Neogene Time Research Articles

The central Fuegian fold and thrust belt in Tierra del Fuego: Strike‐slip tectonics superimposed onto compressional deformation

The boundary between South America and Scotia plates was established during Neogene times when a wrench tectonic regime was developed along the central area of Tierra del Fuego. This boundary includes the Magallanes–Fagnano fault system: a regional diffuse deformation zone, which involves the development of the satellite Yehuin–Chepelmut fault zone and a series of pull‐apart basins overprinting the Fuegian fold and thrust belt. The analysis of regional seismic lines allowed to reconstruct and recognize the structure of the external fold and thrust belt. The interpreted structures were integrated into a regional transect and a 3D block diagram that display the different structural domains and, mainly, the wrench deformation associated with the Magallanes–Fagnano fault system. Geophysical data from gravity and magnetic anomaly maps provided further support for the location and development of the pull‐apart basins along the plate boundary. The deformation of the external fold and thrust belt is characterized by an imbricated fan system with a Paleogene detachment surface, which was later cut across by the Yehuin–Chepelmut fault zone and the Magallanes–Fagnano fault system.

Latest Neogene monsoon of the Chotanagpur Plateau, eastern India, as revealed by fossil leaf architectural signatures

A fossil leaf assemblage from latest Neogene (Pliocene) sediments exposed in Jharkhand of Chotonagpur Plateau, eastern India, is subjected to a CLAMP (Climate Leaf Analysis Multivariate Program) analysis using a new high spatial resolution (~1 km2) WorldClim2 gridded climate data and PhysgAsia2 calibration. The CLAMP analysis of 80 different morphotypes of fossil leaves indicates a mean annual temperature (MAT) of 21.9 °C ± 2.3 °C; a cold month mean temperature (CMMT) of 16.7 °C ± 3.5 °C and a warm month mean temperature (WMMT) of 26.9 °C ± 2.9 °C. Precipitation estimates have high uncertainties but suggest a weak monsoon with a growing season (11.7 ± 1 months) precipitation (GSP) of 201.2 ± 64.3 cm. The new calibration also provides for the first time in India more detailed insights into the hydrological regime through the return of annual and seasonal vapour pressure deficit (VPD) and potential evapotranspiration (PET) estimates, as well as new thermal overviews through measures of thermicity and growing degree days. The new results confirm the overall warmth of the region. Although rainfall estimates have large uncertainties due to year-round wet soils, measures of VPD and PET show persistent high humidity, but with higher evaporative stress in the summer during late Neogene times than now.

LATE NEOGENE DEFORMATION OF ROCK SUCCESSIONS AT RENAH GAJAH MATI I REGION, SELUMA REGENCY IN BENGKULU

Lack of work focusing on deformation mechanism has been undertaken in the Late Tertiary sequence during Late Neogene time at the Renah Gajah Mati I region in Bengkulu basin. The present study was aimed at reconstructing tectonic deformation occurring within the basin during the Late Neogene, employing balancing and restoring techniques, kinematic and dynamic analyses. The Late Neogene deformation was mainly controlled by compression, which has resulted in folding and thrusting. Hence, the rock sections underwent shortening that varied from 1.42-1.83 km or 0.75%-0.78% with the estimated rate of deformation 0.12-0.15 mm/year. Two types of tectonic structures developed within the region, fault propagation folds and trishear faults. The brittle deformation extended sequentially in the direction of tectonic transport, resulting in a series of faults. The generated faults constitute imbricate fans with a relatively closely-spaced thrust system. The array of thrusts is apparently associated with folds that strike NW-SE, implying the geometry of fault-linked folding. The hanging wall anticlines are generally asymmetric overturned folds, indicating a shallow ramping fault with a high shear pattern. In regional context, the general strike of structures within the study area appears relatively parallel to the NW-SE trending Barisan orogen. This feature suggests that tectonic transport responsible for structuring was likely at the NE- SW direction.

