Global Sea-level Changes Research Articles

Quaternary sediment sources and loess transport pathways in the Black Sea - Caspian Sea region identified by detrital zircon U-Pb geochronology

Constraining the controls on the distribution of sediment at a continental scale is a critical step in understanding long-term landscape and climate evolution. In particular, understanding of the role of rivers in wider sediment routing and impacts on aeolian loess formation on a continental scale remains limited. Extensive Quaternary loess deposits are present on the East European Plain and in the Black Sea - Caspian Sea region and are associated with major rivers draining numerous surrounding cratonic and orogenic hinterland areas. Coupled with this, complex changes in local and global sea level have affected the extent and drainage of the Caspian Sea and the Black Sea, and Quaternary glaciations have impinged on the northern margin of the East European Plain. This suggests that sediment routing and loess formation may show complex patterns and controls. Here, we apply UPb dating of detrital zircons from fluvial, marine and aeolian (dominantly loess) sedimentary records on the East European Plain and in the Black Sea - Caspian Sea region. This shows a strong control of large rivers on the distribution of sediments at a continental scale in the region, through long-distance transport of several 1000 km, sourced from continental and mountain glacier areas prior to marine or atmospheric reworking and transportation. Strong spatial variability in zircon UPb data from loess deposits on the East European Plain reveals multiple diverse sources to the different individual loess sections, whereas no significant temporal variability in loess source is detected during the Late Pleistocene of the Lower Volga loess in South Russia. While the sediment supply from glacial areas via rivers plays an important role for the provenance of East European Plain loess deposits, our data indicate that the stark spatial diversity in loess provenance on the East European Plain is often driven by the input of multiple local sources. Similar to the loess, marine sediments from different basins of the Black Sea and the Caspian Sea also show significant spatial variability. This variability is controlled by the bathymetry of the seas, leading to sedimentary intermixing by sea currents within, but not between different separated sea basins. A direct comparison of marine and aeolian sediments at the same depositional site suggests that although loess and marine sediments are both dominantly sourced from river sediments containing far travelled sedimentary material, local sources play a more important role in many loess deposits.

Planktonic Biota Constituents Responses to Global Sea-Level Changes Recorded in the Uppermost Albian to Middle Cenomanian Deep-Water Facies of the Outer Carpathians

Interpretations of sea-level changes over geological time are mainly based on analyses of sediments deposited within stable platforms. One of the criteria for recognizing these changes is the composition of skeleton-bearing protists living in environments close to the shoreline and on the continental shelf. It can be assumed that the source of information about sea-level changes may also be found in assemblages of microfossils redeposited from the shelf to the marginal ocean basin. With such an assumption, this article presents an interpretation of changes in marine plankton communities (radiolarians and planktonic foraminifera), which during late Albian–middle Cenomanian were redeposited with carbonate mud by gravity currents from the peri-Tethyan shelf to the northern, marginal Silesian Basin of the Western Tethys. Planktonic biota identified in sediments deposited by gravity flows and those found in hemipelagic shales separating them, indicate that their composition may be correlated with eustatic changes in the sea level from the late Albian (KAl8) to middle Cenomanian (KCe3).

Relative sea level changes during the Last Glacial Maximum and deglaciation (33–15 ka) inferred from the δ18O records of planktic foraminifera from the Sea of Japan

The Sea of Japan, located in the humid zone, was subjected to significant freshening of surface waters and a decrease in ventilation of deep waters during the glacial eustatic drop in relative sea level (RSL) and a decrease in water exchange with Pacific due to the shallowness of its straits. As a result, the δ18O values of planktic foraminifera (δ18Opf) decreased by several ppm, in contrast to the increase of ones in the Red Sea, depending on the degree of RSL drop.The good preservation of planktic foraminifera in the sediments of the Sea of Japan during the Last Glacial Maximum (LGM) and deglaciation allows us to significantly refine and supplement the available evidences of the global sea level changes over the 33–15 ka. Based on the obtained and published records of δ18Opf of five cores from different parts of the sea and the general chronology of the accumulation of dark layers in the sediments of the Sea of Japan, we calculated the δ18Opf stacks with high and low resolution (0.13 kyr for two cores and 0.5 kyr for other three cores) for the time 33–15 ka.Both stacks showed significant RSL falls at the onset of LGM (32–29 ka), during 21.8–20.3 ka, and an abrupt rise at 17 ka consistently with previously published data. The higher resolution stack additionally showed two phases of RSL falls at the onset of the LGM followed by a slow decrease until 22 ka, with a short and abrupt descent at around 25 ka. According to both stacks the lowest sea level around 18.5–17.5 ka was preceded by a short rise just before 19 ka. A significant RSL rise at 17 ka was followed by an abrupt and short fall at nearly 16.5 ka and then prolonged rise since around 16.2 ka.

