Changes In Sediment Provenance Research Articles

China's Yangtze delta: Geochemical fingerprints reflecting river connection to the sea

This study investigates sediment source to sink relating the connection of the Yangtze River to the sea. A sediment borehole (PD) on the river coast, penetrating thick Quaternary sediments and thin sediments of late Pliocene age down to the bedrock, recorded a change in sediment provenance through time. Geochemical elements and magneto-stratigraphy help identify five zones. Zone I (the late Pliocene–the Early Pleistocene), characterized by Pb, Th, U, Ba, La, Ce, Nd, Hf, Y, Zr, Nb and Mn, indicates a local sediment provenance. This means that the study area was a localized sub-basin. Zone II (the Early Pleistocene–the mid-stage of the Early Pleistocene), with remarkable high Fe, K, As and Rb implies a new sediment provenance joining the sub-basin from the middle Yangtze reach after the opening of the Zhenjiang Gorge. Zone III (the mid-stage of Early Pleistocene–the Middle Pleistocene), featured by Ti, V, Cr, Sr, Sc, Cu, Co, Ni, Mg, Ca, Na and P suggests a further extension of sediment provenance to the upper Yangtze basin, where a large block of the E'mei basalt and carbonate occurs. This suggests that the Three Gorges valley linking the upper and middle Yangtze reaches had developed by that time. Zones IV and V (the Middle Pleistocene–the Holocene) have shown their geochemical similarity to Zone III. Discrimination ratio f(Cr, Th), f(La) and f(K, La), a new approach developed for tracing sediment provenance, confirms a basin-wide sediment source through Zones III–V. These together witness a progressive extension of the sediment provenance towards the upper Yangtze basin, corresponding to the long-term tilting effect of the Cenozoic Topographic Reversal of the eastern China continent. The timing of the Yangtze River running through into the East China Sea appears at ca. 1.0–1.2Ma (bottom of Zone III).

Vertical variations of luminescence sensitivity of quartz grains from loess/paleosol of Luochuan section in the central Chinese Loess Plateau since the last interglacial

The provenance of loess in Chinese Loess Plateau, including origin, transport pathways and source areas, has long been one of the most important questions. In this study, the vertical variations of the luminescence sensitivity of quartz grains from the central Chinese Loess Plateau were investigated by using optically stimulated luminescence (OSL) techniques. Our results indicate that the luminescence sensitivity of quartz grains of paleosols can be much higher than that of loess beds. In addition, the quartz grains from the loess-paleosol sequence exhibit a temporal trend in the strength of luminescence sensitivity, characterized by higher values in soils and lower values in loess beds. The OSL sensitivity of quartz grains of the loess-paleosol sequence also shows very similar trend to the magnetic susceptibility and particle size fluctuations, implying that the luminescence sensitivity might be climatic dependent. The possible factors affecting the variations of luminescence sensitivity were discussed including particle size, natural radioactivity, and the provenance of eolian deposits. We suggest that the temporal variations of luminescence sensitivity can be attributed to the retreat-advance of deserts, the different contributions of glacial origin quartz particles associated with mountain processes, and wind patterns during glacial/interglacial cycles. Therefore, the secular variations of luminescence sensitivity of quartz grains are ultimately influenced by past climatic change through its controlling on sediment provenance changes.

Clay-sized sediment provenance change in the northern Okinawa Trough since 22 kyr BP and its paleoenvironmental implication