Age of the N7/N8 (M4/M5) planktonic foraminifera zone boundary: constraints from the zircon geochronology and magnetostratigraphy of early Miocene sediments in Ichishi, Japan

The age assigned to the Miocene N7/N8 (M4/M5) planktonic foraminifera zone boundary is markedly different from the astronomically tuned Neogene time scales published in 2004 (ATNTS2004) and 2012 (ATNTS2012). This difference is primarily because of the lack of reliable assignment of the zone boundary to magnetostratigraphy, which needs to be resolved for the better refinement of the geologic time scale. Our previous biostratigraphic results from an onland sedimentary sequence of the upper Ichishi Group in central Japan allow location of the stratigraphic position of the lowest occurrence datum (LOD) of Praeorbulina sicana, a key planktonic foraminifera species for defining the N7/N8 (M4/M5) zone boundary. In this study, we performed laser ablation-multiple collector-inductively coupled plasma mass spectrometry U–Pb dating on zircons from two felsic tuff beds in the Ichishi sequence. The age of the zone boundary is approximated by a U–Pb age of 17.03±0.11 Ma for a tuff bed ∼2m above the boundary. We also conducted a magnetostratigraphic analysis in which site-mean characteristic remanent magnetization directions were determined for 19 sites and showed a reverse–normal–reverse (R–N–R) stratigraphic change in polarity. The N7/N8 (M4/M5) zone boundary is within the upper reverse polarity zone. The R–N–R sequence can be correlated with a stratigraphic portion corresponding to chrons C5Dr–C5Dn–C5Cr; hence, the age of the zone boundary is within Chron C5Cr. Our results are thus compatible with the age (16.97 Ma) assigned to the boundary in ATNTS2004 rather than ATNTS2012 and should be considered when the Neogene time scale is updated. A normal polarity subzone found in the upper reverse polarity zone can also be dated at ∼17.0 Ma and is probably correlated with a short normal polarity episode in Chron C5Cr. In terms of tectonic rotation, the site-mean magnetization directions determined in this study suggest an ∼35° clockwise rotation in Ichishi with respect to the North China Block in the Asian continent since ∼17.2 Ma (the upper boundary age of Chron C5Dn). Clockwise rotation of Southwest Japan, which occurred in association with backarc opening of the Japan Sea, was probably in progress during deposition of the upper Ichishi Group sediments.

Late neogen deformation of rock successions at Renah Gajah Mati I Region Seluma Regency in Bengkulu

Studies on tectonic deformation of the Late Tertiary sequence during Late Neogene time has been carried out at the Renah Gajah Mati I region using balancing and restoring techniques, kinematic and dynamic analyses. The Late Neogene deformation was mainly controlled by compression, which has resulted in folding and thrusting. Hence, the rock sections underwent shortening that varied from 1.42-1.83 km or 0.75%-0.78% with the estimated rate of deformation 0.12-0.15 mm/year. Two types of tectonic structures developed within the region, fault propagation folds and trishear faults. The brittle deformation extended sequentially in the direction of tectonic transport, resulting in a series of faults. The generated faults constitute imbricate fans with a relatively closely-spaced thrust system. The array of thrusts is apparently associated with folds that strike NW-SE, implying the geometry of fault-linked folding. The hanging wall anticlines are generally asymmetric overturned folds, indicating a shallow ramping fault with a high shear pattern. In regional context, the general strike of structures within the study area appears relatively parallel to the NW-SE trending Barisan orogen. This feature suggests that tectonic transport was likely at the NE-SW direction.

