Paleomagnetic records of middle Neoproterozoic (820-780 Ma) rocks display high amplitude directional variations that lead to large discrepancies in paleogeographic reconstructions. Hypotheses to explain these data include rapid true polar wander, a geomagnetic field geometry that deviates from a predominantly axial dipole field, a hyper-reversing field (> 10 reversals/Ma), and/or undiagnosed remagnetization. To test these hypotheses, we collected 1057 oriented cores over a 85 m stratigraphic succession in the Laoshanya Formation (Yangjiaping, Hunan, China). High precision U-Pb dating of two intercalated tuff layers constrain the age of the sediments between 809 and 804 Ma. Thermal demagnetization isolates three magnetization components residing in hematite which are not time-progressive but conflated throughout the section. All samples possess a north and downward directed component (in geographic coordinates) at temperatures up to 660°C that is ascribed to a Cretaceous overprint. Two components isolated above 660°C reveal distinct directional clusters: one is interpreted as a depositional remanence, while the other appears to be the result of a mid-Paleozoic (460-420 Ma) remagnetization, which is likely widespread throughout South China. The high-temperature directions are subtly dependent on lithology; microscopic and rock magnetic analyses identify multiple generations of hematite that vary in concentration and distinguish the magnetization components. A comparison with other middle Neoproterozoic paleomagnetic studies in the region indicates that the sudden changes in paleomagnetic directions, used elsewhere to support the rapid true polar wander hypothesis (ca. 805 Ma), are better explained by mixtures of primary and remagnetized components, and/or vertical axis rotations.

Understanding the stress distribution around shallow magma chambers is vital for predicting eruption sites and magma propagation directions. To achieve accurate predictions, comprehensive insight into the stress field surrounding magma chambers and near the surface is essential. Existing stress models for magma chamber inflation often assume a homogenous elastic half-space or a heterogeneous crust with varying mechanical properties in horizontal layers. However, as many volcanoes have complex, non-horizontal, and heterogeneous layers, we enhance these assumptions by considering mechanically diverse layers with varying dips. We employed the Finite Element Method (FEM) to create numerical models simulating two chamber shapes: a circular form and a sill-like ellipse. The primary condition was a 10 MPa excess pressure within the magma chamber, generating the stress field. Layers dips by 20-degree increments, with differing elastic moduli, represented by stiffness ratios (EU/EL) ranging from 0.01 to 100. Our findings validate prior research on heterogeneous crustal modeling, showing that high stiffness ratios disrupt stress within layers and induce local stress rotations at mismatched interfaces. Layer inclination further influences stress fields, shifting the location of maximum stress concentration over varying distances. This study underscores the significance of accurately understanding mechanical properties, layer dip in volcanoes, and magma chamber geometry. Improving predictions of future eruption vents in active volcanoes, particularly in the Andes with its deformed, folded, and non-horizontal stratified crust, hinges on this knowledge. By expanding stress models to incorporate complex geological structures, we enhance our ability to forecast eruption sites and the paths of magma propagation accurately.

The Carrascoy and Palomares faults are two major active faults of the Eastern Betic Shear Zone (SE Iberia), both controlling conspicuous mountain fronts. However, the area in between both faults, corresponding to the Mazarron Graben (MG), is a nearly flat plain bounded by a relief of smooth hills whose tectonic origin and evolution remains uncertain. By means of a morphotectonic analysis, geophysical survey and paleoseismological trenching we point out that this is area of distributed deformation controlled by folds of variable amplitude nucleated in high angle reverse faults with sinistral component without a well-defined deformation front. The MG developed a marine basin during the Upper Miocene evolving into an alluvial environment with calcrete pedogenic development through the Pleistocene, which formed a tableland landscape that favors the identification of tectonic structures. In this study we demonstrate how some of the ancient normal faults controlling the graben were reactivated as reverse during the late Middle Pleistocene within a regional frame of positive tectonic inversion. Such inversion is evidenced by several emblematic structures: (i) presence of harpoon folding, and (ii) newly formed high angle reverse faults, which dips increase and ruptures become younger backwards on the hanging wall. Based on the timing of the observed deformation, we also suggest that the onset of the regional tectonic inversion might be related to the tectonic evolution of the neighboring Carrascoy and Palomares faults, producing a local stress tensor varying dramatically from extension to compression within the neotectonic period in a regional convergence tectonic frame.