Provenances of clay-sized terrigenous sediments and a comprehensive interpretation of their high-resolution variations in the northern Okinawa Trough since the late last glaciation remain unclear, especially in regard to the Huanghe- and Taiwan-derived matter. Grain size, clay mineralogy, typical elemental ratio, oxygen isotope, and AMS 14C dating of core PC-1 in the northern Okinawa Trough were investigated to trace clay-sized sediment provenance and transport process and thus to recover their forcing mechanisms over the last 22kyr. Variations in linear sedimentation rate, grain size, δ18O, Ti/Ca ratio, and clay minerals can be clearly divided into three distinct intervals, consistent with changes in sediment provenance that can be close related to sea-level fluctuation, evolution of the Tsushima Warm Current as well as influence from the East Asian monsoon climate evolution. During the late last glaciation period (Interval 1, 22–16kyrBP) when the Tsushima Warm Current was absent in the East China Sea, the paleo-Huanghe mouth was situated close to the study area and thus the paleo-Huanghe could have played major role in sedimentation therein. In Interval 2 (16–7.3kyrBP), global sea-level rise led to gradually retreating of the paleo-Huanghe mouth and thus decreasing terrigenous sediment supply from it to the study area. Since 7.3kyrBP (Interval 3), some clay minerals from Taiwan might have been transported northward to the study area by the fully evolved Tsushima Warm Current, characterized by higher chlorite/kaolinite ratios. In contrast, the decreasing influence of the Huanghe-derived sediments during the strengthening of the Tsushima Warm Current periods was probably caused by the blocking effect of the Tsushima Warm Current. Particularly, chlorite/kaolinite ratio and smectite content in the Okinawa Trough sediment might be good proxies for indicating the Tsushima Warm Current-related sedimentary environment.

Sedimentary climatic record in the Galician Internal Basin: sediment provenance, transport time and hydrodynamics over the last 60.000 years.

Sedimentary climatic record in the Galician Internal Basin: sediment provenance, transport time and hydrodynamics over the last 60.000 years.

A sedimentary archive of tectonic switching from Emeishan Plume to Indosinian orogenic sources in SW China

Upper Permian to Middle Triassic sedimentary rocks in the Youjiang Basin, SW China, record a change from a within-plate mafic-dominated source to the NW, to a mixed source involving magmatic arc and recycled orogenic detritus that lay to the west and east. Upper Permian and some Lower Triassic sedimentary rocks are characterized by relatively high contents of TiO 2 and Nb, and low ratios of Al 2 O 3 /TiO 2 and Th/Nb. Detrital zircons yield U–Pb ages of c . 260 Ma and have geochemical affinities to those crystallized from the within-plate type magmas. These features, combined with extensive basaltic lithic fragments and plagioclase grains in the sandstones, imply a sedimentary source dominated by the Emeishan Large Igneous Province exposed to the NW of the basin. The Early and Middle Triassic marked a significant change in sediment provenance, with rocks displaying geochemical affinity to upper continental crust. U–Pb ages and trace elements of detrital zircons from this material show input from multiple sedimentary sources including the subduction–collision rocks related to the Indosinian Orogeny to the west of the basin and the recycled Precambrian–early Palaeozoic sedimentary and granitic rocks in the South China hinterland to the east of the basin. The Early Triassic change in the nature of the source supplying detritus to the Youjiang Basin, together with regional sedimentary and tectonothermal events, suggests a tectonic transition from the Emeishan Plume to the Indosinian Orogeny in SW China. Regional stratigraphic correlation and provenance data suggest that the Emeishan basalts provided a large sediment influx for the riverine–littoral–marine systems in the Late Permian. This basaltic particulate and dissolved input may have contributed significant unradiogenic Sr to the Late Permian seawater. Supplementary material: Details of sample preparation, analytical procedure and results, and additional figures are available at www.geolsoc.org.uk/SUP18698.

Assessing tectonic and climatic causal mechanisms in foreland‐basin stratal architecture: insights from the Alborz Mountains, northern Iran

ABSTRACTThe southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3‐km‐thick sequence of Miocene sedimentary rocks, constituting three basin‐wde coarsening‐upward units spanning a period of 106 years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment‐provenance data to characterize the relationships between tectonically‐generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S > 1, typical of each basal unit (17.5–16.0, 13.8–13.1 and 10.3–9.6 Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S < 1 (13.8 and 13.8–11 Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra‐basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S < 1, at 11–10.3 Ma and 9‐6–7.6 Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically‐induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. Copyright © 2013 John Wiley & Sons, Ltd.