The earliest well-documented occurrence of sexual dimorphism in extinct sloths: evolutionary and palaeoecological insights

AbstractSexual dimorphism (SD) is extremely common in species that have reproductive roles segregated into separate sexes, and it has been recognized in several mammalian lineages, both extant and extinct. Sexual dimorphism is low to moderate in living sloths, but it had a more important role for extinct sloth taxa. The presence of SD in extinct sloths was first suggested at the end of the 19th century and it is now commonly advocated as a possible explanation of high intraspecific variation in many extinct sloth species. In this paper, we report the presence of SD in Simomylodon uccasamamensis, a Late Miocene to Late Pliocene sloth from the Bolivian Altiplano. We present evidence of SD in the morphology of cranial and postcranial remains, representing the earliest unequivocal occurrence of size-based SD in an extinct sloth species. Differences between sexes are mainly observed in the morphology of the feeding apparatus and general body size. Comparisons with extant large mammals allow us to hypothesize different food selection between the two sexes, with probable divergent habitat use and concomitant niche separation. This, in turn, could have represented an important selective factor for adaptation to environmental changes experienced by the Bolivian Altiplano in Late Neogene times.

Detecting syn-orogenic extension and sediment provenance of the Cilento wedge top basin (southern Apennines, Italy): Mineralogy and geochemistry of fine-grained sediments and petrography of dispersed organic matter

Wedge-top basins can provide highly sensitive information on the uplift and erosion history of an evolving collisional belt, but their burial and thermal history has generally been neglected because their siliciclastic infill records the very low temperature history, which is difficult to detect. This paper provides an integrated approach for defining the first order tectonic events shaping the southern Apennines in Neogene times through the study of a wedge-top basin. A new dataset of temperature-dependent clay minerals and vitrinite reflectance, alongside whole-rock geochemistry of the fine grained sediments, is provided for the uppermost Burdigalian-lower Tortonian succession of the Cilento Group, deposited in one of the largest wedge-top basins of the southern Apennines (Italy) and its substratum. The distribution of paleothermal indicators allowed us to model a detailed burial and thermal history of the basin, whereas whole-rock geochemistry allowed us to trace the provenance and alteration of sediments through time. Geochemical data on the fine grained fraction of sediments suggest a source area mainly characterized by felsic rocks with a modest mafic contribution, reflecting a prevalent upper crust composition. Chemical paleoweathering processes played a minor role, consistent with medium CIA and CIA′ values and sediments, subdued poor sorting and rapid deposition. The dataset from clay minerals and vitrinite reflectance analyses indicates a basin evolution marked by two phases of intense subsidence, interpreted as the result of syn-orogenic extension at shallow crustal levels intermitted with periods of low sedimentation rates, linked to gravitational instability of a vertically growing orogen.

Origin of oil geochemical compositional heterogeneity in the Radhuma and Tayarat formations heavy oil carbonate reservoirs of Burgan Field, south Kuwait

This is a qualitative assessment study to understand origin controlling lateral/geographic and vertical/stratigrahic heterogeneity of Radhuma (Palaeocene) and Tayarat (Maastrichian) Formation heavy oil reservoirs in the Burgan Field in south Kuwait. Data from oil analyses, including physical properties, bulk chemical composition, sulphur content, molecular chemical composition, and carbon and sulphur isotopes, were used to characterise the different oils in the reservoirs. Geochemical fingerprinting and characterisation suggest that the key impact on compositional heterogeneity has been the mixing of some petroleum—by the addition of lighter oil to extra-heavy oil. Therefore, the proposed complex filling history model for the Radhuma and Tayarat reservoirs consists of six episodes: two oil entrapments and four thermochemical sulphate reduction (TSR) fluid pulses. Finally, it is postulated that lighter fresh charge oils in the Burgan Field were sourced upward from deeper reservoirs associated with the reactivation of deep-seated faults as a result of structural compression events during Upper Cretaceous and Neogene time.

