Erosional History Research Articles

A Novel Protocol for Reconstructing Depositional Histories of Anthropogenic, Sedimentary Records: the Case of the Holocene-Deep Kirkhellaren Cave Deposits in Coastal Arctic Norway

ABSTRACT This paper presents a novel protocol for reconstructing formation processes of archaeological depositional sequences, applied to Holocene-wide cave deposits located on a remote coastal island in Arctic Norway as a case study. Extensive GPR surveying is correlated with geochemical analysis and in situ environmental deposit monitoring for sedimentary fingerprinting and forecasting of future preservation of organic remains. Subsurface deposit characteristics are integrated with a high-precision, laser-based 3D-reconstruction of the cave, enabling triangulation with historic photos and local informant knowledge that facilitate modeling and quantification of erosional history. The results showcase detrimental depletion of critical organic heritage, accelerated by the removal of protective surface layers after the a.d. 1930s. Critically, subsurface deposits are trending towards overshooting a threshold for accelerated in situ degradation. The results act as a direct validation of the methodology. Measures for future protection of similar archaeological deposits are discussed and an outline of the general applicability of the protocol.

Spatial‐Temporal Variation in Erosion Rate of Lohit Bomi‐Chayu Batholith Around Eastern Himalayan Syntaxis (SE of the Namche Barwa Massif)

AbstractMeasuring erosion rates around the Eastern Himalayan syntaxis is crucial to understanding the interaction between tectonic, climate, and landscape associated with Eastern Himalayan termini. The spatio‐temporal deformation history around the eastern syntaxis is unclear due to a lack of comprehensive thermochronological data coverage, especially from the Lohit Bomi‐Chayu (LBC) batholith. This work utilizes 2473 new detrital fission track ages of apatite and zircon grains from 14 catchments, and 17 new bedrock thermochronometric ages (eight AFT, six ZFT, and three ZHe ages) from 12 rock samples collected along rivers flowing through the LBC batholith to quantify the spatio‐temporal erosion history. Bayesian probability, Markov chain Monte Carlo algorithm, and bootstrapping were applied for the inversion of detrital cooling ages to model various erosion histories. Results indicate an increased erosion rate in the batholith at least four times from the Miocene to the present. Specifically, LBC batholith's erosion rates were lower (∼0.16 mm/yr) before the Miocene and increased (∼0.61 mm/yr) during the Early‐Middle Miocene to the present. The post‐Miocene erosion rate is similar to SE Tibet, Bhutan, and Arunachal Pradesh rates. However, it is lower than Nepal. Pre‐Miocene rates are significantly low and comparable only with that of SE Tibet. We envisage that the Early‐Middle Miocene enhanced erosion was related to the tectonic uplift along the Jiali shear zone. This surface uplift was in close concurrence with increased precipitation that might have disconnected the Yigong‐Parlung River from the Irrawaddy River and, subsequently, captured the Lohit River.

Detrital zircon provenance links between outcrop and subsurface, Rocas Verdes and Magallanes-Austral Basins, Patagonia

Analyzing how provenance signatures of tectonically complex ancient sedimentary basins vary between the outcrop and the subsurface provides a more complete sediment provenance history. The 500+-km-long outcrop belt of the Rocas Verdes and the Magallanes-Austral Basins in southern Patagonia and its subsurface to the east allow us to constrain relationships between longitudinal and transverse sediment sources feeding the basin. New detrital zircon U-Pb ages (n = 2558) from nine subsurface core samples from the Springhill, Piedra Clavada, and La Anita Formations along a 140 km E-W seismic reflection transect (50°S, 71.5°W–69.5°W) reveal the provenance of the basin’s eastern subsurface extent and the influence that tectonic activity can have on sediment capture. Detrital zircon ages (n = 1068) were also collected from four outcrop Springhill Formation samples 140 km NW from the transect near Lago San Martín. Maximum depositional ages (MDAs) from the Springhill Formation cores range from 159 to 157 Ma, which are older than correlative outcrop ages of 151–148 Ma. MDAs from the Piedra Clavada and La Anita Formations range from 93.7 to 91.5 Ma and from 79.3 to 78.3 Ma, respectively, and overlap in age or are slightly younger than outcrop ages. The unimodal Late Jurassic age distribution from the Springhill Formation suggests that it almost exclusively was sourced by recycling of the underlying El Quemado Complex. Early–Middle Jurassic ages in the Early Cretaceous Piedra Clavada Formation samples suggest the basin was either sourcing from the North Patagonian Massif to the N-NE and from the Deseado Massif to the NE or recycling exhumed volcaniclastic sequences in the northern margin of the basin. By the Late Cretaceous, the basin fill was more locally sourced, as suggested by the muted abundance of Early–Middle Jurassic ages in La Anita Formation samples and a second mode of Late Jurassic–Early Cretaceous ages locally derived from recycling of the exhumed El Quemado Complex from the Patagonian fold-and-thrust belt. We suggest that the latitudinal and local transverse drainages that sourced the Magallanes-Austral Basin outcrop belt also fed the eastern, subsurface extent of the basin. Results of this work highlight the importance of using several types of provenance methods and a three-dimensional approach to study the erosional history of sedimentary basins.

