Adjacent Sedimentary Basins Research Articles

Climatic significance of clay minerals in Cenozoic marine and lacustrine sediments

Abstract In sediments, clay minerals are mainly detrital. Formed by continental weathering, they are carried by surface transport predominantly by rivers, glaciers and, to a lesser extent, winds to the adjacent sedimentary basins and then are redistributed by oceanic currents. In a sedimentary core, the variability in the clay mineral assemblages reflects either variable physical and chemical weathering conditions in the watershed, typically with a significant link to climatic conditions, or changes in the mineral source, the latter being associated with various transport agents. When different sources are involved, a combination of mineralogical and geochemical proxies allows us to trace the detrital provenance, but they also indirectly provide valuable information on transport pathways and palaeocurrents. This manuscript reviews several examples from the literature and ongoing research on clay mineral variability in marine or lacustrine sedimentary records and interprets them in terms of: (1) climate control at different timescales, from the Neogene to the Quaternary; and (2) transport paths. Examples are selected to review the various clay-derived proxies in existence.

Using U–Pb carbonate dating to constrain the timing of extension and fault reactivation within the Bristol Channel Basin, SW England

The Bristol Channel Basin is a Mesozoic continental rift basin. The basin is an important analogue for offshore reservoirs. Relative cross-cutting relationships and correlation with adjacent sedimentary basins have previously been used to constrain the timing of basin development. In situ U–Pb carbonate geochronology has been used to date calcite slickenfibre development in the cores of normal, thrust and strike-slip faults in the East Quantoxhead and Kilve region of Somerset for the first time. Protracted north–south extension from c. 150 to 120 Ma formed normal faults. Subsequent north–south shortening from c. 50 to 20 Ma was accommodated by (1) mutually cross-cutting strike-slip faults, (2) minor east–west-striking thrust faults and (3) the reactivation of pre-existing normal faults. Throughout Cenozoic contraction, σ 2 and σ 3 remained similar in magnitude and periodically flipped to become vertical; this was probably controlled by local stress permutations and changes in fluid pressure. The timing of inversion is contemporaneous with dominant Pyrenean and later Alpine orogenic events, as well as the opening of the Mid-Atlantic Rift. Early inversion of the Bristol Channel Basin was probably driven by far-field Pyrenean deformation, with later contraction caused by Alpine forces. Ridge push from the Mid-Atlantic Rift exacerbated the reactivation of the basin.

Sequence stratigraphy and petrographic characteristics of Oligocene sediments in the West trough of the Cuu Long Basin, Vietnam

The Cuu Long Basin is the major source of Vietnam's oil and gas production. In clastic sediments, the Oligocene and Lower Miocene formations are the main objects of oil and gas exploration and exploitation activities. Oligocene sediments are both source and reservoir rocks; therefore, studying the petroleum system of these formations is of great interest. This paper discusses detailed stratigraphy and lithological properties to clarify the Oligocene sedimentary characteristics and their significance in the petroleum system. Study results show that Oligocene sediments are divided into three sequences, including eight parasequences and are dominated by the terrestrial sediments. Sequence E, mainly coarse-grained, contains low palynomorphs and rich organic matter with mainly palynomaceral 1 and is deposited in freshwater fluvial settings under high-energy conditions, showing sediments not so far from the original areas. The high level of detrital matrix materials is the main cause of poor or negligible porosity of the rock. The parasequences of Sequence D contain abundant palynomorph assemblages, characterized by swamp and freshwater alga taxa. They are deposited mainly in the shallow lake with a decreasing energy level pointing upward. The volume of organic matter in sediments is very rich, with sapropel organic matter (SOM) rates reaching up to 80%, indicating that the hydrocarbon generation potential is mainly oil-prone and some oil-gas mixtures. The porosity is poor and reservoir quality is affected by detrital matrix and authigenic minerals. The parasequences of Sequence C are characterized by the extreme abundance of freshwater algae, deposited mainly in the shallow-to-deep lake under moderate energy conditions, and rich sapropel organic matter, suggesting mainly oil-prone in hydrocarbon generation potentials. The porosity ranges from fair to good and the reservoir quality is estimated as the best in Oligocene sediments. A new finding of marker assemblages provides evidence to pinpoint the stratigraphic boundary between the Lower Miocene and Upper Oligocene. This finding helps to complete the stratigraphic framework of the area and to correlate the stratigraphy to adjacent sedimentary basins. This study provides information on depositional environmental conditions, organic matter content, hydrocarbon generation potential, and reservoir quality that relate to source rock, reservoir, and seal; these are the elements of a petroleum system. A complete petroleum system assessment requires a holistic view of all the petroleum system elements.