Stratovolcanoes are common globally, with high altitude summit regions that are often glacier-clad and intersect the seasonal and perennial snow line. Explosive eruptions from stratovolcanoes can generate pyroclastic density currents (PDCs). When PDCs are emplaced onto and propagate over glacierised substrates, melt and steam are generated and incorporated into the flow, which can cause a transformation from hot, dry granular flow, to a water-saturated, sediment-laden flow, termed a lahar. Both PDCs and ice-melt lahars are highly hazardous due to their high energy during flow and long runout distances. Knowledge of the physics that underpin these interactions and the transformation to ice-melt lahar is extremely limited, preventing accurate descriptions within hazard models. To physically constrain the thermal interactions we conduct static melting experiments, where a hot granular layer was emplaced onto an ice substrate. The rate of heat transfer through the particle layer, melt and steam generation were quantified. Experiments revealed systematic increases in melt and steam with increasing particle layer thicknesses and temperatures. We also present a one-dimensional numerical model for heat transfer, calibrated against experiment data, capable of accurately predicting temperature and associated melting. Furthermore, we present similarity solutions for early-time melting which are used to benchmark our numerical scheme, and to provide rapid estimates for meltwater flux hydrographs. These data are vital for predicting melt volume and incorporation into PDCs required to facilitate the transformation to and evolution of ice-melt lahars.

The Teisseyre-Tornquist Zone (TTZ) is the longest pre-Alpine tectonic lineament in Europe. Its nature and structural evolution are controversially debated. In this study, we show its structural evolution beneath the southern Baltic Sea both on crustal and basin scale by using three seismic reflection profiles combined with 2-D potential field data. The results demonstrate that the southern Baltic Sea is underlain by a thick crust of the East European Craton (EEC) with a Moho depth in the range of 38-42 km. The overall crustal architecture is shaped by three phases of localized crustal stretching in early Paleozoic, Devonian-Carboniferous, and Permian-Mesozoic. The most spectacular feature of the southern Baltic Sea are zones of thick-skinned compressional deformation produced by Alpine inversion along the TTZ and Sorgenfrei-Tornquist Zone (STZ). Both zones include a system of thrusts and back thrusts penetrating the entire crust in an 80-90 km wide inversion zone superimposed on the EEC crust and its sedimentary cover. ENE-vergent thrusts are traced from the top of the Cretaceous down to the Moho and they are accompanied by back thrusts of opposite vergence, also reaching the Moho. Inversion tectonics resulted in the uplift of a block of cratonic crust as a pop-up structure, bounded by thrusts and back thrusts, and the displacement of the Moho within the STZ and TTZ. The similar mechanism of intra-cratonic inversion was recognized for the Dnieper-Donbas Basin in Ukraine, and it may be characteristic of rigid cratons, where deformation is localized in a few preexisting zones of weakness.

