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SSP1.2

Directly observable relative sea-level (RSL) indicators (e.g. shore platforms, coral reef terraces, beach deposits, etc.) are used to constrain paleo sea levels and ice sheet extents and to improve GIA models and future projections of sea-level and ice-sheet responses. Biological proxies associated with and the physical characteristics of RSL indicators can be used to infer paleoclimate and together help inform climatic change and sea-level fluctuations throughout the Pleistocene. The preservation and distribution of these records assists in understanding regional earth surface processes following their deposition.

Recent advances in sea-level studies have called for increased spatiotemporal density of RSL indicators, including submerged and near-field localities, analyzed using standard definitions and methods. This session welcomes contributions to the global record of well-constrained Pleistocene sea-level indicators and associated proxies from a variety of coastal environments, not limited to peak interglacial periods. Re-interpretations of previously described records due to advancement in methods are also welcome.

This session falls within the purview of PALSEA (PALeo constraints on SEA level rise), a PAGES-INQUA Working Group, and the ERC-funded projects, WARMCOASTS and RISeR.

Public information:
The live chat session will be structured to allow abstract authors, who have uploaded display materials, a specific time slot to chat about their research. Four authors will not be presenting their abstracts. Two of them, Jennifer Walker and Andrei Briceag, have uploaded displays and you are encouraged to initiate chat with them through the abstract link.

The final timetable for the session is below. Time is included for general discussion at the end of the session.

Introduction 8:30-8:34
Martina Conti 8:35-8:44
Gino de Gelder 8:45-8:54
Ciro Cerrone 8:55-9:04
Kim Cohen 9:05-9:14
Patrick Boyden 9:15-9:24
Alessio Rovere 9:25-9:34
Teresa Bardaji 9:35-9:44
Carlos Melo 9:45-9:54
Natasha Barlow 9:55-10:04
General Discussion 10:05-10:15

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Co-organized by CL4/GM6
Convener: Deirdre RyanECSECS | Co-conveners: Victor CartelleECSECS, Kim Cohen, Alessio Rovere
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| Attendance Wed, 06 May, 08:30–10:15 (CEST)

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Download all presentations (156MB)

Chat time: Wednesday, 6 May 2020, 08:30–10:15

D919 |
EGU2020-7153<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
| Highlight
Martina Conti, Martin Bates, Natasha Barlow, Richard Preece, Kirsty Penkman, and Brendan Keely

Targeted analysis of organic matter in soils and sediments is useful for evaluating past environmental conditions, as specific compounds may be directly linked to organisms and hence to the conditions in which they inhabited the environment.  Variations in molecular fossil distributions have become a powerful tool for understanding changes in palaeoclimate conditions.  This work uses molecular fossils to give an insight into the impact of transgressive events on primary producers inhabiting the studied basin, and hence a more detailed record of sea-level change.

The cores studied consisted of unconsolidated immature sediments from the mid-late Pleistocene (< 500,000 years) and the Holocene.  Molecular fossils, such as chlorophyll pigments and lipids, exhibit fluctuations as a response to changes in palaeoenvironmental conditions, providing a useful marker for sea-level changes.  Fluctuations in the pigment and n-alkane distribution reflect changes in primary producer activity, while the GDGT-based index of branched and isoprenoid tetraether lipids (BIT) differentiates between terrigenous and marine organic matter inputs.  Lipids were analysed by GC-FID and HPLC-MS while analysis of chlorophyll pigments was carried out using a new UHPLC-DAD method.

The results from biomarker analyses show excellent time-resolved agreement with previous lithological and ecological studies, but enabled a more sensitive response of different primary producers to changing conditions to be observed.  The molecular fossils were able to detect the onset and cessation of the studied transgressions earlier than it was possible with microfossil evidence.  Linking the pigment and lipid record with more secure dating will enable a more accurate record of Quaternary relative sea-level change.

How to cite: Conti, M., Bates, M., Barlow, N., Preece, R., Penkman, K., and Keely, B.: Molecular fossils inferring Quaternary sea-level changes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7153, https://doi.org/10.5194/egusphere-egu2020-7153, 2020

D920 |
EGU2020-13660<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
Barbara Mauz, Zhixiong Shen, Natasha Barlow, David Hodgson, and Colin Woodroffe

It is generally accepted that sea-level change represents the most important boundary condition that controls stratigraphic architecture in the shallow-marine area and further downdip. The shallow-marine stratigraphic body is then a result of the changing ratio between sediment supply and accommodation space with a range of local (autogenic) processes interplaying with the eustatic (allogenic) sea level. Extracting the sea-level signal from this interplay is typically approached through rigorous interpretation of the indicative meaning of relevant sea-level markers and through comparison with the most appropriate glacio-isostatic adjustment (GIA) model. The latter comparison is insightful for the last glacial period, but for the Pleistocene it suffers from the dilemma that the GIA contribution to sea-level change cannot be predicted for a specific location unless the ice history is known but this is what the shallow-marine record is trying to reconstruct.

