Regional Uplift Research Articles

Chapter 24 Carboniferous–Neogene tectonic evolution of the Fennoscandian transition zone, southern Sweden

Abstract The Fennoscandian transition zone, including the Sorgenfrei–Tornquist Zone, constitutes the weakened and faulted bedrock between a craton, including the ancient continent Baltica to the north, and the boundary between Baltica and Avalonia along the Trans-European Fault Zone to the south. Early Permian subsidence in this transition zone resulted in the development of various basins and the initiation of a more or less continuous Permian–Paleogene depositional cycle. In southwestern Sweden, magmatic activity associated with transtensional deformation along the Sorgenfrei–Tornquist Zone prevailed during the Late Carboniferous–Permian. However, the transition zone is dominated by a Mesozoic sedimentary rock succession displaying both hiatuses and great lateral variability in composition and thickness, which can be related to several tectonic events including the progressive break-up of Pangaea. Much of the deposition took place in continental, coastal and shallow-marine settings. Early–Middle Jurassic block faulting and basanitic or melanephelinitic volcanism, as well as Late Cretaceous tectonic inversion along the Sorgenfrei–Tornquist Zone, related to a changeover to a predominantly compressive tectonic regime coeval with the Alpine orogeny, significantly influenced the depositional setting. Subsequent Paleogene–Neogene regional uplift of the southwestern margin of Baltica resulted in significant erosion of the bedrock.

Emergence of a submarine canyon, Crotone Basin, southern Italy

Abstract The Serra Mulara canyon is a middle Pleistocene submarine canyon developed along the Ionian coast of Calabria, southern Italy, now exposed on land due to the long-term regional uplift of the area. New data have allowed recognizing three depositional sequences in the upper part of the succession, probably glacio-eustatic in origin, documenting an evolution of depositional systems that reflect the emergence of the canyon. Sequence 1 shows a rapid shift from turbidites and hemipelagites accumulated in the upper part of the canyon fill to forced regressive deltaic deposits, which reflect a marked shallowing of the area. Sequence 2 consists of estuarine transgressive and deltaic highstand deposits, whereas Sequence 3 is fully composed of fluvial deposits, testifying the emergence of the area. The upper part of the Serra Mulara succession is an useful example showing the transition from submarine canyon to continental settings, a situation that is not adequately documented in the literature, and is also relevant to better reconstruct the timing of the uplift of this part of Calabria.

The uplift of the Adriatic flank of the Apennines since the Middle Pleistocene: New insights from the Tronto River basin and the Acquasanta Terme Travertine (central Italy)

The Apennines chain is an active Neogene fold-and-thrust belt resulting from the westward subduction of the Adriatic microplate. Starting from the end of the Early Pleistocene, the chain was affected by an increase in regional uplift. Recent GPS data resolved uplift rates of 1–2 mm/yr for the whole Apennines, whereas, in the Adriatic flank, several studies estimated rates between 0.3 and 0.5 mm/yr over the last 1 Myr. A number of works investigated the evolution of the drainage systems along the Periadriatic margin of the Apennines providing long-term incision rates. Studies from the northern part of this sector reported uplift rates varying from 0.2 to 1.1 mm/yr, whereas only few studies concentrated on the central sector of the Adriatic flank of the Apennines, focusing mainly on the evolution of the lower reach of major rivers. This work aims to quantify the long-term rock uplift and incision rates of the eastern portion of the central Apennines through the analysis of the Tronto River basin. Because of its geologic and geomorphological configurations, this basin is an ideal test site to investigate the influence of tectonics and climate on the recent topographic evolution of the central Apennines. The basin extends, with a roughly WSW-ENE direction, from the inner sector of the chain to the Adriatic coast, crossing several tectonic structures such as the Amatrice extensional basin and the Acquasanta and Montagna dei Fiori anticlines. In particular, in the Acquasanta Terme area, the right flank of the Tronto River valley is characterized by fluvial and travertine deposits organized and exposed in several levels. In this work, we investigated the hydrography (river longitudinal profiles) and topography (swath profile, slope, and local relief) of the Tronto River basin coupling these data with field observations and geochronological analysis on the continental sediments (fluvial deposits and travertines) outcropping in the Acquasanta Terme area. To better characterize the nature of travertines, we performed geochemical characterization of three travertine-forming thermal springs obtaining their physico-chemical parameters, the percentage of dissolved gases, and the isotopes content. Finally, we applied a knickpoint celerity model to chronologically constrain the geomorphological evolution of the whole drainage system. The results show the occurrence of a continuous tectonic uplift (~0.5 mm/yr) across the study area since Middle Pleistocene. The uplift, together with climate fluctuations, drove the incision (~0.6 mm/yr) of the landscape and the delineation of the present drainage network. These data are consistent with previous estimates of uplift and incision rates in adjacent areas and provide new constraints on the Quaternary evolution of the central Apennines. This study highlights how the coupling of field surveys with morphometric and topographic analyses of a drainage system is crucial to understand and quantify the influence of tectonic and climate changes in shaping the landscape.