Luminescence dating of a sedimentary sequence in the eastern North Yellow Sea

Sediments from the Yellow Sea (YS) are important archives for investigating the stratigraphic evolution in relation to global and regional sea-level changes. Here, the upper 40-m-thick interval of a 100-m-long drill core (NYS17), retrieved from the eastern North Yellow Sea (NYS), were studied to explore the late Quaternary sedimentary history in this region. To obtain reliable chronological framework of the core, we utilized multiple luminescence signals from sediments for dating. Coarse-grained (CG) and fine-grained (FG) quartz optically stimulated luminescence (OSL), and K-feldspar/polymineral post-infrared (IR) IR stimulated luminescence (pIRIR50/150) signals were analyzed to obtain age estimates for comparison. Primary results show that quartz OSL ages are consistent with the corrected ages of IR50 and pIRIR150 signals. Chronostratigraphy of core NYS17 presents two phases of rapid accumulation. One is at the interval of 35.6–29.8 m deep, as age controls of sedimentary stratigraphy are in the period of 135–130 ka, corresponding to Marine Isotope Stage (MIS) 6/5. Another occurs in the upper section (14.5–0.9 m) as luminescence ages are constrained between 11 and 9 ka. However, the overlying deposits after 9 ka seem to be very thin in the core site. This is likely attributed to the abundant terrestrial sediment supply during the early Holocene and following starvation after further rise of the sea level and transgression. In contrast, the MIS 5–2 interval remains far to be exactly defined in the core as no age constraint is available. Regionally, correlations of chronostratigraphy of our core with other collected cores from the YS and East China Sea, show comparable depositional records for both the late Pleistocene and Holocene sedimentary successions. These findings indicate that the spatiotemporal variations of sedimentary processes in the YS shelf were closely linked to global sea-level changes during the glacial-interglacial cycles.

Sea-level changes in the Bohai Sea, northern China, constrained by coastal loess accumulation over the past 200 ka

Loess sequences are widely distributed in semi-arid regions around the world, and are sometimes also located in coastal zones. The accumulations of coastal loess provide a valuable record of both climate and sea-level changes. Here we report sedimentological and high sampling resolution luminescence dating evidence for such changes from two loess sequences from the Shandong Peninsula and Miaodao Archipelago near the coast of Bohai Sea in northern China. Both the quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared IRSL (pIRIR290) signals show consistent and satisfactory luminescence characteristics up to ∼100 ka, while the K-feldspar pIRIR290 ages provide age control up to ∼200 ka and are in stratigraphic order. With this fully independent age model, our results reveal that coastal loess accumulation is episodic with a high variability in apparent accumulation rates. After comparing with global and regional sea-level records, we find that the intervals with high accumulation rates coincide with global low sea-level stages, and that the loess sedimentary hiatuses indicated by nearly zero or very low accumulation rates at one site mainly correspond to global high sea-level stages, indicating the dominant role of global sea-level changes on coastal loess accumulation in the study area. We therefore conclude that regional marine regression mainly occurred during MIS 6, and MIS 5b to MIS 2, with extremely low regional sea levels possibly around 150 ka, 70–60 ka and 37–24 ka, while high sea-levels occurred during MIS 5e–5c and MIS 1. This study implies that coastal loess deposits with a good chronology could be used to constrain the timing of regional sea level change.

Abrupt Quaternary Ocean-ice Events in the Arctic: Evidence from the Ostracode Rabilimis