Here we aim for Pleistocene sea-level reconstructions that are largely independent of GIA predictions. For this we present Pleistocene shallow-marine records from high-, mid- and low-latitudinal settings. The presentation focuses on four aspects: type and quality of the data (e.g. outcrop, borehole, etc), preservation of the record, separation of allogenic versus autogenic signal and completeness of the eustatic cycle.

We show that in siliciclastic systems the preservation depends on sediment supply and on the coastal energy with which ravinement and regression surfaces obliterate the stratigraphic record. Separating autogenic from allogenic signals depends very much on data quality and the ability to reconstruct the antecedent topography. None of our records show a complete eustatic cycle from lowstand to highstand and back to lowstand where the missing part of the cycle seems to be indicative for the type of shallow-marine record and its location on earth.

We discuss reasons and implications of our findings and emphasise the need for far greater consideration of stratigraphic architecture, carbonate facies and facies correlation.

How to cite: Mauz, B., Shen, Z., Barlow, N., Hodgson, D., and Woodroffe, C.: The sea-level signal in Pleistocene shallow-marine records – examples from carbonate and siliciclastic sequences, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13660, https://doi.org/10.5194/egusphere-egu2020-13660, 2020

D921 |
EGU2020-17606<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Gino de Gelder, Anne-Morwenn Pastier, Denovan Chauveau, David Fernández-Blanco, Kevin Pedoja, Christine Authemayou, and Laurent Husson

Coral reef terraces (CRT) are amongst the most important indicators of Quaternary sea level fluctuations, and are therefore relevant to a wide spectrum of climatic and tectonic studies. The Huon Peninsula in Papua New Guinea accomodates one of the first CRT sequences to be mapped, measured and dated in detail through pioneering studies several decades ago. Those studies were limited by the available techniques to assess the large scale terrace sequence morphology, and thus to constrain spatiotemporal uplift rate variations that are key to determine past relative sea-level (RSL). We re-visit the Huon CRTs with the aim of refining tectonic uplift rates and RSL, using digital surface models calculated from 0.5m Pleiades satellite imagery. This allows us to constrain variations in CRT elevation, and assess tectonic deformation wavelengths in detail. We then use a numerical code for coral reef modeling to reconstruct the sequence morphology and constrain the possible range of RSL over the past few glacial-interglacial cycles. We find that large-scale tilting of the terrace sequence is generally N- instead of NW-directed, which is more compatible with the regional tectonic setting. It also implies changes of several meters for RSL highstand estimates compared to previous studies. We compare our results to other terrace sequences, and discuss the potential of combining high-resolution topography with landscape evolution modeling to constrain RSL.

How to cite: de Gelder, G., Pastier, A.-M., Chauveau, D., Fernández-Blanco, D., Pedoja, K., Authemayou, C., and Husson, L.: High resolution topography and modeling of the Huon coral reef terrace sequence (Papua New Guinea), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17606, https://doi.org/10.5194/egusphere-egu2020-17606, 2020

D922 |
EGU2020-640<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Ciro Cerrone, Ann-Kathrin Petersen, Paolo Stocchi, Alessio Rovere, and Elisa Casella

Detailed geological field mapping is essential for the study of Relative Sea Level (RSL) indicators, that are in turn the only direct proxies to assess paleo sea level changes and long-term land movements. In the last decades, traditional mapping methods started to be complemented by small Remotely Piloted Aircraft Systems (RPAS, a.ka.a. drones) and high-resolution remote sensing datasets.

In this contribution, we show the results of geological mapping in the island of Curaçao (Netherlands Antilles). Here, we mapped a staircase sequence of coral reef terraces. In particular, we used TerraceM-2 Maptools (a Matlab® interface for mapping marine terraces) to extract wide-scale marine terrace elevations from TanDEM-X Digital Elevation Models (DEMs) (German Aerospace Center, DLR and Airbus). We detail the elevation information available for each single terrace with RPAS data processed with Agisoft Metashape, that allows obtaining as final products DEMs and orthophotos of selected sites at the inner margin of reef terraces. We then use land-based photogrammetry coupled with traditional facies analysis to identify geological discontinuities on the lower terrace.