Reconstructing the late Quaternary soil erosion and dust deposition dynamics in the southern Loess Plateau: Insights from Lake Luyanghu sedimentary records

Investigating the history of wind-dust deposition and soil erosion is crucial for understanding the relationship between geomorphologic formation, monsoon evolution and the current state of soil erosion on the Loess Plateau. This study utilizes a 50-m sedimentary record from Lake Luyanghu (LYH) in the southern Loess Plateau. We developed a chronological framework using optically stimulated luminescence (OSL) dating and stratigraphic comparisons. By applying end-member modeling of grain size, we identified various sediment sources and quantitatively reconstructed the dust deposition fluxes and soil erosion modulus during the late Quaternary. Additionally, we examined the patterns of sediment source evolution with environmental changes at LYH. Our findings reveal that dust constitutes an average of 32.3% of the lake sediments, with an average deposition rate of 40.2 g/cm2/ka. Notably, after the Last Glacial period, dust deposition became the dominant component of the lake sediment. During the Marine Isotope Stages (MIS) 5b, 5d, 4 and 2, enhanced dry climatic conditions, decreased vegetation cover and composition, leading to significant soil erosion. Based on the results of this research, future studies should aim to reconstruct the watershed's erosion and deposition processes throughout geological periods by integrating aspects of lake evolution, such as water levels and developmental stages.

Ice-sheet burial and erosion inferred from cosmogenic nuclide bedrock depth profiles: Implications for the glaciation history of northeastern Fennoscandia

In this study, we evaluate the application of shallow (<2.5 m) cosmogenic depth profiles in bedrock to constrain long-term ice-burial and erosion histories. Using Markov Chain Monte Carlo inversion modelling on a series of synthetic scenarios, we demonstrate that cosmogenic 10Be and 26Al profiles provide more robust constraints on ice-burial duration and erosion histories than surface samples alone, particularly when erosion rates are low (<5–10 m Myr−1) and/or non-steady. We apply this method to new depth profiles of 10Be and 26Al measurements from two tors in the Parkajoki region in northeastern Sweden. Our results indicate erosion depths of ∼2–10 m and ice burial for ∼20–35% of the time since 500 ka. These estimates imply more erosion and less ice burial than previously inferred from the same tors. However, by re-assessing the extent of ice cover during the Weichselian from existing records, we show that some cosmogenic nuclide inheritance predates the penultimate glacial maximum (Late Saalian), implying limited glacial erosion in the Parkajoki region during the last glacial cycle.

Varying free-gas zone (FGZ) and bottom-simulating reflection (BSR) response across a deep graben off Trujillo, central Peru