The Arctic Ocean has experienced orbital and millennial-scale climate oscillations over the last 500 kilo-annum (ka) involving massive changes in global sea level and components of the Arctic cryosphere, including sea-ice cover, land-based ice sheets and ice shelves. Although these climate events are only partially understood, micropaleontological studies utilizing ostracodes and benthic foraminifera have demonstrated that major changes in faunas have occurred at different timescales that signify ecosystem regime changes linked to sea-ice cover, surface productivity, bottom temperature and other factors. In addition to faunal changes characterizing glacial-interglacial cycles, Arctic sediments contain several unusual faunal events that cannot be explained by orbital-scale sea level and cryospheric changes. One indicator of such events involves the ostracode Rabilimis mirabilis (Brady 1868), a shallow-water species that inhabits continental shelves in the modern Arctic. We conducted studies of the stratigraphic distribution of R. mirabilis in cores from the Northwind, Mendeleev, Lomonosov, and Alpha Ridges; the Siberian and North American (Beaufort Sea) continental margins; and the Lincoln Sea off North Greenland and in the northern Greenland Sherard Osborn Fjord. Evidence from these records suggests that this species occurs as a fossil in deeper water sediment cores on the upper parts of submarine ridges (mainly 700-900 meters water depth, mwd), in significant numbers (from 1%to 50% of total ostracodes) during Marine Isotope Stages (MIS) 5a (125-109 ka), MIS 4 (71-57 ka), and MIS 3 (57-29 ka). Furthermore, it occurs in cores from various depths on the Siberian margin, the Beaufort and Lincoln Seas during MIS 1 (the Holocene, approx. 11-0 ka). These occurrences involve well-preserved, stratigraphically consistent adult and juvenile populations, which are autochthonous in nature and not caused by downslope transport or ice rafting. Based on their age and associated paleoceanographic conditions in the Arctic, we interpret these R. mirabilis events as signifying basin-ward migration during abrupt changes in growth and decay of massive ice shelves and may be useful as biostratigraphic markers.

Sedimentary noise modeling of lake-level change in the Late Triassic Newark Basin of North America

Two different hypotheses, glacioeustasy and groundwater aquifer eustasy, have been proposed to explain short-term, high-amplitude sea-level oscillations during past greenhouse-dominated intervals. However, the veracity of aquifer eustasy on long-term, high amplitude sea level has never been rigorously tested. We evaluate these competing hypotheses using the objective approach of sedimentary noise modeling for lake-level reconstruction. Statistical tuning and astronomical calibration of paleoclimate and paleoenvironment proxies (depth rank, rock color, gamma ray, and sonic velocity) from the lacustrine Newark Basin enable the construction of a 31.55-Myr long astronomical time scale (ATS) for the Late Triassic that is comparable to the classic Newark ATS previously presented. Using this timescale, sedimentary noise modeling in the lacustrine Newark Basin is carried out through the Late Triassic. Lake level fluctuations reconstructed by sedimentary noise modeling and principal component analysis reveal that million-year scale lake-level variations were linked to astronomical forcing with periods of ~3.3 Myr, ~1.8 Myr, and ~1.2 Myr. Our results demonstrate that astronomical forcing, as a driver of groundwater dynamics, may have had an impact on global sea-level changes during the Late Triassic. This study thus emphasizes the importance of high-resolution, objective reconstruction of sea- and lake-levels for further testing the hypotheses of glacioeustasy and aquifer eustasy under warm conditions. • We reconstruct high-resolution lake-level changes in the Late Triassic. • Long-period astronomical forcing drove lake-level and sea-level variations. • Continental groundwater could have an impact on global sea-level fluctuations. • High-resolution, objective reconstruction of lake- and sea-levels is key to test aquifer eustasy versus glacioeustasy.

Early Permian chemical weathering indices and paleoclimate transition linked to the end of the coal-forming episode, Ordos Basin, North China Craton

The Early Permian is recognized as the peak of the Late Paleozoic Ice Age (LPIA), and ice sheet covered most of Gondwana. During this time interval, the North China Craton (NCC) developed abundant economic coal seams within the Taiyuan Formation and the Lower Shanxi Formation. However, coal seams are absent in the Upper Shanxi Formation. In order to explore whether a change in paleoclimatic conditions may have been a factor in this coal-forming episode termination, we conducted a chemical weathering study on the Shanxi and Xiashihezi formations in the Ordos Basin of the NCC. Multiple chemical weathering indices (CIA, CIW, CIX, PIA and WIP) calculated from geochemical ratios in mudstones and derived paleotemperature estimates indicate that the chemical weathering intensity underwent a rapid decrease near the base of the Sakmarian Stage, remained low through the lower Sakmarian, then fluctuated at relatively high levels through the upper Sakmarian. A second drop in weathering intensity occurred near the base of the Artinskian Stage. This pattern was produced by cool climates during the Early Sakmarian associated with the P1 glacial interval (the first stage of the Permian glaciation), by a high temperature climate corresponding to the interglacial interval during Late Sakmarian, and then by another cooling into the P2 glacial at the beginning of the Artinskian. Similar changes in chemical weathering indices occur in the Paraná Basin of South America in southern high latitudes and in the mid-latitude Junggar Basin that is now in Northwest China. This chemical weathering trend mirrors reconstructed paleotemperature from global sea-level changes, from fusulinids diversity on North American shelves, and from atmospheric CO2 concentrations. A sharp decline of coal seams on the NCC is related to the mass extinction of wetland plants. The Late Sakmarian high-temperature event played an important role, and the continuous drift of the NCC toward higher latitudes and the regression associated with orographic uplift also exacerbated regional aridification.