Rapid topographic growth of the Taiwan orogen since ~1.3–1.5 Ma

We present the first paleotopographic reconstruction of Taiwan by measuring the hydrogen isotope composition of leaf waxes (δ 2 H n C29 ) preserved in 3-Ma and younger sediments of the southern Coastal Range. Plant leaf waxes record the δ 2 H of precipitation during formation, which is related to elevation. Leaf waxes produced across the orogen are transported and deposited in adjacent sedimentary basins, providing deep-time records of the source elevation of detrital organic matter. δ 2 H n C29 exported from the southern Taiwan orogen decreased by more than 40‰ since ~1.3–1.5 Ma, indicating an increase of >2 kilometers in the organic source elevation. The increase in organic source elevation is best explained by rapid surface uplift of the southern Central Range at around ~1.3–1.5 Ma and indicates that this part of the orogen was characterized by maximum elevations of at least 3 km at this time. Further increase in organic source elevation from ~0.85 to ~0.3 Ma indicates continued topographic growth to modern elevations.

Northeastward expansion of the Tibetan Plateau: Topographic evidence from the North Qinling Mts.–Weihe Graben Coupling system, Central China

Mountain-Basin Coupling systems form during late stages of the collisional orogeny when mountains rise compared to the adjacent sedimentary basins. In this study, we focus on the spatial and temporal pattern of uplift, subsidence and related topographic features of the transtensional Weihe Graben–North Qinling Mountain Coupling system, at the northeastern extension of the Tibetan Plateau. The opening of the Weihe Graben and the ongoing high seismicity in the Weihe Graben result from the lateral extrusion of the Qinling Block away from the Tibetan Plateau. We quantify the influence of uplift gradients on topography and drainage divides by (a) carrying out field surveys, (b) conducting a digital elevation model-based analysis of topographic properties, and (c) compiling and integrating data on exhumation, uplift, subsidence, and denudation of numerous previous studies. Together, these morphological analyses show that the influence of the uplift of the Tibetan Plateau on the study area gradually decreases from the westernmost Taibai Mts. to the easternmost Huashan Mts. We found large χ gradients across the drainage divide of the Huashan Mts. and river piracy implying a southward migration of the drainage divide in the Huashan Mts. We conclude that the initial exhumation of the North Qinling Mts. occurred during the Lower Eocene to Oligocene (cycle 1). As peneplanation surfaces formed, this implies discontinuous exhumation and surface uplift. A second stage of uplift occurred in the Oligocene to Middle Miocene (cycle 2), followed by the third stage from Middle to Upper Miocene (cycle 3). The final period of uplift occurred from latest Miocene to Holocene times (cycle 4). The uppermost Miocene to Holocene geomorphological features imply surface uplift within the westernmost North Qinling Mts. and are controlled by the inflation of a mid-crustal magma layer, prograding from the eastern Tibetan Plateau towards the Taibai Mts., associated with lateral extrusion of the Qinling Block away from the rising Tibetan Plateau. The high seismicity of the Weihe Graben implies ongoing tectonic activity influenced by deep-seated lithospheric motion.