Evolutionary insights from comparative transcriptome and transcriptome-wide coalescence analyses in Tetrastigma hemsleyanum

BackgroundTetrastigma hemsleyanum is of great medicinal importance and used as a model system to address the evolutionary history of warm-temperate evergreen (WTE) forest biomes in East Asia over Neogene time scales. However, further studies on the neutral and adaptive divergence processes of T. hemsleyanum are currently impeded by a lack of genomic resources. In this study, we de novo assembled and annotated a reference transcriptome for two cpDNA lineages (Central-South-East vs. Southwest) of T. hemsleyanum. We further used comparative genomic and multilocus coalescent approaches to investigate the tempo and mode of lineage diversification in T. hemsleyanum.ResultsA total of 52,838 and 65,197 unigenes with an N50 of 1,667 and 1,841 bp for Central-South-East (CSE) and Southwest (SW) lineages, respectively, were recovered, and 6,692 putative orthologs were identified between the two lineages. Estimation of Ka/Ks ratios for these orthologs revealed that ten genes had Ka/Ks values significantly greater than 0.5 (P < 0.05), whereas 2,099 (Ka/Ks < 0.5, P < 0.05) were inferred to be under purifying selection. Based on three bioinformatic strategies, we identified a total of 1,018 single-copy nuclear genes (SCNGs) from the orthologs. We successfully designed eight nuclear gene primer pairs with high intraspecific variation (e.g. hT = 0.923, πT = 1.68×10-3), when surveyed across a subset of T. hemsleyanum individuals. Concordant with the previous cpDNA data, the haplotype networks constructed for most nuclear gene loci clearly identified the two lineages. A multilocus coalescence analysis suggested that the separation between the two lineages appears to have occurred during the mid-Pliocene. Despite their ancient divergence, both lineages experienced expansion at rather localized scales and have continued to exchange genes at a low rate.ConclusionsThis study demonstrated the utility of transcriptome sequencing as a basis for SCNG development in non-model species and the advantages of integrating multiple nuclear loci for phylogeographic and phylogenetic studies.

Cenozoic basin evolution of the Central Patagonian Andes: Evidence from geochronology, stratigraphy, and geochemistry

The Central Patagonian Andes is a particular segment of the Andean Cordillera that has been subjected to the subduction of two spreading ridges during Eocene and Neogene times. In order to understand the Cenozoic geologic evolution of the Central Patagonian Andes, we carried out geochronologic (U-Pb and 40Ar/39Ar), provenance, stratigraphic, sedimentologic, and geochemical studies on the sedimentary and volcanic Cenozoic deposits that crop out in the Meseta Guadal and Chile Chico areas (∼47°S). Our data indicate the presence of a nearly complete Cenozoic record, which refutes previous interpretations of a hiatus during the middle Eocene–late Oligocene in the Central Patagonian Andes. Our study suggests that the fluvial strata of the Ligorio Márquez Formation and the flood basalts of the Basaltos Inferiores de la Meseta Chile Chico Formation were deposited in an extensional setting related to the subduction of the Aluk-Farallon spreading ridge during the late Paleocene–Eocene. Geochemical data on volcanic rocks interbedded with fluvial strata of the San José Formation suggest that this unit was deposited in an extensional setting during the middle Eocene to late Oligocene. Progressive crustal thinning allowed the transgression of marine waters of Atlantic origin and deposition of the upper Oligocene–lower Miocene Guadal Formation. The fluvial synorogenic strata of the Santa Cruz Formation were deposited as a consequence of an important phase of compressive deformation and Andean uplift during the early–middle Miocene. Finally, alkali flood basalts of the late middle to late Miocene Basaltos Superiores de la Meseta Chile Chico Formation were extruded in the area in response to the suduction of the Chile Ridge under an extensional regime. Our studies indicate that the tectonic evolution of the Central Patagonian Andes is similar to that of the North Patagonian Andes and appears to differ from that of the Southern Patagonian Andes, which is thought to have been the subject of continuous compressive deformation since the late Early Cretaceous.