Seismic tomography of Earth’s mantle images abundant slab remnants, often located in close proximity to active subduction systems. The impact of such remnants on the dynamics of subduction remains under explored. Here, we use simulations of multi-material free subduction in a 3-D spherical shell geometry to examine the interaction between visco-plastic slabs and remnants that are positioned above, within and below the mantle transition zone. Depending on their size, negatively buoyant remnants can set up mantle flow of similar strength and length scales as that due to active subduction. As such, we find that remnants located within a few hundred km from a slab tip can locally enhance sinking by up to a factor 2. Remnant location influences trench motion: the trench advances towards a remnant positioned in the mantle wedge region, whereas remnants in the sub-slab region enhance trench retreat. These motions aid in rotating the subducting slab and remnant towards each other, reducing the distance between them, and further enhancing the positive interaction of their mantle flow fields. In this process, the trench develops along-strike variations in shape that are dependent on the remnant’s location. Slab-remnant interactions may explain the poor correlation between subducting plate velocities and subducting plate age found in recent plate tectonic reconstructions. Our results imply that slab-remnant interactions affect the evolution of subducting slabs and trench geometry. Remnant-induced downwelling may also anchor and sustain subduction systems, facilitate subduction initiation, and contribute to plate reorganisation events.

The southeastern margin of the Tibetan Plateau has undergone complex deformation since the Cenozoic, resulting in a high level of seismicity and seismic hazard. Knowledge about the seismic anisotropy provides important insight about the deformation mechanism and the regional seismotectonics beneath this tectonically active region. In this study, we conduct fullwave multi-scale tomography to investigate the seismic anisotropy in the southeastern margin of the Tibetan Plateau. Broadband records at 111 permanent stations in the region from 470 teleseismic events are used to obtain 5,216 high-quality SKS splitting intensity measurements, which are then inverted in conjunction with 3D sensitivity kernels to obtain an anisotropic model with multi-scale resolution. Resolution tests show that our dataset recovers anisotropy anomalies reasonably well on the scale of 1º x 1º horizontally and ~100 km vertically. Our result suggests that in the southeastern margin of the Tibetan Plateau the deformation in the lithosphere and asthenosphere are decoupled. The anisotropy in the lithosphere varies both laterally and vertically as a result of dynamic interactions of neighboring blocks as well as lithospheric reactivation. The anisotropy in the asthenosphere largely follows the direction of regional absolute plate motion. The SKS splittings observed at the surface are shown to be consistent with the vertical integral of our depth-dependent anisotropy model over lithospheric and asthenospheric depths.

Astronomical cycles recorded in stratigraphic sequences offer a powerful data source to estimate Earth’s axial precession frequency k, as well as the frequency of rotation of the planetary perihelia (gi) and of the ascending nodes of their orbital planes (si). Together, these frequencies control the insolation cycles (eccentricity, obliquity and climatic precession) that affect climate and sedimentation, providing a geologic record of ancient Solar system behavior spanning billions of years. Here we introduce two Bayesian methods that harness stratigraphic data to quantitatively estimate ancient astronomical frequencies and their uncertainties. The first method (TimeOptB) calculates the posterior probability density function (PDF) of the axial precession frequency k and of the sedimentation rate u for a given cyclostratigraphic data set, while setting the Solar system frequencies gi and si to fixed values. The second method (TimeOptBMCMC) applies an adaptive Markov chain Monte Carlo algorithm to efficiently sample the posterior PDF of all the parameters that affect astronomical cycles recorded in stratigraphy: five gi, five si, k, and u. We also include an approach to assess the significance of detecting astronomical cycles in cyclostratigraphic records. The methods provide an extension of current approaches that is computationally efficient and well suited to recover the history of astronomical cycles, Earth-Moon history, and the evolution of the Solar system from geological records. As case studies, data from the Xiamaling Formation (N. China, 1.4 Ga) and ODP Site 1262 (S. Atlantic, 55 Ma) are evaluated, providing updated estimates of astronomical frequencies, Earth-Moon history, and secular resonance terms.

