Late Neogene Quaternary Research Articles

Subsurface Geological Characterization of the Late Neogene–Quaternary Argive Basin, Peloponnese, Greece Using Transient Electromagnetic Data and Vintage Stratigraphic Logs

The onshore and offshore clastic deposits of the Argive Basin and the Argolic Gulf, respectively, in Peloponnese, Greece, form a Late Neogene–Quaternary half-graben that connects with the Aegean Sea. The onshore Late Neogene–Quaternary sequence, comprised of chaotically intercalated cohesive and granular clastic deposits, is in angular unconformity with bedrock comprised of Triassic–Upper Cretaceous strongly-weathered, highly-fractured karstic limestones thrusted against Paleogene flysch deposits. While the surface geology of the Argive Basin is well-known, the subsurface geology remains both poorly mapped and understood. We utilized transient electromagnetic (TEM) soundings coupled with 185 vintage stratigraphic logs, current surface geology knowledge, and insights from available geophysical surveys to characterize the subsurface conditions of this sedimentary basin. We estimated the thickness of the young deposits (the depth to bedrock) and detected potential subsurface tectonic structures. The TEM-FAST 48HPC data acquisition system with integrated inversion and visualization software package was used with a single-loop dimension of 50 m × 50 m to collect a total of 329 TEM soundings at 151 stations scattered throughout the basin. The TEM station spacing varied from 200 to 750 m allowing the mapping of 80 km2. The total depth of investigation with the inverted TEM data and the lithology logs was 130 m and 183 m, respectively. The joint interpretation produced several quasi-two-dimensional electrical resistivity profiles that traverse the sedimentary basin in various azimuths and depth slices of average electrical resistivity covering the basin. The depth slices and the vintage stratigraphic logs revealed an uneven bedrock topography overlain by an irregularly thick (over 180 m) Late Neogene–Quaternary heterolithic sediment cover.

Palaeoclimate estimates based on the late Miocene to early Pleistocene wood flora of the Bengal Basin: an insight into the climatic evolution of southern Asia

To assess the pattern of climatic evolution during the late Miocene to early Pleistocene in the largest fluvio-deltaic sedimentary system on the Earth, the Bengal Basin (BB), a quantitative palaeoclimatic reconstruction was made, based on 20 fossil wood floras. Those floras show that moisture-loving taxa have decreased considerably since the Miocene, especially at the western margin of the basin. A quantitative reconstruction of climate parameters reveals that the late Miocene−early Pliocene was warmer and wetter than now, yet with spatial variability. Seasonality of temperature was low in the basin and subsequently increased during the late Pliocene−early Pleistocene. Monsoon intensity was weaker during the interval from the late Miocene to early Pleistocene than the present day. A comparison of the retrieved data with some earlier records from sites either influenced by Indian summer monsoon (ISM) or East Asian summer monsoon (EASM) or both, the two branches of the Asian summer monsoon (AM) provide insights into the temporal and spatial patterns of climate evolution in southern Asia during the late Neogene–Quaternary transition. In general, a drop in temperature and a weakening in ISM strength since the early Pleistocene correlate with the global cooling trend, though with spatial differences.

Late Neogene–Quaternary Planktic Foraminiferal Biostratigraphy and Biochronology from ODP Site 807A, Ontong Java Plateau, Western Equatorial Pacific

ABSTRACT A biostratigraphic and biochronological study from the late Neogene–Quaternary section of Ocean Drilling Program (ODP) Site 807A, located on the Ontong Java Plateau, western equatorial Pacific, revealed 50 planktic foraminiferal events, enabling the identification of eight late Neogene–Quaternary biozones, from the Globorotalia plesiotumida Interval Zone to the Globorotalia truncatulinoides Interval Zone. A significant faunal turnover (17 events) from late Pliocene identified in cores 7 and 8, between 70 and 55 meters below seafloor (mbsf), and spanning 0.67 million years (Myr). This noteworthy turnover may be the result of a shift in oceanographic conditions pertaining to the closure of the Indo–Pacific Seaway, followed by the Northern Hemisphere Glaciation. This study provides a high resolution biostratigraphic and biochronological framework for ODP Site 807A that will aid in correlation and timing the various paleoceanographic changes over the last 6 million years in the western equatorial Pacific.