Mesozoic – Cenozoic tectonic evolution of southwestern Tian Shan: Evidence from detrital zircon U/Pb and apatite fission track ages of the Ulugqat area, Northwest China

The Late Tertiary tectonic and topographic evolution of the Tian Shan Range has been widely studied as it represents a key example of active intra-continental mountain belts. Recent studies have shown that both the general tectonic framework of Tian Shan and some of its actual topographic features were inherited from the still poorly constrained Late Paleozoic–Mesozoic evolution of the range. In addition, better understanding of the tectonic and topographic evolution of the area before the last phases of late Cenozoic deformation is required to constrain the unresolved climatic and paleogeographic reconstructions. We present here U/Pb (LA-ICP-MS) dating of detrital zircons and apatite fission track analysis on detrital apatites from the exceptionally well-exposed Jurassic to Cenozoic sediment series of the still poorly constrained southwestern Tian Shan piedmont to investigate changes in sediment provenance through time. The U/Pb detrital zircon ages range widely from 222 to 3179Ma and can be statistically separated in four main groups: 240–320Ma, 400–540Ma, 550–1600Ma and 1640–2800Ma. These zircons were derived from the Tian Shan area to the north and from recycling of the Paleozoic North Tarim margin. The detrital apatite fission track ages encompass sources with preserved Mesozoic ages as well as much younger sources exhumed during middle Miocene times. Combined together those data show a general planation of the range from Middle Jurassic to Late Cretaceous associated to a wide drainage system. The progressive decrease in the variety of sources through the Mesozoic is consistent with burying of the basement exposures by sediments. Detrital zircon U/Pb data indicate an initial Tertiary uplift of the southern Tian Shan piedmont around Eocene times and a possible activation of the Talas Fergana Fault between 18 and 16Ma.

Paleoenvironmental and Paleoclimatic Interpretations of the Late Paleocene Goler Formation, Southern California, U.S.A., Based On Paleosol Geochemistry

The Paleocene was characterized by high global temperatures and elevated concentrations of atmospheric CO2. Paleoclimate records of this epoch are of particular interest to understanding the effects of anthropogenic climate forcing as well as linkages between the Paleocene climate and major tectonic and evolutionary events. However, terrestrial paleoclimatic records of the Paleocene are limited in their spatial extent, and few such records are known from western North America. In this study, paleosols from two members in the late Paleocene Goler Formation of Southern California were used to investigate local paleoclimatic conditions. The paleosols were described in detail and analyzed for morphology, clay mineralogy, and bulk geochemistry. Carbonate nodules present in paleosols from the upper member (member 4a) were characterized using petrographic and cathodoluminescence microscopy and were analyzed for carbon and oxygen stable-isotope composition. Enrichment and retention of soluble elements (Ca, Mg, and Na) and the mobilization of Fe and Mn in the paleosol profiles suggest a climate with strongly seasonal precipitation. This interpretation is further supported by the presence of pedogenic slickensides and the clay minerals smectite and illite. The appearance of pedogenic carbonate nodules in paleosols from the upper member is suggestive of a shift to more arid or more seasonal conditions that is coincident with a prominent change in sediment provenance and an inferred increase in sedimentation rate. Uplift of the ancestral Sierra Nevada during the late Paleocene was likely an important control on regional paleoclimate due to the effects of elevated topography on mean annual precipitation and seasonal distribution of precipitation. The correlation of a shift in pedogenic processes with changes in provenance and sedimentation rate suggests that the evolution of regional tectonic activity was an important control on these processes during the deposition of the Goler Formation.