Silurian ostracods from the Nyalam region, southern Tibet, China and their implications on palaeoenvironment and palaeobiogeography

The overall occurrence, stratigraphical distribution, palaeoenvironmental and palaeobiogeographical significances of the ostracod faunas from the Silurian Pulu Formation in the Yalai West II section, Nyalam region, southern Tibet, China, are documented for the first time. Thirty-two species belonging to 19 genera are identified and figured herein. The ostracod fauna in the Pulu Formation indicates an age of the late Llandovery–Pridoli. The ostracods belong to a podocope-rich association, which suggests an offshore environment for the Yalai West II section. The ostracods of the Pulu Formation have strong affinities with the South China taxa and also share some similarities with those from Baltica. This implies that ostracods could probably benefit from sea-level changes to facilitate faunal exchanges between peri-Gondwana and Baltica. Geographical isolation and global sea-level changes are proposed as the primary factors controlling the palaeobiogeographical distribution of ostracods during the Silurian.

Tilting of the Australian continent: New evidence from the subsidence and deposition history of the Northern Carnarvon Basin

Studies of global sea-level changes, plate kinematics, marine inundation, and morphology of the continental shelves suggest that the Australian continent has been tilting north eastwards since the Late Cretaceous. Here we investigate the direct impact of this phenomenon and the preceding tectonic events on the evolution of the Northern Carnarvon Basin and discuss their implications for hydrocarbon resources. We use backstripping and decompaction techniques to develop subsidence, sedimentation, and porosity evolution models for the basin, which sits on the axis of the tilt. The goal is to highlight the spatial and temporal variation of subsidence and sedimentation rates and assess their impacts on the porosity of the Early Cretaceous reservoirs within the basin, then give insights into the factors that created accommodation space for sediments. The results reveal a north-eastward shift of subsidence and sedimentation rates within the region. Thus, we observe the highest subsidence rates (∼90 m/Ma) in the southwest (Exmouth and Barrow sub-basins) from Early Jurassic to Early Cretaceous. In the Middle Cretaceous, subsidence and sedimentation moved north-east towards the Dampier (∼40 m/Ma) and some parts of the Barrow sub-basin (∼35 m/Ma). In the Cenozoic era, the highest subsidence rates moved further north-east towards the Beagle sub-basin (∼40 m/Ma) and the North Rankin platform. The results show that the Palaeozoic-Mesozoic rifting events produced higher tectonic subsidence (∼3 km) and higher sediment supply in the southwestern Exmouth and Barrow sub-basins, which reduced towards the north-east in the Dampier and Beagle Sub-basins (∼1.5 km). Subsidence plots along a NE-SW transect and the porosity evolution model results also demonstrate the tilting occurring in these sub-basins. We propose that mantle-driven and subduction-driven tilting of the Australian continent caused the observed local tilting of these sub-basins. Additionally, porosity evolution results provide further information for the definition of periods of hydrocarbon migration in the area.

Cyclic variations in paleoenvironment and organic matter accumulation of the Upper Ordovician–Lower Silurian black shale in the Middle Yangtze Region, South China: Implications for tectonic setting, paleoclimate, and sea-level change

