Pleistocene Evolution Research Articles

New 10Be-26Al isochron burial dating informs the Pliocene and Pleistocene evolution of the lower Colorado River, southwestern United States

New ¹⁰Be-²⁶Al isochron burial dating informs the Pliocene and Pleistocene evolution of the lower Colorado River, southwestern United States

Transformation of local kettle holes based on geological and geophysical evidence, Borisoglebsk Upland, Central European Russia

Late Pleistocene evolution of Central European glacial landscapes is often narrowed down to the impact of postglacial linear erosion. Yet extensive watersheds in the marginal zone of MIS6 glaciation were protractedly affected by the postglacial flattening in periglacial and interglacial conditions. Local sediment sinks such as kettle holes and dry valleys infilled throughout the postglacial stage can serve not only as records of paleoenvironmental changes but also for assessing the scales of watershed denudation and landscape transformation since the last glacial cover degradation. We attempted to use electrical resistivity tomography for paleogeomorphological survey of a local flat-bottomed depression previously studied by conventional lithological and stratigraphic approaches. The obtained geophysical profile showed a contrasting picture of the relatively higher-resistive glacial base embedded with low-resistive lenses 3-25 m thick a top. The latter were correlated with the postglacial loamy deposits of colluvial and lacustrine origin that infilled the lows of initial glacial topography. It was revealed that the depression has a particularly complex inner structure embodying at least two buried kettle holes divided by a large glacial ridge almost buried under the postglacial infill. They functioned as separate basins during much of the Late Pleistocene and have probably merged only at its final stages. The geophysical cross-section also showed a quite variable bottom relief of each kettle with significantly steeper slopes than the modern sides of the depression. Thus, electrical resistivity tomography prospecting proved to be useful for detecting the postglacial loamy infills of initial lows of the MIS6 glacial topography and can be further employed to better understand the actual scales of the postglacial redeposition and landscape modeling during the last 150–130 ka.

DISTINCTIVELY HUMAN? MEANING‐MAKING AND WORLD SHAPING AS CORE PROCESSES OF THE HUMAN NICHE

AbstractPart of the task in studying human evolution is developing a deep understanding of what we share, and do not share, with other life, as a mammal, a primate, a hominin, and as members of the genus Homo. A key aspect of this last facet is gained via the examination of the genus Homo across the Pleistocene. By at least the later Pleistocene members of the genus Homo began to habitually insert shared meaning into and onto their world forming one of the bases of contemporary human abilities to develop a distinctive human niche and human culture. Meaning‐laden cultural dynamics constitute the core of a ubiquitous semiotic ecosystem, which in turn structures the architecture of the complex niches and niche construction processes that characterize humanity today. Here, I offer a summary of Pleistocene evolution of the genus Homo and an argument for when and how that extensive and distinctive capacities for shared meaning‐making and a particularly dynamic niche construction emerged.

Late Pleistocene evolution of Robe Range, southern Australia – The timing and carbonate source dynamics of coastal dune development

Robe Range is a coastal barrier that extends for over 155 km along the modern coastline of the Coorong Coastal Plain in southern Australia, a region renowned as preserving one of the world's longest records of Quaternary eolian dune deposition. Previous research has shown that the late Pleistocene dune development in this barrier structure is linked with sea-level highstands, particularly warm interstadials of marine isotope stage (MIS) 5. To better understand the principal depositional phases and sediment provenance of the dune successions of Robe Range, we use a combination of amino acid racemization analyses on the foraminifer Lamellodiscorbis dimidiatus and optically stimulated luminescence dating of associated quartz sand. The new and previously published optical dating results indicate that phases of dune formation correlate with MIS 5c–a (ca. 105–75 ka) and early in MIS 3 (ca. 61–53 ka). More importantly, the distribution of the extent of amino acid racemization on single-foraminifers reveals that the overall barrier successions have complex sources of carbonate sediment, principally derived from contemporaneous inner shelf temperate carbonate factories and reworked skeletal grains from the erosion of older marginal marine successions. The regional narrowing of the Bonney Shelf restricted the degree of lateral changes of the shoreline in response to the glacial–interglacial cycles, in contrast to the wider Lacepede Shelf to the north. The characteristics of offshore shelf topography allow wind-driven onshore transport and delivery of bioclastic sand from mixed-age carbonate sources to onshore coastal dunes during lower sea levels, particularly in association with the intensified wind regime of early MIS 3. This points to other factors influencing coastal dune emplacement besides simply glacio–eustatic sea-level changes, and relates to the availability of biogenic particles and the delicate balance between shelf topography and wind regimes during the interstadials of the late Pleistocene.