The facies analysis allowed to precisely map the unconformity between the Hato (MIS 5.5) and Cortalein (MIS 7) Units (as identified by Muhs et al., 2012). The top of the Hato Unit forms the so-called “Curaçao Lower Terrace”. The top of the Hato Unit, extending few kilometres from the coast, has been mapped with both TanDEM-X and RPAS data up to the paleo-cliff of the Middle Terrace (formerly attributed to MIS 11), where a well-defined notch is preserved. We attribute this notch to the maximum sea ingression during MIS 5e. We compare its elevation with the RSL predicted by Glacio-Isostatic Adjustment (GIA) models.    

We discuss the new data and models for Curaçao in terms of long-term tectonic uplift and eustatic sea level.

Reference: Muhs DR, Pandolfi JM, Simmons KR, Schumann RR (2012) Sea-level history of past interglacial periods from uranium-series dating of corals, Curaçao, Leeward Antilles islands. Quat Res 78:157–169. doi: 10.1016/j.yqres.2012.05.008

Acknowledgments: TanDEM-X digital elevation data is used with permission within the Project DEM GEOL1210 (A. Rovere / M.E. Raymo). The fieldwork for this work was funded by the Helmholtz Exzellenznetzwerks “The Polar System and its Effects on the Ocean Floor (POSY)”. The authors acknowledge also the ZMT,  the Center for Tropical Marine Ecology, and the DAAD, the German Academic Exchange Service.

How to cite: Cerrone, C., Petersen, A.-K., Stocchi, P., Rovere, A., and Casella, E.: 3D mapping of Quaternary coral reef terraces on Curacao Island, Southern Carribean Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-640, https://doi.org/10.5194/egusphere-egu2020-640, 2019

D923 |
EGU2020-3135<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
Kim Cohen

As contribution to the ongoing research programmes RISeR (Dr. Barlow, Univ. Leeds, UK), WARMCOASTS (Dr. Rovere, Marum Bremen, GER) and LOSS (Dr. Stouthamer and consortium, Utrecht Univ., NL), and in more general effort to correctly deal with legacy geological data in the current era of Open Science and Geodata Science, we are populating the WARMCOASTS-WALIS database with entries for the Last-Interglacial sea-level indicator data points as available for the Southern North Sea area. This part of the world in in the immediate near field of the Scandinavian-British ice mass centre at interglacial temperate latitudes.

The majority of the sea-level indicator data points are of siliciclastic sedimentary type: transgressive contacts of marine muds over basal peats, insolation basin lakes becoming brackish marine, regressive peats establishing on tidal flat tops and so on. The abundance of peat and tradition of palynological investigation of these beds is important to date stratigraphical levels. The floating varve-count based PAZ-duration chronology for the Eemian vegetation succession in NW Europe (Zagwijn1996:QSR) allows to resolve floating ages to submillenial scale in the transgressive limb (PAZs E1-E4 and subzones), and to millennial scale in the high stand (coincident with PAZ E5) and regressive limb (starting at the PAZ E5/E6 break; Zagwijn1983:GeologieMijnbouw). Chronostratigraphical database entries for each zone and subzone have been filed in the WALIS database, informing on the varve count durations (floating time scale). Absolute age is left more broad, as there is some uncertainty and wiggle room and difference of opinion in the timing of the palynological NW European Eemian relative to that Termination II in the MIS and coral records (SierEtAl2015:QGeochron; LongEtAl2015:QSR).

Sedimentary environment analogies are drawn with the Holocene transgression and high stand to identify and classify localities as being sea-level indicator points (SLIPs), Marine limiting points, or Terrestrial limiting points. Analogies with the Holocene relative sea-level rise reconstruction practice (e.g. Hijma&Cohen2019:QSR) also echo in the protocols followed to characterize and document the vertical position of the indicator. Data entry requires to assess depth of contact (at present, expressed to a specified datum), implied depth position of past mean sea level (factoring in tidal range, palaeowater depth, background vertical movement, (de)compaction), and uncertainties to that depth (added up according to error propagation rules).

We compare our re-assessed and standardized database entries for longer established sites to the originally reported reconstructed sea-level positions (e.g. Zagwijn1983) and to their discussion in later publications (2000s, 2010s). What is one point in Zagwijn1983, often becomes an assemblage of terrestrial limiting, SLIPs and marine limiting entries in WALIS. We find the North Sea data in some earlier ‘table style’ global compilations to have suffered from generalisations. We find the protocolised database approaches as established by PALSEA activities (e.g. ShennanEtAl(Eds)2015: Handbook of Sea-Level Research; KahnEtAl(Eds)2019: QSR special issue) a more suitable environment to store and open up regional data for correct in-take and reuse by second/third parties - whether LOSS, WARMCOAST, RISeR, or you.

