The Mississippi River gradient plotted between New Orleans and Head of Passes (the site of the first channel bifurcation located 16 km from the mouth), a distance of 165 km. The plot was constructed using daily river stage measurements, where each data point represents the average of over 3700 measurements corresponding to the same days between 1980 and 1999 for which data were available for all gauge stations. For all stations the vertical datum is set to 0 m National Geodetic Vertical Datum of 1929 (NGVD29) which does not correspond to mean sea level. Data provided by the U.S. Army Corps of Engineers New Orleans District ( 

The Mississippi River gradient plotted between New Orleans and Head of Passes (the site of the first channel bifurcation located 16 km from the mouth), a distance of 165 km. The plot was constructed using daily river stage measurements, where each data point represents the average of over 3700 measurements corresponding to the same days between 1980 and 1999 for which data were available for all gauge stations. For all stations the vertical datum is set to 0 m National Geodetic Vertical Datum of 1929 (NGVD29) which does not correspond to mean sea level. Data provided by the U.S. Army Corps of Engineers New Orleans District ( 

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A detailed relative sea-level (RSL) record was constructed for the time interval 600–1600 AD, using basal peat to track sea level and containing 16 sea-level index points that capture ∼60 cm of RSL rise. The study area is in the Mississippi Delta where the spring tidal range is ∼0.47 m, the impact of ocean currents on sea-surface topography is limi...

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... agreement was obtained after rejection of the three 14 C ages highlighted in Fig. 3 (Lydia IV-1a, Lydia XIII-1a and Delahoussaye Canal II-1b). The combined data set for the three areas consists of 28 sea-level index points; the ages of 25 of these represent weighted means of the two subsamples, and only three are based on a single age measurement. Error boxes were constructed for each sea-level index point by incorporating the uncertainties associated with the altitudinal and age components of each sample. In this study, given the subtle nature of the sea-level signal that is being targeted, much effort went into minimizing elevation errors. The errors accounted for included those resulting from non-vertical drilling, sampling, optical surveying, and the vertical indicative range of the material dated. Errors associated with DGPS measurements were incorpo- rated only when index points from the three different cross sections were combined. An error of Æ 1 cm per meter depth was applied to account for non-vertical drilling ( e d ); Æ 2 cm for sampling in the gouge ( e ); Æ 1 cm for the optical surveys between DGPS- measured benchmarks and sampling sites ( e os ) and Æ 5 cm for the DGPS measurements ( e gps ). Determining the indicative range (the modern vertical range occupied by a sea-level indicator measured relative to a given tide level) is a challenging step and it can be a major source of error (Kidson, 1982; Van de Plassche, 1986; Gehrels et al., 1996; Horton et al., 2000). A key assumption when using basal peat for sea level reconstructions is that it closely tracks the interval between MSL and MHW. In the absence of botanical remains that would have enabled an assessment of the degree of marine influence on the peat, we present two observations that support that this assumption is likely valid for our study area. First, the stable carbon isotope signature of the peat provides an approximation of the type of environment in which it accumulated in terms of salinity. Herbaceous marshes in the Mississippi Delta have been subdivided into fresh, intermediate, brackish and saline zones based primarily on vegetation associations (Chabreck, 1972). Chmura et al. (1987) reported the range of d C values for organic carbon-rich sedimentary material for each of these vegetation associations (saline: À 18.5 to À 14.5 & ; brackish: À 20.0 to À 15.0 & ; intermediate: À 25.5 to À 18.5 & ; and fresh: À 28.5 to À 25.5 & ). Most charcoal fragments (41 of 56) used in this study had d 13 C values in the range À 25.5 to À 18.5 & (Table 2), suggesting vegetation associations that thrive in intermediate salinity conditions (0.3–9.8 & ; Chabreck, 1972). This suggest that the marsh received regular inputs of salt water to maintain intermediate salinity