A warm-temperate forest of mixed coniferous type from the upper Pliocene Sanying Formation (southeastern edge of Tibetan Plateau) and its implications for palaeoecology and palaeoaltimetry

Coniferous forests represent one of the most important vegetation types in the southern Hengduan Mountains on southeastern edge of the Tibetan Plateau, but their evolutionary history remains poorly understood. Here, we report an upper Pliocene charcoal assemblage from the Sanying Formation at Fudong in the Lanping Basin, which represents remains of a mixed coniferous forest. Taxonomic studies indicate that the charcoal assemblage is dominated by Pinus armandii with a subordinate component of Cupressoideae, a few other conifers (Abies, Picea, Tsuga) and some angiosperms (Quercus, Rhododendron, Rubus, Sambucus, Zanthoxylum, Aralia, Amaranthaceae, Polygonum, Carex). Based on the present-day climate association of P. armandii, we consider that the reconstructed mixed coniferous forest to be of warm-temperate affinity. Some altitudinal variation of plant communities likely existed, with cool-temperate elements (Abies, Picea) occurring in higher altitudes on the mountain slope, warm-temperate elements (P. armandii, Tsuga, Quercus, Rubus, Rhododendron, Sambucus) in mid-altitudes, and warm elements (Zanthoxylum, Aralia) in lower altitudes. Due to the occurrences of Abies and Picea, we infer the presence of mountains >3000 m altitude near Fudong, which further constrains the timing of significant uplift prior to the late Pliocene. Together with fossil pollen data, our findings indicate that the southern Hengduan Mountains was increasingly dominated by conifers during the late Pliocene, particularly in its subalpine to alpine ecoregions, probably due to the progressive onset of cool and dry climates caused by regional uplift. Synthesising vegetation types, we conclude that the region showed large-scale vegetation zonation during this epoch, which generally ranged from evergreen broadleaved forests of warm affinity in the south to mixed coniferous forests of more temperate affinity in the north. The vegetation zonation can be interpreted as being shaped by large south-to-north altitudinal gradients due to uneven rates of uplift.

Subaqueous effusive and explosive phases of late Deccan volcanism: evidence from Mumbai Islands, India

About 30 m of massive basaltic lava sheets and pillows belonging to the Deccan Traps are exposed at Borivali in the Sanjay Gandhi National Park, Mumbai (India). These lavas are conformably overlain by ~ 100 m of volcaniclastic deposits exposed in the Kanheri Caves. The pillows are plagioclase-clinopyroxene-phyric, very poorly vesicular, tholeiite basalts and commonly develop one to few central large cavities. Pillow rinds are holohyaline with swallow-tailed lanceolate or slender needle-shaped plagioclase and fan-spherulitic or dendritic textures in clinopyroxene that indicate rapid cooling under water. The volcaniclastic succession lying on top of the pillow lavas is chiefly composed of non-vesicular to scoriaceous/pumiceous, basaltic and andesitic clasts. The numerous sediment dykes within the volcaniclastic succession and the conformably underlying pillow lavas imply that the entire sequence was emplaced in a submarine environment. The fluidal texture and quenched margins in some of the volcanic clasts strongly suggest that at least part of the volcanic clasts were produced by underwater explosive eruptions. This study describes subaqueous erupted pillow lavas in context of continental flood basalts and provides a significant analogy to recent submarine-erupted intraplate oceanic basalts. The occurrence of pillow lavas and volcaniclastic deposits well above the present-day high tide line (160 m) indicates either high eustatic sea level during the Danaian age (61.8–62.9 Ma), or post-rifting regional uplift in the western Deccan Traps.