Late Neogene–Quaternary tephrochronology, stratigraphy, and paleoclimate of Death Valley, California, USA

Sedimentary deposits in midlatitude continental basins often preserve a paleoclimate record complementary to marine-based records. However, deriving that paleoclimate record depends on having well-exposed deposits and establishing a sufficiently robust geochronology. After decades of research, we have been able to correlate 77 tephra beds exposed in multiple stratigraphic sections in the Death Valley area, California, United States. These correlations identify 25 different tephra beds that erupted from at least five different volcanic centers from older than 3.58 Ma to ca. 32 ka. We have informally named and determined the ages for seven previously unrecognized beds: ca. 3.54 Ma tuff of Curry canyon, ca. 3.45 Ma tuff of Furnace Creek, ca. 3.1 Ma tuff of Kit Fox Hills, ca. 3.1 Ma tuff of Mesquite Flat, ca. 3.15 Ma tuff of Texas Spring, 3.117 ± 0.011 Ma tuff of Echo Canyon, and the ca. 1.3 Ma Amargosa ash bed. Several of these tephra beds are found as far northeast as central Utah and could be important marker beds in western North America. Our tephrochronologic data, combined with magnetic polarity data and ^(40)Ar/^(39)Ar age determinations, redefine Neogene sedimentary deposits exposed across 175 km^2 of the Death Valley area. The alluvial/lacustrine Furnace Creek Formation is a time-transgressive sedimentary sequence ranging from ca. 6.0 to 2.5 Ma in age. The ca. 2.5−1.7 Ma Funeral Formation is typically exposed as a proximal alluvial-fan facies overlying the Furnace Creek Formation. We have correlated deposits in the Kit Fox Hills, Salt Creek, Nova Basin, and southern Death Valley with the informally named ca. 1.3−0.5 Ma Mormon Point formation. In addition, our correlation of the late Pleistocene Wilson Creek ash bed 15 in the Lake Rogers deposits represents the first unambiguous sequences deposited during the Last Glacial Maximum (marine isotope stage [MIS] 2) in Death Valley. Based on this new stratigraphic framework, we show that the Pliocene and Pleistocene climate in Death Valley is consistent with the well-established marine tropical/subtropical record. Pluvial lakes in Death Valley and Searles Valley began to form ca. 3.5−3.4 Ma in the late Pliocene during MIS MG5. Initiation of lakes in these two hydrologically separated valleys at the same time at the beginning of a cooling trend in the marine climate record suggests a link to a cooler, wetter (glacial) regional climate in North America. The Death Valley lake persisted until ca. 3.30 Ma, at the peak of the M2 glaciation, after which there is no evidence of Pliocene lacustrine deposition, even at the peak of the Northern Hemisphere Glaciation (ca. 2.75 Ma). If pluvial lakes in the Pliocene are an indirect record of glacial climate conditions, as they are for the Pleistocene, then a glacial climate was present in western North America for ∼200,000 yr during the Pliocene, encompassing MIS MG5−M2. Pleistocene pluvial lakes in Death Valley that formed ca. 1.98−1.78 Ma, 1.3−1.0 Ma, and ca. 0.6 Ma (MIS 16) are consistent with other regional climate records that indicate a regional glacial climate; however, Death Valley was relatively dry at ca. 0.77 Ma (MIS 19), when large lakes existed in other basins. The limited extent of the MIS 2 marsh/shallow lake in the Lake Rogers basin of northern Death Valley reflects the well-known regional glacial climate at that time; however, Death Valley received relatively lower inflow and rainfall in comparison.

