Understanding how past coastal systems have evolved is critical to predicting future coastal change. Using over 12,000 trackline kilometers of recently collected, co-located multi-channel boomer, ...sparker and chirp seismic reflection profile data integrated with previously collected borehole and vibracore data, we define the upper (< 115 m below mean lower low water) seismic stratigraphic framework offshore of the Delmarva Peninsula, USA. Twelve seismic units and 11 regionally extensive unconformities (U1-U11) were mapped over 5900 km2 of North America's Mid-Atlantic continental shelf. We interpret U3, U7, U9, U11 as transgressive ravinement surfaces, while U1,2,4,5,6,8,10 are subaerial unconformities illustrating distinct periods of lower sea-level. Based on areal distribution, stratigraphic relationships and dating results (Carbon 14 and amino acid racemization estimates) from earlier vibracore and borehole studies, we interpret the infilled channels as late Neogene and Quaternary courses of the Susquehanna, Potomac, Rappahannock, York, James rivers and tributaries, and a broad flood plain. These findings indicate that the region's geologic framework is more complex than previously thought and that Pleistocene paleochannels are abundant in the Mid-Atlantic. This study synthesizes and correlates the findings of other Atlantic Margin studies and establishes a large-scale Quaternary framework that enables more detailed stratigraphic analysis in the future. Such work has implications for inner continental shelf systems tract evolution, the relationship between antecedent geology and modern coastal systems, assessments of eustacy, glacial isostatic adjustment, and other processes and forcings that play a role in passive margin evolution.
•We define a seismic framework for 5900 km2 of the Mid-Atlantic shelf, USA.•We use 12,000 km of multi-channel boomer, sparker and chirp seismic data.•Paleodrainage and sea-level histories dominate the Quaternary stratigraphy.•An extensive and varied paleochannel network characterizes the passive margin.•This Quaternary framework fills a physical gap on the U.S. Atlantic Margin.
We analysed the interplay between coastal uplift, sea level change in the Black Sea, and incision of the Kızılırmak River in northern Turkey. These processes have created multiple co-genetic fluvial ...and marine terrace sequences that serve as excellent strain markers to assess the ongoing evolution of the Pontide orogenic wedge and the growth of the northern margin of the Central Anatolian Plateau. We used high-resolution topographic data, OSL ages, and published information on past sea levels to analyse the spatiotemporal evolution of these terraces; we derived a regional uplift model for the northward-advancing orogenic wedge that supports the notion of laterally variable uplift rates along the flanks of the Pontides. The best-fit uplift model defines a constant long-term uplift rate of 0.28 ± 0.07 m/ka for the last 545 ka. This model explains the evolution of the terrace sequence in light of active tectonic processes and superposed cycles of climate-controlled sea-level change. Our new data reveal regional uplift characteristics that are comparable to the inner sectors of the Central Pontides; accordingly, the rate of uplift diminishes with increasing distance from the main strand of the restraining bend of the North Anatolian Fault Zone (NAFZ). This spatial relationship between the regional impact of the restraining bend of the NAFZ and uplift of the Pontide wedge thus suggests a strong link between the activity of the NAFZ, deformation and uplift in the Pontide orogenic wedge, and the sustained lateral growth of the Central Anatolian Plateau flank.
•Multiple fluvial, deltaic and coastal terraces along the Black Sea coast of Turkey.•New terrace chronology that spans the last 545 ka (MIS 14).•The uplift of the Central Pontides sustained at a rate of 0.28 ± 0.07 m/ka.•A northward-growing orogenic wedge that spatially coincides with a restraining bend.•The lateral growth of the northern flanks of the Central Anatolian Plateau.