Palaeoenvironmental interpretation of the Pliocene fan-delta system of the Vera Basin (SE Spain): Fossil assemblages, ichnology and taphonomy

The marine fossil assemblages of the Pliocene of south Spain constitute the record of the marine fauna that colonised the western part of the Mediterranean after the Messinian Salinity Crisis. This work focuses on the analysis of lithofacies and fossil assemblages including trace fossils, invertebrates, and vertebrates with special attention to taphonomic features, for interpreting palaeoenvironmental conditions in the Vera Basin (SE Spain). The sedimentary sequences of the northern region of the Vera Basin display diverse stratigraphical, sedimentological, and palaeontological features that correspond to the evolution of a fan-delta in a narrow basin. The Vera Basin was characterised by shallow-marine shelf conditions during the early-mid Pliocene (Cuevas Formation). The basin emergence with the development of Gilbert-type fan deltas (Vera Member), and a protected, partially-enclosed marine embayment (Almanzora Member) occurred during the mid-late Pliocene due to regional uplift and movements of the Palomares strike-slip Fault along the eastern basin margin. The progradation of the central fan-delta lobes and the interaction with marginal fan-delta resulted in the partitioning of the basin that formed a small sub-basin with restricted stagnant conditions that favoured a Konservat Fossil-Lagerstätte. The high input of siliciclasts due to the uplift context of the margins of the basin favoured a high sedimentation rate and the fast burial of vertebrate remains. Fossil marine mammals occurs from shallow shelf deposits (Cuevas Formation) to bottomset (Cuevas Formation-Vera Member transition) and lower part of the clinoforms in the foreset (Vera Member). Cetacean remains are usually recorded not only in the relatively deep-water silty marls and sandy marls of the outer shelf and distal facies of the fan-delta (Espiritu Santo Formation), but also in the shallower coarse sands and conglomerates (Cuevas Formation and Espiritu Santo Formation). Sirenian remains, in contrast, are only recorded in coarse sand facies (Cuevas Formation and Espiritu Santo Formation) associated to charcoal wood fragments deposited in shallow waters near the shoreline. This narrow and relatively protected basin is interpreted as an area of reproduction and nursery of juveniles on the basis of the presence of cetaceans.

Continental‐Scale Landscape Evolution: A History of North American Topography

The generation and evolution of continental topography are fundamental geologic and geomorphic concerns. In particular, the history of landscape development might contain useful information about the spatiotemporal evolution of deep Earth processes, such as mantle convection. A significant challenge is to generate observations and theoretical predictions of sufficient fidelity to enable landscape evolution to be constrained at scales of interest. Here, we combine substantial inventories of stratigraphic and geomorphic observations with inverse and forward modeling approaches to determine how the North American landscape evolved. First, stratigraphic markers are used to estimate postdepositional regional uplift. Present‐day elevations of these deposits demonstrate that >2 km of long‐wavelength surface uplift centered on the Colorado‐Rocky‐Mountain plateaus occurred in Cenozoic times. Second, to bridge the gaps between these measurements, an inverse modeling scheme is used to calculate the smoothest spatiotemporal pattern of rock uplift rate that yields the smallest misfit between 4,161 observed and calculated longitudinal river profiles. Our results suggest that Cenozoic regional uplift occurred in a series of stages, in agreement with independent stratigraphic observations. Finally, a landscape evolution model driven by this calculated rock uplift history is used to determine drainage patterns, denudation, and sedimentary flux from Late Cretaceous times until the present day. These patterns are broadly consistent with stratigraphic and thermochronologic observations. We conclude that a calibrated inverse modeling strategy can be used to reliably extract the temporal and spatial evolution of the North American landscape at geodynamically useful scales.