Middle and Late Pleistocene evolution of the Ardèche Valley archaeological landscapes (France)

Most archaeological and palaeo-environmental archives are preserved in specific environments (buried sediments, rock shelters, cave environments). Hence, the information we can obtain is usually incomplete, and lacking spatial and morphological significance. Studying landscape evolution can help us to understand the location and distribution of past societies and their relation to Quaternary environments. In the Ardèche Valley, most Middle and Late Palaeolithic sites are preserved in caves and rock-shelters and in rare cases in fluvial sediments. Here we apply an integrated geomorphological approach to the study of the evolution of the Ardèche Valley combining multi-method dating, geomorphological mapping and surveys of cave and fluvial formations. We review chronological results obtained through multi-method dating (electron spin resonance (ESR), infrared stimulated luminescence (IRSL), uranium-series (U-series), combined electron spin resonance/uranium-series (ESR/U-series)) on cave and riverine objects and combine them with topographic and stratigraphic observations in an integrated Bayesian hierarchical model. The results are in agreement with those obtained from other rivers in mountainous environment around the Mediterranean Sea and show sedimentation/incision phases that match the 100 ka glacial/interglacial cycles. The mean rate of river incision deduced from the established chronology for the Middle and Late Pleistocene period, 76 ± 7 m.Ma−1, shows adjustments to a moderate uplifting dynamic that shaped the main topographical features seen today in the landscape of the Ardèche Gorge. The spatially reconstructed alluvial features provide a palaeogeographic framework that can be used directly as a chronological and topographical constraint for archaeological research in the Ardèche catchment.

Climatic and tectonic constraints on the Plio–Pleistocene evolution of the Indonesian Throughflow intermediate water recorded by benthic δ18O from IODP site U1482

The Indonesian Throughflow (ITF) is the unique low-latitude connector between the Pacific and Indian oceans. During the Plio–Pleistocene, the ITF may have played a significant role in the global climate associated with the tectonic constriction of the Indonesian gateway, which was possibly one of the factors spurring the Northern Hemisphere glaciation. Persistent constriction of the gateway would have restricted the ITF intermediate water (ITF-IW) with a high priority over the ITF upper waters. Due to limited availability of sediment archives, however, no investigations have been carried out on the Plio–Pleistocene evolution of the ITF-IW. In this study, we present our work on a total of 1368 sediment samples spanning the past ∼3.17–1.07 Ma from Site U1482, which was drilled during the International Ocean Discovery Program Expedition 363 in the Timor Passage, the main exit of the ITF to the Indian Ocean. Site U1482 is bathed by the ITF-IW, the evolution of which could thus be monitored by benthic foraminiferal shells preserved in the sediments of the site. Based on establishment of the first high-resolution (∼1.53 kyr) Plio–Pleistocene benthic δ18O stratigraphy within the ITF region, we recognized that, superimposed over the prominent 41-kyr glacial–interglacial cycles, the long-term change of Site U1482 benthic δ18O was punctuated at ∼2.51–2.43 Ma (Marine oxygen isotope stage (MIS)100/99–96/95) and at ∼1.6 Ma (MIS 56/55), followed by an interval of decreased glacial–interglacial amplitudes in the duration of ∼1.6–1.2 Ma. We propose that Site U1482 benthic δ18O was mainly driven by the global ice-sheet growth prior to ∼1.6 Ma, in addition to possibly influenced by the tectonic constriction of the Indonesian gateway. In contrast, the decreased glacial–interglacial amplitudes in the benthic δ18O during the interval of ∼1.6–1.2 Ma more likely indicate the regional signal carried by the ITF-IW, which is attributed to a freshening of the ITF surface waters that was subsequently transmitted to the intermediate depths via vertical mixing in the Banda Sea, caused by enhanced regional precipitation related to monsoonal and western Pacific warm pool conditions.