Microbiostratigraphy, microfacies analysis and lateral basin evolution of Lower Cretaceous deposits in the south of Kerman region, SE Iran

Detailed microbiostratigraphy and basin evolution of the Lower Cretaceous deposits in the Rayen area, south of Kerman Region, SE Iran are investigated for the first time in two sections. The section no. 1 is 324.6m in thickness and comprises five lithostratigraphic units. The section no. 2 is 218 m in thickness and includes three lithostratigraphic units. The identified fauna and flora include 41 benthic foraminifera and 11 calcareous algae species. The identified assemblage indicates that the marine strata in both sections were deposited during the Barremian to Albian. The microfacies analyses carried out on 22 carbonate and 2 clastic microfacies indicate that the deposits in the section no. 1 were deposited on a homoclinal carbonate ramp, whereas in the section no. 2 they were deposited on a rimmed carbonate shelf. Generally, the Cretaceous deposit in the two studied sections represent different sedimentary models and fossil content indicating different basin evolution histories. The paleogeographic setting of the studied area on the south eastern margin of the Central-East Iranian Microcontinent and the active tectonic history during the Mesozoic suggest that the syndepositional tectonism influenced the basement’s morphology and resulted in changes in the fossil diversity and sedimentary nature of adjacent sedimentary basins.

Geochronology of mafic magmatism and hydrothermal alteration during early stages of South Atlantic opening

40Ar/39Ar laser incremental-heating geochronology of whole-rock fragments and minerals from primitive subalkaline mafic dykes from the Cabo Frio Tectonic Domain, southeastern Brazil, reveals a complex combination of intrusive ages, apparent ages affected by excess argon, and ages that record late-stage hydrothermal alteration. Incremental-heating analysis of encapsulated magmatic amphibole-biotite clusters reveals a minimum intrusive age of 132.83 ± 0.30 Ma. Sericitized plagioclase crystals show the percolation of K-rich fluids at ~106 Ma. Albitized plagioclase phenocrysts suggest the percolation of Na-rich fluids in the 60–30 Ma interval. Hydrothermal alteration events overlap in time with pulses of alkaline magmatism in the extending Brazilian crust, suggesting a link between magmatic activity and generation of fluid circulation cells along the margin and adjacent sedimentary basins. Evidence for pervasive hydrothermal re-setting of the K-Ar system in the Cabo Frio Tectonic Domain dykes suggests that young 40Ar/39Ar geochronology results obtained for mafic dykes here and elsewhere along the continental margins may not record multiple intrusive events, reflecting instead partial or total resetting of the K-Ar system by water-rock interaction during fluid circulation.

Stratigraphy, age, and provenance of the Eocene Chumstick basin, Washington Cascades; implications for paleogeography, regional tectonics, and development of strike-slip basins

Strike-slip faults form in a wide variety of tectonic settings and are a first-order control on the geometry and sediment accumulation patterns in adjacent sedimentary basins. Although the structural and depositional architecture of strike-slip basins is well documented, few studies of strike-slip basins have integrated depositional age, lithofacies, and provenance control within this context. The Chumstick basin formed in central Washington during a regional phase of dextral, strike-slip faulting and episodic magmatism associated with Paleogene ridge-trench interaction along the North America margin. The basin is bounded and subdivided by major strike-slip faults that were active during deposition of the intra-basinal, non-marine Chumstick Formation. We build on the existing stratigraphy and present new, detailed lithofacies mapping, conglomerate clast counts (N = 16; n = 1429), and sandstone detrital zircon analyses (N = 16; n = 1360) from the Chumstick Formation to document changes in sediment provenance, routing, and deposition. These data allow us to reconstruct regional Eocene paleo-drainage systems of Washington and Oregon and suggest that drainage within the Chumstick basin fed a regional river system that flowed to a forearc or marginal basin on the newly accreted Siletzia terrane. More generally, excellent age control from five interbedded tuffs and high sediment accumulation rates allow us to track the evolving sedimentary system over the Formation’s ca. 4−5 m.y. depositional history. This is the first time lithofacies and provenance variations can be constrained at high temporal resolution (0.5−1.5 m.y. scale) for an ancient strike-slip basin and permits a detailed reconstruction of sediment routing pathways and depositional environments. As a result, we can assess how varying sediment supply and accommodation space affects the depositional architecture during strike-slip basin evolution.

