nto computing surface deflection and deflection rate. This is a major difference from the\nactual geophysical problem where crustal buoyancy is more significant, sufficient to cast\nin doubt any kind of quantitative scaling of the surface deflection inferred from the tank\nexperiments.\nResponse: In the revised manuscript, we explain why our initial crustal density is at the\nhigher end compared to known densities for the crust. This is because the density of the\ncrust underneath central Anatolia, specifically the Konya basin, seems to be elevated as\ninferred from geophysical analyses (i.e., +0.25 kg/m3 Bouguer gravity anomaly) (Aydın\nand İşseven, 2018). This is supported by the area being located above a Tethyan suture,\nrepresented by (higher density) ophiolitic rocks. We added this explanation and reference\nto this work in the revised manuscript to clarify the issue. In this model, we used fine-\ngrained, silica sand as the model upper crust. We tested two different crust materials\n(sand and silica spheres/e-spheres) in a series of experiments, and neither crust seemed to\ninfluence the outcome of the experiment but rather the outcome was influenced by how\nthe drip was initiated and the rheology of the mantle lithosphere.\n\n5) In summary, I like the geological concept and the tank experiments are interesting but\ncould be explained in more detail. However, the use of a relatively high density, thin crust\nin the experiments, seems like a problem in that it minimizes crustal buoyancy compared\nto the Earth. Consequently I don’t find that the authors are making a convincing case for\nhow to quantitatively apply the results from the tank experiments to the geological\nproblem. I feel that these problems need to be addressed in more detail before the paper\nwould be acceptable.\nResponse: We thank the reviewer for their positive comments on our work. In the revised\nmanuscript, we explain (including a new figure 3 and 4) how our results may account for\nthe active subsidence of the Konya basin in central Anatolia. The comparison of the\nmodeling results with geophysical observables in Figure 2 reconciles the geodynamics\nwith the geological problem but uncertainties both the in the model and the constraints\ncan make the direct comparison challenging. However, this work can address an\nenigmatic concept in the tectonics of Anatolia and is probably applicable to other areas\naround the globe.\n\nResponse to Reviewer 3\n1) Dear Editor,\nI have read the manuscript entitled Multistage lithospheric drips control active basin\nformation within an uplifting orogenic plateau submitted by Andersen et al. The paper\nstrives to elucidate the formation of the Konya Basin within the Central Anatolian\nPlateau. They suggest that the ongoing 5 cm/yr subsidence rate based on InSAR and\nGNSS analysis is a consequence of deep-rooted geophysical phenomena such as the\ndescent of a lithospheric drip based on fast seismic wave anomaly beneath the basin. This\nmanuscript is not ready to publish in your journal and needs to be more elaborated with\nlocal geology and geomorphology. I am a geomorphologist; therefore, I will particularly\nemphasize a few critical geomorphic points that authors must consider.\nResponse: We thank the review for their comments. In the revised manuscript, we\nimproved the explanation of the two-stage lithospheric drip concept based on geological\ninformation through new figure 4. The new figure 3, which shows subdued tectonic\ndeformation as well as vertical displacement amounts and patterns of uplift and\nsubsidence can address important points in geomorphology and tectonics.\n\n2) The time span that InSAR and GNSS analysis covers is very short from a geological\npoint of view; however, lithospheric dripping takes millions of years. If you combine\nthese two data, there is a considerable time gap between them and it would be better if\nauthors look at local geology and geomorphology to fill this gap. For instance, did they\ncheck the inclination of bedding of sedimentary rocks? Do they tilt to the Konya Basin or\nnot? If we consider 5 cm/yr subsidence, there must be significant tilting, although it is an\nasymptomatic drip.\nResponse: We agree with the reviewer that lithospheric dripping is a rather long-term\ntectonic behavior (millions of years) and we recognize that InSAR/GNSS is a measure of\npresent day subsidence. Nevertheless, to support the lithospheric drip hypothesis with\nscaled laboratory experiments we also incorporated other constraints including crustal\nthickness variations, seismic tomography, non-isostatic (residual topography) topography\ninferred from gravity inversions. These geological and geophysical observations provide\ninformation on the tectonic scales the reviewer is raising (the “time gap”), but this\ndoesn’t preclude us from using InSAR/GNSS as a constraint as well. We note that tilting\nof the bedding of sedimentary layers may not necessarily reflect lithospheric scale\ngeological processes (e.g., dripping, subduction); it can also be formed by local tectonic\nactivities, such as normal faulting.