How to cite: Cohen, K.: Opening up a Last-Interglacial Sea Level Database for the Southern North Sea area, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3135, https://doi.org/10.5194/egusphere-egu2020-3135, 2020

D924 |
EGU2020-18309<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Patrick Boyden, Jennifer Weil Accardo, Pierre Deschamps, and Alessio Rovere

With global average temperatures 2°C higher than pre-industrial and eustatic sea-level ranging between 5 and 9 m above present, the Last Interglacial is often regarded as a good process-analogue for a future warmer climate.  Large uncertainties are associated with Last Interglacial eustatic sea-level estimations. To quantify these uncertainties through standardization of sea-level metadata, the World Atlas of Last Interglacial Shorelines (WALIS) provides a community-wide standard for documenting the geological context of sea-level indicators and their chronology. By applying this standard, WALIS allows for the quantitative cross-comparison between previous studies, often times separated by decades.

 

We use WALIS to review published sea-level indicators for the Last Interglacial within the Western Indian Ocean basin. Located in the far field with respect to past glaciations, the Western Indian Ocean has the potential to provide precisely measured and dated sea level proxies, enabling a reliable estimation of maximum eustatic sea level for the Last Interglacial. This, in turn, would allow to better constrain upper boundaries of melting within ice-sheet models. Furthermore, this review highlights localities that should be revisited based on the presence of geological facies indicative of former highstands where not enough detail has been reported or where advanced dating and geodetic techniques can increase the accuracy of metadata.

How to cite: Boyden, P., Weil Accardo, J., Deschamps, P., and Rovere, A.: Last Interglacial Sea-Level Indicators in the Western Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18309, https://doi.org/10.5194/egusphere-egu2020-18309, 2020

How to cite: Boyden, P., Weil Accardo, J., Deschamps, P., and Rovere, A.: Last Interglacial Sea-Level Indicators in the Western Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18309, https://doi.org/10.5194/egusphere-egu2020-18309, 2020

How to cite: Boyden, P., Weil Accardo, J., Deschamps, P., and Rovere, A.: Last Interglacial Sea-Level Indicators in the Western Indian Ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18309, https://doi.org/10.5194/egusphere-egu2020-18309, 2020

D925 |
EGU2020-13281<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
Alessio Rovere, Maren Bender, Thomas Mann, Paolo Stocchi, Dominik Kneer, Tilo Schöne, Julia Illigner, and Jamaluddin Jompa

We surveyed the elevation and age (14C) of paleo sea-level indicators in five islands of the Spermonde Archipelago. We describe 24 new sea-level index points from fossil microatolls, and we compare our dataset with both previously published proxies and sea-level predictions from a set of 54 Glacial Isostatic Adjustment (GIA) models, using different assumptions on both ice melting histories and mantle structure and viscosity. We then investigate the implications of our data and models in terms of vertical land movements in the study area, with two main results.

First, data from the heavily populated island of Barrang Lompo are significantly lower (ca. 80 cm) than those at all the other islands. In absence of instrumental data (e.g., GPS or tide gauges) in any of the islands, we advance the hypothesis that this difference may be due to groundwater extraction and loading of buildings on Barrang Lompo, that would cause this island to subside at rates in the order of ~3-11 mm/a.

Second, Common Era data (0-400 a BP) seem to indicate that the islands in the archipelago may be affected by tectonically-driven vertical land motions in the order of -0.88±0.61 mm/a (1-sigma), albeit slight uplift cannot be excluded. Different assumptions on vertical land motions affect, in turn, the assessment of which GIA model shows the best match with Late Holocene (ca. 4-5 ka) sea level data. Tectonic stability or slight uplift would favor iterations of ANICESELEN (De Boer et al., 2014), while subsidence would cause the sea level data to fit better with iterations of ICE-6G (Peltier et al., 2015).

References

De Boer, Bas, Paolo Stocchi, and Roderik Van De Wal. A fully coupled 3-D ice-sheet-sea-level model: algorithm and applications." Geoscientific Model Development 7.5 (2014): 2141-2156.

Peltier, W. R., D. F. Argus, and R. Drummond. Space geodesy constrains ice age terminal deglaciation: The global ICE‐6G_C (VM5a) model. Journal of Geophysical Research: Solid Earth 120.1 (2015): 450-487.