Glacial lake terraces at the eastern end of the Vale of Pickering, North Yorkshire, UK

Detailed landform mapping of key areas in the Vale of Pickering, supported by LiDAR interpretation, has produced sufficient evidence to establish a reinterpretation of the Mid to Late Pleistocene chronology of the Vale of Pickering by defining the margins of two temporally distinct proglacial lakes and reaching a new understanding of the origin of some well-documented geomorphological features. The main significance of the mapping has been to establish that the Hutton Buscel terrace probably originated by lateral erosion along the southern edge of the Corallian Group dip slope of the North York Moors prior to deposition of a broad alluvial plain below a 70 m strandline. Traces of a comparable feature were also located below the Chalk Group escarpment on the southern side of the Vale of Pickering. Perhaps of equal significance has been confirmation that the younger of the two lakes, which has a 45 m shoreline, was possibly connected to Lake Humber in the Vale of York through the Derwent Valley. Evidence for such a lake was provided by mapped shorelines at Malton and Pickering that appear compatible with shorelines in Lake Humber. To account for deep erosion of the Derwent and Mere valleys and the occurrence of laminated clays at c. 65 m, below a 70 m shoreline above Crambe, regional uplift has been evoked post the older 70 m lake. In-valley alluvial fans have been mapped for the first time in Newton Dale and Thornton Dale.

Exploring the reservoir potential of Lower Cretaceous Clinoforms in the Fingerdjupet Subbasin, Norwegian Barents Sea

AbstractSandy clinothems are of interest as hydrocarbon reservoirs but there is no proven, economic, clinothem reservoir in the Norwegian Barents Sea. We used high‐resolution, 2D and 3D seismic, including proprietary data, to identify a previously untested, Barremian, clinoform wedge in the Fingerdjupet Subbasin (FSB). Data from recent well 7322/7‐1 plus seismic have been used to characterize this wedge and older Lower Cretaceous clinoforms in the FSB. In the latest Hauterivian – early Barremian, during post‐rift tectonic quiescence, shelf‐edge clinoforms (foreset height > 150 m) prograded into an under‐filled basin. Increased sediment input was related to regional uplift of the hinterland (northern Barents Shelf). Early Barremian erosion in the north‐western FSB and mass wasting towards the SE were followed by deposition of delta‐scale (<80 m high), high‐angle (c. 8°) clinoform sets seaward of older shelf‐edge clinoforms. This may be the local expression of a regional, early Barremian, regressive event. By the close of the Barremian, clinoforms had prograded, within a narrow, elongate basin, across the FSB and towards the uplifted Loppa High. A seismic wedge of high‐angle (10–12°), low‐relief, delta‐scale (25–80 m) clinoform sets occurs between shelf‐edge clinoforms to the NW and the uplifted area to the SE. Well 7322/7‐1, positioned on a direct hydrocarbon indicator, <1 km NNW of the high‐angle, low‐relief, delta‐scale clinoforms, found upward coarsening siltstone‐cycles linked to relative sea‐level fluctuations on a marine shelf. Sand may have accumulated, offshore from the well, in high‐angle, low‐relief foresets of the delta‐scale clinothems (which are typical geometries elsewhere interpreted as ‘delta‐scale, sand‐prone subaqueous clinoforms’). Deposition was controlled by the paleosurface, storms and longshore currents on an otherwise mud‐dominated shelf. The study highlights challenges associated with exploration for sandstone reservoirs in seismic wedges on an outer shelf.

Late Cenozoic uplift history of the Peak District, central England, inferred from dated cave deposits and integrated with regional drainage development: A review and synthesis