Multispectral mapping data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) provide a unique opportunity to characterize south polar ice deposits at higher spectral sampling, spatial resolution, or spatiotemporal coverage than previous work. This new perspective can help to constrain the nature and distribution of different mixtures of CO2 ice, H2O ice, and dust that influence the formation, evolution, and preservation of Mars climate records. We processed 1103 CRISM observations spanning southern summer of six Mars Years (MY) through a combination of k-means clustering and random forest classification. Using a set of 12 spectral endmembers directly tied to previous work with high-resolution CRISM targeted data, we made a series of temporally restricted mosaics showing surface spectral variation over time. The mosaics show the effects of the MY 28 dust storm on the removal of the seasonal CO2 ice cap that year and reveal how this process differed from the years that followed. A mosaic showing residual ice surfaces displays broad agreement with previous compositional maps while resolving new details in the distribution of H2O ice-rich material around the periphery of the bright CO2 ice cap. By showing how surface composition varies across a broad swath of the south polar region though time, the endmember set and classified mosaics produced in this work can provide critical context for future studies of the dynamic processes that shape south polar ice deposits.

Curved mountain belts are spectacular natural features, which contain crucial 3D information about the tectonic evolution of orogenic systems. The Mesozoic units exposed at the Cordilleran Mexican Fold and Thrust belt in NE Mexico show a striking curvature that has not been explained nor included in the existent tectonic models of the region. We have investigated with paleomagnetism and rock magnetism the kinematic history of that curvature, which is observed in the rocks of the Jurassic Nazas igneous province and its overlying red beds. Our results show a complex history of remagnetizations that occurred during the Late Jurassic and Cretaceous, as well as clockwise and counterclockwise vertical axis rotations of up to 50˚ respectively in each limb of the curvature. Although our data cannot provide precise timing for such rotations yet, our results confirm that the Mexican Fold and Thrust Belt underwent post-Late Jurassic orocline bending or bucking in NE Mexico.

Evaluation of the approximate magnitude of the gross discrepancy between the volume of sediment produced on the hinterland and the volume deposited in the basin, over long time and length scales, is required to make source-to-sink sediment mass-balance calculations more accurate so that multiple sources for a single widespread stratigraphic unit, or bypass of the unit, might be more easily detected. This paper outlines a method to characterize the sources of sediments, or provenance lithotypes, according to their relative ability to produce dissolved ions, clay minerals, and unaltered residue at different levels of weathering. Estimating the relative proportion of the hinterland that is dissolved supports mass-balance analysis comparing hinterland denudation with basinal deposition, whereas estimating the relative proportion of clay (both original clay, eroded from mudstone, for example, as well as newly created clay produced by weathering of feldspar) supports potential identification of multiple sediment sources. The method is illustrated with a practical example from the Bohemian Massif and documented with an Excel workbook. This is a mineralogical approach based on mineral inventories of weathering profiles. Even if the prediction is necessarily uncertain because the mineralogical representation of the PLs are gross abstractions, the modelled transformation processes are crude cartoons, and the extent of transformation under different environmental conditions is wild speculation based on sparse examples, quantitative provenance analysis will be more accurate and more precise than it would be if dissolution and alteration were not explicitly accounted. There is ample opportunity for the community to improve the procedure!

Jeff Apple Benowitz1, Michael Everett Mann21 GeoSep Services, 1521 Pine Cone Road, Moscow, ID, USA2 Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI, USACorresponding author: Jeff Apple Benowitz ([email protected])AbstractLong-lived magmatic arcs theoretically should migrate large trench perpendicular distances as convergent margin configurations and slab geometry vary over time, however many arc-magmatic belts are spatially localized over 10’s of millions of years. We document, by compiling published crystallization geochronology data for southern Alaska (6485 total bedrock and single grain detrital ages combined), that since ca. 100 Ma, arc magmatism has been localized along the Alaska Range suture zone, at times over 500-km inboard. However, since ca. 100 Ma incoming subducting slab characteristics, beneath mobile southern Alaska and convergent margin configurations, varied greatly and include both normal oceanic plate and oceanic plateau subduction, plate vector changes, oroclinal bending and reconfiguration of trench shape, terrane accretion, long distance translation and a Paleocene slab break off/slab window event. Therefore, it is inferred that inherited upper-plate lithospheric shape and heterogeneity must control in part the geometry of the subducting slab below a mobile southern Alaskan margin through hydrodynamic (viscous) mantle wedge “suction” forces. Additionally, crustal thickness heterogeneity may preferentially focus magma ascent through melt ponding along Moho offsets, and upper-plate lithospheric-scale strike-slip faults may be acting as passive and active conduits for arc magmatism. Inherited upper-plate controls on slab geometry could be a factor localizing arc magmatism along other long-lived convergent margin settings.

