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Publication High-resolution lithostratigraphy and reconnaissance sedimentology of Changotaung structure, Chittagong Tripura fold belt, Bengal Basin, Bangladesh(Nature Research, 2023-10-18) Sharmili, Noshin; Apu, Saiful Islam; Gazi, Md. Yousuf; Bhuiyan, Md. Anwar Hossain; Lupin, Janifar HakimUnlike other structures in the vicinity of the Chittagong Tripura Fold Belt, the Changotaung anticline is one of Bangladesh's least explored structures. An attempt has been made for the first time to understand and document sedimentary deposits, environments, structure, and tectonic activity based on the high-resolution outcrop and reconnaissance study with the knowledge of broad-brush geology. We found that Changotaung is a symmetrical box-folded structure with an extensive western flank where the amount of dip varies between 11° and 45°. The exposed Cenozoic succession was categorized into three separate sedimentary sequences and correlated with the conventional stratigraphic unit. A first-order simple Markovian approach was presented for the exposed litho-section in an effort to illustrate vertical facies variations in the Upper Surma group. We quantified that heterolithic bed mostly overlies both trough cross-bedding (PijU = 0.706) and parallel laminated bed (PijU=0.955) according to the facies transition probability matrix. According to the results of the stationary distribution, there is a 40% chance of coming across heterolithic beds within the Upper Surma group during any given event that is completely random whereas trough cross-bedding, parallel laminated bed, cumulative sandstone facies, and cumulative shale facies shows around 10.8%, 15.2%, 20.6%, 13.4% probability. We hypothesized, based on the interpretive facies analysis, that the Chittagong Tripura fold belt region's Upper Surma Group underwent three interrelated depositional settings (wave-dominated shallow marine, tide-dominated shallow marine, and fluvio-deltaic distributary).Publication Land loss in the Mississippi River Delta: Role of subsidence, global sea-level rise, and coupled atmospheric and oceanographic processes(Elsevier, 2023-02-05) Blum, Mike; Rahn, David; Frederick, Bruce; Polanco, SaraThe Mississippi River Delta in coastal Louisiana has suffered large-scale land loss during the historic period and is representative of a global phenomenon where low-elevation deltaic coasts are increasingly at risk because of disrupted sediment supply and accelerated global sea-level rise. Land loss is a natural part of deltaic evolution over time, and most of the land loss in the Mississippi River Delta occurred after individual delta-plain headlands were abandoned as active constructional landscapes, but before 1932 when collection of air photos would make repeat land loss measurements possible. A coastwide land loss of ∼5000 km2 is now well documented for the period 1932 to 2016, which corresponds to a mean rate of ∼57 km2 yr−1. We use a LiDAR digital topobathymetric model to hindcast land-area changes through time for 1950–2010 by incrementally restoring elevation lost due to subsidence, global sea-level rise, and annual anomalies in mean sea level. Our results support the view that the magnitude and spatial distribution of 20th century land loss can be explained by an unfortunate convergence of ongoing subsidence, greatly reduced sediment dispersal due to levee construction, and acceleration of global sea-level rise. Other factors have contributed to land loss on local scales, but the magnitude of land loss that has occurred would have occurred anyway due to subsidence, lack of sediment input, and accelerated sea-level rise. Multidecadal accelerations and decelerations in land loss from 1950 to 2010 have been observed, and attributed to accelerations and decelerations in subsidence due to subsurface fluid withdrawals. However, non-linear land loss represents measurements that were made when water levels varied due to annual to multidecadal anomalies in mean sea level. Anomalies in mean sea level are driven by flux of water into and out of the Gulf of Mexico from the Atlantic, as well as the Atlantic Multidecadal Oscillation (AMO), which produces precipitation anomalies in the Gulf of Mexico drainage area, anomalies in Mississippi River discharge to the Gulf of Mexico, and changes in wind directions that serve to trap water along the coast and elevate coastal sea level, or advect water away from the coast to lower coastal sea level. Sea-level anomalies of the scale described here amplify or suppress the secular trend of global sea-level rise and its impacts on low-elevation delta plains as they respond to ongoing subsidence and anthropogenic disruption of