Latest Paleozoic–Early Mesozoic basin–range interactions in South Tian Shan (northwest China) and their tectonic significance: Constraints from detrital zircon U–Pb ages

Since the Late Cenozoic, the Tian Shan area, as for most ranges in continental Asia is rejuvenated by the far-field effects of the India–Asia collision. However, the tectonic processes that affected the area prior to the Cenozoic are still poorly known, especially in the South Tian Shan block. An extensive record of this earlier tectonic history is provided by the thick Paleozoic to Mesozoic sedimentary sequences preserved in the Kapushaliang and Heiyingshan sections in southern Tian Shan. U–Pb (LA-ICP-MS) dating of detrital zircons from eight sandstone samples from these two close sections ranging in age from latest Paleozoic to Early Mesozoic is used to investigate changes in sediment provenance through time and to correlate them with major tectonic phases in the range. The results show that the detrital zircons are mostly magmatic in origin, with some minor metamorphic input. The U–Pb detrital zircon ages range widely from 224 to 3320 Ma and can be statistically divided into four main groups: 224–250 Ma (4%), 251–380 Ma (40%), 380–520 Ma (35%) and 545–3320 Ma (21%). Data analysis associated to already published sedimentary and geochronology information indicate that the zircons were largely derived from the Tian Shan area to the north since the Permian initiation of the basin. From latest Paleozoic to Early Mesozoic, the sediment provenance and basin–range pattern evolution of South Tian Shan can be generally divided into two stages: (1) during Early Permian, the South Tian Shan basin was in a half-graben most probably post-orogenic extensional context. (2) From Late Permian to Early Jurassic times, the South Tian Shan became a passively subsiding basin, with a geographically wider source area characterized by a relatively low topography.

Exploring the temporal change in provenance encoded in the late Quaternary deposits of the Ganga Plain

Temporal analysis of Sr isotopes in soil carbonates and Sr and Nd isotopes in silicate fractions has been carried out in a sedimentary core (Kalpi core; 50m long) raised from the southern bank of the Yamuna river, Ganga Plain, India. The aim of the study is to constrain sediment provenance through comparison with the modern Himalayan and peninsular river systems' water and bank sediments. Sr isotopic data in soil carbonates (0.71874 to 0.71410) and SrNd isotopic data in silicate (0.72865 to 0.74544 and −13.9 to −17.2, respectively) vary significantly with depth and are indicative of both Himalayan and peninsular sources for sediments in the southern Ganga Plain. The positive correlation between 87Sr/86Sr ratio and 1/Sr in soil carbonate and the negative correlation between 87Sr/86Sr and εNd in silicate confirm mixing of sediments from these sources. Variations of 87Sr/86Sr ratios in soil carbonates show that at ~80 and 45ka the Himalaya acted as the major source of sediments in the southern part of the Ganga Plain. The gradual decrease in 87Sr/86Sr ratios after 80 and 45ka indicates change in source to peninsular India which is also supported by limited Sr and Nd isotope data in silicates. The change in sediment provenance corresponds well with the available climatic record and is suggestive of strong climatic control in sediment supply with high supply from the Himalaya during the interglacial period and peninsular sediments during glacial period.

Abrupt drainage cycles of the Fennoscandian Ice Sheet

Continental ice sheets are a key component of the Earth's climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate-lake-FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas.

Geodynamic evolution of the Baguio Mineral District: Unlocking the Cenozoic record from clastic rocks

Geochemical studies done on the Baguio Mineral District had dominantly looked at the igneous rocks. A major gap is the scarcity of studies dealing with the sedimentary rock geochemistry for this district which this paper intends to address. The petrographic data and major and trace element compositions of the siltstones–sandstones from the lower member of the Late Oligocene to Early Miocene Zigzag Formation show that they are generally quartz-rich and have high K2O, Th and La/Sc contents. The chondrite-normalized REE pattern exhibits a negative Eu anomaly, enrichment in LREEs and flat HREEs similar to typical post-Archean shales. Taken together, the data indicate derivation of the lower member of the Zigzag Formation from intermediate to acid igneous rock sources generated in an active margin setting. A likely candidate source is the Cordon Syenite Complex/Palali Formation in the Northern Sierra Madre – Caraballo Mountains. Derivation from mafic source rocks in an oceanic island arc setting is inferred for samples of the Middle to Late Miocene Klondyke, Late Miocene to Early Pliocene Amlang and Late Pliocene Cataguintingan Formations. These samples are characterized by low K2O, Th and La/Sc but high Cr/Th values. Unroofing of the Pugo Metavolcanics and the younger plutons in the Central Cordillera provided the materials which eventually produced the Klondyke and Amlang Formations. Continuous uplift and shallowing of the basin resulted in the deposition of the Cataguintingan Formation. The petrography, geochemistry and geological features of the sedimentary rocks clearly define the change in sediment provenance from quartz-rich during the Oligocene to quartz-deficit in the Miocene. This offers additional constraints in understanding the geological evolution of the mineral district.