Plate Motion Change at ca. 6 MaJacob L. Rosenthal1, Paul G. Fitzgerald1, Jeffrey A. Benowitz2, James R. Metcalf2, Paul M. Betka31Department of Earth and Environmental Sciences, Syracuse University , Syracuse NY 13244, USA2Department of Geological Sciences, University of Colorado Boulder , Boulder Co 80309, USA3Atmospheric, Oceanic, and Earth Sciences Department , George Mason University, Fairfax VA 22030, USACorresponding author: Jacob Rosenthal ([email protected])

Mid-lithosphere discontinuities are seismic interfaces likely located within the lithospheric mantle of stable cratons, which typically represent velocities decreasing with depth. The origins of these interfaces are poorly understood due to the difficulties in both characterizing them seismically and reconciling the observations with thermal-chemical models of cratons. Metasomatism of the cratonic lithosphere has been reported by numerous geochemical and petrological studies worldwide, yet its seismic signature remains elusive. Here, we identify two distinct mid-lithosphere discontinuities at ~89 and ~115 km depth beneath the eastern Wyoming craton and the southwestern Superior craton by analyzing seismic data recorded by two longstanding stations. Our waveform modeling shows that the shallow and deep interfaces represent isotropic velocity drops of 2–9% and 3–10%, respectively, depending on the contributions from changes in radial anisotropy and density. By building a thermal-chemical model including the regional xenolith thermobarometry constraints and the experimental phase-equilibrium data of mantle metasomatism, we show that the shallow interface probably represents the metasomatic front, below which hydrous minerals such as amphibole and phlogopite are present, whereas the deep interface may be caused by the onset of carbonated partial melting. The hydrous minerals and melts are products of mantle metasomatism, with CO2-H2O-rich siliceous melt as a probable metasomatic reagent. Our results suggest that mantle metasomatism is probably an important cause of mid-lithosphere discontinuities worldwide, especially near craton boundaries, where the mantle lithosphere may be intensely metasomatized by fluids and melts released by subducting slabs.

Along the strike of subduction zones, tectonic tremor activity is segmented on a geologic scale, indicating local variations of the tremor-generating process. Here, we study how strong temporal clustering and long-term recurrence of activity can emerge from the synchronization of elementary tremor sources, as they interact through fluid pressure transients. We model tremor sources as rapid openings of low-permeability valves in the permeable fault zone channeling the upward flow of deep metamorphic fluids. Valve openings trigger fast pressure transients that generate seismic waves. In such a system, tremor activity is thus shaped by unsteady fluid circulation. Using numerical simulations of fluid flow for a large number of different valve populations, we show that the synchronized, collective activity of sources generates episodic activity, and that along-strike variations of fluid flux and fluid transport properties can lead to the segmentation of tremor activity. Strong tremor bursts that coherently activate wide parts of the fault and recur with a long period are associated with patches densely populated with valves and characterized by below-average permeability. Long-term tremor episodicity emerges from the synchronous activity of valves in such patches and is responsible for fluid-pressure cycling at the subduction scale. In the tremor zone of the Shikoku, Japan, subduction interface, the most temporally clustered segment coincides with a downgoing seamount chain, suggesting that the segmentation of the fault zone permeability, and hence of tremor activity, could be inherited from the topography of the subducting oceanic plate.