Response to comment on “A high-precision 40Ar/39Ar age for the Nördlinger Ries impact crater, Germany, and implications for the accurate dating of terrestrial impact events” by Schmieder et al. (Geochimica et Cosmochimica Acta 220 (2018) 146–157)

Rocholl et al. (2018) claim that the 40Ar/39Ar age of 14.808 ± [0.038] Ma (2σ; full external error) for the Ries impact, recently obtained from step-heating analysis of tektites (Schmieder et al., 2018, Geochim. Cosmochim Acta 220, 146–157), is “geologically impossible” and violates paleomagnetic constraints. We demonstrate that the moldavite age of Schmieder et al. (2018) is in good agreement with recalculated isotopic ages for ash layers and magnetic (sub-)chrons that define the Langhian stage in the Astronomically Tuned Neogene Time Scale, using updated K decay constants and monitor ages in 40Ar/39Ar geochronology. Moreover, we stress that the normally magnetized basal pelitic sediments of the Ries crater lake, which are separated from the reversely magnetized suevite by a thick unit of post-impact conglomerates and sandstones, may not have been deposited ‘immediately’ after the impact. The paleomagnetic constraints proposed by Pohl (1977, 1978) and Rocholl et al. (2018) are, therefore, questionable.

A Neogene history of mantle convective support beneath Borneo

Most, but not all, geodynamic models predict 1–2 km of mantle convective draw-down of the Earth's surface in a region centered on Borneo within southeast Asia. Nevertheless, there is geomorphic, geologic and geophysical evidence which suggests that convective uplift might have played some role in sculpting Bornean physiography. For example, a long wavelength free-air gravity anomaly of +60 mGal centered on Borneo coincides with the distribution of Neogene basaltic magmatism and with the locus of sub-plate slow shear wave velocity anomalies. Global positioning system measurements, an estimate of elastic thickness, and crustal isostatic considerations suggest that regional shortening does not entirely account for kilometer-scale regional elevation. Here, we explore the possible evolution of the Bornean landscape by extracting and modeling an inventory of 90 longitudinal river profiles. Misfit between observed and calculated river profiles is minimized by smoothly varying uplift rate as a function of space and time. Erosional parameters are chosen by assuming that regional uplift post-dates Eocene deposition of marine carbonate rocks. The robustness of this calibration is tested against independent geologic observations such as thermochronometric measurements, offshore sedimentary flux calculations, and the history of volcanism. A calculated cumulative uplift history suggests that kilometer-scale Bornean topography grew rapidly during Neogene times. This suggestion is corroborated by an offshore Miocene transition from carbonate to clastic deposition. Co-location of regional uplift and slow shear wave velocity anomalies immediately beneath the lithospheric plate implies that regional uplift could have been at least partly generated and maintained by temperature anomalies within an asthenospheric channel.

Cover beds older than the mid-pleistocene revolution and the provenance of their eolian components, La Sal Mountains, Utah, USA

We used uranium-lead (U-Pb) dating of zircons from a tephra layer deposited in the La Sal Mountains to assign an age of more than c. 1.3 Ma to underlying loess-mixed slope deposits (cover beds) and paleosols developed therein. For the first time, we show that properties of cover beds and soils before the Mid-Pleistocene Revolution were similar to those formed after the revolution. However, the deepest exposed carbonate-enriched horizon is much farther developed than younger ones, indicating that there was a period of enrichment by far exceeding intensities of younger calcic horizons some time before the revolution, possibly in Neogene times. Remarkable differences between age distributions of detrital zircons (DZ) within the cover beds allow reconstructing the regional provenance of mixed eolian matter with high accuracy: we were able to trace particular cover beds back to areas with outcropping Permian and Upper Cretaceous rocks.

Why No Porphyry Copper Deposits in Japan and South Korea?