Atteinte cutanée dans la sclérose tubéreuse de Bourneville : intérêt de l’expansion cutanée

In Central and NW Europe, the transition from the Permian to the Triassic (i.e., the Zechstein–Buntsandstein boundary interval) is developed mainly in red bed facies. This continental sedimentary succession is marked by relatively high sedimentation rates providing a high temporal resolution favorable for magnetic polarity stratigraphy. Here, we present a Zechstein to Lower Buntsandstein magnetostratigraphy obtained from the c. 100 m thick Everdingen-1 core from the Netherlands. Seven magnetozones (EV1n to EV4n) and five submagnetozones (EV1n.1r to EV3r.1n) have been delineated. The Everdingen-1 magnetostratigraphy has been integrated into the well-established high-resolution Zechstein–Buntsandstein stratigraphic framework, and verifies the geomagnetic polarity record from Central Germany. This confirms the hypothesis of nearly synchronous base-level cycles within the interior of the Central European Basin. These cycles are related to solar-induced ~ 100 ka eccentricity cycles. The most distinctive feature of the Everdingen-1 magnetostratigraphy is a transition from a thin reverse to a thick dominantly normal magnetic polarity interval. This reversal predates both the terrestrial mass extinction, which is indicated by a palynofloral turnover and a major sediment provenance change at the base of the Buntsandstein, and the marine Permian–Triassic Boundary (PTB). The PTB is located within the lowermost Buntsandstein and is approximated by the last occurrence of the conchostracan Falsisca postera and a negative excursion in the carbon isotope record. According to the Buntsandstein cyclostratigraphy, the R/N reversal predates the marine end-Permian extinction event by about 0.1 Ma and the marine biostratigraphic PTB by about 0.2 Ma. The thick normal magnetozone is estimated to have lasted c. 700 ka, and roughly coincides with the main phase of Siberian Trap volcanism.

Source to sink relations between the Tian Shan and Junggar Basin (northwest China) from Late Palaeozoic to Quaternary: evidence from detrital U‐Pb zircon geochronology

AbstractThe tectonic evolution of the Tian Shan, as for most ranges in continental Asia is dominated by north‐south compression since the Cenozoic India‐Asia collision. However, precollision governing tectonic processes remain enigmatic. An excellent record is provided by thick Palaeozoic – Cenozoic lacustrine to fluvial depositional sequences that are well preserved in the southern margin of the Junggar Basin and exposed along a foreland basin associated to the Late Cenozoic rejuvenation of the Tian Shan ranges. U/Pb (LA‐ICP‐MS) dating of detrital zircons from 14 sandstone samples from a continuous series ranging in age from latest Palaeozoic to Quaternary is used to investigate changes in sediment provenance through time and to correlate them with major tectonic phases in the range. Samples were systematically collected along two nearby sections in the foreland basin. The results show that the detrital zircons are mostly magmatic in origin, with some minor input from metamorphic zircons. The U‐Pb detrital zircon ages range widely from 127 to 2856 Ma and can be divided into four main groups: 127–197 (sub‐peak at 159 Ma), 250–379 (sub‐peak at 318 Ma), 381–538 (sub‐peak at 406 Ma) and 543–2856 Ma (sub‐peak at 912 Ma). These groups indicate that the zircons were largely derived from the Tian Shan area to the south since a Late Carboniferous basin initiation. The provenance and basin‐range pattern evolution of the southern margin of Junggar Basin can be generally divided into four stages: (1) Late Carboniferous – Early Triassic basin evolution in a half‐graben or post‐orogenic extensional context; (2) From Middle Triassic to Upper Jurassic times, the southern Junggar became a passively subsiding basin until (3) being inverted during Lower Cretaceous – Palaeogene; (4) During the Neogene, a piedmont developed along the northern margin of the North Tian Shan block and Junggar Basin became a true foreland basin.