Two-phase fluid flow in fractured porous media impacts many natural and industrial processes but our understanding of flow dynamics in these systems is constrained by difficulties measuring the flow in the interacting fracture and porous media. We present a novel experimental system that allows quantitative visualization of the air and water phases in a single analog fractured porous medium. The fracture system consists of a sintered-glass porous plate in contact with an impermeable glass plate. A reservoir connected to the porous plate allows control of pore pressure within the porous medium. The fracture fills and drains through the porous matrix and flow manifolds along two edges of the fracture. The fracture is mounted in an imaging system that includes a controlled light-emitting diode (LED) panel and a charge-coupled-device (CCD) camera. Flow and pressure are controlled and monitored by a computer during experiments. To demonstrate this system, we carried out a series of cyclic drainage and imbibition experiments in fractures bounded by porous media with different pore-size distributions in the porous matrix. Images of the drainage process demonstrate that the air-water distribution within the fracture evolves differently than has been observed in non-porous fractured systems. Specifically, we observed limited trapping of water within the fracture during drainage. Conversely, during imbibition, because air cannot exit through the porous matrix, significant regions of air became entrapped once pathways to the fracture boundaries became water filled. The differences in phase evolution led to substantial differences in the evolution of estimated relative permeability with saturation.

The Carpathian Mountains form the large collisional orocline stretching from Vienna, Austria to Bucharest, Romania. The Western and Inner Carpathians include the High Tatra mountains, which exhibit the highest elevation peaks of the entire mountain belt. Here we studied the exhumation history of an area near Gerlachovský štít, the topographically highest point of the High Tatras. Granitoid samples from different elevations were collected and analyzed for apatite (U-Th)/He (n=12; 5-6 aliquots) and zircon (U-Th)/He ages (n=22; 2-4 aliquots). In addition, apatite U-Pb dating by LA-ICPMS was conducted to complement existing zircon U-Pb dates to track the evolution of the High Tatra Mountains from the onset of magmatism during the Variscan orogeny. The (U-Th)/He apatite ages show a general increase from 9.6 ± 0.6 Ma to 31.9 ± 2.0 Ma to from lower to higher elevations. The zircon (U-Th)/He ages are more scattered and range from 13.5 ± 1.1 Ma to 47.8 ± 3.9 Ma. These reported ages agree with published low-temperature thermochronometric results. However, the apparent average exhumation rates for zircon and apatite (U-Th)/He data derived from the age-to-elevation profile near Gerlachovský štít are inconsistent with a proposed rapid early Miocene exhumation pulse. Apatite U-Pb ages obtained in this study are between 337.61 ± 2.21 Ma and 372.74 ± 3.09 Ma. These ages agree with previously reported zircon dates from the same or nearby samples. This observation is indicative of rapid cooling of the granitoids following crystallization. However, the greatest variance in both data sets were observed from samples collected near the sub-Tatra fault and along the Ružbachy fault. This observation was used to confine regions about these major structures that have distinct exhumation records. The results of the (U-Th)/He ages captures both pre- and post-Miocene slow cooling interrupted by early Miocene tectonic unroofing. Overall, these results are used to outline the earliest tectonic history of the High Tatra Mountains until the onset of more recent exhumation and impacts our understanding of the origin and development of this section of the arcuate mountain belt.

A document by Elizabeth Catlos. Click on the document to view its contents.

Geomechanical simulations of induced seismicity generally involve a simple reservoir geometry in terms of reservoir structure and fault distribution. Because the depletion of the reservoir controls the incremental stress field, the geometry of the reservoir has a substantial influence on the occurrence of induced earthquakes. We develop geomechanical models based on a realistic geological model of the reservoir in the Groningen gas field. The model captures the main characteristics of the reservoir structures in the Zeerijp region. Through quasi-static and dynamic simulations, we observe that a smaller intersection angle between the two normal faults in the Zeerijp region causes an increase in the incremental Coulomb stress at the lower reservoir juxtaposition adjacent to the intersection. As a result, this intersection angle strongly affects the location of the initial seismic slip, the rupture pattern, and the location of the maximum slip. Our simulation produces an earthquake of magnitude MW 3.0, due to fault reactivation occurring at a reservoir depletion value of 26 MPa. These values are similar to those for the Zeerijp 2018 earthquake of ML 3.4. The location of the simulated rupture is close to the inverted hypocenter location for the 2018 earthquake. Our results suggest that it is crucial to incorporate realistic reservoir structures when simulating induced seismicity in a specific region.