AbstractThis analysis concludes that there is little realistic likelihood of discovering large, high‐grade porphyry Cu deposits in Japan and South Korea because of an unusual combination of geological factors. First, weak inter‐plate coupling, trench retreat, and extension – a tectonic regime unfavorable for porphyry Cu formation – appears to have characterized the convergent margin during much of Cretaceous through Neogene time. Second, Cretaceous through Quaternary magmatism involved widespread ash‐flow caldera development, a volcanic style that suppresses porphyry Cu formation because the all‐important Cu‐bearing magmatic fluids – if present – would be explosively discharged during silicic ignimbrite eruption and lost to the atmosphere. Third, due to the trench retreat, crustal profiles beneath Japan are dominated by accretionary complexes containing chemically reduced lithologies, which decrease the redox state of subduction‐related magmas during their ascent. The most reduced intrusions belong to the ilmenite‐series, which may lock up chalcophile elements at depth and produce magmatic fluids that are incapable of transporting the Cu required for significant porphyry deposit formation. Fourth, many of the caldera‐related magmatic rocks, including the principal intrusions, are not only derived by partial melting of reduced crust but are commonly also highly fractionated; hence, any associated mineralization tends to be Mo ± W‐rich rather than Cu dominated. Fifth, intrusive rocks with high Sr/Y, typical of hydrous magmas responsible for porphyry Cu belts worldwide, appear to be present only locally. Sixth, two important magmatic and metallogenic tracts in Japan, the Kuroko‐bearing Green Tuff belt and Kitami low‐sulfidation epithermal Au region, are characterized by bimodal magmatism, which worldwide is compositionally unsuited to porphyry Cu generation. Seventh, the Pliocene‐Quaternary andesitic–dacitic volcanoes that could be the surface expressions of porphyry Cu systems are mostly too shallowly eroded to reveal underlying deposits should they exist. Consequently, few magmatic suites in Japan and South Korea provide propitious environments for porphyry Cu exploration, with the last hope believed to lie at depth below late Miocene–Pliocene advanced argillic lithocaps, several of which contain relatively minor high‐sulfidation epithermal Au mineralization. However, even there, the reduced crust may have militated against effective Cu transport into the porphyry environment. The magmatic and metallogenic factors that downgrade the porphyry Cu potential of Japan and South Korea are believed to be equally applicable to other subduction‐related magmatic arc segments worldwide.

Neogene Uplift and Magmatism of Anatolia: Insights From Drainage Analysis and Basaltic Geochemistry

AbstractIt is agreed that mantle dynamics have played a role in generating and maintaining the elevated topography of Anatolia during Neogene times. However, there is debate about the relative importance of subduction zone and asthenospheric processes. Key issues concern onset and cause of regional uplift, thickness of the lithospheric plate, and the presence/absence of temperature and/or compositional anomalies within the convecting mantle. Here, we tackle these interlinked issues by analyzing and modeling two disparate suites of observations. First, a drainage inventory of 1,844 longitudinal river profiles is assembled. This database is inverted to calculate the variation of Neogene regional uplift through time and space by minimizing the misfit between observed and calculated river profiles subject to independent calibration. Our results suggest that regional uplift commenced at 20 Ma in the east and propagated westward. Second, we have assembled a database of geochemical analyses of basaltic rocks. Two different approaches have been used to quantitatively model this database with a view to determining the depth and degree of asthenospheric melting across Anatolia. Our results suggest that melting occurs at depths as shallow as 60 km in the presence of mantle potential temperatures as high as 1400°C. There is evidence that temperatures are higher in the east, consistent with the pattern of subplate shear wave velocity anomalies. Our combined results are consistent with isostatic and admittance analyses and suggest that elevated asthenospheric temperatures beneath thinned Anatolian lithosphere have played a first‐order role in generating and maintaining regional dynamic topography and basaltic magmatism.

Continental climate gradients in North America and Western Eurasia before and after the closure of the Central American Seaway