sediment dispersal.Publication Berriasian–Valanginian Geochronology and Carbon-Isotope Stratigraphy of the Yellow Cat Member, Cedar Mountain Formation, Eastern Utah, USA(MDPI, 2023-01-26) Joeckel, Robert M.; Suarez, Celina A.; McLean, Noah M.; Möller, Andreas; Ludvigson, Gregory A.; Suarez, Marina B.; Kirkland, James I.; Andrew, Joseph; Kiessling, Spencer; Hatzell, Garrett A.The Early Cretaceous Yellow Cat Member of the terrestrial Cedar Mountain Formation in Utah, USA. has been interpreted as a “time-rich” unit because of its dinosaur fossils, prominent paleosols, and the results of preliminary chemostratigraphic and geochronologic studies. Herein, we refine prior interpretations with: (1) a new composite C-isotope chemostratigraphic profile from the well-known Utahraptor Ridge dinosaur site, which exhibits δ13C features tentatively interpreted as the Valanginian double-peak carbon isotope excursion (the so-called “Weissert Event”) and some unnamed Berriasian features; and (2) a new cryptotephra zircon eruption age of 135.10 ± 0.30/0.31/0.34 Ma (2σ) derived from the CA-ID-TIMS U-Pb analyses of zircons from a paleosol cryptotephra. Our interpretations of δ13C features on our chemostratigraphic profile, in the context of our new radiometric age, are compatible with at least one prior age model for the “Weissert Event” and the most recent revision of the Cretaceous time scale. Our results also support the interpretation that the Yellow Cat Member records a significant part of Early Cretaceous time.Publication StraboTools: A Mobile App for Quantifying Fabric in Geology(Geological Society of America, 2020-08) Glazner, Allen F.; Walker, J. DouglasQuantification of field observations is an essential step in making them reproducible and shareable, but field geologists have few tools for quantifying field observations of important features such as foliation intensity, crystal alignment, vesicle elongation, joint intensity, and mineral proportions. Here we describe a mobile app, StraboTools, which offers two ways to rapidly and objectively quantify these variables. The edge fabric tool examines grayscale gradients in a photograph and summarizes them with the edge fabric ellipse. For deformation of a homogeneous material with passive markers, this ellipse tracks the strain ellipse. Edge fabric ellipses can be determined on the outcrop and make quick work (5 seconds) of formerly time-consuming and subjective strain-analysis tasks (e.g., Fry and Rf /Φ analysis). They are remarkably sensitive to subtle deformations that are difficult to see by eye. The color index tool determines the proportion of any component in the photograph whose grayscale level can be isolated (e.g., dark minerals in a granitic rock, feldspar phenocrysts in a lava, or blue epoxy in a thin section). Estimating proportions by eye has poor precision and accuracy; the color index tool is both accurate and precise if a suitable rock face is available. These tools can be used with photomicrographs and aerial photographs as well as in the field.Publication Pliocene–Pleistocene basin evolution along the Garlock fault zone, Pilot Knob Valley, California(Geological Society of America, 2020-08-06) Rittase, William M.; Walker, J. Douglas; Andrew, Joe; Kirby, Eric; Wan, ElmiraExposed Pliocene–Pleistocene terrestrial strata provide an archive of the spatial and temporal development of a basin astride the sinistral Garlock fault in California. In the southern Slate Range and Pilot Knob Valley, an ∼2000-m-thick package of Late Cenozoic strata has been uplifted and tilted to the northeast. We name this succession the formation of Pilot Knob Valley and provide new chronologic, stratigraphic, and provenance data for these rocks. The unit is divided into five members that record different source areas and depositional patterns: (1) the lowest exposed strata are conglomeratic rocks derived from Miocene Eagle Crags volcanic field to the south and east across the Garlock fault; (2) the second member consists mostly of fine-grained rocks with coarser material derived from both southern and northern sources; and (3) the upper three members are primarily coarse-grained conglomerates and sandstones derived from the adjacent Slate Range to the north. Tephrochronologic data from four ash samples bracket deposition of the second member to 3.6–3.3 Ma and the fourth member to between 1.1 and 0.6 Ma. A fifth tephrochronologic sample from rocks south of the Garlock fault near Christmas Canyon brackets deposition of a possible equivalent to the second member of the formation of Pilot Knob Valley at ca. 3.1 Ma. Although the age of the base of the lowest member is not directly dated, regional stratigraphic and tectonic associations suggest