Record Of Relative Sea-level Change Research Articles

Holocene relative sea-level changes on the southern east coast of the Yellow Sea

Projections indicate increasing coastal hazards in the Yellow Sea region owing to relative sea-level rise. Accordingly, regional studies of such change over the Holocene timescale could be helpful in mitigating these threats. Here, we describe the Holocene record of relative sea-level change in the Gochang-Yeonggwang area of South Korea. We compared this record with that of other sites around the coast of the Yellow Sea, including Bohai Bay (China), the Tando Estuary and Gunsan Bay (South Korea), and sites on the east coast of the South Sea and Toyo-oka Basin, Japan. The findings are based on a multi-proxy study, including lithostratigraphy combined with radiocarbon dating and analyses of grain size distribution, magnetic susceptibility, and geochemistry, which facilitated the generation of 89 paleo-sea-level points reconstructed from 28 borehole cores. The early Holocene transgression was found to start later at Gochang-Yeonggwang than at Gunsan Bay, although the distance between them is only 150 km. This result was inferred from substantial differences in sediment delivery owing to Holocene differences in river basin size, topography, and tectonic context. Before ∼7 ka, the slope and highstands from the predicted mean sea-level models at Bohai Bay, Tando Estuary, and Gochang-Yeonggwang were steeper and lower, respectively, from north to south in the Yellow Sea, approaching the slope of the glacio-eustatic sea-level curve. Therefore, the levering effect of transgression in the early Holocene decreased southward in the Yellow Sea. The slight fluctuation in mean sea-level points of the late Holocene resulted from the formation of storm deposit layers in the coastal area, erosion and redeposition in the channel, and geomorphic effects. A partial difference occurred between the relative sea levels at Gochang-Yeonggwang and Toyo-oka. Future relative sea-level research at the southernmost part of the east coast of the Yellow Sea would further improve understanding of the coastal evolution of the region.

A 5000-year record of relative sea-level change in New Jersey, USA

Stratigraphic data from salt marshes provide accurate reconstructions of Holocene relative sea-level (RSL) change and necessary constraints to models of glacial isostatic adjustment (GIA), which is the dominant cause of Late-Holocene RSL rise along the U.S. mid-Atlantic coast. Here, we produce a new Mid- to Late-Holocene RSL record from a salt marsh bordering Great Bay in southern New Jersey using basal peats. We use a multi-proxy approach (foraminifera and geochemistry) to identify the indicative meaning of the basal peats and produce sea-level index points (SLIPs) that include a vertical uncertainty for tidal range change and sediment compaction and a temporal uncertainty based on high precision Accelerator Mass Spectrometry radiocarbon dating of salt-marsh plant macrofossils. The 14 basal SLIPs range from 1211 ± 56 years BP to 4414 ± 112 years BP, which we combine with published RSL data from southern New Jersey and use with a spatiotemporal statistical model to show that RSL rose 8.6 m at an average rate of 1.7 ± 0.1 mm/year (1σ) from 5000 years BP to present. We compare the RSL changes with an ensemble of 1D (laterally homogenous) and site-specific 3D (laterally heterogeneous) GIA models, which tend to overestimate the magnitude of RSL rise over the last 5000 years. The continued discrepancy between RSL data and GIA models highlights the importance of using a wide array of ice model and viscosity model parameters to more precisely fit site-specific RSL data along the U.S. mid-Atlantic coast.