Results of Modeling of Generation and Accumulation Hydrocarbon Systems in the Sedimentary Basins of the Sea of Okhotsk

The paper presents the results of modeling of generation and accumulation hydrocarbon systems in the sedimentary basins of the sea of Okhotsk. The results of modeling HC migration showed that the most likely zones of hydrocarbon accumulation are the side parts of sedimentary basins. The anticline zones located on the border of two or more basins have the most favorable conditions. These areas, in general, are among the most promising in terms of hydrocarbon prospecting. However, such zones are characterized by complex conditions for the formation and preservation of deposits due to the non-synchronous evolution of adjacent sedimentary basins. This leads to uncertainties when assessing their prospects at the regional research level, for example, when predicting the type of fluid in deposits. For example, Vostochno-Shmidtovsk (East Schmidt) anticline zone is located on the border of two large centers of oil and gas generation: Severo-Sakhalinsky (North-Sakhalin) and Deryugin basin. The results of numerical modeling of the regional level allowed us to establish that HC migration towards the anticline zone occurs from the East (from the Deryugin basin) and the West (from the Severo-Sakhalinsky (North-Sakhalin) basin). The type of fluid in the predicted clusters is controlled by the type and maturity of the organic matter of the generation centers.

Regional correlation and seismic stratigraphy of Triassic Strata in the Greater Barents Sea: Implications for sediment transport in Arctic basins

AbstractThe Greater Barents Sea Basin (GBSB) in Arctic Russia and Norway is an intracratonic basin that accommodated an enormous amount of sediment during the Triassic. These deposits are up to 4.5 km thick over an area 2,500,000 km2, and consist of marine mudstones and mudstone‐rich fluvio‐deltaic topsets with sandstone‐dominated fluvial channels. The basin is well‐studied and data‐rich, but regional correlation between different parts is lacking. Provenance data from adjacent Arctic basins have been interpreted to imply sediment transport from the Ural orogen across the GBSB, but these are disputed because of great transport distances, poorly constrained sediment‐transport directions and unknown timing of bypass. We integrated data from 3,238 seismic lines, 257 wells and palynostratigraphy, as well as published outcrop data, to create the first unified stratigraphic framework for the Triassic deposits across the entire GBSB. Results show that (1) sediment was transported northwest by one linked sedimentary system stretching across the entire basin; (2) sediment was derived from a source in the east comprising the Urals and West Siberia; (3) the main stratigraphic boundaries are major flooding surfaces which can be traced throughout the basin; and (4) significant amounts of sediment overspilled from the Barents Sea into adjacent sedimentary basins, starting with the Lomonosov Ridge from the Early Triassic, and into basins to the northwest (e.g. Sverdrup, Chukotka) during the late Carnian. These results provide a better understanding of geodynamics and provenance data in the Arctic, to improve the prediction of reservoirs in the area, and indicate a protracted uplift‐history of the northernmost Urals that started in the Carnian ~237 Ma. Furthermore, it shows how large intracratonic basins interact with uplands and subside over tens of millions of years.