A new sediment core from Padul, Padul-15-05, provides a long and continuous sedimentary and paleoenvironmental record of the last ∼200 kyr. Here we present a detailed palynological study from this ...sedimentary sequence with new vegetation and paleoenvironmental data and a climatic interpretation for the last two climatic cycles from the southern Iberian Peninsula in the western Mediterranean region. Pollen analysis from this core shows orbital-scale vegetation oscillations (mainly forced by precession and eccentricity) pointing into insolation as the principal factor controlling vegetation changes at this latitude. The last two glacial-interglacial cycles (from MIS 6 to the present) as well as stadial and interstadial phases are well represented and characterized by significant oscillations in Mediterranean forest in the area, but several differences with respect to other Mediterranean long pollen records can be recognized. Some of these disparities between regions seem to be more related to different precipitation rates linked to the specific geographical features (e.g. strong topographic relief) than to latitudinal differences between the sites. In addition, a lake level reconstruction based on palynological data was developed and compared with the previous reconstruction from this record, representing local environmental changes in the Padul wetland that seems to be related to precipitation/evapotranspiration balance, and therefore, to changes in regional climate conditions. During glacial/stadial conditions recorded by maxima in xerophytes, the p/e increased due to very low evapotranspiration, resulting in high lake levels, while during warmer interglacial/interstadial phases (except for the MIS 5e), mainly represented in this record by maxima in the Mediterranean forest, water level decreased as a result of high evapotranspiration exceeding precipitation input. The comparison of the new Padul-15-05 pollen record with the two previous palynological studies from Padul shows significant differences mainly due to disagreements in the age control of the sequences. This study shows that an accurate age-depth model becomes essential when interpreting long paleoenvironmental and paleoclimate records.
•Padul-15-05 sediment core shows paleoenvironmental and paleoclimate changes during the last ca. 200,000 years.•In this study glacial/interglacial and stadial/interstadial periods have been identified.•Vegetation changes at Padul are linked to oscillations in the elevation of the bioclimatic vegetation belts of Sierra Nevada.•Vegetation changes are related to Padul lake level oscillations, conditioned by the precipitation/evapotranspiration balance.
We here reconstruct a glacial and climate history of arctic NW Siberia for the last ~600,000 years, based on the stratigraphy and chronology of 35 studied river sections on the southern Taimyr ...Peninsula. From this stratigraphic mosaic we have identified four glacial events, marked by tills/glaciotectonics, which are intercalated with mainly marine sediments deposited in proglacial settings during transitions from glacial conditions into subsequent interglacials/interstadials. The traces of early shelf-based Kara Sea Ice Sheet (KSIS) glaciations in marine isotope stages (MIS) 12–14 and 8 are sparsely preserved, but these ice advances are suggested to have terminated far south into the central Siberian uplands, as also was the case with the younger Taz glaciation (MIS 6). The inception phase of the latter glaciation was complex, with ice advancing into a proglacial marine basin both from the south (Putorana – Anabar uplands) and the north. The deglaciation leading into the Karginsky interglacial (MIS 5e) was marked by the development of the southernmost ice-marginal zones (IMZs) on the Taimyr lowlands – the Urdakh and Sampesa IMZs. The most recent (late Pleistocene) glacial cycle is recorded by three successively smaller KSIS advances from the Kara Sea shelf onto Taimyr, of which only the first, during Early Zyryanka (MIS 5d), reached south of the Byrranga Mountains, with its maximum extent marked by the Jangoda – Syntabul – Severokokorsky IMZ. Retreat of the ice margin during MIS 5c-b was accompanied by deposition of glaciomarine sediment in the proglacial basin and deposition of large successions of delta sediments in the foothills of the Byrranga Mountains, reaching ≥100 m above present sea level. The region north of the Byrranga Mountains was subjected to two subsequent KSIS glaciations, during MIS 4 and MIS 2, while the area south of the Byrranga Mountains transitioned to a terrestrial environment from the Middle into the Lower Zyryanka, as evidenced by deposition of fluvial, aeolian and ice-complex (Yedoma) sediments.
Reconstruction of the Atlantic Meridional Overturning Circulation (AMOC) based on long-term records spanning multiple glacial-interglacial transitions is essential for understanding the interplay ...between ocean dynamics and global climate change. However, despite valuable previous studies, many uncertainties remain, especially regarding the distribution of glacial water masses in the Atlantic and the AMOC intensity. Such long-term reconstructions are highly constrained by sedimentary geochemical records. Here, we present isotope, geochemical, and micropaleontological records from the core ANS-33047 retrieved from the southern part of the Cape Verde Basin at a water depth of 4027 m. The data reflect the glacial–interglacial changes in surface and near-bottom conditions in the area over the last 513 kyr. Within the upper ocean layer, enhanced bioproductivity associated with northward ITCZ migration has been determined during MIS 13/12, early MIS 11, 9, 7, and MIS 1. A gradual deepening of the mixed layer is inferred from MIS 5 to the present. Stronger deep-water upwelling and shoaling of the mixed layer over the study site preceded these intervals. In the deep-water environment, we propose three different regimes within the interglacials: a “classical model” and “local productivity effect” associated with a stronger advection of paleo-NADW into the study area (MIS 11, 5, 1, warm early phases of MIS 9 and 7, MIS 13/12 boundary), as well as “amplified paleo-AABW influence” (late MIS 13 and 7). The bottom-water chemistry was affected by organic matter degradation coinciding with intervals of northward ITCZ migrations and enhanced surface bioproductivity. The most prominent signal of southern-sourced deep water was reconstructed during the late MIS 12, MIS 8, and at the MIS 10/9 boundary. During MIS 3 and sub-stage 12b, the study area was bathed by a mixture of paleo-NADW and paleo-AABW. A comparison of the carbon isotope records from the northeastern and southeastern equatorial Atlantic demonstrates a larger difference in the deep-water properties within glacials in contrast to interglacials.