conditions, and, thus, that the peat accumulated within the intertidal zone, defined here as the interval between MTL (mean tide level) and MHSW (mean high spring water). The possibility that charcoal might not be representative of the stable carbon isotope content of the original plant material was considered, but there is evidence indicating that this is unlikely to be the case for our samples. Turney et al. (2006) replicated forest fires and observed that isotopic fractionation of up to w 1.3 & can take place during burning. This fractionation, however, is toward more depleted values and is temperature dependent. It is likely that the d 13 C values reported for our samples do not differ much from those of the original plant material, given that fires in coastal marshes do not reach the high temperatures of forest fires. More importantly, any such a d C shift would place our samples more firmly within the intermediate salinity range. Although the d 13 C signature of the peat is used here to argue for a periodic input of salt water in the environment in which the peat formed, and thus to demonstrate marine influence in our samples, we advise that the use of carbon isotope ratios as an indicator or marine influence should be treated with caution in the absence of macro- or microfossil evidence. It should also be noted that to our knowledge no study has as of yet attempted to establish the link between d 13 C values of sedimentary organic matter and surface elevation with respect to tide levels along the U.S. Gulf Coast. Second, water levels in deltaic environments tend to slope very gently in a seaward direction due to a river-gradient effect (Van de Plassche, 1980). Detailed studies of the impact of river gradient on the GWL in the Rhine–Meuse Delta have shown that it only becomes significant at a distance of w 50 km upriver from the coast (Van Dijk et al., 1991; Cohen, 2003, 2005). Although this relationship has not been firmly established for the Mississippi Delta, it is likely that this distance is considerably larger given the extremely low gradient of this large river system. The present-day gradient of the lowermost 165 km of the Mississippi River is 1.0 cm km À 1 (Fig. 4). While the Atchafalaya River has a shorter route to the Gulf of Mexico (about half that of the Mississippi) and a proportionally steeper slope, it is clear that river gradients in this area are very low. Therefore it appears plausible, given the close proximity of the study area to the coast, that river-gradient effects were unlikely to raise local GWL above the intertidal level. Thus, sea level is the dominant control of GWL in the study area. Considering a present-day spring tidal range along the Mississippi Delta of w 47 cm (Table 1) we have adopted a value of Æ 12 cm derived from the difference between MTL and MHSW to account for the indicative range ( e ir ). It should be noted that we applied this value to index points with d 13 C signatures indicative of both intermediate salinity and fresh water conditions, but as will be explained below, for the final analysis we excluded those samples that lacked direct isotopic evidence of marine influence. The total vertical error was calculated by taking the root mean square of the values given for each error following Shennan et al. (2000) and Horton et al. (2000), as ...

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... A mid-Holocene highstand on the Texas (Morton et al., 2000;Blum et al., 2001) and Alabama (Blum et al., 2003) coasts has been interpreted. However, numerous sea-level curves from Louisiana (Törnqvist et al., 2004a(Törnqvist et al., , b, 2006González and Törnqvist, 2009;Li et al., 2012), Texas and Alabama (Milliken et al., 2008), and Florida (Hawkes et al., 2016;Gerlach et al., 2017) have shown no evidence of a mid-Holocene highstand. Blum et al. (2008) suggested that a lithospheric flexural deformation process associated with unloading and loading of the Mississippi Delta has caused alongshore variability in relative-sea-level change (reviewed in Blum and Roberts, 2012). ...
... Saltmarshes (peat layer) are often used for reconstructing the Holocene sea level because they form at an elevation corresponding to the contemporary position of mean sea level (Chen and Stanley, 1998;González and Törnqvist, 2009;Wilson et al., 2020). Our dated peat layers, together with dated lagoon muds can highlight more precisely the sea-level positions of the central Nile coast during the Holocene (Fig. 3). ...