that the basin started forming ca. 4–5 Ma. By ca. 3.6 Ma, the northward progradation fanglomerate sourced in the Eagle Crags region waned, and subsequent deposition occurred in shallow lacustrine systems. At ca. 3.3 Ma, southward progradation of conglomerates derived from the Slate Range began. Circa 1.1 Ma, continued southward progradation of fanglomerate with Slate Range sources is characterized by a shift to coarser grain sizes, interpreted to reflect uplift of the Slate Range. Overall, basin architecture and the temporal evolution of different source regions were controlled by activity on three regionally important faults—the Garlock, the Marine Gate, and the Searles Valley faults. The timing and style of motions on these faults appear to be directly linked to patterns of basin development.Publication Investigation of Geological Anomalies at Pile Foundation Location in Urban Karst Areas Using Single Borehole Radar(MDPI, 2020-06-16) Liu, Liu; Shi, Zhenming; Peng, Ming; Tsoflias, Georgios P.Karst geological anomalies at pile locations significantly affect the bearing capacity and construction safety of the piles, posing a significant challenge for urbanization. Borehole geophysical methods are required to extend the detection range and identify karst voids that are at pole locations and near drilled boreholes. In this paper, we developed a near offset and small diameter single borehole ground penetration radar (GPR) prototype. A signal processing method combining complex signal analysis by Hilbert transform (HT) and medium filtering was suggested to differentiate the weak backscattered wave from borehole background noise. A controlled horizontal borehole experiment was used to demonstrate the applicability of the prototype and the advantages of the signal analysis method prior to application in a real project. The controlled test presented three typical wave events corresponding to a soil–rock interface, rock fractures, and karst voids. Field tests were conducted at a freeway bridge extension project in an urban karst area. Multiple karst voids, sinkholes, rock fractures, and integrated bedrock were identified by analysis of four typical detection scenarios. The remediation of the karst voids and a rotary bored piling with real-time steel casing construction strategy were designed based on the investigation results. The construction feedback demonstrates that single borehole radar detection is effective for the investigation of anomalies at pile locations in urban karst areas.Publication Structure-From-Motion Photogrammetry of Antarctic Historical Aerial Photographs in Conjunction with Ground Control Derived from Satellite Data(MDPI, 2020-12-23) Child, Sarah F.; Stearns, Leigh A.; Girod, Luc; Brecher, Henry H.A longer temporal scale of Antarctic observations is vital to better understanding glacier dynamics and improving ice sheet model projections. One underutilized data source that expands the temporal scale is aerial photography, specifically imagery collected prior to 1990. However, processing Antarctic historical aerial imagery using modern photogrammetry software is difficult, as it requires precise information about the data collection process and extensive in situ ground control is required. Often, the necessary orientation metadata for older aerial imagery is lost and in situ data collection in regions like Antarctica is extremely difficult to obtain, limiting the use of traditional photogrammetric methods. Here, we test an alternative methodology to generate elevations from historical Antarctic aerial imagery. Instead of relying on pre-existing ground control, we use structure-from-motion photogrammetry techniques to process the imagery with manually derived ground control from high-resolution satellite imagery. This case study is based on vertical aerial image sets collected over Byrd Glacier, East Antarctica in December 1978 and January 1979. Our results are the oldest, highest resolution digital elevation models (DEMs) ever generated for an Antarctic glacier. We use these DEMs to estimate glacier dynamics and show that surface elevation of Byrd Glacier has been constant for the past ∼40 years.Publication Assessment of Geological, Hydrogeological and Geotechnical Characteristics of a Proposed Waste Disposal Site: A Case Study in Khon Kaen, Thailand(MDPI, 2020-03-18) Arjwech, Rungroj; Somchat, Kittipong; Pondthai, Potpreecha; Everett, Mark; Schulmeister, Marcia; Saengchomphu, SakhonOccasionally, a selected site suitable for landfill construction is severely protested against by locals. This issue can cause the proposed landfill to be relocated to an environmentally sensitive area. The proposed Khon Kaen waste disposal site has been planned as