The complexity of marine gas hydrate systems at the Peruvian convergent margin has been linked to the post-Miocene history of vertical tectonics and subduction erosion that affected the forearc. Here, multichannel seismic data and published findings reveal that such a complexity has been further extended by the occurrence of the pre-Miocene deep Morsa Norte Graben (MNG) off Trujillo (8°–9° S) in the Central Peru margin. At water depths of 650–750 m in the upper slope, directly above the MNG depocentre (which has a 4–6 km overburden thickness), continuous bottom-simulating reflections (BSRs) and concentrated sub-BSR high-amplitude reflections are confined beneath a layered basin with a low–moderate near-seafloor heat flow (7–33 mW m −2 ). A deeper BSR modelled with a thermogenic gas composition is associated with the enhanced reflections. At a water depth of 900 m, sub-BSR reflections become less frequent in an area with a layered sediment cover defined by a moderate near-seafloor heat flow (15–33 mW m −2 ). At a water depth of 1200 m, where the MNG is relatively thick (3–4 km overburden thickness), faults connect patchy BSRs with a moderate–high near-seafloor heat flow (52–110 mW m −2 ). There, sub-BSR enhanced reflections are scarce. Immediately above the top of the gas hydrate stability zone (GHSZ), the near-seafloor heat flow reaches 81 mW m −2 . Modelling suggests a water depth-dependent transport of heat towards the seafloor with respect to the top of the GHSZ, implying that the closer the seafloor is to the top of the GHSZ, the lower the advection of heat, and vice versa. Recent seafloor-related depositional and structural features amplify such relations in agreement with near-seafloor heat-flow variability. However, towards the area outside the extent of the MNG (&lt;3 km overburden thickness), continuous BSRs are not linked either to a deeper BSR or to sub-BSR enhanced reflections. The continuity of one of these BSRs is deflected upwards beneath a slump, suggesting an incomplete thermal re-equilibration of the GHSZ. Therefore, we conclude that the BSR responds to: (1) the confinement and thickening of the free-gas zone (FGZ) above the MNG depocentre due to the sealing effect of recent sedimentation close to the top of the GHSZ; (2) the seepage of gas-rich fluids from a thinned FGZ above the relatively thick MNG, due to the enabling effect of faults cutting the GHSZ far from the top of the GHSZ; (3) the undisturbed state of the FGZ outside the extent of the MNG; and (4) the disequilibrium state of the base of the GHSZ due to the unloading of sediments in an unstable slope environment prone to failure.

Glacial geomorphology of Newfoundland, Canada

ABSTRACT We present a synthesis of glacial geomorphology comprising Newfoundland and the surrounding continental shelf. During the last glaciation, this region was encompassed by the Newfoundland Ice Cap that coalesced with the Laurentide Ice Sheet and extended to the continental shelf edge. The subglacial geomorphic signal of terrestrial and marine portions of this ice sheet has been mapped using aerial photography, satellite imagery, SRTM DEMs, multibeam bathymetric data and onshore field mapping over the last 50 years. Here, we build on this, digitizing ∼146,380 features identified in published literature. Using newly available digital elevation data and multibeam bathymetric data, we identify ∼38,550 new features, such as undocumented ice thrust, crevasse and esker ridges and meltwater channels. This updated geomorphological map provides a record of paleo landforms over Newfoundland, enabling future efforts to reconstruct the dynamics, timing and erosion history of ice advance and retreat during the last glacial period..

Maastrichtian-Cenozoic erosional history of the northern Peruvian Amazonian Andes implications for the Eastern Cordillera evolution (Huallaga Basin, northern Peru)

Late Cretaceous-Cenozoic Andean mountain building may have experienced various phases of orogenesis in response to variations the dip angle of the subducting slab, distinct magmatic pulses, and shortening rates of the orogen. The timing of the Eastern Cordillera (EC) erosion and the relationship between the Andean orogenesis and the establishing of the transcontinental Amazon River remains unclarified. The erosional history of the Amazon Andes and the timing of these orogenic events may be revealed by the late Cretaceous-Cenozoic sedimentary record of the Amazonian retroarc foreland basin. We investigate the provenance of the Maastrichtian-Cenozoic deposits of the Huallaga Basin based on major and trace elements concentrations, SmNd isotopic composition, and UPb zircon dating. We also refined the Oligocene paleoenvironment and calculated Paleogene sedimentation rates. Our results show that despite the 25 Myr-long sedimentary hiatus, both the Maastrichtian and Eocene units show dominant sourcing from the magmatic arc of the Western Cordillera (WC). Increases in Paleozoic and Famatinian zircon grains and a shift toward more negative ƐNd(0) values, indicate dominant EC sources during the Oligocene to middle Miocene. This change in provenance area is Rupelian in age based on the Maximum Likelihood Age (MLA) of JUA22 (29.70 ± 0.62 Ma), suggesting that the onset of Peruvian EC erosion started at ∼30 Ma. The erosion of the EC was accompanied by an increase in sedimentation rates and the development of a meandering fluvial system. Finally, a substantial decrease in zircon grains derived from the Cretaceous and Cenozoic Andean arcs from late Miocene to Recent sediments suggests no contribution of the WC. In contrast, an increase in Paleozoic magmatic arc zircon grains indicates sources in the EC. We compare our findings to constrain the erosional history of the Amazonian Andes and investigate the relationship between the timing of EC uplift and the onset of the transcontinental Amazon drainage system during the Cenozoic.