\n\n3) Similarly, local geomorphology. In our paper (Melnick et al., 2017), we studied paleolake\nshorelines in Tuz Gölü and Konya Basin. These are the shorelines belonging to LGM (20\nka) Lake. As you know, the shorelines are the best geomorphic markers to quantify\nvertical deformations. It would be really useful for the authors if they checked these data\nand correlated them with their model. If we consider 5 cm/yr subsidence, all these paleo\nshorelines need to be strongly deformed, which is not the case.\nResponse: In the revised manuscript we added a discussion to clarify the point raised by\nthe reviewer here (e.g., comparative scales between the experiments and nature). We note\nthat the Melnick et al. (2017) work was cited in the introduction of the original\nsubmission, but we have also added related discussion in the revised Introduction. It is\nnot our finding of the high rate of active surface subsidence (5 cm/yr); rather it has been\nestimated by INSAR and GNSS studies. While our experimental findings are in accord\nwith this subsidence controlled by lithospheric instabilities/drip crust-uppermost mantle\nscale, and are consistent with geophysical and geological studies, more localized\ngeomorphic features cannot develop in these experiments. Owing to the limitations of the\nexperimental work (essentially the challenge of dealing with extreme widths in spatial\nand temporal scales) we cannot simulate exact development of the local geological\nprocesses, such as erosion, deposition, groundwater extraction in these tectonic-scale\nmodels.\n\n4) Authors suggest there is no crustal deformation within the Konya Basin. Still, in our\npaper (Melnick et al., 2017), we showed the 12 m vertical displacement along the\nSultanhanı Fault and a surface rupture that might be produced by an earthquake\nmagnitude 6.5 or higher. Additionally, an earthquake ML 5.1 occurred on August 1 2023,\nin Konya within the subsidence circle of the paper, indicating obvious crustal\ndeformation. It is rare but exists.\nResponse: As the active fault map of Anatolia as well as earthquake database below\nshow, central Anatolia is associated with subdued tectonic activity unlike the east and the\nwest of the country. We agree that the region is not completely absent of tectonic\ndeformation; rather—and as the reviewer notes--it is rare, and this region represents a\nrelatively quiet tectonic deformational region of Anatolia.\n\n[Figure Redacted]\n\n5) I think this comment is the most critical because the authors did not consider the Konya\nBasin's karstic characteristics and the human effect. If you look at the subsidence pattern,\nthe centre of the Konya Basin is stable and not subsiding. This area corresponds to\nBozdağ Mountain National Park, with no agriculture. All the rapidly subsiding areas\noverlap with karstic plains that are intensively cultivated. Since the area is semiarid, the\nfarmers pump more underground water every year, and this extraction of groundwater\ngives rise to subsidence of the land surface, like in San Joaquin Valley, California, in the\n1950-60s. This is a well-known process in the region, and every year we have news about\nthe formation of sinkholes within the Konya basin because of the drop in underground\nwater level.\nResponse: In the revised manuscript, we added this point into the Discussion section—\nthat such surficial level activities (hydrological basin) may accompany larger-scale\nsubsidence in the Konya region. This is an important point, and indeed the groundwater\nextraction may account for the very high InSAR/GNSS rates that our models can’t fully\nexplain, but it does not invalidate our findings. Our proposal for lithospheric drip\nhypothesis is in good agreement for a range of observations (e.g thicker crust above\nsubsiding region, high speed seismic anomaly) where deep tectonic effects drive the\nanomalous topography."}, {"round": 2, "reviewer_comments": {"reviewer_1": "This is a revised version of an original manuscript submitted by Anderson and colleagues. I have read the new manuscript and the responses to the three reviewers comments. I note also that the comments by Reviewer 2 raised many of the same concerns as in my original review. Overall, I am satisfied that the authors have addressed most of the substantive comments provided in all three reviews and I congratulate the authors on a much improved manuscript.\n\nThat said, I think that a number of minor improvements could be made before publication. Firstly, I have provided an annotated PDF with a few editorial suggestions and comments. Secondly, I have several trailing questions about the work summarised below:\n\n1. As requested, the authors have provided some additional information about the first 25 hours of the drip experiment, when the \"primary\" drip was most active. However, it would also be useful to provide additional information on the surface topography evolution before the secondary drip started to form. This is because it is impossible to tell from Fig. 3e what aspects of the surface topography are related to the secondary drip and what is l\"inherited\" from the behaviour of the primary drip. This could be handled by adding some more information and figures to the Supplement.