an integrated municipal solid waste management system, although the site is situated in an environmentally sensitive area. A site assessment can guarantee the suitability of waste disposal construction, with procedures that aim to assess the potential of geological and hydrogeological characteristics, geological barriers, geotechnical properties of material for landfill construction and groundwater conditions for future monitoring of such facilities. The study area is located on foothills where no geohazard or seismic impacts have been recorded. The geology is composed of sandstone, siltstone, and mudstone bedrocks mostly overlain by unconsolidated sediments. The natural geological barriers are clay and regolith. The clay layer lies locally and is rather thin, at around 2–3 m thickness. The study area is situated in an area that is highly vulnerable to groundwater pollution. The distinct weaknesses of this site along the foothill are a prominent transport path of shallow flows; high groundwater fluctuation, especially during the rainy season; that it is a recharge area with a high fracture zone; and the high permeability of colluvium. The material characteristics in the site make it suitable for use as landfill cover and liner. Following compaction, the coefficient of permeability ranges from 1.2 × 10−7 to 7.1 × 10−7 cm/s, which is acceptably impervious.Publication A Three-Dimensional, Virtual Tour of the Johnston Geology Museum(Geological Society of America, 2020-12) Schulmeister, Marcia K.; Edwards, BrianaPublication Eustatic, Climatic, and Oceanographic Influences on Geomorphology and Architecture of Isolated Carbonate Platforms: Miocene, Northwest Shelf, Australia(GeoScienceWorld, 2020-12-17) Rankey, Eugene C.The Miocene represents an interval of marked global change, and this evolution is reflected in carbonate platforms from this epoch. Seismic stratigraphic characterization of high-resolution (ca 60 Hz) 3D seismic data from the Browse Basin, offshore Australia, reveals a middle to upper Miocene three-part seismic stratigraphic subdivision. Each unit consists of several seismic sequence sets and their component sequences. Seismic stratal geometries and seismic facies define a prograding shelf (Langhian and older), a barrier-reef complex with scattered platforms (upper Langhian–early Tortonian), and aggrading and prograding isolated platforms (early Tortonian–Messinian). The data permit description and interpretation of high-fidelity stratigraphic details of the initiation, expansion, termination, and geomorphology of over 100 platforms in this interval. The results reveal that the isolated platforms initiated following the Middle Miocene Climatic Optimum. The succession includes major seismic stratigraphic boundaries and overall patterns of platform growth and demise that correspond roughly with periods of pronounced eustatic change associated with initiation of eastern Antarctic ice sheets. Although invoking a eustatic control for coarse trends may be tempting, mismatch between the numbers and ages of sequences, as well as the variable stacking patterns among contemporaneous platforms regionally, precludes such an interpretation; conversely, some globally recognized eustatic changes do not have a pronounced manifestation in this area. Thus, it appears that the eustatic signal combined with dynamic physical regional processes such as waves, currents, and variable subsidence creates the complex architecture and geomorphology of platforms. These results illustrate how global changes can interact with local controls to create diverse patterns of birth, growth, and demise of carbonate platforms and drive local stratal heterogeneity.Publication A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America(Nature Research, 2022-06-14) Pullen, Alex; Barbeau, David L.. Jr.; Leier, Andrew L.; Abell, Jordan T.; Ward, Madison; Bruner, Austin; Fidler, Mary KateThe Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7° (1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper- and lower-level) wind system over the southern Puna Plateau (to at least ~27° S) during periods of high dust accumulation in Tafí del Valle.Publication "Maybe this is just not the place for me:" Gender harassment and discrimination in the geosciences(Public Library of Science, 2022-05-18) Mattheis, Allison; Marín-Spiotta, Erika; Nandihalli, Sunita; Schneider, Blair; Barnes, Rebecca T.Rampant gender-based harassment and discrimination are recognized problems that negatively impact efforts to diversify science, technology, engineering and mathematics (STEM) fields. We explored the particularities of this phenomenon in the geosciences, via focus groups conducted at STEM professional society meetings, with