Petrographic signature of the gravel fraction from late Quaternary glacigenic sediments in the Ross Sea (Antarctica): Implications for source terranes and Neogene glacial reconstructions

The Ross Embayment is a key region to study the dynamics of the ice sheets during colder and warmer than present climatic conditions, because both the East and West Antarctic Ice sheets shed into the Ross Sea. Numerical modeling and reconstructions of the paleo ice flows during the Last Glacial Maximum show variable contribution of East and West Antarctic Ice sheets based on a variety of proxies. In this study, we present the first petrographic and minero-chemical investigation of the gravel-sized fraction of Last Glacial Maximum subglacial-glacimarine sediments collected with piston cores in a W–E transect across the Ross Sea. The clast petrographic features are compared with outcropping geology to individuate the sediment source regions. The gravel content of the glacigenic diamictite was classified on the basis of petrographic and minero-chemical features, and three main petrofacies were identified. They reflect changes in the basement geology of the source regions, allowing the reconstruction of the paleo ice flow pattern and their comparison with scenarios built up with other datasets. Moreover, the comparison with the Oligocene to Pleistocene glacigenic sediments provided information about the changes of the gravel signature across the Ross Sea and the erosion history of the source regions during Cenozoic.

Natural History of Artificial Urinary Sphincter Erosion: Long-term Lower Urinary Tract Outcomes and Incontinence Management

Natural History of Artificial Urinary Sphincter Erosion: Long-term Lower Urinary Tract Outcomes and Incontinence Management

The natural history of marginal erosions in hands with and without osteoarthritis.

Among people with or without hand osteoarthritis, we aimed to identify characteristics of people (e.g., age and gender) with marginal erosions (MEs). We also examined changes in MEs during 48months. We described radiographic severity and progression among joints with MEs, changes in MEs, or central erosions (CEs). We studied participants from the Osteoarthritis Initiative with baseline and 48-month hand radiographs. A radiologist and rheumatologist evaluated the radiographs for disease severity (Kellgren-Lawrence grades) and erosions (central or marginal), respectively. We used descriptive statistics to characterize participants and calculated frequencies at the joint level. Of the 3558 participants, 89 had a ME at baseline. People with MEs were more often male, older, and ever (former and current) smokers than those without a ME. There was no difference in inflammatory biomarkers or the presence of hand pain between individuals with and without a baseline ME. Almost all hands had only one ME (80%), whereas only 50% of individuals with CEs had only one CE at baseline. Compared to CEs, MEs appeared more frequently in joints without osteoarthritis (54% vs. < 1%). Approximately 18% of joints with an ME progressed in Kellgren-Lawrence grade versus 4% without ME. Among the joints with an ME at baseline, 10% resolved by 48months. Less than 0.1% of joints developed a new ME. MEs appear to be distinct from CEs. MEs are predominantly present in males, isolated to one specific joint without osteoarthritis within a hand, and possibly predictive of radiographic progression. Key Points • Marginal erosions appear to be distinct from central erosions. • Most marginal erosions occur in joints without radiographic osteoarthritis. • Radiographic progression but not hand pain is more common in joints with a marginal erosion than without one.

(203) RISK FACTORS FOR REPEAT EROSION IN RADIATED PATIENTS UNDERGOING REIMPLANTATION OF ARTIFICIAL URINARY SPHINCTER DEVICES