•ITCZ shifts northwards and bioproductivity is enhanced during interglacial intervals.•Increased surface bioproductivity affects δ13C composition of paleo-NADW.•Three deep-water regimes occurrs within interglacials.•Stronger meridional variability of deep-water circulation in cold climatic phases.
Climate changes determined the repeated connections between the Black Sea, Caspian Sea and Mediterranean Sea. The landlocked anoxic Black Sea basin was exposed to several transgressions throughout ...Quaternary by the Mediterranean Sea through the Straits of Istanbul (Bosphorus) and by the Caspian Sea through the Manych-Kerch spillway. Sedimentological records of these connections are limited mostly to the marine terrace deposits of Marine Isotope Stage (MIS) 5e while the pre-MIS 5e period remains uncertain due to a lack of robust facies and chronological data from deep-sea sedimentary sequences. Here we discuss the imprints of multiple Mediterranean transgressions during Middle Pleistocene in the Black Sea based on facies analysis and the optical age of coastal carbonate aeolianites. Contrary to today's hydro-climate of the Black Sea, the aeolianites bear witness to the transformation of the Black Sea into a warm inland sea during successive Mediterranean invasions. Prior to the onset of aeolian deposition, paleosols were formed on the Eocene-aged hardened sandy silts, suggesting strongly washed soil. This is evidenced by no calcium carbonate and a high Rb/Sr ratio, with quartz amounting to of 99.8%. According to our OSL ages, carbonates deposited on the shelf plain under higher temperature and increased evaporation conditions in MIS 15 and the later interglacial phases were transported to the coastal sand dunes during the transitional phases of MIS 15–14, MIS 13–12, MIS 11–10 and MIS 9–8. We suggest that the carbonate-rich and ooid-containing aeolianites were repeatedly formed in the multiple Mediterranean transgression stages, beginning with an increasingly severe dry phase following the Brunhes-Matuyama magnetic reversal.
•The aeolianite is a robust record for Mediterranean transgressions of the Black Sea.•The ooid-rich aeolianites was repeatedly formed in multiple transgression stages.•The aeolianites bear witness to the transformation of the Black Sea into a warmer sea.
The Black Sea experienced multiple episodes of connection with both the Mediterranean and Caspian seas during the Quaternary. Global sea-level variation has been proposed as the main driver of ...changes in Mediterranean-Black Sea connectivity, while positive water budgets drove Caspian overspill. We present a new, two proxy, low-resolution record from the Black Sea that allows reconstruction of connectivity history from 430 to 50 ka: dinoflagellate cysts (dinocysts) provide direct evidence for properties of surface waters and strontium isotopes constrain the source(s) of water entering the basin. Dinocysts and 87Sr/86Sr suggest that the Black Sea was isolated from the Mediterranean during global sea-level lowstands associated with glacials MIS 4, 8 and 10. Both proxies also strongly suggest that marine (Mediterranean) water flowed into the Black Sea during the eustatic highstands associated with peak interglacials during MIS 5 and 9. However, while the contribution of marine waters during MIS 5e was similar to the present day, lower 87Sr/86Sr during MIS 9 suggests lower than present input. Connectivity during MIS 11, MIS 7 and MIS 6 is more enigmatic. Lower 87Sr/86Sr than those of the isolated Black Sea and dinocyst assemblages dominated by species of Paratethyan lineage are compatible with input from the Caspian Sea. Dinocyst taxa recovered in MIS 11 can be found in both the Caspian Sea and the Black Sea today. All four interglacials studied contain different dinocyst assemblages, suggesting that different conditions may have prevailed during each warm period. However, high-resolution studies are needed to confirm this observation. Further work on the same sequence could be valuable in elucidating the connectivity history of the Black Sea over the glacial-interglacial cycles of the late Quaternary.