Acknowledgments

This project is funded by SEASCHANGE (RO-5245/1-1) and HAnsea (MA-6967/2-1) from the Deutsche Forschungsgemeinschaft (DFG), part of the Special Priority Program (SPP)-1889 "Regional Sea Level Change and Society". Parts of this study are under review in Climate of the Past (https://www.clim-past-discuss.net/cp-2019-63/)

How to cite: Rovere, A., Bender, M., Mann, T., Stocchi, P., Kneer, D., Schöne, T., Illigner, J., and Jompa, J.: Holocene sea-level changes in the Spermonde Archipelago, Indonesia: implications for vertical land movements, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13281, https://doi.org/10.5194/egusphere-egu2020-13281, 2020

D926 |
EGU2020-12416<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Jennifer Walker, Robert Kopp, Nicole Khan, Timothy Shaw, Niamh Cahill, Don Barber, Matt Brain, Jennifer Clear, Reide Corbett, and Benjamin Horton

Last millennium relative sea-level (RSL) changes along the U.S. Atlantic coast are spatially variable. Glacial isostatic adjustment (GIA) has been a significant driving factor in RSL rise during the last millennium, producing maximum rates of vertical land motion in the mid-Atlantic region due to its proximity to the margin of the former Laurentide Ice Sheet. However, there is uncertainty surrounding the influence of other regional and local processes on RSL changes such as ocean and atmosphere circulation dynamics; gravitational, rotational, and deformational signals associated with ice mass and distribution changes; sediment compaction; and tidal range change.

Here, we examined the high spatial density of high-resolution RSL records along a ~200 km stretch of coastline from New York City to southern New Jersey to distinguish between local, regional, and global scale drivers. We produced a new high-resolution (decimeter vertical, decadal temporal) RSL record of the last millennium in northern New Jersey and integrated it into an updated global database of instrumental and proxy sea-level records of the Common Era. We used a spatiotemporal empirical hierarchical model to estimate past RSL and rates of RSL change and their associated uncertainties in the context of broader regional changes by decomposing the records into global, regional linear, regional non-linear, and local components.

We found that RSL in northern New Jersey continuously rose over the last 1000 years at a rate of 1.2 ± 0.2 mm/yr (2σ) from 1000 to 1700 CE before increasing to 1.3 ± 0.7 mm/yr from 1700-1800 CE to 1.8 ± 0.6 mm/yr from 1800-1900 CE to 3.0 ± 0.6 mm/yr from 1900-2000 CE. Most of the RSL rise during the past 1000 years is attributed to regional-scale linear processes that we interpret primarily as GIA. The linear component of the RSL records exhibits a north to south gradient, with a greater contribution of RSL rise in southern New Jersey and a smaller contribution in New York City. The regional-scale non-linear contribution from the records have a magnitude <10 cm and are nearly identical because they fall within the same regional scale determined by the spatiotemporal model. The rate of the regional non-linear component fluctuated between -0.1 and 0.1 mm/yr until the late 19th century when it increased to a rate of 0.6 ± 0.1 mm/yr in the late 20th century. These trends are likely explained by a combination of physical processes, including the evolving mass of the Greenland Ice Sheet, steric effects, or ocean mass changes from atmospheric circulation and ocean currents. The local-scale contribution is <10 cm at all sites, but varies in magnitudes and rates of change, which may be due to sediment compaction or tidal range change.

How to cite: Walker, J., Kopp, R., Khan, N., Shaw, T., Cahill, N., Barber, D., Brain, M., Clear, J., Corbett, R., and Horton, B.: Driving mechanisms of sea-level variability in the U.S. mid-Atlantic during the last millennium, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12416, https://doi.org/10.5194/egusphere-egu2020-12416, 2020

D927 |
EGU2020-1678<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Simon Dominik Steidle, Sophie Warken, Norbert Frank, Julius Förstel, Nils Schorndorf, Andrea Schröder-Ritzrau, Gina Moseley, Wolfgang Stinnesbeck, and Jerónimo Avilés Olguín

The loading of the North American continent with ice sheets causes a geomorphologic response. As a result of this process, a NW-SE gradient of relative sea level developed in the Caribbean during periods of glaciation. In order to distinguish geomorphologic and eustatic contributions it is important to resolve timing and amplitude of relative sea level at different positions in the Caribbean.

The cave systems around Tulum, Quintana Roo, Mexico are presently submerged and well-connected to the nearby Atlantic with a low hydraulic head gradient. Speleothems must have formed during periods of lower sea level, thus providing constraints on the maximum elevation of relative sea level for given periods of time. Conversely, periods of growth cessation could have been caused by sea level rise thus indicating minimum relative sea level during highstands.

Here, we present 230Th/U dated submerged speleothems that grew during MIS5a-d as well as MIS1/2, MIS6 and MIS11/12.

Growth of a single stalagmite (QUE01) at -10.8±0.1m (relative to today's sea level) was interrupted twice. Petrographical studies and trace element analysis indicate that submergence caused millennial-scale growth stops in QUE01 during MIS5. The proposed highstands are between 109.4±0.3ka and 105.0±0.3ka as well as between 104.5±0.4ka and 96.9±0.4ka.