the goal of informing interventions specific to the discipline. Using grounded theory analysis, two primary drivers for the persistence and perpetuation of gender-based harassment in the geosciences were identified: a particular history of power dynamics and maintenance of dominant stereotypes, and a pattern of ineffective responses to incidents of harassment and discrimination. Informed by intersectional feminist scholarship by women of color that illustrates how efforts to address the underrepresentation of women in STEM without attending to the overlapping impacts of racism, colonialism, ableism, and classism will not succeed, we view harassment and discrimination as structural problems that require collective solutions. Continuing to recruit individuals into a discipline without changing its fundamental nature can tokenize and isolate them or encourage assimilation and acceptance of deep-seated traditions no matter how damaging. It is the responsibility of those in power, and especially those who hold more privileged status due to their social identities, to contribute to the dismantling of current structures that reinforce inequity. By providing explanatory illustrative examples drawn from first-person accounts we aim to humanize the numbers reported in workplace climate surveys, address gaps in knowledge specific to the geosciences, and identify interventions aligned with an intersectional framework that aim to disrupt discriminatory practices endemic to the geosciences and larger STEM community.Publication Evolution of the central Garlock fault zone, California: A major sinistral fault embedded in a dextral plate margin(Geological Society of America Bulletin, 2014) Andrew, Joseph; Walker, J. Douglas; Monastero, FrancisPublication Fault slip in the central Mojave Desert region: Resolving discrepancies between geologic and geodetic slip rates in the Eastern California shear zone(Geological Society of America Bulletin, 2017) Andrew, Joseph; Walker, J. DouglasPublication Reconstructing late Cenozoic deformation in central Panamint Valley, California: Evolution of slip partitioning in the Walker Lane(Geosphere, 2009-06) Andrew, Joseph; Walker, J. DouglasPublication Phylogenetic and structural diversity of aromatically dense pili from environmental metagenomes(Wiley, 2019-11-07) Bray, Marcus S.; Wu, Jieying; Padilla, Cory C.; Stewart, Frank J.; Fowle, David A.; Henny, Cynthia; Simister, Rachel L.; Thompson, Katharine J.; Crowe, Sean A.; Glass, Jennifer B.Electroactive type IV pili, or e-pili, are used by some microbial species for extracellular electron transfer. Recent studies suggest that e-pili may be more phylogenetically and structurally diverse than previously assumed. Here, we used updated aromatic density thresholds (≥9.8% aromatic amino acids, ≤22-aa aromatic gaps and aromatic amino acids at residues 1, 24, 27, 50 and/or 51, and 32 and/or 57) to search for putative e-pilin genes in metagenomes from diverse ecosystems with active microbial metal cycling. Environmental putative e-pilins were diverse in length and phylogeny, and included truncated e-pilins in Geobacter spp., as well as longer putative e-pilins in Fe(II)-oxidizing Betaproteobacteria and Zetaproteobacteria.Publication Shifting microbial communities sustain multiyear iron reduction and methanogenesis in ferruginous sediment incubations(Wiley, 2017-04-17) Bray, M. S.; Wu, J.; Reed, B. C.; Kretz, C. B.; Belli, K. M.; Simister, R. L.; Henny, C.; Stewart, F. J.; DiChristina, T. J.; Brandes, J. A.; Fowle, D. A.; Crowe, S. A.; Glass, J. B.Reactive Fe(III) minerals can influence methane (CH4) emissions by inhibiting microbial methanogenesis or by stimulating anaerobic CH4 oxidation. The balance between Fe(III) reduction, methanogenesis, and CH4 oxidation in ferruginous Archean and Paleoproterozoic oceans would have controlled CH4 fluxes to the atmosphere, thereby regulating the capacity for CH4 to warm the early Earth under the Faint Young Sun. We studied CH4 and Fe cycling in anoxic incubations of ferruginous sediment from the ancient ocean analogue Lake Matano, Indonesia, over three successive transfers (500 days in total). Iron reduction, methanogenesis, CH4 oxidation, and microbial taxonomy were monitored in treatments amended with ferrihydrite or goethite. After three dilutions, Fe(III) reduction persisted only in bottles with ferrihydrite. Enhanced CH4 production was observed in the presence of goethite, highlighting the potential for reactive Fe(III) oxides to inhibit methanogenesis. Supplementing the media with hydrogen, nickel and selenium did not stimulate methanogenesis. There was limited evidence for Fe(III)-dependent CH4 oxidation, although some incubations displayed CH4-stimulated Fe(III) reduction. 