•Black Sea was isolated during glacial periods MIS 10, 8 and 4.•Black Sea was connected to the Mediterranean during MIS 5 and 9.•Black Sea received Caspian overflow and/or enhanced runoff during MIS 7 and 6.•87Sr/86Sr and dinocysts provide strong tool for connectivity reconstructions•Dinocysts could be useful to fingerprint late Quaternary interglacial stages.
Two speleothems from the Demänova Cave of Liberty, located in the Low Tatras in Slovakia, were studied in detail. Age-depth modelling based on U-series dating allowed us to constrain the growth ...period for both speleothems to between approximately 375 and 157 ka. Based on a multiproxy approach, it was possible to identify periods with dominant warm climatic conditions, which enabled long and continuous speleothem growth during most of the marine isotope stage (MIS) 9 and in MIS 7c. Unfavourable for speleothem growth climate included glacial conditions, such as in MIS 10 or MIS 8, and periods connected with diminished rainfall or lower temperature such as in MIS 9b, MIS 7e or MIS 7b. The growth interruptions of the speleothems are related to maximum glacial episodes like in MIS 10a and late MIS 6, or were connected with a decrease in rainfall in MIS 9a and cold, harsh climate conditions in MIS 7d. The obtained records suggest relatively mild glacial periods (MIS 8 and MIS 10) and warm interglacial periods (MIS 9 and MIS 7) enabling long periods of speleothem growth. Gathered results indicate a large diversity of climate conditions during MIS 7, with atypical MIS 7d major stadial occurring within the interglacial complex. Compared records also showed the important role of local factors and changes in the alimentation area, which affected the isotopic composition of speleothem and may cause significant differences in the isotope records from the same cave system, especially during intense climate changes.
•A history of climatic changes from two Low Tatras speleothems.•Stable isotope and trace element records covering the MIS 11a – MIS 6c period.•The climate conditions of MIS 10, MIS 8 and MIS 6 enable speleothem growth.•A large diversity of paleoclimate conditions during MIS 7 was recorded in speleothem.
We investigated the deep-sea sedimentary sequence of core MD012422 corresponding to the last 350 ka (since marine isotopic stage, MIS 10) from off Shikoku Island, NW Pacific Ocean, and refined its ...tephrostratigraphy. We detected many tephras and cryptotephras and correlated them with terrestrial tephras on the basis of the major- and trace-element compositions of their glass shards. Then we cross-checked our results against the reported marine tephrostratigraphy in the NW Pacific area and assessed the relative timing of tephra eruptions and bioevents. Many widespread tephras and cryptotephras originated from the Kyushu volcanic zone (Kuju, Aso, Kakuto, Aira, Ata, and Kikai volcanoes/calderas), along with the Takayama-Ng1 tephra (Tky-Ng1) from Suiendani volcano in central Honshu, were detected in the core. These tephras were used to validate and refine the reported NW Pacific marine tephrostratigraphy and to develop useful time-synchronous markers for this ocean area. Among the tephras, Ata-Torihama (Ata-Th) occurs at the MIS 7/8 transition (ca. 240 ka) and its horizon overlaps with a calcareous nannofossil biohorizon, the first appearance datum (FAD) of Emiliania huxleyi. Ata-Th and this biohorizon are stratigraphically above the Tky-Ng1 (MIS 8/9 transition, 290–300 ka) and Kakuto (Kkt, MIS 9/10 transition, 330–340 ka) tephras, and these tephras have the same stratigraphic relationship with this biohorizon in deep-sea sediments from the East China Sea, off Shikoku Island, and off central Honshu. However, in deep-sea cores from off northern Honshu, an inconsistency between the tephrostratigraphy and the FAD of E. huxleyi has been reported. This inconsistency can be explained by poor preservation of calcareous fossils in the deep waters off northern Honshu, which are more corrosive to calcium carbonate than the shallower waters off Shikoku Island. These findings emphasize the importance of cross-checking biohorizons against tephra horizons and of linking tephras between terrestrial and marine sequences to assess the synchronicity of globally correlated age indicators.
•Glass shards in core MD012422 were characterized by compositional analyses.•Tephras with similar shard chemistries were discriminated by the shard morphologies.•All tephras except one from central Honshu were derived from the Kyushu volcanic zone.•Ages of revised tephra horizons are consistent with the reported δ18O stratigraphy.•Ages of the tephra horizons are consistent with reported regional biohorizons.
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