\n\n2. I like Figure 4 as it captures the main concepts nicely. However, it doesn't quite match with the experiment presented, in which the \"secondary\" drip is effectively a pulse of new material that has flowed into the tail of the primary drip. I.e., both drips are co-located, while Figure 4 portrays the secondary drip as as a new R-T instability that forms in a different location, after the primary drip has detached from the mantle lithosphere. This is not what happened in the experiment reported, although such truly secondary drips have been observed in other experiments (e.g., Pysklywec & Crude, 2004). Some comment/explanation on this in the text needs to be added to build confidence in the applicability of the experimental results to the Konya Basin.\n\n3. I still have some questions about material properties in the experiments. Firstly, what makes the mantle lithosphere denser than the asthenosphere to drive a Rayleigh-Taylor instability in the first place? Is there an explanation for what made this happen in the Anatolian mantle? And can the scaled lithospheric mantle density of 3418 kg/m^3 in the experiment can be justified? Secondly, the density of the dry quartz sand (1100 kg/m^3) used for the upper crust in the experiment seems unusually low. This is because silica (SiO2) has a density of 2.65 kg/m^3 (this cannot be changed) such that the bulk density of pure quartz sand (= f(silica grain density + air density) is typically ~1400 kg/m^3 for most reasonable porosities (=vol % sand vs vol% air). So the silica sand reported in Table 1 must either have an enormously high porosity or it has been reduced by adding some lower density particles.", "reviewer_2": "First a complaint about the management of this manuscript – whether a failing of the authors or of Nature Communications - Figure 1 is in the wrong orientation and half of the map is truncated and not visible. If you are sending a manuscript for review, why can’t it include the figures in a coherent package with a consistent page size, even if not in-line. You could make the reviewer’s task a little simpler. Also, why aren’t the figures for the Supplementary Information also included with the text in the reviewer package?\n\nI reviewed an earlier version of this manuscript. I think the authors have taken on board one of my key criticisms by describing in more detail the experiment on which the paper is based. The physical process now makes more sense to a reader, even if the conditions that establish the analog experiment are somewhat different to those that presumably established the actual geological environment. The context of the geological environment differs most notably from the experiment because of the Cyprus slab, which is imaged as the major feature in the seismic tomography (Fig 2a), but has no parallel in the analog experiment. The authors ignore this difference, but still the experiment has something to say about the process of secondary drips forming, and the relevance to the Koyna basin seems plausible. The study therefore should justify a publication – if they rectify the following problem:\n\nThe authors have also retreated to some degree from the claims that their surface deflection measurements can be related to observed surface subsidence in the Konya basin. However they have not retreated far enough in my opinion. Put simply, it is misleading and irrelevant that a rate of 5 cm/yr subsidence observed today in the basin is mentioned in the 2nd sentence of the abstract, and given a paragraph of the text, as if it has something to do with the mechanism that they propose here. Reviewer 3 point 5 offers a more likely explanation of the geodetic observation. The scaled rate of subsidence indicated in their own experiment (roughly 60 m in 3 Myr) is orders of magnitude slower than the GNSS rate. They should be looking for geological / sedimentological evidence of subsidence rate for the process they invoke (they mention sedimentation, but don’t infer a rate from it), but they cite the geodetic evidence that is relevant to a different process, and then paper over the inconsistency with a statement like: “Groundwater extraction may account for part of the high InSAR/GNSS displacements, but it does not invalidate our findings”. This sort of misleading and inconsistent logic does not belong in the paper.\n\nOther minor comments:\nline 376, 377: I guess they mean integrated along the line of sight rather than over the volume of the whole box, but even so, is it really integrated, or are the particles illuminated on a particular plane orthogonal to the line of sight ?