The White Peak upland in the Peak District region of central England extends over an area of >100 km2, locally exceeding 400 m above sea-level, formed in extensively karstified limestone of Early Carboniferous age. Historically regarded as palaeo-karst, following the availability of U-series dates since the 1980s, it has become apparent that the superimposed cave levels in this region formed during the succession of Pleistocene interglacials, their differences in height reflecting downcutting by the River Derwent and its tributaries, in response to regional uplift. However, quantitative interpretation is complicated because of effects of glaciation, most importantly glacial diversion of rivers in adjoining lowland regions, making the determination of uplift from fluvial incision particularly difficult. The Derwent terrace dataset is also complicated by lithologically-controlled knickpoints, which can remain localized or propagate upstream depending on individual details. Cave, fluvial, and glacial datasets for this region are integrated to quantify the uplift history, establishing the Quaternary uplift history of a wide region of Britain. Uplift of >100 m since the Mid-Pleistocene Revolution, and by ~300–400 m since the Miocene, is thus inferred. These amounts exceed the uplift deduced over corresponding timescales in surrounding regions, indicating that the Quaternary uplift has slightly accentuated the overall domal form of this Carboniferous limestone inlier. The analysis supports the previous assignment of the Wragby Glaciation in the surrounding lowland regions to MIS 8 and constrains the most recent glaciation within the Peak District, represented by the Bakewell Till, also to MIS 8. Overall, this work provides an important case study demonstrating integrated use of multi-disciplinary datasets to quantify Late Cenozoic landscape development.

Constraining the regional uplift rate of the Corinth Isthmus area (Greece), through biostratigraphic and tectonic data

The eastern Corinth Gulf is constantly uplifted at least since Middle Pleistocene. This uplift is the combined result of the regional uplift and the activity of major active faults which influence the area. These tectonic movements which control the sedimentation processes of the study area resulted in a complex stratigraphy, paleogeography and paleoenvironment of the Corinth Isthmus. Stratigraphy supported with nannofossil biozonation data, demonstrates that marine sedimentation processes occurred during MIS 7 and MIS 5, providing some important constraints regarding the uplift rate of the area. An 0.22 ± 0.12 mm/yr uplift rate is extracted through nannofossils biozonation which is in agreement with published data from U/Th coral dating in a neighboring setting, adding confidence to the measured uplift rates. In order to constrain the regional uplift of the area, the influence of the surrounding active faults has been extracted. The latter has been implemented by extracting the influence of each individual active fault to the study site (using the fault geometry, fault slip-rates, the fault dip and the fault footwall uplift/ hangingwall subsidence ratio), in order to calculate the regional uplift rate. By considering the stratigra- phy and the biostratigraphy of the eastern part of the Corinth Isthmus and by extracting the influence of the active faults, a~0.34 ± 0.04 mm/yr regional uplift is calculated.

Reconstructing large‐scale karst paleogeomorphology at the top of the Ordovician in the Ordos Basin, China: Control on natural gas accumulation and paleogeographic implications

AbstractKarstification in carbonate successions has an important influence on hydrocarbon accumulation. Taking the Ordos Basin, currently the largest petroliferous basin in China, as an example, this study examines the large‐scale, long‐term (~120 Myr) paleokarst at the top of the Ordovician. The objectives of the study are to characterize the karst paleogeomorphology of this area, to explain the inconsistency between existing understandings of karst paleogeomorphology and exploration in the eastern Ordos Basin, and to reveal the control of paleokarst on natural gas accumulation and its paleogeographic significance. A total of 860 exploration wells were used for detailed stratigraphic correlation and analysis, along with core observations, well‐logging analyses, physical property characterization, and isotope analyses. Results of residual thickness and moldic thickness reconstruction reveal variation in karst paleogeomorphology between north and south in the eastern Ordos Basin, differing from the traditionally recognized E‐W variation. Two geomorphic units are classified as follows: the karst highland and the karst slope from north to south, with the karst slope being subdivided into northern and southern slope areas. The karst highland area has negligible reservoir capacity and hydrocarbon accumulation owing to the enhanced denudation that occurred there. In contrast, the northern karst slope shows favorable reservoir properties and has abundant gas wells according to well‐logging interpretations, whereas the southern karst slope is of poor reservoir quality and hosts mainly water wells. Differences in dissolution‐filling effects controlled by the surface paleodrainage system are suggested to be the main contributor to differential reservoir space preservation, which, together with the variable width and depth of source rocks in the grooves (thereby variably exposing source rock), further promoted differential gas accumulation. The Ordos Basin and its periphery in the southwestern North China Craton (NCC) show inheritance of sedimentary‐tectonic patterns from the Middle Ordovician to the Late Carboniferous. These results should provide a reference for hydrocarbon exploration in the Ordovician of other basins in the NCC in which karst occurs and karst basins worldwide, and deepens understanding of the paleogeographic framework in the context of regional uplift of the North China Platform.