While a previous study [1] constrains the amplitude to <9.9m, this study further improves the timing. This is the first record in this area that yields bracketing ages for those highstands from a speleothem that is very close to the peak height. In order to reconstruct a Caribbean sea level gradient, the combined Yucatán record acts as a counterpiece to a similar study from the northern end of the Caribbean sea level gradient which reports highstands at that time with a higher relative sea level [4].

Speleothem growth during MIS1/2 (19-8ka) relates to conflicting local sea level markers [2,3] and contains century-scale growth stops. Samples dating back to MIS6 and MIS11/12 highlight the potential for sea level reconstruction in this area before MIS5.

[1] Moseley et al. (2013) Journal of Quaternary Science 28 293-300
[2] Moseley et al. (2015) The Holocene 25 1511-1521
[3] Hering et al. (2018) Journal of Quaternary Science 33 444-454
[4] Wainer et al. (2017) Earth and Planetary Science Letters 457 325-334

How to cite: Steidle, S. D., Warken, S., Frank, N., Förstel, J., Schorndorf, N., Schröder-Ritzrau, A., Moseley, G., Stinnesbeck, W., and Olguín, J. A.: Relative sea level highstands of the Yucatán Peninsula, Mexico, constrained by speleothem growth periods, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1678, https://doi.org/10.5194/egusphere-egu2020-1678, 2019

D928 |
EGU2020-18523<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
Teresa Bardají, José Luis Goy, Caridad Zazo, Claude Hillaire-Marcel, Cristino J. Dabrio, Ángel Gozález, Bassam Ghaleb, Ana Cabero, Vicente Soler, and Javier Lario

The volcanic Cape Verde archipelago constitutes one of the few sites in low latitude eastern Atlantic Ocean, where a long record of Pleistocene sea-level indicators develops, particularly beach deposits and marine terraces. The extreme aridity of the easternmost islands (Sal, Boa Vista and Maio) allows the exposure of long sedimentary sequences, the altitudinal and spatial distribution of which must be related both to sea level behaviour in low latitude settings and also to the volcanic nature of the archipelago.

The particular case of Maio Island reveals the occurrence of a flight of at least 18 marine terraces, between +85 and 0m. The chronology has been approached by a paleomagnetic sequence (Early - Middle Pleistocene transition), U-series measurements (Last Interglacial deposits) and 14C (Holocene units).

The results have revealed a differential behaviour in the vertical motion of the island along the Pleistocene, with unequal uplift rates during Early and Middle Pleistocene. An anomalously low-lying MIS5 unit in this island fits well with the predictions done by GIA models of Crevelling et al., (2017) although the proper evolution of volcanic islands cannot be discarded.

A comparison with Sal (Zazo et al., 2007, 2010) and Boa Vista islands is done, especially in what the MIS5 sea level record is concerned. MIS 5e deposits are scarce along the coasts of Maio and Boa Vista, and always at very low heights above mean sea level (0-0,5 m). On the island of Sal the deposits corresponding to the MIS 5e are located at a maximum height of +2.5m asml, in its most southern sector, being also very frequent to find them at 0m (Zazo et al., 2010).

The geomorphological distribution of the Pleistocene sedimentary sequences along these three islands reveals a complex history of uplift and subsidence that must be conciliated with the far-field sea level behavior, especially for the MIS5 units.

Creveling et al., 2017. QSR 163.

Zazo et al., 2007. QSR 26.

Zazo et al., 2010. GPCh 72.

Acknowledgements: This work has been supported by FEDER-MINECO Spanish project CGL15-69919-R.

How to cite: Bardají, T., Goy, J. L., Zazo, C., Hillaire-Marcel, C., Dabrio, C. J., Gozález, Á., Ghaleb, B., Cabero, A., Soler, V., and Lario, J.: Pleistocene sea-level record in low latitude settings: the Cape Verde Islands., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18523, https://doi.org/10.5194/egusphere-egu2020-18523, 2020

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EGU2020-10423<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"><span title="Early career scientist: an ECS is an undergraduate or postgraduate (Masters/PhD) student or a scientist who has received their highest degree (BSc, MSc, or PhD) within the past seven years. Provided parental leave fell into that period, up to one year of parental leave time may be added per child, where appropriate.">ECS</span></span>
Carlos Melo, José Madeira, Ricardo S. Ramalho, Ana C. Rebelo, Michael Rasser, Esther González, Alfred Uchman, Patrícia Madeira, Emílio Rolán, Luís Silva, Carlos M. da Silva, Deirdre Ryan, Alessio Rovere, Mário Cachão, and Sérgio P. Ávila