Late Neogene–Quaternary submarine mass wasting along the margins of the Ulleung Basin, East Sea: Geomorphologic controls and geohazard potential

Seismic reflection data from the Ulleung Basin, East Sea, provide extensive evidence for Plio-Quaternary mass transport deposits (MTDs). We identified 23 MTDs embedded in 7 MTD bearing seismic units (U1–U7, from oldest to youngest) and estimated their geometric characteristics and source areas. The thicknesses and volumes of these MTDs range between 25 m and 392 m, and 13 km3–550 km3, respectively. The depth of the acoustic basement below sea level varies between about 100 m in the western margins to over 5900 m in the central part of the basin and highlights eight structural highs in the central and southern parts of the basin. These structural highs had a major role in controlling the pathway and distribution of the MTDs in the basin. In general, the thickest MTD units are sourced from the southern parts of the basin and the volume of these MTDs has remained relatively constant throughout the Plio-Quaternary. The seismic reflection data also reveal about 50 m high slide/slump scars formed on the seafloor by the latest submarine landslides which mainly concentrate on the southern and western margins of the basin. High-sedimentation rates and pore pressure build-up are likely the predominant factor controlling initiation of slope failures in the southern margin. Tectonics and gas hydrates likely play a role, too. The initial water depth of submarine landslides and volume and runout of the MTDs originating from the southern margin imply significant geohazard to the region.

Late Palaeogene emplacement and late Neogene–Quaternary exhumation of the Kuril island-arc root (Kunashir island) constrained by multi-method thermochronometry

The Kuril islands constitute a volcanic island arc-trench system, stretching from eastern Hokkaido (Japan) to Kamchatka (Russia) along the northwestern Pacific subduction system. The current arc consists of several volcanic islands mainly with Neogene basement and capped by several, predominantly andesitic, active subduction stratovolcanoes. Kunashir Island is the southwestern-most island of the arc, just off the Hokkaido coast and represents the study area in this paper. The island is composed of a Lower Complex of mainly late Miocene to Pliocene volcanic rocks, covered by an Upper Complex of younger (basaltic) andesitic lava flows and tuffs on which currently four active volcanic edifices are built. In the Lower Complex sub-volcanic and deeper-seated intrusives of the so-called Prasolov and Dokuchaev magmatic complexes are found. More differentiated, tonalitic–granodioritic rocks were collected from these small intrusive bodies. An early Oligocene zircon LA-ICP-MS U/Pb age of 31 Ma for the Prasolov Complex was obtained, showing that the basement of Kunashir Island is older than previously thought. Thermochronometry (apatite fission-track and U-Th-Sm/He and zircon U-Th/He analyses) further shows that the magmatic basement of the island was rapidly exhumed in the Pleistocene to present levels in a differential pattern, with He-ages ranging from 1.9 to 0.8 Ma. It is shown that the northern section of the island was hereby exhumed more intensely.

Palustrine carbonates and pedogenic calcretes in the Çal basin of SW Anatolia: Implications for the Plio-Pleistocene regional climatic pattern in the eastern Mediterranean

Abstract Sedimentologic and stable isotopic studies in the Cal basin-fill provide new insights on the late Neogene–Quaternary climatic pattern in the eastern Mediterranean. Long-term subsidence and terrestrial sedimentation in the basin beginning in the late Miocene are recorded in alluvial fan and fluvial deposits overlain by Pliocene palustrine carbonates. An erosional unconformity separates the Pleistocene siliciclastic and calcrete deposits above as a single sedimentary unit resting on top of floodplain fines and restricted to the basin center. The stable isotopic analysis of the palustrine carbonates and pedogenic calcretes displays a wide range of values (− 7.98

Detrital fission-track-compositional signature of an orogenic chain-hinterland basin system: The case of the late Neogene Quaternary Valdelsa basin (Northern Apennines, Italy)