\n\nThe figures are improved, but still in a couple of cases the figures are not particularly suitable for providing easily accessible quantitative information. Why for example are Fig 2c and 2d shown with different colour scales, when they nominally show the same quantity computed by two different groups. We could compare them more easily if you use the same colour scale. It is also not clear how to interpret what is shown in Fig 3c and 3h. What are we supposed to infer from those figures ? The caption does not help.", "reviewer_4": "The manuscript has already been through 1 round of review, and I’m asked to assess the authors’ responses to the referees’ previous concerns, as well as commenting on the robustness, novelty and importance of this manuscript for Nature Communication.\n\nI read the revised submission in accordance with the comments by 3 reviewers who provided extensive and stimulating contributions as being experts on the relevant fields of geophysics, geomorphology, geology and experimental modelling. The authors have considered all comments and implemented meticulously to improve their submission as the geodynamic model presented in the paper demonstrates how an internally drained sedimentary basins within the interior of orogenic plateaus originates and such a basin can form in response to a secondary lithospheric dripping event without crustal shortening. To support this phenomenon, the authors attempt to use an analogue laboratory model to experiment how an active formation in a particular basin (i.e. Konya basin of central Anatolia) may be accounted for by the descent of a lithosphere drip causing local subsidence. Eventually the authors interpret the development of the basin through a secondary drip pulse concurrent with broad plateau uplift caused by a larger-scale lithospheric drip. Therefore, the research reveals that basin evolution and plateau uplift may be linked in a multistage process of lithospheric removal during episodic development of orogenic systems. Eventually the authors attempted to modify the term recycling and explain how multistage removal may be an important mechanism for orogenic cycle.\n\nOverall the model presented in this study is consistent with the actual Konya basin case as well as in accordance with the other examples elsewhere World and enhance our understanding on the interaction between surface and subsurface dynamics which is still enigmatic, then need to be tested as in present case. Finally, as noted by the authors, underscores what might be an overlooked multistage process of lithospheric removal within a large-scale orogenic system.\n\nIn the meantime, I particularly focussed on the comments by the Reviewer 3, who emphasised the effect of karstic processes due to groundwater extraction may account for high InSAR/GNSS rates forming the subsidence. The authors noted this point and included satisfactory justification on this possibility; it is meaningful, needs to be considered but doesn’t invalidate their proposal at all.\n\nApart from all comments by 3 reviewers, I have a concern on the Fig.3 (i) on which there are several other depressions even deeper than the secondary drip-induced indicated by dashed rectangle. In the overall experimental model, there is a single primary drip followed by a secondary trip that causes subsidence which is attributed to as an analogy for the Konya basin. So, what would be the explanation for the other depressions (even deeper) around? The authors may note these multi-depressions caused by secondary drip, and may favour a depression complex rather than single depression attributed to a single drip event. In fact, basins are not single depressions, but constituted by several depressions eventually forming a basin with several depressions in it.\n\nAs a consequence, I found the idea of two stage drip hypothesis robust and novel to better understand surface-subsurface interactions and explain basin formation along that. This is indeed a new approach and the current case is another example to support multi-stage drop mechanism causing basin formation. Therefore, it is important for Nature Communication as it is present in revised and improved form."}, "author_response": "REVIEWERS' COMMENTS\nReviewer #1 (Remarks to the Author):\nThis is a revised version of an original manuscript submitted by Anderson and\ncolleagues. I have read the new manuscript and the responses to the three reviewers\ncomments. I note also that the comments by Reviewer 2 raised many of the same\nconcerns as in my original review. Overall, I am satisfied that the authors have\naddressed most of the substantive comments provided in all three reviews and I\ncongratulate the authors on a much improved manuscript.\nResponse: We thank the reviewer for their positive statements.