Quaternary sea level change in Scotland

ABSTRACTThis paper summarises developments in understanding sea level change during the Quaternary in Scotland since the publication of the Quaternary of Scotland Geological Conservation Review volume in 1993. We present a review of progress in methodology, particularly in the study of sediments in isolation basins and estuaries as well as in techniques in the field and laboratory, which have together disclosed greater detail in the record of relative sea level (RSL) change than was available in 1993. However, progress in determining the record of RSL change varies in different areas. Studies of sediments and stratigraphy offshore on the continental shelf have increased greatly, but the record of RSL change there remains patchy. Studies onshore have resulted in improvements in the knowledge of rock shorelines, including the processes by which they are formed, but much remains to be understood. Studies of Late Devensian and Holocene RSLs around present coasts have improved knowledge of both the extent and age range of the evidence. The record of RSL change on the W and NW coasts has disclosed a much longer dated RSL record than was available before 1993, possibly with evidence of Meltwater Pulse 1A, while studies in estuaries on the E and SW coasts have disclosed widespread and consistent fluctuations in Holocene RSLs. Evidence for the meltwater pulse associated with the Early Holocene discharge of Lakes Agassiz–Ojibway in N America has been found on both E and W coasts. The effects of the impact of storminess, in particular in cliff-top storm deposits, have been widely identified. Further information on the Holocene Storegga Slide tsunami has enabled a better understanding of the event, but evidence for other tsunami events on Scottish coasts remains uncertain. Methodological developments have led to new reconstructions of RSL change for the last 2000 years, utilising state-of-the-art GIA models and alongside coastal biostratigraphy to determine trends to compare with modern tide gauge and documentary evidence. Developments in GIA modelling have provided valuable information on patterns of land uplift during and following deglaciation. The studies undertaken raise a number of research questions which will require addressing in future work.

Faunal and facies changes through the mid Homerian (late Wenlock, Silurian) positive carbon isotope excursion in Podolia, western Ukraine

The late Wenlock is characterized by two global regressive-transgressive eustatic cycles in association with a double-peaked positive carbon isotope excursion. The onset of the excursion coincides with an extinction event affecting graptolites (the lundgreni event) and proposed to affect conodonts (the Mulde Event) and proliferation of non-skeletal carbonates. In order to test the hypothesized relationships between eustatic and ecological changes, the tropical carbonate Homerian succession in Podolia has been examined with respect to conodont, sequence and δ13C stratigraphy. Four depositional sequences (DS) have been identified. The onset of the δ13C excursion occurs at the boundary between DS1 and DS2, corresponding to a forced regression of proposed glacioeustatic origin. The following rapid eustatic transgression associated with the highest δ13C values of 5.2‰ includes a higher-order shallowing episode recorded in Podolia as normal regression and a boundary between DS2 and DS3. This interval is distinguished by the presence of oncoids and thrombolitic buildups. The latest Wenlock eustatic fall and the corresponding second peak of the δ13C excursion corresponds in Podolia to a stratigraphic gap. The first δ13C peak (top of DS1 and DS2) corresponds to the O. bohemica longa conodont Zone, the interval between the two peaks (DS3) – to K. ortus absidata and C. murchisoni zones, and DS4 is tentatively placed in the lowermost Ludlow Series. The record of relative sea-level changes in Podolia is consistent with reconstructions based on successions in England and Sweden. The moderate drop in conodont taxonomic richness may reflect the primary depositional control over their proposed extinction.

Miocene sea-level changes in northernmost Anatolia: Sedimentary record of eustasy and tectonism at the peri-Pontide fringe of Eastern Paratethys

This study from the Central Pontide Miocene foredeep basin compares the local record of relative sea-level changes at the Turkish southern periphery of the Eastern Paratethys with the general Paratethyan eustatic history. Detailed sedimentary facies analysis is used to decipher high-resolution sequence stratigraphy of the basin-fill succession. The Tarkhanian–Chokrakian Sinop Formation overlies directly the pre-Cenozoic bedrock and consists of neritic to littoral, foreshore and barrier–lagoon deposits, which form transgressive–regressive parasequences with estimated time spans of ca. 60 to 700ka. The overlying Konkian–Bessarabian Gelincik Formation occurs as the infill of fluvial valleys, up to >120m deep, which were incised during the Karaganian and filled with deltaic to non-deltaic bayhead shoreline deposits passing up-valley into alluvium. The valley-fill deposits form parasequences with an estimated mean time span of ca. 300ka, organized into a lower regressive and an upper transgressive set. These 1st-order parasequences consist of smaller, 2nd-order parasequences with an estimated mean time span of ca. 5ka.All the main mid-Miocene Paratethyan eustatic events are recognizable in the basin-fill succession, although their record appears to have been modulated by the local tectonism and high rate of post-orogenic sediment supply. The signal of 3rd-order eustatic cycles is recorded on a stratigraphic scale of parasequence sets. The 1st-order parasequences are attributed to pulses of the basin subsidence, which was initially driven by the thrust loading of the collapsing Pontide orogen and later by the neotectonic inception of the strike-slip North Anatolian Fault System. The 2nd-order parasequences represent minor subsidence pulses and/or the Milankovitch eustatic cycles. The study shows how a comparative analysis of local sequence stratigraphy and eustatic sea-level record can serve to recognize the relative role of eustasy, tectonics and sediment supply in a sedimentary basin.