Pleistocene northward thrusting of the Danghe Nanshan: Implications for the growth of the Qilian Shan, northeastern Tibetan Plateau

Understanding the tectonic history of the Qilian Shan provides significant insights into the growth pattern of the northern Tibetan Plateau. Due to the limitation of methodology and lack of detailed geological information over remote mountain ranges, there has been less information on the Pleistocene evolution of the southern Qilian Shan. Existing models for the Qilian Shan growth also fail to specify whether the southern Qilian Shan grew northward or southward during the late Cenozoic. Here we present provenance data on fieldwork paleocurrents, petrography, heavy mineral analysis, and zircon UPb ages from the Danghe valley between Danghe Nanshan and Yema Nanshan, southern Qilian Shan. Results show a ‘seesaw-like’ change of provenance from Yema Nanshan to the north during the early Pleistocene to Danghe Nanshan to the south, which suggests the northward thrusting of Danghe Nanshan. Integrated with previous studies, our inference of a Quaternary rapid exhumation of the southern Qilian Shan reinforces the argument of northward propagation of the southern Qilian Shan during the Pleistocene and suggests a complex growth pattern of the Qilian Shan, northeastern Tibetan Plateau.

The meeting place of backarc and foreland rifting: The example of the offshore western Sicily (Central Mediterranean)

Coeval rifting processes affecting both backarc, thrust belt and foreland occurred in offshore western Sicily (Central Mediterranean) as indicated by the analysis of a large seismic data set calibrated with well data, onshore data and dredges in a dedicated GIS software environment. Structural pattern of the investigated area, 3-D geological models and a Pliocene-Lower Pleistocene evolution of extensional sedimentary basins have been reconstructed. In detail, two zones characterized by basins with different directions of extension have been recognized: one trending NE-SW, located south of the Egadi Islands; another trending E-W, positioned north of the Egadi Islands. The first group of basins represents the continuation of those of the Africa foreland basin (Pelagian Block), as the second one characterizes the opening of the backarc (southern Tyrrhenian margin). Both basins affect the collisional chain (Maghrebian thrust belt). An eastward progression of extension, from lower Pliocene to lower Pleistocene, based on different onset of the basin fill, has been documented in the Southern Tyrrhenian margin. The study area represents the meeting place of backarc and foreland rifting that affected the late Miocene thrust belt. The recognized pattern of extensional deformation of the upper plate adds some constraint on the geodynamic evolution of the African and Eurasia plates and supports a model of westward dipping slab in the Central Mediterranean. It is hypothesized that the along-trench variation of the nature of the plates, due to paleo-margin configuration, has a profound impact on the upper crustal deformation during the convergence and thus the meeting place of backarc and foreland rifting could represent the surficial signature of the slab detachment since Pliocene times. • 3D models are constructed from geological and subsurface data • The study area represents the meeting place of backarc and foreland rifting affecting the late Miocene thrust belt. • A lower Pliocene-lower Pleistocene eastward progression of extension has been documented in the Southern Tyrrhenian margin. • The geological signature of slab detachment during Pliocene times is where backarc and foreland rifting meets.