A document by Alessio Testa. Click on the document to view its contents.

Minibasins on continental margins trap turbidity currents transporting material downslope, but little is known about the inherently three-dimensional (3-D) mechanics of these confined flows. Utilizing new methodology, experimental results quantify flow dynamics in minibasins for the first time. It is shown that dynamics are dominated by 3-D circulation cell structures, across the fill-to-strip-to-spill transition that are controlled by flow discharge. Measurements of velocity throughout circulation cells indicate vorticity dominates strain rate with fluid rotating into the center of cells where it upwells: this influences minibasin sediment trapping potential and deposit heterogeneity. Flow properties link to depositional patterns on minibasin slopes. Specifically, higher input discharges are correlated with higher fluxes into the center of minibasins and reduced deposit tapering on minibasin slopes. This geometry is linked to the amount of sediment rich flow runup on the distal minibasin wall, where flow and sediment is delivered to circulation cells.

A document by John Paul Platt. Click on the document to view its contents.

Coral reef islands are amongst the most vulnerable environments to sea-level rise (SLR). Recent physical and numerical modelling studies have demonstrated that overwash processes may enable reef islands to keep up with SLR through island accretion. Sediment supply to these islands from the surrounding reef system is critical in understanding their morphodynamic adjustments, but is poorly constrained due to insufficient knowledge about sediment delivery rates. This paper provides the first estimation of sediment delivery rates to coral reef islands. Analysis of topographic and geochronological data from 28 coral reef islands indicates an average rate of sediment delivery of c. 0.1m3.m-1.yr-1, but with substantial inter-island variability. Comparison with carbonate sediment production rates from census-based studies suggests that this represents c. 26% of the amount of sediment produced on the reef platform. Results of this study are useful in future modelling studies for predicting morphodynamic adjustments of coral reef islands to SLR

The Martian North Polar Layered Deposits (NPLD) are composed of alternating water-ice and dust-rich layers resulting from atmospheric deposition and are key to understanding Mars’ climate cycles. Within these deposits are spiral troughs, whose migration affects deposition signals. To understand the relationship between NPLD stratigraphy and Martian climate, we must identify modern-day drivers of NPLD ice migration. Prevailing theory posits migration driven by upstream-migrating bed undulations bounded by hydraulic jumps, caused by katabatic winds flowing over trough walls with asymmetric cross-sectional relief. This is supported by trough-parallel clouds, whose formation has been attributed to hydraulic jumps. We present a cloud atlas across the Martian north pole using ~13,800 THEMIS images spanning ~18 Earth years. We find trough-parallel clouds in ~400 images, with regions nearer to the pole having higher cloud frequency. We compare spiral trough geometry to our cloud atlas and find regions with trough-parallel clouds often correlate with metrics associated with modern-day sublimation-deposition cycles (i.e., relief and asymmetry), but not always. In some regions, troughs with morphologies conducive to cloud formation have no clouds. Overall, trough geometry varies greatly across the deposits, both within and between troughs, suggesting localized differences in deposition relative to migration, varying katabatic wind intensities, differing past climatic states influencing the troughs, varying trough initiation properties, or the possibility of additional mechanisms for trough initiation and migration (e.g., in-situ trough erosion). Understanding what controls trough shape variability across the NPLD and how these controls change through time and space is key when interpreting Martian paleoclimate. Abstract content goes here