Hydrogeochemistry of granitic mountain zones and the influence of adjacent sedimentary basins at their tectonic borders: the case of the Spanish Central System batholith

The hydrogeochemical characteristics of springs in the granites of the Spanish Central System (SCS), a mountain range affected by cortical tectonic structures, are described, along with an investigation of the spring water origin. In springs with variable flow and where they are associated with minor alterations and fractures, water type is Ca-(Na)-HCO3 with low total dissolved solids (TDS; 54–200 ppm) and a neutral or slightly acid pH. In springs that have continuous flow and association with relevant fractures, water type is Na-HCO3, with higher pH and TDS (240–563 ppm). There are five springs with water type Na-(Ca)-Cl and high TDS (780–9,205 ppm) near the SCS’s southern tectonic borders. Within 5,000 years of apparent residence time, Ca-(Na)-HCO3 water progresses to Na-HCO3 type, slightly increasing HCO3 content, losing Ca due to calcite precipitation and ionic exchange, and gaining S due to sulphate reduction. No changes are observed after 20,000 years of apparent age. The influence of internal CO2 is compatible with Na-HCO3 water type characteristics, facilitated by fracturing. Most of the springs yield cold water; thus, a flow depth up to 500 m can be deduced. Only the Messejana-Plasencia fault region shows Na-HCO3-type thermal springs. Chloride type water is a result of the influence of the Tertiary basins’ water moving towards the southern border of the SCS. The reverse fault in such contact, together with the subvertical structures affected by it, are responsible for the springs emerging in the granite. The northern border of the SCS shows the opposite behaviour.

Sandstone provenance analysis in Longyan supports the existence of a Late Paleozoic continental arc in South China

Because of the limited magmatic and metamorphic record, the Late Paleozoic tectonic setting in South China remains controversial. This paper presents sedimentologic data and provenance analysis of Upper Paleozoic sandstones in Longyan, which are rich in quartz (73–90%) and poor in lithic fragments (2–12%) and feldspar (3–25%). Devonian sandstones contain mostly metamorphic lithic fragments (e.g., quartzite), whereas Carboniferous-Permian sandstones contain mostly felsic volcanic and subvolcanic lithic fragments indicating provenance from felsic volcanic rocks. Detrital zircon U-Pb age spectra of Devonian-Carboniferous sandstones display modes at ~440 Ma and 420–380 Ma, with subordinate Mesoproterozoic age components, pointing at the Nanling terrane and the western-middle part of the Wuyi terrane as most likely ultimate sediment sources. Permian sandstones inherited the age components mentioned above, but also include peaks at ~290 Ma and ~1850 Ma. The ~290 Ma component corresponds to the age of Late Paleozoic magmatism in southeastern China and southwest Japan. Numerous detrital zircons aged at 350–250 Ma also occur in Permo-Triassic strata exposed across South China and southwest Japan. Based on regional data and on the ages and Hf isotope signatures of detrital zircon, we infer that a Late Paleozoic continental arc existed in the coastal area of southeastern China and contributed detritus to the adjacent sedimentary basins. The Permo-Triassic igneous rocks locally exposed in the area may represent the remnant of that continental arc. Arc growth may have been responsible for the westward retreat of a broad Upper Paleozoic carbonate platform.

Habitat associations of zoophagic bat ensembles in north-western Australia

North-western Australia comprises the Kimberley Craton and parts of three adjacent sedimentary basins. It has a tropical climate and habitats that range from semiarid plains supporting grasslands to mesic uplands supporting woodlands as well as narrow riparian forests and patches of rainforest; mangrove forests occur along the coast. Its bat fauna comprises three obligate phytophages and 27 obligate zoophages. Analysis of zoophagic bats at 171 sites scattered throughout this study area revealed two compositionally distinct ensembles. One, comprising 19 species, occupies mangrove forest and includes three species known only to occupy mangroves in Western Australia. The other, comprising 20 species, occupies landward habitats and includes four species that are found only in landward ecosystems. Both ensembles are structured in terms of resource allocation, but nestedness observed in assemblage composition can be explained by environmental factors, implying the influence of environmental controls. Sixteen species belong to both ensembles, but seven of these require cave roosts and occur only near cavernous country while three others are confined to rocky riparian habitats. The richest assemblages were recorded in rugged cavernous landscapes in complex vegetation structures near permanent freshwater pools in the most mesic areas.