During the Ordovician–Silurian transition, the Yangtze Block in South China experienced intense tectonic movements and climate change and was covered by the widely distributed black shales of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation, which recorded key information about these major geological events. By geochemical and petrological analyses of three profiles located in the Middle Yangtze Region, at least four long-term sedimentary cycles can be identified in the Upper Ordovician–Lower Silurian black shale. These cycles are mainly controlled by paleoclimate changes and tectonic activity. The Late Ordovician tectonic subsidence related to the Kwangsian Orogeny promoted a gradual sea-level rise and the deposition of the Wufeng black shale in the Middle Yangtze Region, while a significant sea-level fall related to the Hirnantian intensifying glaciation terminated this process. Subsequently, post-Hirnantian warming climate and glacier ablation triggered a significant sea-level rise, reduced the water restriction, increased the productivity, and intensified the anoxic environment, promoting the deposition of black shale in the second sedimentary cycle. However, after the short period of climate warming, global climate cooling occurred again with a regional tectonic uplift in the study area. This led to a gradual sea-level fall, reduced anoxic environment, and increased water restriction during the Rhuddanian, as well as the deposition of black shale with a decreased amount of organic matter. Moreover, intensified glaciation occurred during the Rhuddanian–Aeronian transition significantly accelerated the falling speed of the relative sea level, resulting in a stratigraphic gap and a small thickness of the Silurian black shale in the Middle Yangtze Region. Afterward, the study area experienced a significant climate warming event during the Early Aeronian, which led to a large-scale glacier ablation and a short period of sea-level rise. This promoted the deposition of the Aeronian black shale in the third sedimentary cycle. Nevertheless, the intensified weathering condition related to a continuously warming climate and tectonic uplift led to sufficient supply of terrigenous deposits, sustained sea-level fall, and finally terminated the development of Ordovician–Silurian black shale in the Yangtze region. Thus, these cyclic variations of the black shale not only recorded the shift of the Ordovician–Silurian tectonic movement (from Ordovician subsidence to Silurian uplift) in the Middle Yangtze area and the Hirnantian glaciation, but also provide strong evidence for the global intensified glaciation during the Rhuddanian–Aeronian transition and the subsequent climate-warming event. In addition, this study also provides new perspectives for the understanding of global sea-level change during the Ordovician–Silurian transition.

Coralline algal assemblages record Miocene sea-level changes in the South China Sea

We have previously shown that the coralline algal assemblages (CAAs) of the South China Sea may indicate post-Pliocene paleo-water depth changes; however, the pre-Pliocene coralline algal compositions and related sea-level significance remain to be elucidated. In the present study, we explore the Miocene coralline algal compositions and their role in recording the sea level, and show the distribution, classification, type, abundance, and diversity of Miocene coralline algae from 213 petrologic thin sections using a coral-reef carbonate sequence from the northern South China Sea. The diversity and abundance of coralline algae in the early and late Miocene are higher than those in the middle Miocene. Eleven genera were identified and grouped into seven CAAs, showing a water depth range from <5 m to >25 m. At 18.67–17.98 Ma, the coral reef was in a stagnation/drowning stage, with rising sea levels exceeding the development of the coral reef. At 17.98–16.78 Ma, the coral reef was in a rapid development during a rapid rise in sea level. Additionally, at 16.78–14.79 Ma, low coralline algal abundance was observed, and the corals were sporadically distributed at a relatively stable sedimentation rate, suggesting a decline in coral reef development. At 14.79–10 Ma, the coral reef development was remarkably slow or stagnant. Furthermore, at 10–5.3 Ma, the coral reefs developed slowly, indicating a gradual rise in the sea level. The sea-level changes indicated by coral reef development are consistent with the long-term global sea-level changes, indicating that the composition and assemblage of Miocene coralline algae can be used to accurately relay the sea-level history. • Eleven coralline algal genera were identified in a Miocene carbonate sequence. • Miocene coralline algae were divided into 7 coralline algal assemblages (CAAs). • Sea-level changes due to coral reef development were consistent with global values.

Reservoir characterization of the upper Turonian – lower Coniacian Khasib formation, South Iraq: Implications from electrofacies analysis and a sequence stratigraphic framework

The Upper Turonian – Lower Coniacian Khasib Formation is a significant hydrocarbon reservoir in southern Iraq. The present study integrates multiple data sets of 33 wireline wells, available core, and thin sections from two important oilfields: Amara and Noor to interpret the lateral and vertical facies changes and petrophysical reservoir variability within a sequence stratigraphic framework. Cluster analysis based on well log data including gamma ray, sonic, neutron, bulk density data were used to classify the Khasib Formation into five carbonate electrofacies and determine the petrophysical properties. These electrofacies consists of compacted marly, argillaceous, chalky, porous, and vuggy limestones which are interpreted to have been deposited in a ramp setting. Sequence stratigraphic analysis shows that the Khasib Formation consists of two third-order sequences with three sequence boundaries refer to global sea-level changes: the Mishrif-Khasib regional unconformity, the intra-Khasib unconformity, and the Khasib-Tanuma formational boundary. Each sequence consists of a transgressive system tract (TST) and a highstand systems tract (HST) which are separated by a maximum flooding surface (MFS). Reservoir correlation and mapping of the Khasib Formation in both the Amara and the Noor oilfields show the best important oil-bearing zones are located dominantly in transgressive system tracts (TSTs).