\n\nThat said, I think that a number of minor improvements could be made before\npublication. Firstly, I have provided an annotated PDF with a few editorial\nsuggestions and comments. Secondly, I have several trailing questions about the work\nsummarised below:\n\n1. As requested, the authors have provided some additional information about the first\n25 hours of the drip experiment, when the \"primary\" drip was most active. However,\nit would also be useful to provide additional information on the surface topography\nevolution before the secondary drip started to form. This is because it is impossible to\ntell from Fig. 3e what aspects of the surface topography are related to the secondary\ndrip and what is \"inherited\" from the behaviour of the primary drip. This could be\nhandled by adding some more information and figures to the Supplement.\nResponse: As recommended by the reviewer, in the supplementary section of the\nrevised manuscript, we added relevant figures of evolution of surface topography for\nthe primary drip development. We created a new plot that shows topography at\n10h/5.0 My and 25h/12.6 My (corresponding to Figure 3a&b), and for comparison\n50.6h/25.4 My and 57.1h/28.7 My (corresponding to Figure 3e&g but plotted at a\ndifferent scale). We added relevant text in the Supplementary section to explain this\nnew figure (LINES 451-460). Characteristic to lithospheric drip models, in these\nearlier stages there is a surface subsidence above the downwelling, and around it,\nthere is uplift. We note in the manuscript that the experiment presented here does not\naccount for the complete geodynamic evolution of central Anatolia, since 10 Ma. The\nfoundations of our interpretations are also based on a previous contribution (Göğüş et\nal., 2017) where the origin of plateau uplift was discussed (LINES 76-78)\n\n2. I like Figure 4 as it captures the main concepts nicely. However, it doesn't quite\nmatch with the experiment presented, in which the \"secondary\" drip is effectively a\npulse of new material that has flowed into the tail of the primary drip. I.e., both drips\nare co-located, while Figure 4 portrays the secondary drip as as a new R-T instability\nthat forms in a different location, after the primary drip has detached from the mantle\nlithosphere. This is not what happened in the experiment reported, although such\ntruly secondary drips have been observed in other experiments (e.g., Pysklywec & Cruden,\n2004). Some comment/explanation on this in the text needs to be added to build\nconfidence in the applicability of the experimental results to the Konya Basin.\nResponse: We appreciate the reviewer’s comment on this. The new illustration in\nFigure 4 was intended to show how primary and secondary drips are related and is a\nsimplified view on drip tectonics in central Anatolia. Namely, consecutive drips as in\nthe figure were interpreted based on the seismic tomography model of Fichtner et al.\n(2013, EPSL) where the first one is supposedly detached (therefore causing plateau\nuplift) and the secondary one we believe to be driving the active subsidence of the\nKonya basin. In the revised manuscript, based on the suggestions of the reviewer, we\nclarified this point in the discussion section.\n\n“In Figure 4 the primary drip is depicted as being fully detached on the basis of\nseismic tomography (Fichtner et al 2013). Whether a thin neck attaching the primary\ndrip remains-as in the model-is uncertain owing to the resolution limitations of\nseismic imaging. We also note that mantle flow induced by the subduction of the\nCyprus slab may have also offset the secondary drip to the south of the Kırşehir arc\ntowards the Konya Basin.” (LINES 241-245).\n\nWe also cited Pysklywec and Cruden (2004, G-cubed), which recognizes the\ndevelopment of secondary mantle lithospheric instabilities in analogue experiments.\n“Notably, a secondary drip event (Fig. 3d-h) develops following the primary drip\n(similar to the phenomenon observed in Pysklywec and Cruden, 2004).” (LINES 189-\n190).\n\nIn the original manuscript we explained why there may be an offset between the\nprimary and secondary drips. Namely, in the response above we mention that this may\nbe due to the flow induced by the Cyprus slab which did not exist in our experiments.\nWe also note that the new Supplementary Figure 3 suggested by the Reviewer shows\nthat there is a shift in the center of the depressions induced by the primary and\nsecondary drips, and make a note of that in the explanation of the figure.\n\n3. I still have some questions about material properties in the experiments. Firstly,\nwhat makes the mantle lithosphere denser than the asthenosphere to drive a Rayleigh-\nTaylor instability in the first place? Is there an explanation for what made this happen\nin the Anatolian mantle? And can the scaled lithospheric mantle density of 3418\nkg/m^3 in the experiment be justified?