Reply to the comments by Mauz, B. and Antonioli, F. on “Sea Level and Climate Changes during OIS 5e in the Western Mediterranean”

We really appreciate the comments by Mauz and Antonioli on our paper (Bardaji et al., 2009geomorphologic maps are often lacking in studies related to the reconstruction of past sea level changes. In most cases these maps would be the only way of reconstructing past sea level oscillations (see for example, ), but here we respond to the erroneous statements made in their critical reading of our work. We agree with the authors' historic review of the problems raised when effects of tectonics and sea level oscillations are observed in the record of relative sea-level changes in Western Mediterranean. We should not forget that the Mediterranean itself constitutes a collision plate boundary, with few stable areas within it. Therefore, the study of the Last Interglacial shorelines cannot be simply analysed according to altitude, as they say. What we do not share with Mauz and Antonioli is that “the only solution to this seemed to be determining the age of a coastal deposit using radiometric, dosimetric and chemical dating techniques”. It is obvious that we need a chronological approach to be as accurate as possible. First of all, however, an exhaustive field analysis is needed, and this is overlooked by Mauz and Antonioli at least in the Spanish Mediterranean sector. To begin with, field analysis would yield a deeper wider geological knowledge, not only of the precise sections but also on a regional scope. Second, a geomorphologic understanding of the selected sections is necessary. Geomorphology is the best tool that enables us to understand how many different sea level highstands or intervals we are dealing with in terms of their relation to former and younger sea level indicators (i.e. 3D stratigraphic architecture). Sampling for dating purposes can only be done when the sedimentary sequence is clear, and after detailed geomorphologic mapping. Unfortunately, Radtke and Schellmann, 2004

SEA-LEVEL CHANGE AND THE STRUCTURE OF MARINE ECOSYSTEMS

The emergence of sequence stratigraphy—the study of genetically related facies within a framework of chronostratigraphically significant surfaces—triggered a conceptual breakthrough in stratigraphy (Van Wagoner et al., 1990; Baum and Vail, 1998) and vastly improved our understanding of the fossil record (Holland, 1999). Sequence-bounding unconformities and transgressive surfaces are the record of relative sea-level changes and a signature of time intervals not represented in the geological record. This is a key issue for those interested in documenting the steps in the history of life. Despite a good sampling of the rock record (Donovan and Paul, 1998), concern that the sedimentary record is biased remains widely justified by recent studies (Smith, 2001; Crampton et al., 2003). Rock biases and sedimentary gaps strongly determine what we perceive as abundance and diversity patterns (Raup, 1972; Smith, 2001; Peters, 2005). Sequence stratigraphic architectures, however, also allow the role of sea-level changes to be tested as a driving force of ecology and evolution in the marine realm. Sea-level variations as sources of minor and major environmental perturbations (Hallam and Wignall, 1999) are factors in ecosystem structure (Olszewski and Erwin, 2004) and macroevolution (Peters, 2006). A session of the 2004 American Association of Petroleum Geologists Dallas Meeting entitled, “Sea-level change, climate variation, and the restructuring of shallow marine communities,” addressed paleobiological factors related to this important aspect of sequence stratigraphy. Some participants of that session and other researchers have contributed their thoughts on the subject in this special issue of PALAIOS. Before sequence stratigraphic concepts made their way into paleontologic practice, authors studying the biotic effects of relative sea-level change used formations as the natural subdivisions of the rock record and derived sea-level templates from 106–107-year duration transgressive-regressive cycles (e.g., Rollins et al., 1979; Jablonski, 1980; Hallam, …

Mid-to late-Holocene relative sea-level change in southwest Britain and the influence of sediment compaction