Late Quaternary evolution model for a coastal embayment with low sediment input and bedrock control (southeast Brazil)

This study developed the first palaeoenvironmental evolutionary model for the coastal plain of the region of Vitoria (ES, Brazil). Most previous research in Brazil has focused on large estuarine and deltaic plain systems, whereas Vitoria is characterized by a narrow fluvial-marine plain within an embayed rocky coast, with limited sediment input. Fluvial, embayment, estuarine and beach palaeoenvironments have been interpreted in a previous study from 4 boreholes (each 20 m long) retrieved across the coastal plain. The chronological evolution of these palaeoenvironments is reconstructed based on taxonomic molluscan classification and dating (radiocarbon and OSL). The results show that all mollusk shells are marine, which corroborates the sedimentological interpretations. A wide estuarine bay with a free connection to the sea is inferred to have formed during the last interglacial maximum (MIS 5e). The low-energy environment inhibited formation of sandy Pleistocene barriers in the inner part of the plain. Results from this research evidence a MIS 3 transgression in the study area suggesting a sea level higher than generally shown in established sea-level curves. A shallow embayment with sub-environments is formed around 14C 50-38 ka BP. These sub-environments vary along the embayment, as shown by distinct facies and mollusk shells. The Pleistocene radiocarbon ages match with the OSL fluvial sand age (36 OSL ka) in the upper part of the plain, representing the subsequent regression, where there is no marine influence. During the Holocene transgression (8900 and 7100 cal BP) an estuarine bay connected to the sea was again formed. Around 7800 cal BP, a transgressive sandy barrier was formed at the entrance of the embayment and was subsequently drowned (7500 cal BP) due to sea-level rise. During the Holocene regression (last 5000 years), inner areas were filled and transformed into wetlands. Seaward, a regressive sand barrier developed, dated between 3200 and 3000 cal BP. The Pleistocene evolution presented for the Vitoria region partially agrees with the existing models for the Brazilian coast. The main difference is the limited contribution of quartz sands transported from nearshore under low-energy hydrodynamic conditions during the filling of the embayment.

Middle to Late Pleistocene Evolution of the Bengal Fan: Integrating Core and Seismic Observations for Chronostratigraphic Modeling of the IODP Expedition 354 8° North Transect

AbstractWe investigate chronology and age uncertainty for the middle to upper Pleistocene lower Bengal Fan using a novel age‐depth modeling approach that factors lithostratigraphic, magnetostratigraphic, biostratigraphic, cyclostratigraphic, and seismic stratigraphic constraints, based on results from the International Ocean Discovery Program Expedition 354 Bengal Fan and analysis of the GeoB97‐020/027 seismic line. The initial chronostratigraphic framework is established using regionally extensive hemipelagic sediment units, and only age‐depth models of fan deposits that respect the superposition of channel‐levee systems between sites are accepted. In doing so, we reconstruct signals of regional sediment accumulation rate and lithogenic sediment input through the perspective of a two‐dimensional ~320 km transect at 8°N that are consistent with more distal and more ambiguous regional records. This chronology allows us to discuss the depositional history of the middle to upper Pleistocene lower Bengal Fan within the context of sea level, climate, and tectonic controls. We hypothesize, based on the timing of accumulation rate changes, that progradation and intensification of the Bengal Fan's channel‐levee system at 8°N was largely driven by increases in sea level amplitude during this time. However, it is also possible this progradation was influenced by changes in Pleistocene climate and increased Himalayan erosion rates, driving greater sediment flux to the fan.

Middle Pleistocene formation of the Rio Grande Gorge, San Luis Valley, south-central Colorado and north-central New Mexico, USA: Process, timing, and downstream implications