ANCHORS: A multi‐decadal tide gauge dataset to monitor Australian relative sea level changes

AbstractHere, we describe a new national tide gauge‐based sea level dataset for monitoring sea level changes around Australia, and the novel homogenization methodology used to develop it. Homogenization is a two‐step process that involves the detection of jumps or steps in the data (inhomogeneities) followed by a correction applied to remove the change. This new dataset is called the Australian National Collection of Homogenized Observations of Relative Sea Level (ANCHORS). ANCHORS provides coastal sea levels at hourly resolution with homogenization performed on annual means. ANCHORS is intended to be a national tide gauge‐based sea level dataset to monitor changes in mean sea level and resultant coastal flood frequency changes around Australia. Whilst sea levels are rising around Australia in response to global mean sea level changes, coastal water levels represent a notable gap in the suite of in situ high‐quality datasets available for researchers, governments and industry. Tide gauge datasets are well suited to impact‐based assessments of changes in flood frequency, duration and risk. In this regard, ANCHORS will sit alongside existing satellite‐ and numerical modelling‐based sea level datasets to provide enhanced insights into the physical impacts of sea level rise on Australian coastlines. We have adapted established homogenization techniques to develop a national collection of homogenous long tide gauge records. The dataset comprises 38 tide gauge records from around Australia, varying in length from 34 to 123 years, with an average of 57 years. Finally, we discuss limitations and potential applications for ANCHORS and how these have informed the design of this coastal sea level dataset.

Interpretation of IPCC AR6 report: monitoring and projections of global and regional sea level change

Interpretation of IPCC AR6 report: monitoring and projections of global and regional sea level change

Elastic deformation plays a non-negligible role in Greenland\u2019s outlet glacier flow

Future projections of global mean sea level change are uncertain, partly because of our limited understanding of the dynamics of Greenland’s outlet glaciers. Here we study Nioghalvfjerdsbræ, an outlet glacier of the Northeast Greenland Ice Stream that holds 1.1 m sea-level equivalent of ice. We use GPS observations and numerical modelling to investigate the role of tides as well as the elastic contribution to glacier flow. We find that ocean tides alter the basal lubrication of the glacier up to 10 km inland of the grounding line, and that their influence is best described by a viscoelastic rather than a viscous model. Further inland, sliding is the dominant mechanism of fast glacier motion, and the ice flow induces persistent elastic strain. We conclude that elastic deformation plays a role in glacier flow, particularly in areas of steep topographic changes and fast ice velocities.

Relict inland mangrove ecosystem reveals Last Interglacial sea levels

Climatic oscillations during the Pleistocene played a major role in shaping the spatial distribution and demographic dynamics of Earth's biota, including our own species. The Last Interglacial (LIG) or Eemian Period (ca. 130 to 115 thousand years B.P.) was particularly influential because this period of peak warmth led to the retreat of all ice sheets with concomitant changes in global sea level. The impact of these strong environmental changes on the spatial distribution of marine and terrestrial ecosystems was severe as revealed by fossil data and paleogeographic modeling. Here, we report the occurrence of an extant, inland mangrove ecosystem and demonstrate that it is a relict of the LIG. This ecosystem is currently confined to the banks of the freshwater San Pedro Mártir River in the interior of the Mexico-Guatemala El Petén rainforests, 170 km away from the nearest ocean coast but showing the plant composition and physiognomy typical of a coastal lagoon ecosystem. Integrating genomic, geologic, and floristic data with sea level modeling, we present evidence that this inland ecosystem reached its current location during the LIG and has persisted there in isolation ever since the oceans receded during the Wisconsin glaciation. Our study provides a snapshot of the Pleistocene peak warmth and reveals biotic evidence that sea levels substantially influenced landscapes and species ranges in the tropics during this period.