Paleoenvironmental changes in the northern Okinawa trough since 25 ka BP: REE and organic carbon evidence

Paleoenvironmental changes in the northern Okinawa trough covering the last 25 ka were synthetically reconstructed using REE and organic carbon indices of core CSH1. Variations of these parameters revealed three distinct intervals of major sediment provenance changes that can be related to sea-level fluctuation and Tsushima Warm Current evolution. Interval 1 (16-24.7 ka BP) is characterized by dominantly fluvial discharge from the Changjiang (Yangtze River) and Huanghe (Yellow River) as well as high primary productivity. In Interval 2 (7.3-16 ka BP), the Changjiang and Huanghe mouths regressed with sea-level rising. The newly formed Tsushima Warm Current could carry some sediment loads of Taiwan to the study core, especially during its late phase (7.3-8.2 ka BP). Modern oceanographic conditions were finally established since the beginning of Interval 3, leading to more terrigenous contribution from Taiwan, whereas low sea-surface productivity in the study area.

Regressive depositional architecture on a Mesoproterozoic siliciclastic ramp: Sequence stratigraphic and Nd isotopic evidences from Bhalukona Formation, Singhora Group, Chhattisgarh Supergroup, central India

A paleo-environmental and sequence stratigraphic study of the Mesoproterozoic Bhalukona Formation, Singhora Group, central India provides new interpretations applicable to understanding sedimentation and stratigraphic architecture in the Proterozoic siliciclastic ramp settings under falling and lowstand sea level conditions. Beside delineation of two diachronous surfaces, process-based facies analysis identified fourteen facies types that are grouped under five different facies associations. Paleo-environments range among continental fluvial, beach-foreshore, upper shoreface, lower shoreface and wave-dominated delta front. From the paleocurrent measurement within the fluvial channel sandstones and measurement of crest line orientations of wave generated swash bedforms, it is inferred that the Bhalukona Sea had NNE-SSW shoreline trajectory and the south-easterly flowing river system carried sediment on the shoreline from a source in the west-northwest. Such inference though in clear discordance with the earlier proposed south-southeastern sediment source for the Singhora basin, finds support in the shift in εNdt (t=1.42Ga) values (from −3.5±3.3 to −9.3±2.2) indicating change in sediment provenance at the early Bhalukona sedimentation history; sediments in the Bhalukona Formation derived from more evolved or older continental crustal sources in comparison to those of the underlying Saraipalli Formation. A tectonic forcing behind the shift in sediment provenance and fall in relative sea level is inferred that established the forced regressive and lowstand shoreline in the Singhora basin during the Bhalukona time.Abrupt basin-ward shift of facies tract and incision on shelf is exhibited by the occurrence of poorly sorted, coarse granular Bhalukona fluvial system (carrying rip-up mud clasts) directly above the argillaceous highstand Saraipalli shelf with ∼10m incision and is inferred as the signal for forced regression and development of Type-I sequence boundary. In low-gradient Proterozoic ramp settings without shelf-slope break, we interpret that the Bhalukona fluvial system incised the coastal prism developed on the Saraipalli highstand coastline. The low-gradient of the ramp, however, prompted long distance (∼15km) regression represented by the offlapped and detached delta front lobe away from the shoreline. The slow, steady rise in sea level, onset of lowstand and establishment of a wave-dominated coastline caused reworking of fluvial sediments in the basinal part (within the wave base) and resulted development of ravinement deposit. Basin-ward, the surface grades into correlative conformity. With aggradational and weak retrogradational stacking the beach-foreshore, upper- and lower-shoreface, in order of superposition, record the lowstand depositional history. The basin-scale transgression is witnessed with formation of Transgressive surface of erosion (TSE) and establishment of the Chuipalli shelf system, dominantly beyond storm wave base. Taking into consideration ∼23m preserved shoreface succession, 1m per year eustatic rise consistent with present day rate and average rate of shoreface retreat 0.5m per year, ∼11.5km retreat for the Bhalukona shoreline is estimated in its lowstand history.