Abstract Introduction With limited alternatives to achieve continence, radiated patients with prior artificial urinary sphincter (AUS) erosion represent a challenging population at risk for a subsequent erosion event. Though prior analyses have assessed risk factors for the development of subsequent AUS erosion after an initial erosion event, these investigations are often limited by the inclusion of non-radiated erosion patients in the study design. Objective We analyze a multi-institutional cohort to identify independent predictors of repeat erosion events in a large series of radiated prostate cancer survivors. Methods A multi-institutional, retrospective review was performed of all radiated patients with history of prior AUS erosion. Clinical features, procedural specifics and surgical outcomes were collected for all patients who experienced an erosion event and underwent repeat AUS implantation. Univariate and multivariate logistic regression analyses were performed to identify independent factors predictive of secondary AUS erosion event. Results A total of 118 patients with history of pelvic radiation (55% salvage, 32% adjuvant, 13% primary radiation) underwent a second AUS implantation at a median of 6.2 months after a prior AUS erosion event. Median age at time of second AUS implantation was 76.6 years and 35% of patients had a history of low testosterone (low T). The overall rate of second AUS device erosion was 47%. The median time to AUS erosion of the initial device was 22.4 months compared to 14.2 months for the second AUS device (p &amp;lt; 0.01). On univariate analysis, history of radiotherapy in the adjuvant (OR 2.54, CI 1.113-5.432, p = 0.034) and salvage (OR 2.66, CI 1.234-4.345, p = 0.012) settings were associated with increased risk of erosion. Uncorrected (OR 2.43, CI 1.143-6.432, p = 0.032) and corrected (OR 2.22, CI 1.116-6.345, p = 0.041) low T as well as history of urethroplasty (OR 2.23, CI 1.231-4.324, p = 0.08) also conferred additional risk of erosion. On multivariate analysis, independent risk factors for a secondary AUS erosion event in radiated patients included uncorrected low T (OR 2.03, 95% CI 1.435-3.456, p = 0.041), history of urethroplasty (OR 2.14, 95% CI 1.123-4.237, p = 0.045), and salvage radiotherapy (OR 2.23, 95% CI 1.24-5.435, p = 0.026). Conclusions Radiated patients with a history of salvage radiotherapy, prior urethroplasty, and uncorrected low T contemplating AUS re-implantation following initial AUS device removal for erosion events are at increased risk of repeat erosion events. Disclosure No.

Editorial Comment on “Natural History of Artificial Urinary Sphincter Erosion: Long-term Lower Urinary Tract Outcomes and Incontinence Management”

Editorial Comment on “Natural History of Artificial Urinary Sphincter Erosion: Long-term Lower Urinary Tract Outcomes and Incontinence Management”

Geologіcal structure of the lower terraces of the Prut valley іn the «Chernіvetsky gate dіstrіct» (accordіng to engіneerіng and geologіcal exploratіon data)

The article provides a detailed examination of the geological structure of Quaternary deposits at the bottom of the Prut River valley in the «Chernivtsi Gate» area based on engineering and geological survey data. The primary focus is on analyzing the structure and composition of geological formations, as well as studying geological processes and phenomena that influence the formation of the relief. During the research, materials from engineering and geological surveys were analyzed. This allowed for obtaining reliable information about the composition and physico-mechanical properties of the Quaternary deposits that form the bottom of the Prut River valley. The studies revealed significant variability in the thickness of the alluvium in the «Chernivtsi Gate» area, directly influenced by the relief of the river's bedrock. The relief of the Neogene clay surface shows significant irregularities that are not reflected on the surface of the valley. This indicates a complex erosional history of the valley, determined by both hydrological and tectonic factors. The results of the surveys provide important information for assessing the stability of the area, planning construction, and other engineering works. The conclusions of the study emphasize the need to consider geological conditions during the design and development of infrastructure in this region. Overall, the article makes a significant contribution to understanding the geological structure and processes that influence the formation of the relief at the bottom of the Prut River valley. Keywords: floodplaіn terraces, geologіcal sectіons, engіneerіng geology, «Chernіvetskі Vorota», Quaternary deposіts, stratіgraphy.