\nResponse: Petrological studies argue that basaltic melts in central Anatolia contain\nhigh density pyroxenite which may be the reason for the growth of the instability and\nhence a drip process in central Anatolia (Kürkçüoğlu and Yürür, 2022,\nGeochemistry). The presence of garnet pyroxenites has been used to account for\nlithospheric foundering in other areas, including the Sierra Nevada (e.g., Saleeby et\nal., 2003, Tectonics; Lee and Anderson, 2015, Sci. Bull.). In the revised manuscript,\nwe have added explanation and reference to these potential petrological\nconsiderations on the development of the instability in central Anatolia (LINES 396-\n398).\n\nSecondly, the density of the dry quartz sand (1100 kg/m^3) used for the upper crust in\nthe experiment seems unusually low. This is because silica (SiO2) has a density of\n2.65 kg/m^3 (this cannot be changed) such that the bulk density of pure quartz sand\n(silica grain density + air density) is typically ~1400 kg/m^3 for most reasonable\nporosities (=vol % sand vs vol% air). So the silica sand reported in Table 1 must\neither have an enormously high porosity or it has been reduced by adding some lower\ndensity particles.\nResponse: We thank the reviewer for raising this point as the initial manuscript did\nnot clearly explain the properties of crustal materials in the model. A review of our\nlaboratory notes reveal that the material used for the upper crust was not pure silica\nsand. The upper crust was a combination of silica sand and e-spheres (hollow ceramic\nspheres), which was the same material used in analogue models of Santimano &\nPysklywec (2020). This explains the lower density listed in Table 1. The manuscript\nhas been revised accordingly to more clearly explain the nature of the model crust\n(LINES 301-303).\n\nReviewer 1 kindly provided a pdf document with further comments. Below are\nresponses to these comments. The line numbers correspond to the line numbers in the\npdf document.\n\n1. Line 28: \"Crustal thickening\" is not a noun. This should read: reveal thickened\ncrust OR reveal a region of crustal thickening.....\nResponse: The revised manuscript now reads as “thickened crust”.\n\n2. Line 31: Should be: calculated residual topography...\nResponse: The revised manuscript now reads as “calculated residual topography”.\n\n3. Line 188: Should really say: gravitationally unstable lithosphere.\nResponse: The revised manuscript now reads as “gravitationally unstable\nlithosphere”.\n\n4. Line 209: How do you define the basin width here? A certain topographic\ncontour value? I am asking this question because the 0 km contour does not seem to\nhave moved much between frames.\nResponse: We are defining the basin width on the 0 km contour. The Reviewer is\nright that any widening (movement of the 0 km contour) is too subtle to notice. In the\nrevised manuscript we have removed reference to “widening” of the basin here.\n\n5. Line 210: This statement is hard to assess because no information on the state\nof the surface topography before the secondary drip feature develops is provided.\nResponse: In the revised manuscript, we have included a new supplementary figure\n(Supplementary Figure 3) which shows topography at earlier stages of the experiment\nin relation to the primary drip. We have added a reference to this new figure here and\nhave added a sentence to reference the figure in the manuscript (LINES 186-188).\n\n6. Line 304: The density in Table 1 (1100 kg/m^3) seems too low for silica sand\n(usually ~1400 kg/m^3). This suggests that something else has been added to reduce\nthe density or that the density reported in the table is incorrect.\nResponse: This comment was addressed above. We consulted our lab notes and\nrealized that the Reviewer was correct. There were e-spheres added to the sand, which\nreduced the density of the crust.\n\n7. Line 340: This sentence seems out of place here.\nResponse: This sentence has been removed from the revised manuscript.\n\n8. Line 369: Imaging.\nResponse: Particle Image Velocimetry now reads as “Particle Imaging Velocimetry”\nin the revised manuscript.\n\n9. Line 406: Does this need to be repeated here?\nResponse: This sentence was removed from the revised manuscript.\n\nReviewer #2 (Remarks to the Author):\nFirst a complaint about the management of this manuscript – whether a failing of the\nauthors or of Nature Communications - Figure 1 is in the wrong orientation and half\nof the map is truncated and not visible. If you are sending a manuscript for review,\nwhy can’t it include the figures in a coherent package with a consistent page size,\neven if not in-line. You could make the reviewer’s task a little simpler. Also, why\naren’t the figures for the Supplementary Information also included with the text in the\nreviewer package?\nResponse: It is unfortunate that the Reviewer received the half of the figure because\nwe properly uploaded each figure into the system according to the instructions. It\nseems like a problem occurred somewhere with the document handling to cut off part\nof the figure. Sorry for the inconvenience.