The world-wide study of the geological record of the Last Interglacial is key to reconstruct the climatic and oceanographic conditions during that time interval. Here we present preliminary results of a comprehensive field analysis of one of the most extensive and least studied Quaternary fossiliferous sequences in Cabo Verde attributed to the Last Interglacial. It is located at Nossa Senhora da Luz, which is a protected inlet at the SE coast of Santiago Island. The studied sequence shows a set of transitions between fluvial and marine environments, and emersion and immersion events within a confined, highly protected bay environment. The presence, in the upper part of the sequence, of a thick layer of very fine-branched rhodoliths indicates particular ecological conditions within this bay (e.g., shallow and turbidity free waters, stable environmental conditions and/or fast growth) that are absent today and presumably played an important role for the presence of particular invertebrate species during that time. The presence of tidal specimens of the clam Senilia senilis in life position at an altitude of ~12m above sea-level allowed a re-interpretation of relative sea-level changes, suggesting that the uplift trend of Santiago Island for the Last Interglacial period onwards (3m/100ky) is possibly 70% lower than previously calculated (10m/100ky). Fossils include five phyla, with molluscs being the most diverse and abundant. Despite the abundance of some species (e.g., the bivalves Saccostrea cuccullata, S. senilis, and Aequipecten opercularis, and the gastropods Persististrombus latus and Thais nodosa), the general biodiversity is low. The presence of S. cuccullata and S. senilis, absent from extant Cabo Verdean faunas, indicates a more humid climate, unlike the dry climate found today. Some horizons are intensively bioturbated with the crustacean burrow Thalassinoides suevicus. Our new data agree with the hypothesised palaeoclimatic framework of more wet conditions than today for the Last Interglacial in the archipelago.

Keywords: Eemian, Cabo Verde Archipelago, sheltered bay, Senilia senilis, volcanic oceanic islands, NE Atlantic

Acknowledgments

C.S.M. and A.C.R. acknowledge, respectively, his PhD grant M3.1.a/F/100/2015 from FRCT/Açores 2020 and her Post-Doc grant SFRH/BPD/117810/2016 by FCT. R.R. and S.Á. acknowledges his IF/01641/2015 and IF/ 00465/2015 grants funded by FCT. A.R. and M.R. were supported by the by DFG grant RA1597/3-1. This work was supported by FCT project PTDC/CTA-GEO/28588/2017 and LISBOA-01-0145-FEDER-028588 UNTIeD and DRCT 2019-2022 – ACORES-01-0145_FEDER-000078 – VRPROTO.

How to cite: Melo, C., Madeira, J., Ramalho, R. S., Rebelo, A. C., Rasser, M., González, E., Uchman, A., Madeira, P., Rolán, E., Silva, L., Silva, C. M. D., Ryan, D., Rovere, A., Cachão, M., and Ávila, S. P.: Last Interglacial fossiliferous sequences from Santiago Island (Cabo Verde Archipelago): the palaeoecology of the Nossa Senhora da Luz section, a rare example of a protected bay in volcanic oceanic islands, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10423, https://doi.org/10.5194/egusphere-egu2020-10423, 2020

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EGU2020-14805<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
| Highlight
Natasha Barlow, Victor Cartelle, Oliver Pollard, Lauren Gregoire, Natalya Gomez, David Hodgson, Stephen Eaton, Freek Busschers, Kim Cohen, Carol Cotterill, Claire Mellett, and Ivan Haigh

Current models that project sea-level rise beyond 2100 have large uncertainties because recent observation encompass a too limited range of climate variability to provide robust tests against which to simulate future changes. It is crucial to turn to the geological record where there are large-scale changes in climate, but the current interglacial provides limited evidence for how the Earth-system responds to increased temperatures, and therefore it is necessary to study previous climatically-warm periods. Global temperatures during the Last Interglacial were ~1oC warmer than pre-industrial values and 3-5oC warmer at polar latitudes, during which time global mean sea level was likely 6-9 m above present. Though the drivers of warming during the Last Interglacial are different to those of today, it is the amplified warming at polar latitudes, the primary locations of the terrestrial ice masses likely to contribute to long term sea-level rise, which makes the Last Interglacial an ideal palaeo-laboratory to understand coastal response to sea-level rise.  However, our understanding of Last Interglacial sea level change is primarily limited to tropical and sub-tropical latitudes and it is important to understand the response of temperate estuarine settings to rising sea level.