Corrigendum to: Habitat associations of zoophagic bat ensembles in north-western Australia

North-western Australia comprises the Kimberley Craton and parts of three adjacent sedimentary basins. It has a tropical climate and habitats that range from semiarid plains supporting grasslands to mesic uplands supporting woodlands as well as narrow riparian forests and patches of rainforest; mangrove forests occur along the coast. Its bat fauna comprises three obligate phytophages and 27 obligate zoophages. Analysis of zoophagic bats at 171 sites scattered throughout this study area revealed two compositionally distinct ensembles. One, comprising 19 species, occupies mangrove forest and includes three species known only to occupy mangroves in Western Australia. The other, comprising 20 species, occupies landward habitats and includes four species that are found only in landward ecosystems. Both ensembles are structured in terms of resource allocation, but nestedness observed in assemblage composition can be explained by environmental factors, implying the influence of environmental controls. Sixteen species belong to both ensembles, but seven of these require cave roosts and occur only near cavernous country while three others are confined to rocky riparian habitats. The richest assemblages were recorded in rugged cavernous landscapes in complex vegetation structures near permanent freshwater pools in the most mesic areas.

Fault activity and diapirism in the Mississippian to Late Cretaceous Sverdrup Basin: New insights into the tectonic evolution of the Canadian Arctic

The opening and pre-opening history of the Amerasia Basin is poorly constrained. Key tectonic events have been interpreted from outcrop data in adjacent sedimentary basins or from geophysical data along its continental margins. However, due to its location in a polar region, data are scarce and the existing models of tectonic evolution are controversial. The northernmost exposed adjacent basin is the Mississippian to Late Cretaceous Sverdrup Basin, the original structural framework of which is unclear because it was overprinted by the latest Cretaceous to Paleogene Eurekan Orogeny. This paper presents a restored structural cross-section of the eastern half of the Sverdrup Basin in order to remove deformation attributed to Eurekan shortening and identify previous Mississipian to Late Cretaceous structures. Our results reveal that the evolution of the Sverdrup Basin during the Mesozoic was dominated by the rising of salt diapirs in the basin centre and by Triassic to Jurassic extensional fault development at the basin’s margins. Diapirs were squeezed during Eurekan tectonic inversion whilst extensional faults formed thrusts. The discovery of Triassic fault activity is a new finding in the Sverdrup Basin and forms an extra element to be considered in tectonic models for the opening of the Amerasia Basin.

Diagenesis of sandstones and carbonates of the Ignacio Quartzite and McCracken Sandstone Member of the Elbert Formation, southwestern Colorado, U.S.A.

Syndepositional events that affected fluvial, estuarine, and shallow-marine sediments of the units studied in southwest Colorado—the McCracken Sandstone Member of the Elbert Formation and the Ignacio Quartzite—included bioturbation, local formation of glaucony grains and phosphate crusts, local carbonate pedogenesis, and possibly silcrete pedogenesis. Although the sediments were ultimately buried up to approximately 4 km, shallow burial was the site of: (1) reddening of feldspathic sand and shale of the Ignacio Quartzite; (2) initial loss of porosity in both units by compaction of locally abundant clay clasts and clay drapes; and (3) initial partial cementation by overgrowths of feldspar and microquartz crystals. During deeper burial, the quartzarenite sands of the McCracken Sandstone Member of the Elbert Formation underwent compaction to porosity values below that typical of stable packing patterns of rigid grains followed by complete cementation by megaquartz overgrowths to produce highly indurated sandstones. Silica derived from intergranular pressure dissolution in local sandstone beds and during stylolite formation was inadequate to provide the amount of silica present in the cement. Much silica apparently was imported in fluids expelled from adjacent sedimentary basins. Such fluids were also responsible for bleaching red beds in the Ignacio Quartzite, dolomitizing limestone in the McCracken Member, and introducing small amounts of oil, some of which survives as pyrobitumen. Values of stable carbon and oxygen isotopes in dolostones in the McCracken indicate that dolomitization was accomplished by hot fluids. Kaolinite—an alteration product of K-feldspar, illite, and trace amounts of barite and sphene—formed during intermediate to deep burial.