The anatomy of uppermost mantle shear-wave speed anomalies in the western U.S. from surface-wave amplification

We build SWUS-amp, a three-dimensional shear-wave speed model of the uppermost mantle of the western U.S. using Rayleigh wave amplification measurements in the period range of 35–125 s from teleseismic earthquakes. This represents the first-ever attempt to invert for velocity structures using Rayleigh wave amplification data alone. We use over 350,000 Rayleigh wave amplitude measurements, which are inverted using a Monte Carlo technique including uncertainty quantification. Being a local seismic observable, Rayleigh wave amplification is little affected by path-averaged effects and in principle has stronger depth resolution than classical seismic observables, such as surface wave dispersion data. SWUS-amp confirms shallow mantle heterogeneities found in previous models. In the top 100 km of the mantle, we observe low-velocity anomalies associated with Yellowstone and the Basin & Range province, as well as a fast-velocity anomaly underneath the Colorado Plateau, where a strong velocity gradient at its edges shows a drastic contrast with its surroundings. SWUS-amp also gives additional insights into the current state of the uppermost mantle in the region. We image a high-velocity anomaly beneath the high-topography Wyoming province with a maximum depth extent of about 150–170 km, which is shallower than in previous tomographic models, and resolves previous inconsistencies with geological information. Beneath the Snake River Plain, a finger-like low-velocity anomaly dips to the west, suggesting lateral flow in the region. Below about 150 km depth, SWUS-amp shows a north-south dichotomy in shear-wave speed structure, with the northern region showing mostly high-velocity anomalies, whereas the southern region shows low-velocity anomalies. This is consistent with the continuous subduction history of the western U.S. and with the recent extension and uplift of the southern region.

Tectonic and stratigraphic evolution of southern Jacuípe Basin (Brazil) based on seismic sequence stratigraphy

Jacuípe Basin, located at the northeastern Brazilian passive margin, has great hydrocarbon potential, but is considered a new frontier basin due to the lack of integrated studies. The present paper aims to comprehend the history of the basin based on the interpretation of several 2D seismic lines and well data. No pre-rift strata were detected. Within the rift supersequence, which overlies the crystalline basement of the São Francisco craton, four unconformity-bounded third-order sequences (labeled Rift 1 to 4) were recognized. Rift sequences 1 and 2 have scattered depocenters, reflecting the process of synthetic and antithetic fault installation and linkage. Rift sequence 3 has a widespread record throughout the basin. Rift sequence 4 records the ending of mechanical subsidence with minor faulting, and is followed by an uplift which caused the initial continental shelf to be exposed during most of the subsequent depositional events. The drift supersequence was split in two phases or stages. The first drift stage has sedimentation confined to the continental slope due to the uplift of the shelf region, whereas during the second drift stage sedimentation surpasses the border fault and the sedimentary succession overlies directly the rift supersequence. A structural fault map was built, depicting main faulting controls and trends, basin hinge line, main depocenters, the Jacuípe External High and a volcanic plug. The paper also clarified the still controversial southern geologic limit of the basin, and closes with a suggestion of an updated chronostratigraphic chart.

Back-arc basin evolution in the southern Lhasa sub-terrane, southern Tibet: Constraints from U-Pb ages and in-situ Lu-Hf isotopes of detrital zircons