The ERC-funded RISeR project (Rates of Interglacial Sea-level Change, and Responses) focuses on specifically targeting palaeo shorelines buried within the southern North Sea, preserved beyond the limit of the Last Glacial Maximum ice sheets. Buried Last Interglacial sequences in this area provide a valuable record of marine transgression and are being unveiled in new geophysical and geotechnical datasets acquired to support the offshore renewable energy development. This offshore sedimentary archives offer significant advantages over the geomorphologically restricted onshore records allowing us to trace the transgression over a much large area, and should capture the earliest flooding of the Last Interglacial North Sea basin, when the far-field data suggests ice sheet melt was at it maximum. By integrating the already available datasets with newly acquired samples as part of the project, we aim to develop new palaeoenvironmental reconstructions of the Last Interglacial sea-level change from northwest Europe, providing the first chronological constraints on timing, and therefore rates. This has the potential to allow us to ‘fingerprint’ the source of melt (Greenland and/or Antarctica) during the interglacial sea-level highstand.

How to cite: Barlow, N., Cartelle, V., Pollard, O., Gregoire, L., Gomez, N., Hodgson, D., Eaton, S., Busschers, F., Cohen, K., Cotterill, C., Mellett, C., and Haigh, I.: The southern North Sea as a natural palaeo-laboratory to reconstruct the coastal response to Last Interglacial sea-level rise, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14805, https://doi.org/10.5194/egusphere-egu2020-14805, 2020

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EGU2020-4450<span style="font-size: .8em!important; font-weight: bold; vertical-align: super; color: green!important;"></span>
Andrei Briceag, Gabriel Ion, Mihaela Melinte-Dobrinescu, Dan Vasiliu, and Naliana Lupascu

The Danube Deep-Sea Fan, situated in NW Black Sea, is one of the most developed deep-sea sedimentary structures in Europe (Panin & Jipa, 2002). In 2018, in the framework of the uBiogas Project (24PCCDI/2018), several cores were acquired from the aforementioned area. In this study, high resolution microfaunal analyses coupled with sedimentological and geochemical ones, were performed on two gravity cores that revealed changes since the Last Glacial Maximum. The cores have been collected from two secondary canyons, situated in the E of the Danube Canyon, at 655,7 m (MN183_3_GC_1) and 1315 m water depths (MN183_8_GC_1). In both cores, three stratigraphic units as described by Ross & Degens (1974) were identified (oldest first): Unit 3 (Lacustrine lutite), Unit 2 (Sapropel Mud) and Unit 1 (Coccolith Mud).

The sediments of Unit 3 correspond to the Last Glacial Maximum and are marked by the presence of the cold-water ostracod species. The cores contain a reddish-brown clay and silty interval belonging to the post-glacial melt-water pulse of the Heinrich Event 1. In these deposits the ostracod assemblages display a high diversity and abundance. The CaCO3 amount is very low, i.e. below 15%, except for the upper part where it reaches more than 50%. The samples of Unit 3 contain nannofossil assemblages that are entirely composed of reworked species from Cretaceous, Paleogene, Early and Middle Miocene intervals.

In Unit 2 (the sapropel), very few specimens of ostracods were identified, towards the top. During this depositional interval CaCO3 values are dropping again below 15%. The high abundance of the calcareous nannoplankton species Braarudosphaera bigelowii in the upper part of Unit 2 suggests the first strong influx of marine waters into the Black Sea basin.

In the youngest Unit 1, a brackish-marine ostracod assemblage, with low diversity and abundance was identified. This interval is characterized by the presence of polyhaline ostracods with Mediterranean origin. The ostracods from this assemblage tolerate salinities comprised between 17-21 ‰ and characterize a sub-littoral environment. The CaCO3 values are increasing to more than 50%. During the depositional interval of Unit 1 the environmental was definitely a marine one, probably with a constant salinity of surface waters over 17 ppm, allowing the calcareous nannoplankton species Emiliania huxleyi and Braarudosphaera bigelowii to proliferate. The great abundance of the two taxa and especially of Emiliania huxleyi indicates the existence in the basin of a high nutrient input.

The financial support for this paper was provided by the Romanian Ministry of Research and Innovation, through the Programme 1 – Development of the National System of Research – Institutional Performance, Project of Excellence in Research-Innovation, Contract No. 8PFE/2018 and by the Project uBiogas, contract no. 24PCCDI/ 2018.

 

Panin, N., Jipa, D., 2002. Danube river sediment input and its interaction with the northwestern Black Sea. Estuarine Coastline Shelf Science 54: 551–562.

Ross, D.A., Degens, E.T., 1974. Recent sediments of the Black Sea. In: Degens E.T. and Ross D.A. (Eds.), The Black Sea: Geology, Chemistry, and Biology. American Association of Petroleum Geologists, Tulsa, USA: 183–199.

How to cite: Briceag, A., Ion, G., Melinte-Dobrinescu, M., Vasiliu, D., and Lupascu, N.: Late Pleistocene – Holocene sea level and climate changes in the Black Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4450, https://doi.org/10.5194/egusphere-egu2020-4450, 2020