Relative sea-level changes in southwest Britain are poorly constrained because of limitations in the quality and quantity of existing geological data. As a consequence, in contrast to most other regions in the UK, it is not possible to reliably infer rates of land and sea-level change during the last few thousand years. Furthermore, geologically based sea-level reconstructions from this area display significant misfits with relative sea-level predictions based on a recent global model of the glacio-isostatic adjustment process. This paper presents a new record of relative sea-level change for the last 4000 years derived from radiocarbon-dated sea-level index points. In addition to providing information concerning the pattern and rates of late Holocene sea-level change, these data are used to evaluate the suggestion that the apparent misfits between model predictions and geological reconstructions can be satisfactorily explained as a consequence of the lowering of sea-level index points by sediment compaction. The results indicate that a simple, first-order method of decompaction based on the stratigraphic position of sea-level index points, can eliminate much of the misfit between reconstructions and predictions, and substantially reduce vertical scatter in geological data. They also suggest that the influence of compaction on sea-level data from this region may be larger than previously thought. The simple addition of reliable stratigraphic data, in combination with targeted sampling, has the potential to improve our understanding of the compaction process, and increase the utility of existing data. This is increasingly important as the partnership between geophysical modelling and geological investigation becomes more commonplace in sea-level studies around the world.

Developing detailed records of relative sea-level change using a foraminiferal transfer function: an example from North Norfolk, UK

This paper provides a brief overview of the transfer function approach to sea-level reconstruction. Using the example of two overlapping sediment cores from the North Norfolk coast, UK, the advantages and limitations of the transfer function methodology are examined. While the selected cores are taken from different sites, and display contrasting patterns of sedimentation, the foraminiferal transfer function distils comparable records of relative sea-level change from both sequences. These reconstructions are consistent with existing sea-level index points from the region but produce a more detailed record of relative sea-level change. Transfer functions can extract sea-level information from a wider range of sedimentary sub-environments. This increases the amount of data that can be collected from coastal deposits and improves record resolution. The replicability of the transfer function methodology, coupled with the sequential nature of the data it produces, assists in the compilation and analysis of sea-level records from different sites. This technique has the potential to bridge the gap between short-term (instrumental) and long-term (geological or geophysical) records of sea-level change.

Modern Vertical Deformation above the Sumatran Subduction Zone: Paleogeodetic Insights from Coral Microatolls

Coral microatolls from the coast and outer-arc islands of Western Sumatra retain a stratigraphic and morphologic record of relative sea-level change, which is due in large part to vertical tectonic deformation above the Sumatran subduction zone. Low water levels, whose fluctuations produce measurable changes in coral morphology, limit the upward growth of the microatolls. Annual rings, derived from seasonal variations in coral density, serve as an internal chronometer of coral growth. The microatolls act as natural long-term tide gauges, recording sea-level variations on time scales of decades. Field observations and stratigraphic analysis of seven microatolls, five from the outer-arc islands and two from the mainland coast, indicate that the Mentawai Islands have been submerging at rates of 4–10 mm/yr over the last four or five decades, while the mainland has remained relatively stable. The presence of fossil microatolls up to several thousand years old in the intertidal zone indicates that little permanent vertical deformation has occurred over that time. Thus, most of the strain accumulated in the past few decades represents interseismic deformation that is recovered during earthquakes. Elastic dislocation models using these submergence data suggest that elastic strain is being accumulated in the interseismic period and that the subduction zone in this region is fully coupled.

Global meltwater discharge and the deglacial sea‐level record from northwest Scotland

Quantitative models of Earth–ice-sheet–ocean interactions predict that periods of rapid eustatic sea-level rise, indicating enhanced meltwater discharge to the oceans, should be manifest in the relative sea-level histories from sites within the limits of Late Devensian ice sheets. Analysis of a record of relative sea-level change for the last 16000 calendar years from Northwest Scotland constrains the magnitude and timing of two major pulses of meltwater, ca. 14000 and ca. 11300 cal. yr BP, inferred from coral records. The ca. 14000 cal. yr BP event saw a temporary doubling of the flux of meltwater, but existence of the second major event at ca. 11300 cal. yr BP is not supported by the data from northwest Scotland. Copyright © 1999 John Wiley & Sons, Ltd.