Detrital thermochronological data collected in syn-tectonic basin deposits are a promising tool for deciphering time and processes of the evolution of orogenic belts. Our study deals with the Valdelsa basin, one of the wider basins of central Tuscany, Italy. The Valdelsa basin is located at the rear of the Northern Apennines, a collisional orogen whose late Neogene Quaternary development is alternatively attributed to extensional and compressional regimes. These contrasting interpretations mostly rely on different reconstructions of the tectono-sedimentary evolution of several basins formed at the rear of the chain since the late Tortonian. Here, we explore the detrital thermochronological–compositional signature of tectonic and surface processes during the Valdelsa basin development. For this aim, detrital apatite fission-track analysis of 21 sand samples from the latest Messinian Gelasian fluvial to shallow marine basin deposits, has been accompanied by a clast composition analysis of 7 representative outcrops of the conglomerate facies. The grain-age distributions of the sediment samples are generally characterized by two distinct components, one younger peak (P1) varying between 5.5±2.8 and 9.5±1.0Ma and one older peak (P2) varying from 15.0±8.0 to 41.0±10Ma. By comparison with some bedrock ages obtained from the E-NE basin shoulder, we attributed the P2 peak to the Ligurian Units and the P1 peak to the Macigno Formation (Tuscan Units). These units are arranged one upon the other in the complex nappe pile forming the Northern Apennines orogen. While the gravel composition indicates a predominant feeding from the Ligurian units all along the sedimentary succession with a subordinate occurrence of Macigno pebbles slightly increasing upsection, the P1 peak is present even in the oldest collected sandy sediments. The early P1 occurrence reveals that the Macigno was exposed in the E-NE basin shoulder since at least the latest Messinian–early Zanclean. This means that deeper part of the structural edifice was exposed earlier than previously reported. This was likely made possible by exposures of Macigno at the cores of anticlines or on the footwall of backthrusts. Thus, the Macigno early supply claims a role for shortening in the Northern Apennines hinterland basin evolution. Our study revealed the suitability of the detrital thermochronological/compositional analysis on syn-tectonic infill of hinterland basins in discriminating between different tectonic processes affecting the late evolution of an orogenic chain.

Late Neogene exhumation and relief development of the Aar and Aiguilles Rouges massifs (Swiss Alps) from low‐temperature thermochronology modeling and 4He/3He thermochronometry

The late Neogene–Quaternary exhumation history of the European Alps is the subject of controversial findings and interpretations, with several thermochronological studies arguing for long‐term steady state exhumation rates, while others have pointed to late Miocene–Pliocene exhumation pulses associated with tectonic and/or climatic changes. Here, we perform inverse thermal‐kinematic modeling on dense thermochronological data sets combining apatite fission track (AFT) data from the literature and recently published apatite (U‐Th‐Sm)/He (AHe) data along the upper Rhône valley (Aar and Aiguilles Rouges massifs, Swiss Alps) in order to derive precise estimates on the denudation and relief history of this region. We then apply forward numerical modeling to interpret cooling paths quantified from apatite 4He/3He thermochronometry, in terms of denudation and relief‐development scenarios. Our modeling results highlight the respective benefits of using AFT/AHe thermochronology data and 4He/3He thermochronometry for extracting quantitative denudation and relief information. Modeling results suggest a late Miocene exhumation pulse lasting until ∼8–10 Ma, consistent with recently proposed exhumation histories for other parts of the European Alps, followed by moderate (∼0.3–0.5 km Myr−1) denudation rates during the late Miocene/Pliocene. Both inverse modeling and 4He/3He data reveal that the late stage exhumation of the studied massifs can be explained by a significant increase (∼85–100%) in local topographic relief through efficient glacial valley carving. Modeling results quantitatively constrain Rhône valley carving to 1–1.5 km since ∼1 Ma. We postulate that recent relief development within this part of the Swiss Alps is climatically driven by the onset of major Alpine glaciations at the mid‐Pleistocene climate transition.