The Rio Grande is the fourth longest river in North America extending over 3,000 km from the Rocky Mountains to the Gulf of Mexico. The Pleistocene evolution of this river from individual subbasins into a coalesced fluvial system has been long debated. Herein, we constrain the middle Pleistocene evolution of the northernmost and largest Rio Grande basin, the San Luis basin, and the timing of incision of the Rio Grande Gorge, based on new geologic mapping, 3He surface exposure dating, and U-series dating on pedogenic carbonates. 3He dating of shoreline deposits of closed basin Lake Alamosa and fluvially scoured bedrock along the Rio Grande gorge rim indicate the San Luis basin was connected with southerly Rio Grande basins and progressively incised since ∼400 ka. Waning tectonic activity, coupled with the hydrologic response to intensified middle Pleistocene glaciation, drove southward spillover of Lake Alamosa ∼400 ka, expanding the river's drainage basin by nearly 24,000 km2, and adding recharge areas in the high-altitude, glaciated San Juan, Tusas, and Sangre de Cristo Mountains. Geologic barriers to streamflow on the Taos Plateau were breached and basin tributary drainages were integrated and inset into their present canyons ∼250-200 ka, with approximately 120 m of incision during ∼400-200 ka. Previous work demonstrates that southerly streamflow through basins south of the SLB terminated into a large, rift-related bolson complex until the middle Pleistocene, and most axial Rio Grande river incision has occurred since 630 ka. We propose that middle Pleistocene integration of the SLB was the major geomorphic event that eroded Plio-Pleistocene tectonic and volcanic barriers and re-established flow of the Rio Grande from the Rocky Mountains to the Gulf of Mexico.

From cylindrical to non‐cylindrical foreland basin: Pliocene–Pleistocene evolution of the Po Plain–Northern Adriatic basin (Italy)

AbstractThe architecture of foreland basins and the resulting distribution of clastic sediments are related to the constant interplay between tectonics and sedimentation. Specifically, basin floor modifications strongly influence dimensions, continuity and connections of sand‐size and fine‐grained deposits. Given the increasing need to identify deep potential reservoir deposits, the large‐scale definition of clastic porous targets and their seals is a matter of interest for oil and gas industry. Here, we present the reconstruction of the Po Plain and Northern Adriatic Foreland Basin (with an extent of ca. 40,000 km2) and its Pliocene–Pleistocene evolution, as an example of a sedimentary clastic system controlled by strongly non‐cylindrical foreland geometry. The study is based on the basin‐scale mapping of six unconformity‐bounded sequences, performed by interpreting a dense network of seismic lines and correlating well‐log data. This provides a three‐dimensional model of the step‐by‐step evolution of the basin and a description of the sediment dispersal pattern. We found that the basin records the change from a continuous (cylindrical) to highly fragmented (non‐cylindrical) foredeep geometry during Late Pliocene. In the Northern Apennines case, the main factors driving the development of a non‐cylindrical geometry are mainly related to inherited inhomogeneity in the downgoing block linked to its Mesozoic extensional faulting, and the relative orientation of these lineaments with respect to the direction of orogen migration. During the late Pliocene–Pleistocene the two directions progressively became close to parallel, and the Northern Apennines system reacted changing from a cylindrical to a non‐cylindrical state.

Pleistocene Evolution of a Scandinavian Plateau Landscape

AbstractThe origins and Pleistocene evolution of plateau landscapes along passive continental margins of the North Atlantic have been debated for more than a century. A key question in this debate concerns whether glacial and periglacial surface processes have substantially eroded plateau areas during late Cenozoic climatic cooling or whether the plateaus have mainly been protected from erosion by cold‐based and largely nonerosive ice sheets. Here we investigate the Pleistocene evolution of a prominent plateau landscape in Reinheimen National Park, southern Norway. We estimate erosion rates across the plateau via inverse modeling of 141 new cosmogenic 10Be and 26Al measurements in regolith profiles and bedrock. We combine these results with sedimentological analyses of the regolith. In the vicinity of Reinheimen's regolith‐covered summits, the combination of uniformly slow erosion (<10 m/Myr) and near‐parabolic slope geometry suggests long‐term equilibrium with the presently active periglacial mass‐wasting processes. Outside summit areas, erosion is faster (up to >50 m/Myr), possibly due to episodic glacial erosion. Despite some indications of chemical alteration, such as grusic saprolite and small amounts of secondary minerals, the fine regolith comprises low clay/silt ratios and is dominated by primary minerals with no sign of dissolution. Together with our modeled erosion rates, this indicates that the regolith cover formed, and continues to develop, during the cold climate of the Late Pleistocene.