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This study presents high-resolution multi-proxy analyses of a well-dated sediment core (BR-1, 19.20 m long) retrieved from the Nile Delta, aiming to reconstruct the Holocene evolution of the Burullus lagoon. In particular, we focus on the morphodynamical processes, sediment provenances and related hydro-climatic changes. The Holocene strata of the lagoon coast comprise Early-Holocene marine transgressive facies and the Mid-Late Holocene retrogressive deltaic facies. Although BR-1 shows no river-channel facies, two peaks of magnetic susceptibility (MS) at ca. 8.0–7.0 ka (also associated with a high sedimentation rate of 50 mm/yr) and 3.5–2.0 ka evoke phases of greater morphodynamic influence of palaeo-Nile branches on the lagoon's development. Both dated peat layers (ca. 13 m and 8 m below MSL) and lagoon muds intercalated in BR-1, together with previously-dated peat strata were benchmarked relatively to MSL for the reconstruction of relative Holocene sea level in the study area. Our results show considerable land lowering on the Burullus coast indicated by a sea-level elevation, ca. 4–1 m lower than the one reconstructed along adjacent coastlines where less land subsidence occurred. The lagoon system began to form after ca. 6.0 ka in response to deceleration in sea-level rise and, being a shallower water body, both macrofauna (Cerastoderma glaucum etc.) and ostracods (Cyprideis torosa) of brackish-water nature emerged. In addition, geochemical data from BR-1 provide insights into environmental change in association with basin-wide hydro-climate fluctuations. Concomitant peaks in Fe/Al, Ti/Al and Cr/Al ratios (mafic origin), together with higher Zr/Al and Hf/Al ratios (felsic origin) before ca. 8.0 ka suggest sediment provenances derived from the White and the Blue Nile during the main African Humid Period (AHP). Since then, Ti/Al kept slightly ascending core-upwards with two pulses at 7.8–7.3 ka and 3.5–2.0 ka, which was asynchronous to Zr/Al and Hf/Al. This corroborates more sediments of basaltic origin transported to the delta coast after the main AHP due to southerly shift in the position of the ITCZ. The two periods of Ti/Al pulse are consistent with the MS peaks in BR-1, suggesting that palaeo-Nile branches remained active during 8.0–7.0 ka and 3.0–2.0 ka nearby. You can access the paper until March 27th 2022 via this link https://authors.elsevier.com/c/1eXap73N~6fYt
... A mid-Holocene highstand on the Texas (Morton et al., 2000;Blum et al., 2001) and Alabama (Blum et al., 2003) coasts has been interpreted. However, numerous sea-level curves from Louisiana (Törnqvist et al., 2004a(Törnqvist et al., , b, 2006González and Törnqvist, 2009;Li et al., 2012), Texas and Alabama (Milliken et al., 2008), and Florida (Hawkes et al., 2016;Gerlach et al., 2017) have shown no evidence of a mid-Holocene highstand. Blum et al. (2008) suggested that a lithospheric flexural deformation process associated with unloading and loading of the Mississippi Delta has caused alongshore variability in relative-sea-level change (reviewed in Blum and Roberts, 2012). ...
Chapter
This chapter reviews the morphodynamics of open-ocean barrier systems, synthesizing classic studies, current scientific knowledge, and future research directions regarding 14 barrier provinces worldwide. Within a coastal tectonic framework, it addresses: (1) Amero-trailing-edge coasts (USA's New England coast, Mid-Atlantic Bight coast, North Carolina Outer Banks, Georgia Bight coast, Florida Atlantic coast; Brazil's Santa Catarina coast; Europe's German Bight coast; Australia's southern and western coasts); (2) marginal-sea coasts (USA's Florida Gulf Coast; Gulf Coast of Louisiana, Mississippi, and Alabama; Texas Gulf Coast; Australia's eastern coast); and (3) collision coasts (USA's Alaskan Pacific coast, Japan's and New Zealand's coasts). This chapter also provides a glossary, important conclusions, specific recommendations regarding future coastal research, and a robust, current set of references.