The Gulf Stream, as part of the Atlantic Meridional Overturning Circulation (AMOC), is known as a major driver of latitudinal energy transport in the North Atlantic presently causing mild winters over northwestern Eurasia. The intensity of the AMOC throughout the Neogene, prior to the final closure of the Central American Seaway (CAS) in the early Pliocene, is still poorly known, but most authors assume that the circulation was considerably weaker than present. Here we address this issue from a continental point of view. We studied the past AMOC intensity by analyzing Neogene continental climate patterns along North American and Western Eurasian transects. Based on a total of 317 palaeofloras thermal latitudinal gradients are reconstructed for three Neogene time slices, namely the middle Miocene, late Miocene, and late Pliocene using the Coexistence Approach to obtain quantitative climate data. The obtained proxy-based, continental temperature gradients are evaluated against data from a selection of published General Circulation Model (GCM) simulations for the three time slices studied.Our study suggests that shallow thermal latitudinal gradients existed in North America and Western Eurasia throughout the Miocene but became strongly steepened in the late Pliocene. In both Miocene time slices studied, the higher latitudes were by up to 30 °C warmer than present (cold month mean), also at times with presumed pre-industrial CO2 such as the late Miocene. In the late Pliocene high-latitude, the temperature difference with respect to the present had decreased by up to 10 °C (cold month mean). Both mean annual temperatures and cold month means of the lower mid and low latitudes were at the present-day level throughout all three time slices, or even slightly below. In both Miocene time slices, zonal temperature means at both continental transects were similar in the mid and higher latitudes. However, several northwest European sites reveal very mild winter condition suggesting the early existence of a probably less intense Palaeo-Gulf Stream. The distinct thermal anomaly (annual and cold month means) today existing between North America and Western Eurasia appeared for the first time in the late Pliocene, attaining about 50% of the present-day magnitude. This supports the assumption that the AMOC intensified after the final closure of the CAS during the early Pliocene. The results obtained from the palaeobotanical proxies are in line with data from coeval marine archives, particularly with North Atlantic sea surface temperatures (SSTs) inferred from oxygen isotopes. However, the proxy-based thermal gradients are not well reproduced by a selection of GCM simulations, due to a well-known systematic underestimation of high latitude warming by GCMs for the Miocene and Pliocene time slices.

Spatial and temporal uplift history of South America from calibrated drainage analysis

AbstractA multidisciplinary approach is used to analyze the Cenozoic uplift history of South America. Residual depth anomalies of oceanic crust abutting this continent help to determine the pattern of present‐day dynamic topography. Admittance analysis and crustal thickness measurements indicate that the elastic thickness of the Borborema and Altiplano regions is km with evidence for sub‐plate support at longer wavelengths. A drainage inventory of 1827 river profiles is assembled and used to investigate landscape development. Linear inverse modeling enables river profiles to be fitted as a function of the spatial and temporal history of regional uplift. Erosional parameters are calibrated using observations from the Borborema Plateau and tested against continent‐wide stratigraphic and thermochronologic constraints. Our results predict that two phases of regional uplift of the Altiplano plateau occurred in Neogene times. Regional uplift of the southern Patagonian Andes also appears to have occurred in Early Miocene times. The consistency between observed and predicted histories for the Borborema, Altiplano, and Patagonian plateaux implies that drainage networks record coherent signals that are amenable to simple modeling strategies. Finally, the predicted pattern of incision across the Amazon catchment constrains solid sedimentary flux at the Foz do Amazonas. Observed and calculated flux estimates match, suggesting that erosion and deposition were triggered by regional Andean uplift during Miocene times.

Impact of tectonic and volcanism on the Neogene evolution of isolated carbonate platforms (SW Indian Ocean)

Understanding the impact of tectonic activity and volcanism on long-term (i.e. millions years) evolution of shallow-water carbonate platforms represents a major issue for both industrial and academic perspectives. The southern central Mozambique Channel is characterized by a 100km-long volcanic ridge hosting two guyots (the Hall and Jaguar banks) and a modern atoll (Bassas da India) fringed by a large terrace. Dredge sampling, geophysical acquisitions and submarines videos carried out during recent oceanographic cruises revealed that submarine flat-top seamounts correspond to karstified and drowned shallow-water carbonate platforms largely covered by volcanic material and structured by a dense network of normal faults. Microfacies and well-constrained stratigraphic data indicate that these carbonate platforms developed in shallow-water tropical environments during Miocene times and were characterized by biological assemblages dominated by corals, larger benthic foraminifera, red and green algae. The drowning of these isolated carbonate platforms is revealed by the deposition of outer shelf sediments during the Early Pliocene and seems closely linked to (1) volcanic activity typified by the establishment of wide lava flow complexes, and (2) to extensional tectonic deformation associated with high-offset normal faults dividing the flat-top seamounts into distinctive structural blocks. Explosive volcanic activity also affected platform carbonates and was responsible for the formation of crater(s) and the deposition of tuff layers including carbonate fragments. Shallow-water carbonate sedimentation resumed during Late Neogene time with the colonization of topographic highs inherited from tectonic deformation and volcanic accretion. Latest carbonate developments ultimately led to the formation of the Bassas da India modern atoll. The geological history of isolated carbonate platforms from the southern Mozambique Channel represents a new case illustrating the major impact of tectonic and volcanic activity on the long-term evolution of shallow-water carbonate platforms.