16S rRNA profiles continuously changed over the course of enrichment, with ultimate dominance of unclassified members of the order Desulfuromonadales in all treatments. Microbial diversity decreased markedly over the course of incubation, with subtle differences between ferrihydrite and goethite amendments. These results suggest that Fe(III) oxide mineralogy and availability of electron donors could have led to spatial separation of Fe(III)-reducing and methanogenic microbial communities in ferruginous marine sediments, potentially explaining the persistence of CH4 as a greenhouse gas throughout the first half of Earth history.Publication Maternal care in Mid-Cretaceous lagonomegopid spiders(The Royal Society, 2021-09-15) Guo, Xiangbo; Selden, Paul A.; Ren, DongMaternal care benefits the survival and fitness of offspring, often at a cost to the mother's future reproduction, and has evolved repeatedly throughout the animal kingdom. In extant spider species, this behaviour is very common and has different levels and diverse forms. However, evidence of maternal care in fossil spiders is quite rare. In this study, we describe four Mid-Cretaceous (approx. 99 Ma) amber specimens from northern Myanmar with an adult female, part of an egg sac and some spiderlings of the extinct family Lagonomegopidae preserved, which suggest that adult lagonomegopid females probably built and then guarded egg sacs in their retreats or nests, and the hatched spiderlings may have stayed together with their mother for some time. The new fossils represent early evidence of maternal care in fossil spiders, and enhance our understanding of the evolution of this behaviour.Publication Dynamically Triggered Changes of Plate Interface Coupling in Southern Cascadia(American Geophysical Union, 2019-10-23) Materna, Kathryn; Bartlow, Noel; Wech, Aaron; Williams, Charles; Bürgmann, RolandIn subduction zones, frictional locking on the subduction interface produces year-by-year surface deformation that is measurable with GPS. During the interseismic period of the earthquake cycle, lasting hundreds of years between major earthquakes, these ground motions are usually constant with time because the locking on the plate interface is relatively unchanging. However, at the Mendocino Triple Junction in Northern California, we find evidence for slight changes in GPS interseismic motion within the last decade that challenge the assumption of constant interseismic deformation. Our results suggest changes in interseismic coupling on the southernmost Cascadia Subduction Zone. Interestingly, these coupling changes appear to be related to large offshore earthquakes and are perhaps triggered by the seismic shaking during those events. These results have important implications for our understanding of seismic hazard in subduction zones.Publication An Improved Analytical Solution for the Temperature Profile of Ice Sheets(American Geophysical Union, 2019-01-11) Rezvanbehbahani, Soroush; van der Veen, C. J.; Stearns, Leigh A.The one-dimensional steady state analytical solution of the energy conservation equation obtained by Robin (1955, https://doi.org/10.3189/002214355793702028) is frequently used in glaciology. This solution assumes a linear change in surface velocity from a minimum value equal to minus the mass balance at the surface to zero at the bed. Here we show that this assumption of a linear velocity profile leads to large errors in the calculated temperature profile and especially in basal temperature. By prescribing a nonlinear power function of elevation above the bed for the vertical velocity profile arising from use of the Shallow Ice Approximation, we derive a new analytical solution for temperature. We show that the solution produces temperature profiles identical to numerical temperature solutions with the Shallow Ice Approximation vertical velocity near ice divides. We quantify the importance of strain heating and demonstrate that integrating the strain heating and adding it to the geothermal heat flux at the bed is a reasonable approximation for the interior regions. Our analytical solution does not include horizontal advection components, so we compare our solution with numerical solutions of a two-dimensional advection-diffusion model and assess the applicability and errors of the analytical solution away from the ice divide. We show that several parameters and assumptions impact the spatial extent of applicability of the new solution including surface mass balance rate and surface temperature lapse rate. We delineate regions of Greenland and Antarctica within which the analytical solution at any depth is likely within 2 K of the actual temperatures with horizontal advection.