Stratigraphic constraints on the late Miocene–Pleistocene evolution of the North Island Fault System and axial ranges in the central Hikurangi subduction margin, New Zealand

ABSTRACTThe North Island Fault System (NIFS), coincides with North Island’s axial ranges, accommodating crustal strain associated with the Hikurangi subduction margin. Detailed geological mapping along c. 80 km of the NIFS constrains uplift/subsidence and displacement patterns since c. 12 Ma. Uplift within the NIFS area and/or vertical displacement on faults occurred at 12–10, 7–6.5, 5–4.5, 3.5–3.0, 2.5–2, and post-1 Ma. Each deformation episode was associated with vertical offsets across the NIFS of >300–500 m (total c. 5 km). Total dextral strike-slip across the NIFS since 5 Ma is <20 km. Little of the relative plate motion is accommodated on the NIFS (<10%) or in the upper plate (<20%), the majority occurring on the subduction interface. The tectonic evolution of North Island is best explained by reconstructions incorporating vertical axis block rotations and <30 km strike-slip distributed across the entire margin on multiple discrete structures.

Middle–Late Pleistocene landscape evolution of the Dover Strait inferred from buried and submerged erosional landforms

Prominent landforms, either buried or preserved at the seafloor, provide important constraints on the processes that led to the opening and present-day configuration of the Dover Strait. Here, we extend previous investigations on two distinct landform features, the Fosse Dangeard and Lobourg Channel, to better understand the poly-phase history of their formation and inferences for the opening and Pleistocene evolution of the Dover Strait.The Fosse Dangeard consist of several interconnected palaeo-depressions. Their morphology and spatial distribution are interpreted to be the result of plunge-pool erosion generated at the base of north-eastward retreating waterfalls. Their infills comprise internal erosional surfaces that provide evidence for the occurrence of several erosional episodes following their initial incision.The Lobourg Channel comprises various sets of erosional features, attesting to the occurrence of several phases of intense fluvial and/or flood erosion. The last one of these carved a prominent inner channel, which truncates the uppermost infill of the Fosse Dangeard. The morphology of the Lobourg inner channel and the erosional features associated with its incision strongly resemble landforms found in megaflood-eroded terrains, indicating that this valley was likely eroded by one or several megafloods.Our study therefore corroborates the existence of waterfalls in the Dover Strait at least once during the Pleistocene Epoch. It also provides evidence of the occurrence of multiple episodes of fluvial and flood erosion, including megafloods. Finally, this study allows us to establish a relative chronology of the erosional/depositional episodes that resulted in the present-day morphology of this region.

Late Pleistocene evolution of the mixed siliciclastic and carbonate southwestern New Caledonia continental shelf/lagoon

The main island of New Caledonia (NC) is surrounded by the second largest barrier reef in the world after the Australian Great Barrier Reef. The Upper Pleistocene evolution of this barrier reef–lagoon complex offers the opportunity to examine the response of a modern mixed tropical siliciclastic/carbonate system to relative sea-level changes and to better constrain the relative role of lagoon backfilling and paleo-drainage system in sediment transfer across the shelf. This paper mainly focuses on the results of chronostratigraphic and sedimentological interpretations of new seismic, bathymetric and coring data collected in the SW NC lagoon. Several significant points are highlighted from this study and allow the construction of a refined model which includes the evolution of both the SW NC mixed shelf and lagoon. New results show that the NC lagoon has not recorded a reciprocal sedimentation during glacial-interglacial sea-level cycles but a unique mixed regime. Strong contrasts are observed and these depend above all on the two lagoon domains: the outer coral plateau and the inner lagoon depression corresponding to a semi-closed proximal basin which is separated from the plateau by a basement ridge. In the depression, clastic sediments remain dominant from early flooding to highstand stages while carbonate sedimentation continued through time across the coral plateau. This spatial contrast between terrigenous and carbonate deposits was maintained throughout various sea level cycles. Thus, even if spatial segregation is also observed for other examples of mixed shelf environments, the SW NC shelf appears quite unique in comparison to the other mixed systems when considering conceptual models of reciprocal sedimentation. Moreover, the presence of a semi-enclosed lagoon depression allows the preservation of larger volume of terrigenous deposits. This semi-filled geometry of the lagoon is assumed to be the result of several factors: a significant subsidence that offers accommodation for aggrading deposits, evacuation through channels of sediments mobilized during storm events, the tidal currents, and fairweather wave dynamics. Lastly, the inherited morphologic and structures may explain the geomorphic evolution of the “escarpment margin” type of the SW NC rimmed shelf and its differentiation with the opposite SE NC ramp type shelf.