Sedimentary rocks in the Gangdese magmatic arc document a long but poorly constrained series of tectonic events that led to basin formation. We investigate one of these events by using detrital zircon grains from Mesozoic sedimentary rocks from the Linbuzong Formation located within the Gangdese magmatic arc. Our aims are to determine the provenance of the rocks in this back-arc basin and to document the paleo-topographical uplift of the Gangdese region in southern Tibet. Detrital zircons from the Linbuzong Formation, located in the middle-eastern segment of the southern Lhasa sub-terrane, have ages in four dominant populations: 140–300 Ma, 480–700 Ma, 1000–1250 Ma, and 1400–1700 Ma. The youngest detrital zircon cluster has a weighted age of ca. 149 Ma which, in conjunction with previously published data, indicates that sedimentary rocks in the Linbuzong Formation were deposited after 149 Ma. The youngest detrital zircon grains have low 176Hf/177Hf isotopic ratios and negative εHf(t) values, similar to igneous zircons from the central Lhasa sub-terrane which is considered to be the predominant source for sediments. However, few zircon grains from the youngest age cluster have high 176Hf/177Hf ratios with significantly positive εHf (t) values, suggesting derivation of some sediments from the southern Lhasa sub-terrane, primarily the Gangdese magmatic arc. Combined with the evidence for two conspicuous age populations (480–700 Ma and 1000–1250 Ma) and the Hf isotopic characteristics of the Linbuzong Formation, we propose that the Carboniferous-Permian metasedimentary rocks from the central Lhasa sub-terrane serve as the main source of sediments for the Linbuzong Formation. We conclude that the central Lhasa sub-terrane was exhumed to the surface and attained a high relief, whereas the Gangdese magmatic arc had a relatively low relief (near sea-level) during the Late Jurassic to the Early Cretaceous.

Shallow necking depth and differential denudation linked to post‐rift continental reactivation: The origin of the Cenozoic basins in southeastern Brazil

AbstractThe southeastern Brazilian margin presents post‐breakup Cenozoic tectonism that created a series of grabens and small sedimentary basins, known as the Continental Rift of Southeastern Brazil. The formation of this rift occurred long after the South Atlantic ocean opening and has been attributed to different mechanisms like regional uplift induced by hotspot activity, pulses of Andean orogeny and reactivation of pre‐existing faults. However, the proposed models lack an analytical or numerical verification from a geodynamic point of view. Based on finite element modelling of the lithospheric stress field evolution we conclude that a shallow necking depth, consistent with the hyperextended southeastern Brazilian margin, combined with differential denudation of the continent, resulted in an extensional stress field in the upper crust that induced the observed Cenozoic tectonism.

Combined glacio-eustatic forcing and volcano-tectonic uplift: Geomorphological and geochronological constraints on the Tiber River terraces in the eastern Vulsini Volcanic District (central Italy)

Abstract In the present paper, we analyze the regional interplay between glacio-eustasy and volcano-tectonic uplift on the Tyrrhenian Sea margin of central Italy. We reconstruct a succession of fluvial terraces in the Tiber River Valley east of the Vulsini Volcanic District and we provide geochronologic constraints allowing for correlation with the sea-level highstands of the Marine Isotope Stage timescale. Results of this study show that glacio-eustatic forcing affected the hydrographic network of the Tiber River, as far as 70 km inland with respect to the present Tyrrhenian coast, consistent with a regional uplift on the order of several tens of meters that affected this region over the last 250 ky. Using six new 40Ar/39Ar dates, we demonstrate the synchronicity between sea-level rise during glacial termination IV and the deposition of a fining-upward sedimentary succession of the Paleo-Tiber River in this area. A detailed reconstruction of the chronostratigraphic setting enabled us to assess local uplift and fault displacement due to volcano-tectonic processes associated with the activities of Bolsena-Orvieto and Latera volcanoes since 350 ka, and develop an uplift curve for the different sectors of the investigated area. Moreover, we estimate sedimentation rate during post-glacial sea-level rise. Strong differential uplift, with rates on the order of 0.6–1.2 mm/yr corresponded with the onset of major eruptive phases, whereas a homogeneous regional uplift of 0.24 mm/yr during the last 125 ky followed this climactic phase. These uplift rates are significantly smaller than sedimentation rate during the glacial termination, consistent with the observed independence of the glacio-eustatic signal.