Manual of Neogene foraminifera from off-shore Nile Delta (Egypt) and their biostratigraphic significance

The Mediterranean Nile Delta is a major target for hydrocarbon reservoirs. In the search for hydrocarbons, high-resolution biostratigraphy has long been established as high-impact and low-cost solution to face the challenges in the move towards structurally more complex and unexplored areas. To date, the biozonation of the Nile Delta is largely provided by benthic and planktonic index foraminifera. We have examined the foraminifera assemblages from NDOB-1, a borehole in the northern part of the Nile Delta. The material recovered provides unique and exceptionally well-preserved microfossil biotas that completely cover the Neogene succession (Middle Miocene to Pleistocene). This allows the establishment of an intact biozonation scheme for the Nile Delta region with reliable chronostratigraphic correlation and suitable industrial applications.The stratigraphic succession of the Nile Delta region consists of seven formations: Sidi Salim Formation, Qawasim Formation, Rosetta Formations, Abu Madi Formation, Kafr El Sheikh Formation, El Wastani Formation and Mit Ghamr Formation. Examination of the planktonic foraminifera assemblages of the NDOB-1 borehole from the deep part of the Nile Delta lead to the identification of twelve biozones: Globorotalia inflata Interval Zone, Globorotalia aemiliana Interval Zone, Globorotalia puncticulata Interval Zone, Globorotalia puncticulata- Globorotalia margaritae Concurrent Range Zone, Globorotalia margaritae Interval Zone, Sphaeroidinellopsis seminulina Acme Zone, Non-distinctive Zone, Globorotalia suterae Interval Zone, Globigerina woodi Interval Zone, Globorotalia mayeri Interval Zone, Globorotalia fohsi peripheroronda Interval Zone and Praeorbulina glomerosa Interval Zone. The biozones fully cover the time span from the Middle Miocene to the Pleistocene. The benthic foraminifera recovered allow the identification of five benthic biozones for the Pliocene and Pleistocene: Hyalinea balthica Interval Zone, Bulimina marginata Interval Zone, Bulimina aculeata Interval Zone, Gyroidinoides laevigata Interval Zone and Uvigerina rutila Interval Zone. The identified planktonic bioevents were used to calibrate the studied Neogene section with the Astronomically Tuned Neogene Time Scale (ATNTS, 2012).

A new species of Africanacetus (Odontoceti: Ziphiidae) found on the deep ocean floor off the coast of Brazil

A fossil skull of a beaked whale was newly collected by a manned submersible from the São Paulo Ridge of the Atlantic floor about 2900m deep off the coast of Brazil. It was found in the middle of the manganese nodules on the seafloor. The whale fossil can be dated sometime between the middle Miocene and the early Pliocene based on the timing of the onset of the tectonic movements of the São Paulo Ridge whence the specimen came and the precipitation of the manganese layers, which entirely encrusted the specimen. This is the first instance of a fossil beaked whale skull retrieved from such great depths. This skull belongs to a new species of Africanacetus, which may be a genus with a broad distribution in southern oceans in Neogene times, expands the geographic distribution of the genus as the northernmost record, and adds the taxonomic and morphological diversity within the genus.