Heavy Minerals and Geochemical Characteristics of Sandstones as Indices of Provenance and Source Area Tectonics of the Ogwashi-Asaba Formation, Niger Delta Basin

Heavy mineral petrographic and geochemical compositions (major and trace/rare earth elements) of sandstones obtained from the Oligocene-Miocene Ogwashi-Asaba Formation, Niger Delta were studied to determine their provenance, source area weathering conditions and tectonic setting. The heavy mineral suite (opaque minerals, zircon, tourmaline, and rutile) revealed that the sandstones are mineralogically mature and implied rapid disintegration and chemical decomposition of sediments mostly of recycled orogen. The sandstones were geochemically classified as Fe-sand and partly quartz arenitic. Chemical Index of Alteration and Chemical Index of Weathering values of 89.92% and 91.87% respectively suggest that the source region was predominantly felsic and was subjected to intense chemical weathering probably under tropical palaeoclimatic conditions with abundant rainfall that enhanced sediment recycling. Major element concentration discriminant plots also indicated that the sediments were derived from mixed sources (granitic, gneissic or recycled orogen) under passive margin setting. Chondrite normalized plot of the rare earth element pattern is marked by light rare earth element enrichment and negative Eu anomalies, interpreted to mean that provenance was mainly continental crustal rocks. Trace elemental ratios that are provenance diagnostic (La/Sc, Th/Sc, Cr/Th, La/Co, Th/Co, Th/Cr, Eu/Eu*, and Eu*) all point to sediments derived from felsic source and upper continental crust. The mixed provenance of the sandstones can be traced to the southwestern and southeastern Basement Complex (consisting of granites, gneisses, etc.) and sediments derived from the adjacent sedimentary basins (Anambra and Benue Trough).

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

Erosional history of the Karkonosze Granite Massif – constraints from adjacent sedimentary basins and thermochronology

The long-term erosional history of the Karkonosze Granite Massif is revised and reconstructed using different sources of information, including the sedimentary record of adjacent basins, previously published low-temperature thermochronological data and geomorphic features. Although the evidence is still incomplete, this work has identified a number of intervals, of unequal duration, characterized by different denudation regimes and rates. Several major phases of rapid exhumation are inferred – in the Permian and the Early Triassic as seen in the sedimentary record, and in the Late Cretaceous as shown by both the thermochronological and sedimentary records. Neotectonic uplift of the Karkonosze Mts. in the late Cenozoic is not recorded in the thermochronological record and there is no evidence of any accelerated denudation close to the massif. Apatite fission track data show that >~3.6 km of rock must have been eroded since the Turonian, while the results of zircon (U-Th)/He analysis suggest that in places erosion of >~6 km of rock must have taken place. This picture differs from previous estimates of denudation which suggested that only 2–2.5 km has been eroded from the axial part of the Karkonosze dome since the exposure of granite batholith in the Permian.

Actualistic snapshot of the early Oligocene Alps: the Alps–Apennines knot disentangled

Terra Nova, 24, 1–6, 2012AbstractThe geological framework of eastern Papua New Guinea allows us to obtain direct insight into how the Alpine region might have looked like during its earliest stages of tectonic growth, and to shed light on the spatial and temporal relationships between subduction and formation of relief before tightening of the Alps–Apennines junction. In both Alpine and Papuan cases, exhumation of high‐pressure rocks was not associated with any significant erosion, but took place while adjacent sedimentary basins were virtually starved of orogenic sediments and largely characterized by slow accumulation of deep‐water mudrocks and limestones. The subduction and exhumation stages were thus well distinct and separated in time from the genesis of topographic relief, which did not take place until many millions years later.