... The bayhead-delta apex is indicated by the open black circle. The inset shows the location of the study area (green box) within the Lafourche subdelta (blue shaded region), the Lafourche-Modern avulsion site (red open triangle), the study areas of González and Törnqvist (2009) (orange box) and Törnqvist et al. (2008) (blue box), and the Wax Lake Delta (purple box). Additional information about oil and gas production is provided in Supporting Information S1. ...
... Note that this cartoon does not consider compaction. (b) Compaction-free RSLR during the time of Lafourche subdelta progradation (after González & Törnqvist, 2009;Törnqvist et al., 2006). (c) Method for calculating subsidence uses the change in elevation of the M-O boundary (ΔE) from time of formation (E 0 ) to present (E 1 ), relative to NAVD 88 and corrected for RSLR (ΔRSL) since the time of M-O boundary formation (T 0 ) obtained from OSL dating of the mouth-bar deposits (Chamberlain et al., 2018). ...
... Chronologic data are from Chamberlain et al. (2018). Relative sea-level rise (ΔRSL) is determined using data from González and Törnqvist (2009) and Törnqvist et al. (2006). Holocene succession thickness data are from Heinrich et al. (2015). ...
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The ability of deltas to persist by building new land is critical to maintaining these vital ecologic environments that are often home to major economic and population centers. However, the deposition of land-building sediment triggers load-induced shallow subsidence which may undermine the effectiveness of natural and engineered emergent landforms. Here, we present a new method to quantify shallow subsidence in a 6,000–8,000 km2 relict bayhead delta of the Mississippi Delta using the mouth bar to overbank stratigraphic boundary that formed near sea level, temporally constrained by optically stimulated luminescence dating. Vertical displacement rates at this boundary, averaged over 750–1,500 years, are on the order of a few mm/yr. Total subsidence scales to ∼50% of the thickness of overlying deposits, significantly greater than the 28%–35% loss estimated for inland localities underlain by peat, indicating that bay muds in the study area are more compaction-prone than terrestrial organic-rich deposits. Modeling shows a modest reduction of ∼13% in deltaic land-area gain under a realistic compaction scenario for 1,000 years of simulated delta progradation, compared to a no-compaction scenario. Our findings indicate that load-driven compaction does not majorly hinder land-area gain and may in fact promote long-term growth at engineered sediment diversions through channel maintenance driven by compaction, thereby adding further support to this restoration strategy.
... The rate of change occurring late in the 19th century are seen in all high resolution salt-marsh records-e.g., in New Zealand (c) (Gehrels et al., 2008;Gehrels and Woodworth, 2013) and in Spain (d) (Leorri et al., 2008;García-Artola et al., 2009)-that extend into modern time and is consistent with Roman archaeological evidence (Lambeck et al., 2004b). The oscillation in sea level seen in the North Carolina record at about 1000 years ago occurs in some (González and Törnqvist, 2009) but not all records (cf. Gehrels et al., 2011;Kemp et al., 2011). ...
... Regionally, as along the US Atlantic coast and Gulf of Mexico coast, the salt-marsh records reveal some consistency in multi-decadal and centennial time scales deviations from the linear trends expected from the GIA signal (see e.g., panels (a) and (b) in Figure 5.17) (van de Plassche et al., 1998;González and Törnqvist, 2009;Kemp et al., 2011) but they have not yet been identified as truly global phenomena. For the past 5 millennia the most complete sea level record from a single location consists of microatoll evidence from Kiritimati (Christmas Island; Pacific Ocean) that reveals with medium confidence that amplitudes of any fluctuations in GMSL during this interval did not exceed approximately ±25 cm on time scales of a few hundred years. ...