Small-scale convection at the edge of the Colorado Plateau: Implications for topography, magmatism, and evolution of Proterozoic lithosphere

The Colorado Plateau of the southwestern United States is characterized by a bowl-shaped high elevation, late Neogene–Quaternary magmatism at its edge, large gradients in seismic wave velocity across its margins, and relatively low lithospheric seismic wave velocities. We explain these observations by edge-driven convection following rehydration of Colorado Plateau lithosphere. A rapidly emplaced Cenozoic step in lithosphere thickness between the Colorado Plateau and adjacent extended Rio Grande rift and Basin and Range province causes small-scale convection in the asthenosphere. A lithospheric drip below the plateau is removing lithosphere material from the edge that is heated and metasomatized, resulting in magmatism. Edgedriven convection also drives margin uplift, giving the plateau its characteristic bowl shape. The edge-driven convection model shows good consistency with features resolved by seismic tomography.

Orogenic float of the Venezuelan Andes

The Venezuelan (or Mérida) Andes are a NE-trending intracontinental orogen that started to rise from the Middle Miocene due to the E–W far field convergence between the Maracaibo block to the northwest and the Guyana shield to the southeast. Oblique convergence is responsible for strain partitioning with thrusting along both foreland basins and right-lateral strike–slip faulting along the NE–SW Boconó fault cutting the Venezuelan Andes along-strike. The central part of the belt is also cut by the N–S left-lateral strike–slip Valera fault that connects the Boconó fault, both faults bounding the Trujillo block that escapes towards the NNE. Even though the regional geology of belt is well known, its structure at depth remains a matter of debate. Our work, based on the integration of geological and geophysical data aims to better constrain the deep geometry of faults and the tectonic evolution of the mountain belt. We used the orogenic float model to construct two NW–SE trans-Andean crustal scale balanced sections. The Late Neogene–Quaternary shortening varies from 40 km in the south to 30 km in the north across the Trujillo block, indicating that a quarter of the deformation seems to be absorbed by the tectonic escape process. More importantly, a major reorganization in the crust took place in the Early Pliocene. It is characterized by the imbrication of the Maracaibo crust into the Guyana crust. This resulted in the subduction of the Guyana lower crust and the formation of a NW-vergent basement thrust propagating upwards and surfacing along the Las Virtudes thrust. Rapid uplift of the northern flank of the belt subsequently occurred together with massive deposition of the Plio–Quaternary coarse grained Betijoque formation in the northwestern foreland basin.

Six million years of glacial history recorded in volcanic lithofacies of the James Ross Island Volcanic Group, Antarctic Peninsula

Basaltic volcanism in the James Ross Island region has been persistent over the last 6 million years resulting in at least 50 mainly effusive eruptions that are preserved predominantly as lava-fed deltas and a small number of tuff cones. Most of the eruptions took place during glacial periods, and the deltas have enabled the characteristics of the palaeo-glacier cover to be deduced for the first time, for multiple time slices. The resolution of 40Ar/39Ar dating of young basaltic lavas is relatively poor compared with the duration of glacial–interglacial periods and precludes any Milankovitch-scale cyclicity being identified, a problem that is now becoming acute in palaeoenvironmental investigations of this type. Our results indicate that glacial periods were characterised by a relatively thin glacier cover in this area, typically just 200–350 m. They were interspersed with fewer periods of thicker ice c. 600–750 m in thickness. These are likely maximum estimates and they may be too high by a few tens of metres. The glacier cover increased in thickness toward the present. However, as evidenced by 4.6 myr-old surfaces at c. 620 m a.s.l. that are glacially unmodified other than frost shattering, no evidence has been found for a substantially thicker ice sheet at any time during the last 6 myr. The glacier cover was formed predominantly of ice (sensu stricto) that was wet-based and erosive. Thus it had a temperate or, probably more likely, sub-polar (i.e. polythermal) thermal regime and, if the ice reached the continental shelf edge, it must have had a low profile. After an early history (c. 6.2–4.6 Ma) dominated by an areally extensive Antarctic Peninsula Ice Sheet (APIS), the local glacial morphodynamics were determined by a local ice cap that draped James Ross Island and was presumably confluent with the APIS along its western margin. These results are the first evidence for the morphology, thickness and thermal regime of the glacier cover in the northern Antarctic Peninsula region for the late Neogene–Quaternary period.

