A geoarchaeological perspective on the challenges and trajectories of Mississippi Delta communities

Chamberlain, E. L.; Mehta, Jayur Madhusudan; Reimann, Tony; Wallinga, Jakob

doi:10.1016/j.geomorph.2020.107132

Cited by 11 publications

(9 citation statements)

References 49 publications

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“…Considering the HIME-derived sedimentation results in terms of net change in elevation instead of terms of mass deposition, the HIME method allowed this study to estimate an average total WLD aggradation of about 0.125 m over about 21 years (1993-2013), which equates to an average net rate of 0.6 cm/yr. This was remarkably close to the rate of 0.7 cm/yr derived by Chamberlain et al (2020) for the Lafourche subdelta [107]. The difference is that the Lafourche subdelta aggradation was averaged (sustained) over centennial to millennial timescales, consisted of sand/sandy loam mouth bar deposits overlain by silty clay loam overbank deposits [40], and was of more considerable thickness, with likely important compaction and subsidence.…”

Section: Eco-geomorpohological Insights From Hindcast Delta Topographysupporting

confidence: 87%

Short-Term Ecogeomorphic Evolution of a Fluvial Delta from Hindcasting Intertidal Marsh-Top Elevations (HIME)

Smith¹,

Moffett

Mohrig

2020

Remote Sensing

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Understanding how delta islands grow and change at contemporary, interannual timescales remains a key scientific goal and societal need, but the high-resolution, high frequency morphodynamic data that would be most useful for this are as yet logistically prohibitive. The recorded water levels needed for relative elevation analysis are also often lacking. This paper presents a new approach for hindcasting intertidal marsh-top elevations (HIME) to resolve ecogeomorphic change, even in a young, rapidly changing fluvial delta setting, at sub-decadal temporal resolution and at the spatial resolution of widely available optical remote sensing imagery (e.g., 30 m Landsat). The HIME method first calculates: (i) the probability of land exposure in a set of historical imagery from a user-defined discrete timespan (e.g., months or years); (ii) the probability of water level non-exceedance from water level records, which need not be complete nor coincident with the imagery; and (iii) the systematic variation in local mean water level with distance along the primary hydraulic gradient. The HIME method then combines these inputs to estimate a marsh-top elevation map for each historical timespan of interest. The method was developed, validated, applied, and results analyzed to investigate time-lapse evolution of the Wax Lake Delta in Louisiana, USA, every three years, over two decades (1993–2013). The hindcast maps of delta island extents and elevations evidenced ecogeomorphic system self-organization around four stable attractors, or elevation platforms, at about −0.3 m (subtidal), 0.2 m, 0.4 m, and 0.9 m (supratidal) NAVD88. The HIME results also yielded a time series of net subaerial sediment accumulation, and specific locations and magnitudes of gains and losses, at scales from 30 m to delta-wide (~100 km3) and 6 to 21 years. Average subaerial net sediment accumulation at the Wax Lake Delta (WLD) was estimated as 0.6 cm/yr during the study period. Finally, multiple linear regression models were successfully trained on the HIME elevation maps to model evolving delta island morphologies based on simple geometric factors, such as distance down-delta and position on a delta island; the models also successfully reproduced an average delta topset slope of 1.4 cm. Overall, this study’s development and application of the HIME method added detailed insights to recent, transient ecogeomorphological change at the WLD, and demonstrated the potential of the new approach for accurately reconstructing past intertidal topographies and dynamic change.