The continental Permian–Triassic boundary in the Netherlands: Implications for the geomagnetic polarity time scale

In Central and NW Europe, the transition from the Permian to the Triassic (i.e., the Zechstein–Buntsandstein boundary interval) is developed mainly in red bed facies. This continental sedimentary succession is marked by relatively high sedimentation rates providing a high temporal resolution favorable for magnetic polarity stratigraphy. Here, we present a Zechstein to Lower Buntsandstein magnetostratigraphy obtained from the c. 100m thick Everdingen-1 core from the Netherlands. Seven magnetozones (EV1n to EV4n) and five submagnetozones (EV1n.1r to EV3r.1n) have been delineated. The Everdingen-1 magnetostratigraphy has been integrated into the well-established high-resolution Zechstein–Buntsandstein stratigraphic framework, and verifies the geomagnetic polarity record from Central Germany. This confirms the hypothesis of nearly synchronous base-level cycles within the interior of the Central European Basin. These cycles are related to solar-induced ~100ka eccentricity cycles. The most distinctive feature of the Everdingen-1 magnetostratigraphy is a transition from a thin reverse to a thick dominantly normal magnetic polarity interval. This reversal predates both the terrestrial mass extinction, which is indicated by a palynofloral turnover and a major sediment provenance change at the base of the Buntsandstein, and the marine Permian–Triassic Boundary (PTB). The PTB is located within the lowermost Buntsandstein and is approximated by the last occurrence of the conchostracan Falsisca postera and a negative excursion in the carbon isotope record. According to the Buntsandstein cyclostratigraphy, the R/N reversal predates the marine end-Permian extinction event by about 0.1Ma and the marine biostratigraphic PTB by about 0.2Ma. The thick normal magnetozone is estimated to have lasted c. 700ka, and roughly coincides with the main phase of Siberian Trap volcanism.

Climatically driven changes in sediment supply on the SW Iberian shelf since the Last Glacial Maximum

The assemblages of marine sediments on the SW Iberian shelf have been controlled by contributions from distinct sources, which have varied in response to environmental changes since the Last Glacial Maximum (LGM). The rapid, decadal scale Mediterranean overturning circulation permits mixing of suspended particles from the entire Mediterranean Sea. They are entrained into the suspended particulate matter (SPM) carried by Mediterranean Outflow Water (MOW), which enters the eastern North Atlantic through the Strait of Gibraltar and spreads at intermediate depths in the Gulf of Cadiz and along the Portuguese continental margin. Other major sediment sources that have contributed to the characteristics and budget of SPM along the flow path of MOW on the SW Iberian shelf are North African dust and river-transported particles from the Iberian Peninsula. To reconstruct climate- and circulation-driven changes in the supply of sediments over the past ~ 23 000 cal yr B.P., radiogenic Nd, Sr and Pb isotope records of the clay-size sediment fraction were obtained from one gravity core in the Gulf of Cadiz (577 m water depth) and from two gravity cores on the Portuguese shelf (1745 m, 1974 m water depth). These records are supplemented by time series analyses of clay mineral abundances from the same set of samples. Contrary to expectations, the transition from the LGM to the Holocene was not accompanied by strong changes in sediment provenance or transport, whereas Heinrich Event 1 (H1) and the African Humid Period (AHP) were marked by significantly different isotopic signatures reflecting changes in source contributions caused by supply of ice rafted material originating from the North American craton during H1 and diminished supply of Saharan dust during the AHP. The data also reveal that the timing of variations in the clay mineral abundances was decoupled from that of the radiogenic isotope signatures.