The evolution of the Carpathians–Pannonian system: Interaction between neotectonics, deep structure, polyphase orogeny and sedimentary basins in a source to sink natural laboratory

The Carpathians–Pannonian Basin system provides a natural laboratory for analysing lithospheric to surface controls on tectonic topography development in a coupled source-to-sink environment. To link processes taking place at depth and at the surface, recent research focused on the interplay between basin evolution, active tectonics, topography evolution and intraplate folding mechanisms. Neotectonic processes control landscape development and natural hazards, in particular the seismicity, during the late-stage (Late Neogene–Quaternary) evolution of both the Carpathians–Pannonian Basin system and its interaction with the adjacent Dinarides and Balkans. The deep structure of the SE Carpathians exerts a strong control on the post-collisional evolution of the system. New constraints are available from seismic tomography, deep seismic reflection and refraction profiling and detailed studies of the Vreancea seismicity. Inherited orogenic fabric and structure of the active Black Sea sink has a strong influence on the localisation of the Neogene sediment pathways. A close relationship has been established between the timing and mechanisms of stress changes in the Pannonian and Transylvania basins and structural episodes in the surrounding thrust belts, pointing to an intrinsic mechanical coupling with these basins, the orogen and its foredeep. Basin inversion taking place during the Pliocene–Quaternary times in the entire Carpathians–Pannonian system is related to changes in the regional stress field leading to differential vertical movements associated with a laterally variable folding mechanism active in the entire system. Short, crustal folding patterns alternate with lithospheric wavelengths in the SE Carpathians foreland, East and South Carpathians, Transylvania and Pannonian basins. The lateral variability is the result of a marked contrast in rheology between these areas, directly related to the crustal configuration, thermal properties and late-stage collision kinematics with the Carpathians foreland. Lateral variations in the properties of the downgoing plates largely control the collision mode in the Carpathians and the post-collisional evolution of the entire system.

Late Neogene–Quaternary evolution of the intermontane Clusone Basin (Southern Alps, Italy): integration of seismic and geological data

AbstractIn the Clusone Basin (a large intermontane basin filled by thick late Neogene–Quaternary sediments in the Middle Val Seriana, Southern Alps), two high‐resolution seismic profiles have been acquired in order to reconstruct the geometries of the sediments that fill the depression, with a maximum thickness of more than 200 m as documented by available well data, and to define their relationships with the bedrock, consisting of Late Triassic carbonates. In addition to standard seismic reflection processing, a seismic refraction inversion technique has been applied. The integration of geological (both surface and well data) and seismic data indicates a complex history of the drainage patterns of the Clusone Basin, documenting a shift of the Serio River from a palaeodrainage toward the southeast (Val Borlezza) to the present situation, toward the south (Val Seriana): between the older and the present‐day drainages an important depositional stage occurred, as documented by the thick sediments that fill the Clusone Basin, controlling the capture of the Serio River along the Val Seriana. Copyright © 2004 John Wiley & Sons, Ltd.

An interpretation of high montane conifers in western Tertiary floras

Megafossil remains of conifers allied to taxa of the high montane fir-spruce-hemlock-white pine zone often occur in relatively lowland Tertiary floras together with taxa typical of the mixed-conifer and broadleaved sclerophyll forest zones. Even though these forests are now separated in elevation by fully 1,000 m and in distance by 10–20 km or more, it has been generally accepted that the structures of the high montane conifers were transported to the basins of deposition from distant, high mountains. Several lines of evidence show that montane conifers were regular members of both mixed-conifer and montane conifer forests. They were restricted to higher elevations in the late Neogene–Quaternary; as summers became drier and hotter, the germinating seedlings failed to become established in the mixed-conifer forest zone. They were further isolated from the broadleaved sclerophyll zone, which was confined to lower levels as winters became colder and snow more frequent.