\n\nI reviewed an earlier version of this manuscript. I think the authors have taken on\nboard one of my key criticisms by describing in more detail the experiment on which\nthe paper is based. The physical process now makes more sense to a reader, even if\nthe conditions that establish the analog experiment are somewhat different to those\nthat presumably established the actual geological environment. The context of the\ngeological environment differs most notably from the experiment because of the\nCyprus slab, which is imaged as the major feature in the seismic tomography (Fig 2a),\nbut has no parallel in the analog experiment. The authors ignore this difference, but\nstill the experiment has something to say about the process of secondary drips\nforming, and the relevance to the Koyna basin seems plausible. The study therefore\nshould justify a publication – if they rectify the following problem:\n\nThe authors have also retreated to some degree from the claims that their surface\ndeflection measurements can be related to observed surface subsidence in the Konya\nbasin. However they have not retreated far enough in my opinion. Put simply, it is\nmisleading and irrelevant that a rate of 5 cm/yr subsidence observed today in the\nbasin is mentioned in the 2nd sentence of the abstract, and given a paragraph of the\ntext, as if it has something to do with the mechanism that they propose here. Reviewer\n3 point 5 offers a more likely explanation of the geodetic observation. The scaled rate\nof subsidence indicated in their own experiment (roughly 60 m in 3 Myr) is orders of\nmagnitude slower than the GNSS rate. They should be looking for geological /\nsedimentological evidence of subsidence rate for the process they invoke (they\nmention sedimentation, but don’t infer a rate from it), but they cite the geodetic\nevidence that is relevant to a different process, and then paper over the inconsistency\nwith a statement like: “Groundwater extraction may account for part of the high\nInSAR/GNSS displacements, but it does not invalidate our findings”. This sort of\nmisleading and inconsistent logic does not belong in the paper.\nResponse: We appreciate the Reviewer’s comments on this. Based on their comments,\nin the revised manuscript we modified our explanations—specifically backing away\nfrom a direct comparison with the present day (GNSS derived) subsidence rate. To\navoid being misleading, we removed the rate of subsidence from the abstract.\nUnfortunately, to the best of our knowledge, there does not exist published\nsedimentological data that constrains the rate of subsidence in the Konya basin. We\nremoved some of the previous text that made direct comparisons and added a new\ndiscussion with references for the hydrological effects of subsidence in the Konya\nbasin. Based on the Reviewer’s comments and suggestions here, the relevant passage\nnow reads as follows:\n\n“Our model interpretations account for long-term tectonic deformations, specifically ~\n60 m of basin subsidence in 3 Myr. We note that other factors, such as groundwater\nextraction may contribute to a large percentage of the high rate of current active\nsubsidence recorded by the InSAR/GNSS measurements (Caló et al., 2017; Weiss et\nal., 2020) (LINES 280-283).\n\nOther minor comments:\nLine 376, 377: I guess they mean integrated along the line of sight rather than over the\nvolume of the whole box, but even so, is it really integrated, or are the particles\nilluminated on a particular plane orthogonal to the line of sight?\nResponse: Based on the Reviewer’s comments, in the revised manuscript, we clarified\nour statement as such:\n\n“The contrast between the black background and the instability allowed us to track the\nmotion of the drip and the flow in the mantle, however, this means that the results\nshow flow velocities through the volume of the entire box projected onto the front\nplane of the image.” (LINES 362-365)\n\nThe figures are improved, but still in a couple of cases the figures are not particularly\nsuitable for providing easily accessible quantitative information. Why for example are\nFig 2c and 2d shown with different colour scales, when they nominally show the same\nquantity computed by two different groups. We could compare them more easily if\nyou use the same colour scale. It is also not clear how to interpret what is shown in\nFig 3c and 3h. What are we supposed to infer from those figures ? The caption does\nnot help.\nResponse: As suggested by the Reviewer, Figure 2c and 2d have been adjusted so that\nthey now use the same colour scale. For Figure 3c and 3h, we rewrote the caption and\nadded manuscript text to clearly explain what these figure frames demonstrate.\nNamely, they show that there is no visible horizontal deformation recorded at the\nsurface sand/crust layer. We also link this with the relevant Supplementary Figure 2\nthat explains symptomatic vs. asymptomatic drips. As explained in the text, such\nasymptomatic behaviour seems to agree with the evolution of the Konya basin in\ncentral Anatolia.