Variable Eocene-Miocene sedimentation processes and bottom water redox conditions in the Central Arctic Ocean (IODP Expedition 302)

In 2004, Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition, ACEX) to the Lomonosov Ridge drilled the first Central Arctic Ocean sediment record reaching the uppermost Cretaceous (~ 430 m composite depth). While the Neogene part of the record is characterized by grayish–yellowish siliciclastic material, the Paleogene part is dominated by biosiliceous black shale-type sediments. The lithological transition between Paleogene and Neogene deposits was initially interpreted as a single sedimentological unconformity (hiatus) of ~ 26 Ma duration, separating Eocene from Miocene strata. More recently, however, continuous sedimentation on Lomonosov Ridge throughout the Cenozoic was proclaimed, questioning the existence of a hiatus. In this context, we studied the elemental and mineralogical sediment composition around the Paleogene–Neogene transition at high resolution to reconstruct variations in the depositional regime (e.g. wave/current activity, detrital provenance, and bottom water redox conditions). Already below the hiatus, mineralogical and geochemical proxies imply drastic changes in sediment provenance and/or weathering intensity in the hinterland, and point to the existence of another, earlier gap in the sediment record. The sediments directly overlying the hiatus (the Zebra interval) are characterized by pronounced and abrupt compositional changes that suggest repeated erosion and re-deposition of material. Regarding redox conditions, euxinic bottom waters prevailed at the Eocene Lomonosov Ridge, and became even more severe directly before the hiatus. With detrital sedimentation rates decreasing, authigenic trace metals were highly enriched in the sediment. This continuous authigenic trace metal enrichment under persistent euxinia implies that the Arctic trace metal pool was renewed continuously by water mass exchange with the world ocean, so the Eocene Arctic Ocean was not fully restricted. Above the hiatus, extreme positive Ce anomalies are clear signs of a periodically well-oxygenated water column, but redox conditions were highly variable during deposition of the Zebra interval. Significant Mn enrichments only occur above the Zebra interval, documenting the Miocene establishment of stable oxic conditions in the Arctic Ocean. In summary, extreme and abrupt changes in geochemistry and mineralogy across the studied sediment section do not suggest continuous sedimentation at the Lomonosov Ridge around the Eocene–Miocene transition, but imply repeated periods of very low sedimentation rates and/or erosion.

Lead isotopic record of Barremian–Aptian marine sediments: Implications for large igneous provinces and the Aptian climatic crisis

We present initial isotopic ratios of lead for Early Cretaceous (Barremian–Aptian) sections from Shatsky Rise (Pacific) and Gorgo a Cerbara (Italy). Our Pb isotopic data track an interval representing Oceanic Anoxic Event (OAE)-1a, which is characterized by quasi-global deposition of organic carbon-rich black shale. Pb isotopic compositions of sediments from Shatsky Rise decrease at the end of Barremian time, from radiogenic continental values to unradiogenic values, and subsequently remained less radiogenic until the end of early Aptian time. We explain the isotopic shift by a significant increase in supply rate of unradiogenic Pb, most likely due to massive volcanism. In contrast, the Pb isotopic compositions from the Italian section, which was situated at the western end of Tethys, are mostly identical to those of upper continental crust, showing no significant change in supply rate of unradiogenic Pb. The discrepancy between two sites is attributed to quiescent deep-submarine eruptions of Pacific large igneous provinces (LIPs) such as the Ontong Java Plateau (OJP), which severely limited dispersion of Pb-carrying particles out of the Pacific Ocean. Published Os isotopic data from the Italian section indicate two episodes of massive eruptions of OJP or contemporaneous Manihiki and Hikurangi plateaus starting from earliest Aptian time, slightly later than that indicated by the sedimentary Pb isotopic record from Shatsky Rise. Differences in isotopic variations between Pb and Os likely reflect differences in their chemical behaviors in the oceans, i.e., Pb isotopic compositions would have varied in response to local or regional changes in sediment provenances, whereas large-scale changes in Os inputs are required to explain variations in seawater Os isotopic compositions. Our Pb isotopic data, together with the published Os isotopic record, provide new evidence for the eruptive history of OJP together with contemporaneous Pacific plateaus and its environmental consequences, starting from end-Barremian time and extending through early Aptian time.