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International Ocean Discovery Program Expedition 382, Iceberg Alley and Subantarctic Ice and Ocean Dynamics, investigated the long-term climate history of Antarctica, seeking to understand how polar ice sheets responded to changes in insolation and atmospheric CO2 in the past and how ice sheet evolution influenced global sea level and vice versa. Five sites (U1534–U1538) were drilled east of the Drake Passage: two sites at 53.2°S at the northern edge of the Scotia Sea and three sites at 57.4°–59.4°S in the southern Scotia Sea. We recovered continuously deposited late Neogene sediments to reconstruct the past history and variability in Antarctic Ice Sheet (AIS) mass loss and associated changes in oceanic and atmospheric circulation. The sites from the southern Scotia Sea (Sites U1536–U1538) will be used to study the Neogene flux of icebergs through “Iceberg Alley,” the main pathway along which icebergs calved from the margin of the AIS travel as they move equatorward into the warmer waters of the Antarctic Circumpolar Current (ACC). In particular, sediments from this area will allow us to assess the magnitude of iceberg flux during key times of AIS evolution, including the following: The middle Miocene glacial intensification of the East Antarctic Ice Sheet, The mid-Pliocene warm period, The late Pliocene glacial expansion of the West Antarctic Ice Sheet, The mid-Pleistocene transition (MPT), and The “warm interglacials” and glacial terminations of the last 800 ky. We will use the geochemical provenance of iceberg-rafted detritus and other glacially eroded material to determine regional sources of AIS mass loss. We will also address interhemispheric phasing of ice sheet growth and decay, study the distribution and history of land-based versus marine-based ice sheets around the continent over time, and explore the links between AIS variability and global sea level. By comparing north–south variations across the Scotia Sea between the Pirie Basin (Site U1538) and the Dove Basin (Sites U1536 and U1537), Expedition 382 will also deliver critical information on how climate changes in the Southern Ocean affect ocean circulation through the Drake Passage, meridional overturning in the region, water mass production, ocean–atmosphere CO2 transfer by wind-induced upwelling, sea ice variability, bottom water outflow from the Weddell Sea, Antarctic weathering inputs, and changes in oceanic and atmospheric fronts in the vicinity of the ACC. Comparing changes in dust proxy records between the Scotia Sea and Antarctic ice cores will also provide a detailed reconstruction of changes in the Southern Hemisphere westerlies on millennial and orbital timescales for the last 800 ky. Extending the ocean dust record beyond the last 800 ky will help to evaluate dust-climate couplings since the Pliocene, the potential role of dust in iron fertilization and atmospheric CO2 drawdown during glacials, and whether dust input to Antarctica played a role in the MPT. The principal scientific objective of Subantarctic Front Sites U1534 and U1535 at the northern limit of the Scotia Sea is to reconstruct and understand how intermediate water formation in the southwest Atlantic responds to changes in connectivity between the Atlantic and Pacific basins, the “cold water route.” The Subantarctic Front contourite drift, deposited between 400 and 2000 m water depth on the northern flank of an east–west trending trough off the Chilean continental shelf, is ideally situated to monitor millennial- to orbital-scale variability in the export of Antarctic Intermediate Water beneath the Subantarctic Front. During Expedition 382, we recovered continuously deposited sediments from this drift spanning the late Pleistocene (from ~0.78 Ma to recent) and from the late Pliocene (~3.1–2.6 Ma). These sites are expected to yield a wide array of paleoceanographic records that can be used to interpret past changes in the density structure of the Atlantic sector of the Southern Ocean, track migrations of the Subantarctic Front, and give insights into the role and evolution of the cold water route over significant climate episodes, including the following: The most recent warm interglacials of the late Pleistocene and The intensification of Northern Hemisphere glaciation.
... Sediment type and depth to an underlying non-compacting pre-Holocene or basement surface are main factors controlling such subsidence (Allen, 1999). Understanding land subsidence plays a key role in Holocene reconstructions of coastal basins, both in larger river deltas such as the Mississippi (Törnqvist et al., 2008;González and Törnqvist, 2009), the Rhine (Van Asselen et al., 2018;Erkens et al., 2016;Hijma and Cohen, 2019), the Tagus (Vis et al., 2008), the Po (e.g. Teatini et al., 2011;Fontana et al., 2017) and smaller deltaic and coastal back-barrier regions, such as in Southern England (Long et al., 2006;Massey et al., 2006) and several coastal basins along the Italian coast. ...