Global meltwater discharge and the deglacial sea-level record from northwest Scotland

Quantitative models of Earth–ice-sheet–ocean interactions predict that periods of rapid eustatic sea-level rise, indicating enhanced meltwater discharge to the oceans, should be manifest in the relative sea-level histories from sites within the limits of Late Devensian ice sheets. Analysis of a record of relative sea-level change for the last 16000 calendar years from Northwest Scotland constrains the magnitude and timing of two major pulses of meltwater, ca. 14000 and ca. 11300 cal. yr BP, inferred from coral records. The ca. 14000 cal. yr BP event saw a temporary doubling of the flux of meltwater, but existence of the second major event at ca. 11300 cal. yr BP is not supported by the data from northwest Scotland. Copyright © 1999 John Wiley & Sons, Ltd.

Sea level, climate change and coastal evolution in Morar, northwest Scotland

Analyses of geomorphologically contrasting sites in Morar, NW Scotland, describe the forcing mechanisms of coastal change. Isolation basins (i.e. basins behind rock sills and now isolated from the sea following isostatic uplift) accumulated continuous marine and freshwater sediments from c.12 to 2 ka BP. Raised dune, marsh and wetland sites register breaching, migration and stability of dunes from c. 9 to 2 ka BP. High-resolution methods designed to address issues of macroscale and microscale sea-level changes and patterns of storminess include 1-mm sampling for pollen, dinocyst and diatom analyses, infra-red photography, X-ray photography and thin-section analysis. The data enhance the record of relative sea-level change for the area. Major phases of landward migration of the coast occurred during the period of low sea-level rise in the mid-Holocene as the rate of rise decreased from c. 3 to < 1 mm/year. Relative sea-level change controls the broad pattern of coastal evolution at each site; local site-specific factors contribute to short-term process change. There is no record of extreme events such as tsunami. Within a system of dynamic metastable equilibrium, the Holocene records show that site-specific factors determine the exact timing of system breakdown, e.g. dune breaching, superimposed on regional sea-level rise. The global average sea-level rise of 3 to 6 mm/yr by AD 2050 predicted by IPCC would only partly be offset in the Morar area by isostatic uplift of about 1 mm/yr. A change from relative sea-level fall to sea-level rise, in areas where the regional rate of uplift no longer offsets global processes, is a critical factor in the management of coastal resources.

Late Devensian and Holocene relative sea-level changes in northwestern Scotland: New data to test existing models

Abstract Pollen, diatom, lithostratigraphic and radiocarbon data from five sites in northwestern Scotland provide new data from an area previously devoid of reliable and precise information on Late Devensian and Holocene sea-level changes. The sites cover a range of palaeoenvironments, indicative of diversity in coastal evolution since deglaciation. For each site and palaeoenvironment the reference water (tide) level, indicative range, age and tendency of sea-level movement of all sea-level index points are quantified to enable correlation of the diverse coastal environments. The data record patterns of relative sea-level change and tendencies of sea-level movement from 12 ka BP to 1 ka BP. This is the longest and most comprehensive published record of relative sea-level change from the area. The information is used to test the accuracy of existing models of relative sea-level change. The results are only broadly consistent with a quantitative rebound model, and there is significant disagreement with empirical models during the Late Devensian and the early Holocene.

Climate and sea level during oxygen isotope stage 7b: On-land evidence from New Zealand

Strata at Landguard Bluff, near Wanganui, New Zealand preserve a clear record of relative sea-level changes during oxygen-isotope stage 7. Two relative high sea-level stands (during stages 7a about 210,000 yr ago and 7c about 240,000 yr ago) are separated by a relative low sea level (stage 7b) that was at least 32 m lower than present. Pollen analysis of sediment deposited during stage 7b indicates climate at the time was up to 3°C cooler than present. The climate and sea-level evidence from Landguard Bluff are consistent with oxygen-isotopic evidence from deep-sea cores indicating a marked cooling during stage 7, which is closely associated with a summer radiation minimum centered at about 230,000 yr ago in the Northern Hemisphere.