\n\nReviewer #4 (Remarks to the Author):\nThe manuscript has already been through 1 round of review, and I’m asked to assess\nthe authors’ responses to the referees’ previous concerns, as well as commenting on\nthe robustness, novelty and importance of this manuscript for Nature\nCommunication.\n\nI read the revised submission in accordance with the comments by 3 reviewers who\nprovided extensive and stimulating contributions as being experts on the relevant\nfields of geophysics, geomorphology, geology and experimental modelling. The\nauthors have considered all comments and implemented meticulously to improve their\nsubmission as the geodynamic model presented in the paper demonstrates how an\ninternally drained sedimentary basins within the interior of orogenic plateaus\noriginates and such a basin can form in response to a secondary lithospheric dripping\nevent without crustal shortening. To support this phenomenon, the authors attempt to\nuse an analogue laboratory model to experiment how an active formation in a\nparticular basin (i.e. Konya basin of central Anatolia) may be accounted for by the\ndescent of a lithosphere drip causing local subsidence. Eventually the authors\ninterpret the development of the basin through a secondary drip pulse concurrent with\nbroad plateau uplift caused by a larger-scale lithospheric drip. Therefore, the research\nreveals that basin evolution and plateau uplift may be linked in a multistage process\nof lithospheric removal during episodic development of orogenic systems. Eventually\nthe authors attempted to modify the term recycling and explain how multistage\nremoval may be an important mechanism for orogenic cycle.\n\nOverall the model presented in this study is consistent with the actual Konya basin\ncase as well as in accordance with the other examples elsewhere World and enhance\nour understanding on the interaction between surface and subsurface dynamics which\nis still enigmatic, then need to be tested as in present case. Finally, as noted by the\nauthors, underscores what might be an overlooked multistage process of lithospheric\nremoval within a large-scale orogenic system.\n\nIn the meantime, I particularly focussed on the comments by the Reviewer 3, who\nemphasised the effect of karstic processes due to groundwater extraction may account\nfor high InSAR/GNSS rates forming the subsidence. The authors noted this point and\nincluded satisfactory justification on this possibility; it is meaningful, needs to be\nconsidered but doesn’t invalidate their proposal at all.\n\nApart from all comments by 3 reviewers, I have a concern on the Fig.3 (i) on which\nthere are several other depressions even deeper than the secondary drip-induced\nindicated by dashed rectangle. In the overall experimental model, there is a single\nprimary drip followed by a secondary trip that causes subsidence which is attributed\nto as an analogy for the Konya basin. So, what would be the explanation for the other\ndepressions (even deeper) around? The authors may note these multi-depressions\ncaused by secondary drip, and may favour a depression complex rather than single\ndepression attributed to a single drip event. In fact, basins are not single depressions,\nbut constituted by several depressions eventually forming a basin with several\ndepressions in it.\nResponse: We appreciate the Reviewer’s positive comments on the work. In Figure 3i\n(change in elevation between 50.6 h and 57.1 h) the localized depressions on the\nmargins of the main basin shown in the centre are only transient expressions of\nsurface elevation differences at these specific times (i.e., showing up by calculating a\ndifference in elevation with these data to create 3i). Since they are just transient\nmotions in the model, they do not play a role in the overall basin development—i.e.,\nthe evolution of the main subsidence in the central part of the model.\n\nWe appreciate the Reviewer’s comment that basins can develop as depression\ncomplexes, but in this case these particular features in the model are not sufficiently\nlong-lasting to modify the local basin development.\n\nAs a consequence, I found the idea of two stage drip hypothesis robust and novel to\nbetter understand surface-subsurface interactions and explain basin formation along\nthat. This is indeed a new approach and the current case is another example to support\nmulti-stage drop mechanism causing basin formation. Therefore, it is important for\nNature Communication as it is present in revised and improved form."}, {"round": 3, "reviewer_comments": {"reviewer_1": "This is the third version of this manuscript that I have been asked to review. The authors have addressed all of my previous concerns and suggestions and I consider the manuscript ready for publication. Congratulations on a well-presented and though-provoking paper."}, "author_response": "Response: We thank the reviewer for their positive statements."}]

Decision letter