Natural History of Artificial Urinary Sphincter Erosion: Long-term Lower Urinary Tract Outcomes and Incontinence Management

ObjectivesTo describe long-term lower urinary tract outcomes and incontinence management after AUS erosion, including risk factors associated with each outcome. MethodsWe retrospectively reviewed our prospectively maintained AUS database for men undergoing device explantation for urethral erosion from 1/1/1986-10/31/2023. Outcomes included development of urethral stricture and management of post explant incontinence (e.g. pads/clamp, catheter, salvage AUS, supravesical diversion). Risk factors were tested for association with stricture formation and repeat AUS erosion using logistic regression. Results1943 unique patients underwent AUS implantation during the study period, and 217 (11%) had a device explantation for urethral erosion. Of these, 194 had complete records available and were included for analysis. Median follow-up from implantation was 7.5 yrs (IQR 2.7-13.7) and median time to erosion was 2 yrs (IQR 0-6). 96 patients (49%) underwent salvage AUS placement. Of those, 38/96 (40%) were explanted for subsequent erosion. On multivariable analysis, no factors were significantly associated with risk of salvage AUS erosion. On multivariable model, pelvic radiation (OR 2.7; 95% CI 1.0-7.4) and urethral reapproximation during explant for erosion (OR 4.2; 95% CI 1.5-11.2) were significantly associated with increased risk of urethral stricture (p<0.05). At the time of last follow-up, 69/194 (36%) patients had a functioning salvage AUS, including both initial and subsequent salvage implants. ConclusionsFollowing AUS erosion, radiation history and urethral reapproximation at explantation were risk factors for development of urethral stricture. Salvage AUS replacement can be performed, but has a higher rate of repeat urethral erosion.

Variation of vertical stress in the McArthur and Beetaloo basins

The McArthur and Beetaloo basins have been the focus of unconventional hydrocarbon exploration, specifically targeting shale gas and tight gas resources. Vertical stress (SV), which is one of the three principal stresses, is a critical parameter in geomechanical analysis of sedimentary basins and has implications in fracture gradient calculation, pore pressure prediction, assessing the present-day stress regime, and hydraulic fracturing design. In addition, variations in vertical stresses can yield additional insights into the tectonic history of an area. In this study, we examine the variability of vertical stress magnitude and vertical stress gradients by employing a systematic analysis of density log and check-shot velocity data obtained from 31 wells located within the McArthur and Beetaloo basins. Our analysis revealed that vertical stress gradients range from 23 to 27 MPa/km (equivalent to ~1.0–1.2 psi/ft), with an average gradient of 25 MPa/km ± 1.0 (1.1 psi/ft). This variability in SV gradients underscores the inadequacy of the commonly assumed 1.0 psi/ft approximation for geomechanical analyses within these basins. The origins of such diverse SV gradients can be attributed to several factors; however, the likely cause of the SV gradient within this region is the presence, thickness, and depth of the shallow high-density volcanic rocks and a complex history of uplift and erosion.

An efficient approach for inverting rock exhumation from thermochronologic age–elevation relationship

Abstract. This study implements the least-squares inversion method for solving the exhumation history from the thermochronologic age–elevation relationship (AER) based on the linear equation among exhumation rate, age and total exhumation from the closure depth to the Earth surface. Modeling experiments suggest significant and systematic influence of initial geothermal model, the a priori exhumation rate and the time interval length on the a posteriori exhumation history. Lessons learned from the experiments include that (i) the modern geothermal gradient can be used for constraining the initial geothermal model, (ii) a relatively high a priori exhumation rate would lead to systematically lower a posteriori exhumation and vice versa, (iii) the variance of the a priori exhumation rate controls the variation in the inverted exhumation history, and (iv) the choice of time interval length should be optimized for resolving the potential temporal changes in exhumation. To mitigate the dependence of inverted erosion history on these initial parameters, we implemented a new stepwise inverse modeling method for optimizing the model parameters by comparing the observed and predicted thermochronologic data and modern geothermal gradients. Finally, method demonstration was performed using four synthetic datasets and three natural examples of different exhumation rates and histories. It is shown that the inverted rock exhumation histories from the synthetic datasets match the whole picture of the “truth”, although the temporal changes in the magnitude of exhumation are underestimated. Modeling of the datasets from natural samples produces geologically reasonable exhumation histories. The code and data used in this work are available on Zenodo (https://doi.org/10.5281/zenodo.10839275).