Multi-level Domica–Baradla cave system (Slovakia, Hungary): Middle Pliocene–Pleistocene evolution and implications for the denudation chronology of the Western Carpathians

The trans-boundary Slovak-Hungarian Domica–Baradla cave system (Slovak and Aggtelek karsts), >26 km in length, consists of evolution levels that have been formed in relation to the incision phases of the Jósva Valley. Existing opinions on the age of the well-known cave system have not been based on the dating of cave sediments deposited during older evolution phases. Previous U-series dating and the first paleomagnetic analyses of dripstones, flowstones and fine-grained allochthonous sediments identified only younger accumulative phases of the cave evolution in Late Pleistocene. Our cosmogenic nuclide dating (10Be and 26Al) of allochthonous fluvial gravels from the upper and lower levels of the Domica Cave (Slovakia) reveal much older evolution phases. Two burial ages at 3.47 ± 0.78 Ma and 2.94 ± 0.50 Ma show that the upper level of the cave system originated in, or before, the Middle Pliocene. Its younger accumulation phases (Early–Middle Pleistocene) are documented based on magnetostratigraphy and U-series dating of fine-grained sediments and flowstones. The Brunhes/Matuyama boundary (780 ka), Kamikatsura excursion (~900 ka), Santa Rosa excursion (~932 ka) and Jaramillo magnetozone (~1.001–1.069 Ma) were identified from the newly studied profile in the Suchá chodba Passage (the ages of flowstones in upper part of this profile are ~130 ka, 173 ka and 199 ka). In some places, several small older (paleokarst?) solutional phreatic cavities are cut by this cave level. The lower evolution level, located 12–18 m below the upper level, originated in the Early Pleistocene (the burial age of allochthonous fluvial gravels is 1.92 ± 0.25 Ma). Low pre-burial denudation rates (3.1–5.6 m/Ma) correspond with the slowdown or interruption of tectonic uplift of the area and the long-term stabilized erosion base level during the formation of these cave levels. Their origin was linked with the formation of large pediments, of which remnants are preserved on both sides of the Jósva Valley (Hungary). The pediments probably correlate to the ‘foothill’ (Middle Pliocene) and ‘river-side’ (Late Pliocene–Early Pleistocene) levels in the denudation chronology of the Western Carpathians.

Ice-sheet modulation of deglacial North American monsoon intensification

The North American monsoon, the dominant source of rainfall for much of the arid US Southwest, remains one of the least understood monsoon systems. The late Pleistocene evolution of this monsoon is poorly constrained, largely because glacial changes in winter rainfall obscure summer monsoon signatures in many regional proxy records. Here, we develop deglacial records of monsoon strength from isotopic analyses of leaf wax biomarkers in marine sediment cores. Reconstructions indicate a regional decrease in monsoon rainfall during the Last Glacial Maximum, and that the deglacial trajectory of the North American monsoon closely tracks changes in North American ice cover. In climate model simulations, North American ice cover shifts the westerlies southwards, favouring the mixing of cold, dry air into the US Southwest. This process, known as ventilation, weakens the monsoon by diluting the energy fluxes required for convection. As the ice sheet retreats northwards, the monsoon strengthens, and local ocean conditions may play a larger role in regulating its intensity. We conclude that on glacial–interglacial timescales, ice-sheet-induced reorganizations of atmospheric circulation have a dominant influence on the North American monsoon. The intensity of the North American summer monsoon was modified by changes in the extent of the Laurentide Ice Sheet during the Last Glacial Maximum and subsequent deglaciation, according to isotope records and numerical simulations.