Provenance and weathering index of the Upper Cretaceous São Carlos Formation and its tectonic significance in the eastern Bauru Basin, SE Brazil

Geochemistry of major and trace elements has been used as an important tool for the study of provenance and tectonic and climatic evolution of sedimentary basins. The São Carlos Formation is an Upper Cretaceous unit that lies on the eastern border of the Bauru Basin. Despite the paleontological and paleodepositional studies performed in this unit in the last years, little is known about the correspondence between tectonic and climatic conditions acting during the first stages of sedimentation. The hypothesis of this paper is to evaluate São Carlos and Araçatuba formations and understand the evolution of the eastern border of the basin. Thus, were conducted geochemical studies using X-ray fluorescence on sandstones, siltstones, and shales from the São Carlos Formation. According to the chemical weathering index, which presented values ranging from 57.12 to 71.58%, the oxides of major elements indicate that moderate weathering processes affected the source area, possibly associated with the arid-semiarid climate. Alkaline rocks, granites, gneisses, and metasediments were the main lithotypes of the source area. Ternary diagrams show that the tectonic environment was equivalent to the passive continental margin, coinciding with the Serra do Mar and, secondarily, Alto Paranaíba Uplift regions. Based on major and trace elements, their ratios, and published data on the basin, was elaborated a paleogeographic model of the eastern border of the Bauru Basin, concluding that the source area of the sediments was constituted by intermediate and felsic rocks, sometimes recycled by sedimentary processes.

A multi–methodological approach to reconstruct the configuration of a travertine fissure ridge system: The case of the Cukor quarry (Süttő, Gerecse Hills, Hungary)

Travertines are continental carbonates that precipitate from spring waters, mainly due to CO2 degassing. They are widely quarried as building stone, which has led to numerous (often abandoned) travertine quarry outcrops. These and other outcrops, however, merely represent the surface expressions of the complex architecture of travertine bodies and their deep–rooted feeding systems. Integration of field observations and geochemical analyses with crucial subsurface geophysical data is required in order to fully understand travertine systems and their relationship to the local geological framework. Such a multi-methodological approach is illustrated here for the case of the abandoned Cukor quarry. Radio-magnetotelluric (RMT) and Electrical Resistivity Tomography (ERT) surveys provide unique insights into local tectonics, geobody architecture and the topography preceding travertine deposition. Altogether, the lens–shaped, isolated domal geobody with spring-proximal lithofacies and subvertical bedding, in addition to the contrasting geochemistry and age with surrounding travertine, enabled the unequivocal reconstruction of the dismantled Cukor fissure ridge. This study illustrates the high potential of this multi–methodological approach on poorly exposed, strongly weathered, quarried and tectonically deformed travertine bodies, and provides information on the complex feeding system beneath travertine deposits. Their reconstruction can be interpreted in light of the neo–tectonic expression of regional uplift, helps to complete the regional tectonic history and provides insights into older landscapes that lack preservation or would no longer be immediately recognized at the surface.

Landscape Response to Lateral Advection in Convergent Orogens Over Geologic Time Scales

AbstractConvergent orogens exhibit high elevations and relief, features characteristic of active rock uplift, the latter influencing normalized channel steepness (Ksn). In systems with significant horizontal displacement, Ksn values and interfluves are elevated over a region of tens of kilometers and gradually decline in the direction of rock advection. To evaluate potential relationships between elevated Ksn, a gradual decline in interfluve elevation (i.e., tapered topography), and lateral advection, we integrated kinematic models that simulate advection over a midcrustal ramp with a 2‐D surface processes model. Varying convergence rate, bedrock erodibility, and ramp angle, we tracked topographic evolution over time. The process of advection through the region of active rock uplift above a midcrustal ramp is preserved in the geomorphic record through transient legacy landscapes characterized by (i) high‐relief, advection‐parallel interfluves, (ii) tapered topography, (iii) elevated and gradually declining Ksn values, and (iv) higher Ksn in trunk relative to tributary streams likely reflecting the influence of increased sediment flux, elevated interfluves, and changes in drainage area. The width of legacy landscapes provides a minimum constraint on the total lateral displacement, controlled by the duration of ramp activity and the rates of advection and erosion. The development of legacy landscapes is facilitated by spatial variations in flow convergence that occur in a 2‐D setting but are not captured in idealized 1‐D approaches. The presence of elevated Ksn and high relief, advection‐parallel interfluves beyond the region of active rock uplift likely reflects the horizontal advection component inherent to convergent orogenic systems.