... Because the selected locations for lake level reconstruction (Fig. 9) are on top of the stable Pleistocene surface, the tephra-bearing strata barely suffered post-depositional compaction or subsidence and can be regarded as basal peats or lake sediments (e.g. Van de Plassche et al., 2010;González and Törnqvist, 2009;Fontana et al., 2017;Hijma and Cohen, 2019). The reconstructed near-coastal lake level of −1.5 to −1.3 m asl is therefore also a best estimate of local Relative Sea Level, fitting well with the recent standardization of Sea Level indicators around the Mediterranean (Vacchi et al., 2016). ...
... Salt marshes lie at the elevation close to the sea-level and maybe a good indicator of the historical sea-level (Kelsey, 2015). Some geologic studies have used the radiocarbon dating of peat materials to understand the past sea-level in coastal Louisiana (González and Törnqvist, 2009;Wang et al., 2019). Additional isotopic, sedimentary, and radiocarbon analysis may be essential to understand the depositional environment of the vertical carbon profiles in Barataria Basin, Louisiana. ...
Article
Marsh-edge erosion is one of the major causes of land and associated carbon loss in wetland-dominated coastlines. Assessing carbon stocks and understanding fate of eroding carbon is an essential component of wetland carbon budget. This study aims to understand the vertical soil carbon profile of an eroding marsh and potential mineralization of carbon in estuaries. Eleven soil cores (~2 m deep) were collected from the edge of four highly eroding marsh sites and three cores from the bottom surface of the estuary (~50 cm deep). Cores were sectioned into 10-cm intervals and analyzed for total, labile and refractory carbon, carbon density, select enzyme and microbial activities, and organic and inorganic phosphorus forms. The total carbon, labile carbon, and carbon density increased with depth at all sites. The carbon density at 1–1.5 m deep (0.04 ± 0.003 g cm⁻³) was significantly higher (p < 0.001) than the top 1 m soil (0.032 ± 0.002 g cm⁻³), indicating the need for considering deeper carbon profile for blue carbon stock assessment. The age of the carbon at the estuarine bottom was 388 ± 84 years before present (ybp) indicating the recently eroded wetland carbon is not reburied in the estuary. Significant anaerobic microbial activity was present at all the soil depths suggesting high potential of mineralization of eroded carbon in the aerobic estuarine water. The coastlines experiencing high relative sea-level rise at present or coastlines that are projecting high sea-level rise in the near future are susceptible to losing an enormous amount of previously sequestered carbon over a relatively short period of time.
... Rates of RSL rise ( Fig. 1) approach 10 mm year −1 during the earliest phase of the record and then progressively decrease to ~0.5 mm year −1 during the preindustrial millennium (19). As a result, this record enables us to study paleo-marsh response to a wide range of rates of RSL rise as determined with respect to the preexisting land surface. ...
... Because the Holocene RSL history of this region is dominated by glacial isostatic adjustment (peripheral bulge subsidence) as reflected by continuous but progressively decreasing rates of RSL rise (36), we only considered curves characterized by monotonic RSL rise. Subtle, century-scale RSL fluctuations with amplitudes of a few decimeters (19) likely existed, but would have a relatively small impact on the most important portion of our RSL record when rates of RSL rise were the highest (i.e., the effect would be limited to subtle accelerations and decelerations). RSL curves were graphically evaluated and assessed for goodness of fit (R 2 ) and the standard error between the data and the fitted curve. ...