Deep‐Water Carbonate Ion Concentrations in the Western Tropical Pacific Since the Mid‐Pleistocene: A Major Perturbation During the Mid‐Brunhes

AbstractWe present a new deep‐water carbonate ion concentration ([CO32−]) record, reconstructed from the “size‐normalized weight” of the planktonic foraminifer Neogloboquadrina dutertrei in core MD06‐3047B, representing a middepth site (2.5 km) in the western tropical Pacific since 700 ka. On glacial‐interglacial time scales, deep‐water [CO32−] exhibits an inverse relationship with global sea‐level elevations, consistent with the “coral reef hypothesis” that the deep Pacific carbonate system responded to variations in shelf‐carbonate production through the past 700 kyr. On longer time scales, a decoupling between deep‐water [CO32−] and δ13C around the globe can be explained by a combination of continental weathering and nutrient inputs. During the mid‐Brunhes interval (~600–200 ka), [CO32−] reached a maximum of ~100 μmol kg−1 at the marine isotope stage (MIS) 12/11 boundary, followed by a steep decrease to a minimum of ~40 μmol kg−1 during middle MIS 11, representing the largest‐amplitude change in [CO32−] over the past 700 kyr. The [CO32−] maximum records the largest deglacial oceanic carbon release since 700 ka, and the [CO32−] minimum was a response to a global increase in pelagic carbonate production. From MIS 3 to 2 and from early to middle MIS 13, [CO32−] showed rising trends opposite to those at water depths greater than 3.4 km, implying enhanced Pacific stratification during these intervals. These findings provide new insights into the Pleistocene evolution of the carbonate system in the Pacific Ocean.

Successful combination of electron spin resonance, luminescence and palaeomagnetic dating methods allows reconstruction of the Pleistocene evolution of the lower Moulouya river (NE Morocco)

Based on a combination of Electron Spin Resonance (ESR) dating of quartz, luminescence dating of K-feldspar and palaeomagnetism, this study presents the first chronostratigraphic framework for the Pleistocene fluvial deposits of the lower Moulouya river in the Triffa basin (NE Morocco). K-feldspar pIRIR225 and pIRIR290 signals of all samples are saturated, suggesting fluvial deposition at least as early as the Middle Pleistocene (∼0.39–0.80 Ma). Consequently, further chronological information was obtained with ESR dating of quartz grains from the ancient Pleistocene fluvial deposits. As for ESR, the multiple centres approach provides equivalent dose values derived from the Al and Ti centres that mostly agree within 1σ-error, suggesting complete signal resetting from the former during fluvial transport. ESR dating results yield Calabrian deposition ages for all river profiles from ∼1.1 to ∼1.5 Ma. These ages are remarkably consistent with the palaeomagnetic results: the occurrence of mostly reversed polarity in the deposits indicates a Matuyama age (>0.78 Ma). While low incision rates in the Triffa basin (0.025 ± 0.003 mm/a) related to thrusting activity during the Calabrian could be inferred, the fluvial record points to an acyclic and discontinuous sedimentation pattern over the last ∼1.3 Ma. It thereby probably rules out climate as the main driver for fluvial aggradation in the lowermost sedimentary basin. At a regional scale, several indicators point to transient fluvial response resulting from major Quaternary tectonic activity along the Beni Snassen gorge, located directly upstream of the investigated basin. We suggest that a capture event at the margin of the uplifting Beni Snassen massif occurred between 1.04 and 1.36 Ma at the latest and subsequently led to the creation of the gorge.