The Early Paleozoic sedimentary record in northeastern Brazil: Unravelling the sedimentary provenance and evolution of fluvial systems after the Western Gondwana assembly

The sedimentary units of the geographically isolated basins of NE Brazil are historically interpreted as coeval and part of the same depositional system that was ultimately responsible to the deposition of the first sedimentary sequence of the intracratonic Parnaíba Basin. We present the first integrated detrital zircon U-Pb age dataset from the Early Paleozoic basins of NE Brazil, providing new insights into the depositional evolution and erosional history after Western Gondwana assembly. The lowermost sedimentary units (Ipu, Cariri, and Tacaratu formations) of eleven NE Brazil sedimentary basins (Parnaíba, Araripe, Tucano-Jatobá, Lavras da Mangabeira, Fátima, São José do Belmonte, and Mirandiba) were analyzed by a multi-proxy approach aiming to propose new insights on the paleogeographic reconstruction and stratigraphic correlations. Sedimentary provenance data, together with paleocurrents measurements consistently towards NNW-NW, suggests that the primary source for all the Early Paleozoic sedimentary units of NE Brazil were elevated orogenic areas related to the Brasiliano Orogeny to the south of Borborema Province (e.g., Riacho do Ponta, Rio Preto, and Sergipano belts). Based on detrital zircon U-Pb ages, we position the beginning of sedimentation of these basins in the Ordovician. The U-Pb age spectra for all analyzed sedimentary successions are remarkably similar. The analysis of KDE plots, CA-DA gap curves, and (dis)similarity tests, reinforced the correlation and contemporaneity of all the Ordovician sedimentary successions of NE Brazil. The conceived paleogeography model points to deposition of all the analyzed successions in a ramp, slightly tilted towards NW, where continental-scale fluvial system drained Neoproterozoic orogenic areas (i.e., Brasiliano Orogeny) dispersing huge volumes of sediments towards Borborema Province interior.

New insights into Cenozoic evolution of the Shijiutuo uplift, Bohai Bay basin, China: Constraints from apatite fission track analysis and seismic data

The Shijiutuo Uplift within the Bohai Bay Basin(BBB)has experienced a complex evolutionary history since the Cenozoic. Studies of the Cenozoic evolution of the Shijiutuo Uplift are important for basin tectonics and petroleum geology. The formation of uplifts in rift basins is generally controlled by regional tectonic event and fault-block tilting. In this study, apatite fission track (AFT) data from fourteen samples and seismic data analysis were used to study the processes of regional uplift and fault-block tilting. We further investigated the Cenozoic evolution and formation mechanism of the Shijiutuo Uplift. The results indicated that the Shijiutuo Uplift experienced a two-phase differential tectonic uplift and erosion history (1) Widespread rapid uplift and erosion during the early Cenozoic (65–55 Ma) (2) Widespread uplift and erosion from 40 Ma to 16 Ma. The uplift and erosion substages of 40–38 Ma and 26–16 Ma were mainly caused by regional uplift, whereas those of 38–26 Ma resulted from fault-block tilting. Since the end of the third member from the Eocene Shahejie Formation, the Shijiutuo Uplift began to rise, causing the greater Bozhong Depression to be separated into the independent Qinnan and Bozhong Sags. These tectonic uplift and erosion events have a wide range of responses and regional dynamics in eastern China. The findings of this study will lead to a better understanding of the evolution and formation of uplifts within the BBB.

Inherited terrestrial cosmogenic nuclides in landscapes of selective glacial erosion: lessons from Lochnagar, Eastern Grampian Mountains, Scotland

ABSTRACTInheritance from prior exposure often complicates the interpretation of terrestrial cosmogenic nuclide (TCN) inventories in glaciated terrain. Lochnagar, a mountain in eastern Scotland, holds a clear geomorphological record of corrie glaciation and the thinning of the last Scottish ice sheet over the last ~15 ka. Yet attempts to date the main stages in deglaciation after sampling of 21 granite boulders for 10Be, 26Al and 14C from corrie moraines, an ice sheet lateral moraine and boulder spreads revealed widespread, but variable, TCN inheritance. Only the youngest boulder ages fit within the range of expected deglaciation ages. To identify the sources of geological uncertainty, we provide simple models of ice cover duration and erosion histories for plateau, corrie and strath landscape domains, identify the variable nuclide inheritance that derives from different sources for boulders in these domains, and outline the effects of rotation, splitting and erosion of boulders during glacial transport. The combined effects increase clustering around arbitrary mean TCN values that exceed deglaciation ages. A further implication is that boulders have survived beneath overriding ice sheets. Such boulder trapping at Lochnagar may have resulted from topographic controls on katabatic winds and surface ablation acting on a thinning, cold‐based ice sheet.