Article
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Coastal marshes are threatened by relative sea-level (RSL) rise, yet recent studies predict marsh survival even under the high rates of RSL rise expected later in this century. However, because these studies are mostly based on short-term records, uncertainty persists about the longer-term vulnerability of coastal marshes. We present an 8500-year-long marsh record from the Mississippi Delta, showing that at rates of RSL rise exceeding 6 to 9 mm year−1, marsh conversion into open water occurs in about 50 years. At rates of RSL rise exceeding ~3 mm year−1, marsh drowning occurs within a few centuries. Because present-day rates of global sea-level rise already surpass this rate, submergence of the remaining ~15,000 km2 of marshland in coastal Louisiana is probably inevitable. RSL-driven tipping points for marsh drowning vary geographically, and those for the Mississippi Delta may be lower than elsewhere. Nevertheless, our findings highlight the need for consideration of longer time windows in determining the vulnerability of coastal marshes worldwide.
... In addition to the resource benefits, fluvial landscapes are shaped by and subject to dynamic processes ranging from annual river flooding (e.g., Davis et al., 2018) to multi-centennial channel avulsions (e.g., Fisk, 1944;Saucier, 1994). Deltaic systems are further complicated by coastal phenomena such as ongoing subsidence (e.g., Karegar et al., 2015;Nienhuis et al., 2017), sea-level rise (e.g., González and Törnqvist, 2009), and episodic storm (e.g., tropical cyclone or hurricane) events (e.g., Bregy et al., 2018). Deltas are therefore inherently difficult to lock-in-place in a way that is compatible with the establishment and maintenance of hard infrastructure. ...
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Recent geochronology of the Mississippi Delta of coastal Louisiana, USA, provides a high-resolution record of land growth that facilitates the study of ancient settlement patterns in relation to delta evolution. We use stratigraphy and optically stimulated luminescence (OSL) dating to show that two Late Holocene earthen mounds were constructed several hundred years after the land emerged from open water. This multi-century pause allowed natural processes of overbank and crevasse splay deposition to elevate the land surface, reduce flood risk, and foster desirable environmental conditions prior to human occupation. These results are applied to obtain new age constraints for a large number of at-risk or lost archaeological sites with little-to-no absolute chronology. We use our findings to comment on prehistoric, contemporary, and future human-landscape interactions in the Mississippi Delta and other deltaic environments.
... Our coral data alone do not exclude the possibility of some smaller-scale (a few meters) or higher frequency variability in sea level, given the temporal and vertical resolution of this type of indicator; however, such oscillations are not apparent when combined with the non-coral data which have less vertical uncertainty (mean ± 0.8 m). Furthermore, studies by Törnqvist et al. (2004), Gonzalez & Törnqvist (2009), Milne & Peros (2013), and Khan et al. (2015 also found no evidence of sea-level oscillations or highstands with comparable magnitude or timing from the Gulf of Mexico. The smaller sea-level jump around ∼4.5 ka depicted in the Blanchon (2005) SLR occurs during an interval of coeval peat data that are offset in elevation; however, our coeval coral data agree better with the shallower peat trend, which suggest that no such jump occurred (Fig. 4B). ...
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The coral reefs and mangrove habitats of the south Florida region have long been used in sea-level studies for the western Atlantic because of their broad geographic extent and composition of sea-level tracking biota. The data from this region have been used to support several very different Holocene sea-level reconstructions (SLRs) over the years. However, many of these SLRs did not incorporate all available coral-based data, in part because detailed characterizations necessary for inclusion into sea-level databases were lacking. Here, we present an updated database comprised of 303 coral samples from published sources that we extensively characterized for the first time. The data were carefully screened by evaluating and ranking the visual taphonomic characteristics of every dated sample within the database, which resulted in the identification of 134 high-quality coral samples for consideration as suitable sea-level indicators. We show that our database largely agrees with the most recent SLR for south Florida over the last ∼7,000 years; however, the early Holocene remains poorly characterized because there are few high-quality data spanning this period. Suggestions to refine future Holocene SLRs in the region are provided including filling spatial and temporal data gaps of coral samples, particularly from the early Holocene, as well as constructing a more robust peat database to better constrain sea-level variability during the middle to late Holocene. Our database and taphonomic-ranking protocol provide a framework for researchers to evaluate data-selection criteria depending on the robustness of their sea-level models.