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Section: Eco-geomorpohological Insights From Hindcast Delta Topographysupporting

confidence: 87%

Short-Term Ecogeomorphic Evolution of a Fluvial Delta from Hindcasting Intertidal Marsh-Top Elevations (HIME)

Smith¹,

Moffett

Mohrig

2020

Remote Sensing

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“…Consequently, in terms of the soil formation process, cerritos are a combination of the typical midden mounds, burial mounds, and platform mounds from the Americas (e.g., Chamberlain et al, 2020; Howard, 2017; Schmidt, 2013; Sherwood & Kidder, 2011). Thus, the soil classification of Pampean earthen mounds is difficult.…”

Section: Resultsmentioning

confidence: 99%

Geoarchaeological signatures of anthropogenic soils in southeastern Uruguay: Approaches to formation processes and spatial–temporal variability

et al. 2021

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This contribution focuses on the interpretation of earthen mound formation processes in the lowlands of the Pampa biome, southeastern Uruguay, through the integrated analysis of sedimentological and archaeological data. The three analyzed mounds from the La Tapera site have different heights and radiocarbon chronologies, indicating different construction periods across the last 4000 years. In addition, soils from surrounding plains were analyzed to provide a comparative basis for geoarchaeological characterization. From granulometric, compositional, and geochemical results, we identified different soil classes and several anthropogenic layers inside the earthen structures. Mound soils stood out from the rest due to higher levels of P, soil organic matter (SOM), and micro‐artifact content, leading to their classification as hortic Anthroportic Udorthent soils or hortic‐cultural cumulic archaeo‐anthrosols. Geoarchaeological differences between mounds are inferred as variations in the formation processes and/or construction technologies, possibly related to the functionality and height of the structures. Evidence from this contribution demonstrated the existence of ancient ways to produce nutrient‐rich long‐lasting anthropogenic soils that left persistent geoarchaeological signatures on the landscape. These findings highlight the need to broaden the discussion, culturally and geographically, about the genesis and development of management practices and associated indigenous knowledge to include the lowlands of southeastern South America.

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“…Three sites exhibit anthropogenic modification of the overbank deposits. The Dulac transect features an ∼800 year old prehistoric earthen mound that appears to have enhanced subsidence of the underlying deposits (Chamberlain, Mehta, Reimann, & Wallinga, 2020), and the Cocodrie transect features ∼20 cm of historic construction fill; no correction was made for this because the anthropogenic sediments were consolidated and have contributed to subsidence for decades to centuries. The Fourchon transect is in a region that has been actively elevated by dredge spoil pumping and features ∼0.7–1.4 m of soft unconsolidated mud slurry overlying the overbank deposits at the time of coring; Google Earth imagery shows that the slurry was added within one year prior to our sampling.…”

Section: Methods and Study Areamentioning

confidence: 99%

“…The overbank unit is thickest at the bayhead delta apex and thins seaward (Figures 2a and 4) due to a shorter sedimentation time, that is, the time between the emergence of the mouth bar and the abandonment of the Lafourche subdelta at 0.6 ka (Chamberlain et al, 2018). Overbank deposits accumulated at an average rate of 0.7 cm/yr over the lifespan of the bayhead delta (Chamberlain, Mehta, Reimann, & Wallinga, 2020) and range in thickness from about 1-8 m at the sites studied herein (Table 1). These rates were determined from present-day (compacted) overbank-deposit thicknesses.…”

Section: Stratigraphic Tectonic and Other Factorsmentioning

confidence: 99%

Does Load‐Induced Shallow Subsidence Inhibit Delta Growth?

et al. 2021

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Despite a reduction in the sediment flux from continents to oceans on a global scale (Syvitski et al., 2005), many river deltas have continued to grow in recent decades (Nienhuis et al., 2020). However, it is unlikely that this growth can be sustained under future scenarios of relative sea-level rise (RSLR), in part due to the commonly high subsidence rates in deltas. RSLR is a major threat to the sustainability of these ecologically, economically, and culturally significant regions (e.g.

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A geoarchaeological perspective on the challenges and trajectories of Mississippi Delta communities

Cited by 11 publications

References 49 publications

Short-Term Ecogeomorphic Evolution of a Fluvial Delta from Hindcasting Intertidal Marsh-Top Elevations (HIME)

Short-Term Ecogeomorphic Evolution of a Fluvial Delta from Hindcasting Intertidal Marsh-Top Elevations (HIME)

Geoarchaeological signatures of anthropogenic soils in southeastern Uruguay: Approaches to formation processes and spatial–temporal variability

Does Load‐Induced Shallow Subsidence Inhibit Delta Growth?

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