An Investigation into Sea Level Rise in Sri Lankan Waters with Satellite AltimetryCorrected version of this article has been publshed under the section "Corrigendum" in the same issue on 15th October

Most of the socio-economic activities of Sri Lanka are centred in the coastal regions, which can be described according to its unique geographical and geophysical backgrounds. It is estimated that Sri Lanka has a shore line about 1,700 km in length. Therefore, better knowledge and understanding of the characteristics of sea level is very essential. The sea level has traditionally been measured mainly at tide gauges set up along the coast line. However, the number of tide gauge stations is few and sparse in most countries. But, with the advancements of satellite altimetry technology, it is now accepted as an alternative technique to study regional and global sea level changes. The basic concept in altimetry is the range measurements to the water surface measured from the altimeter antenna. The surface of the sea, or sea level, is continuously changing for many reasons. Here, some changes are fast whereas others occur gradually. Among them, some factors are natural causes, while others occur due to man-made activities such as the greenhouse effect. These changes can be regional or extend at a global scale. The main aim of this research was to examine the trends in sea level rise around the Sri Lankan coastline using two decades of satellite altimetry data from 1993 to 2012. The computed sea level rise trends around Sri Lanka is around 2.5 to 3 mm per year, with a variance of +/- 0.6 mm accuracy. The obtained trend of sea level rise from the altimetry data was validated with tide gauge data in Colombo, and found to be highly correlated, with a correlation coefficient (R2) of 0.93 for annual mean sea level. This study confirms that satellite altimetry can be successfully used to investigate the long term sea level trend studies, particularly in the absence of long term tide data.

Magnetic Properties and Initiation of Biogenic Reefs in Xisha Islands, South China Sea, at the Oligo–Miocene Boundary

Biogenic reefs and carbonate platforms are valuable natural resources, playing an important role in modulating the global climate and in carbon cycles through biological processes. Biogenic reefs in the Xisha (Paracel) Islands began in the late Oligocene and covaried with the deep-sea basin of the South China Sea and with the aeolian deposit in the Chinese Loess Plateau. Core XK-1 was drilled into the Xisha Islands to their granitic base and well dated by magnetostratigraphy, offering an opportunity to reveal the details of how the Xisha reefs initiated. In this report, the lower section of the biogenic reefs (23.0–24.5 Ma) was sampled for studying magnetic properties. The main results are as follows: (1) magnetic minerals in the XK-1 biogenic reefs are dominated by low-coercivity and relatively coarse-grained magnetite; (2) the variabilities of magnetic parameters can be clustered into two sections around 23.6 Ma, and the differences between the two units are evident both in the amplitudes and the means; and (3) changes in the concentration-dependent magnetic parameters can be well correlated with the records of global deep-sea oxygen and carbon isotopes, and the sea level during the Oligo–Miocene boundary. Based on these results, a close link was inferred between biogenic reef evolution in the Xisha Islands and global climate change. This link likely highlights the covariation or the dominant role of the Asian monsoon in biogenic reefs and involves different responses to global temperature, CO2, and sea-level changes on various timescales. Therefore, we proposed that the origin of biogenic reefs in the Xisha Islands was likely paced by orbital obliquity from a long-term perspective.

Climate changes, paleogeography and geological development of the northern part of Bulgarian Black Sea shelf and coast during the Quaternary

The article represents a synthesized reconstruction of the geological development of the northern part of Bulgarian Black Sea shelf and coast during the Quaternary. Marine Quaternary sediments are considered as a component of the marine ecosystem that is strongly affected by the climate changes. As a result, changes in the stratigraphic and sedimentological characteristics of the Pleistocene sediments and in particular the Holocene deposits were recorded. During the Quaternary, which is characterized by short-term, cyclic climatic fluctuations, marine shelf sediments have sealed traces of the alternation of glacial and interglacial phases. Based on detailed lithostratigraphic and biostratigraphic analysis of mollusk fauna and pollen, not only are the complex dynamics of the transgressiveregressive cycles traced, but also their relationship to global and regional changes of climate and sea level is confirmed. As a result of an integrated lithofacies, biostratigraphic, and geomorphological analysis, the stratigraphic sequence of the Quaternary sediments is established as well paleogeographic conclusions are reached. Today, knowledge of natural processes such as coastal abrasion, landslides, storms, tsunami waves, etc., are directly linked to the geological risk forecast and correlate with the geoecology and sustainability of the environment in which we live. In this sense, the reconstruction of the components of the geological environment from the closest geological past – Pleistocene and Holocene, is key to forecast climate change and sea level today.