Understanding late Holocene to present relative sea-level changes at centennial or sub-centennial scales requires geological records that dovetail with the instrumental era. Salt marsh sediments are ...one of the most reliable geological tide gauges.
In this paper we review the methodological and technical advances that promoted research on ‘high resolution’ late Holocene sea-level change. We work through an example to demonstrate different pathways to quantitative reconstructions of relative sea level based on salt marsh sediments. We demonstrate that any reconstruction is in part a result of the environment from which the record is taken, the modern dataset used to calibrate the fossil changes, statistical assumptions behind calibrating microfossil assemblages and choices made by the researchers. With the error term of typical transfer function models ~10–15% of the tidal range, micro-tidal environments should produce the most precise sea-level reconstructions. Sampled elevation range of the modern dataset also has a strong influence on model predictive ability. Model-specific errors may under represent total uncertainty which comes from field practices, sedimentary environment, palaeo-tidal changes and sediment compaction as well as statistical uncertainties. Geological tide gauges require a detailed chronology but we must be certain that apparent relative sea-level fluctuations are not simply a consequence of an age–depth model.
We make six suggestions to aid the development and interpretation of geological tide gauge records.
The threat hunting lifecycle is a complex atmosphere that requires special attention from professionals to maintain security. This paper is a collection of recent work that gives a holistic view of ...the threat hunting ecosystem, identifies challenges, and discusses the future with the integration of artificial intelligence (AI). We specifically establish a life cycle and ecosystem for privacy-threat hunting in addition to identifying the related challenges. We also discovered how critical the use of AI is in threat hunting. This work paves the way for future work in this area as it provides the foundational knowledge to make meaningful advancements for threat hunting.
The Albemarle Embayment, a Cenozoic depositional basin on the Atlantic coast of the USA, is an ideal setting to understand the temporal and spatial variation of eustatic sea-level fluctuations, ...glacio-hydro-isostasy, tectonics, subsidence, environments and sedimentation patterns of a passive margin Quaternary section. A NE–SW transect of cores and seismic data in the southern Albemarle Embayment were analyzed using micropaleontologic (foraminifera, diatoms, pollen), sedimentologic, stratigraphic, and geochronologic data to reconstruct the paleoenvironmental evolution and paleoclimates in the nearly 90m thick Quaternary section. The study area is a very low gradient Quaternary landscape that is cross-cut by several Pleistocene incised valleys; a Holocene barrier island complex forms its eastern margin. In the subsurface, the Albemarle Embayment is bordered to the north by the Norfolk Arch and to the south by the depositionally-constructed Cape Lookout High, which is positioned on the northern flank of the structural Carolina Platform.
The Quaternary section overlies mid-Pliocene carbonates in three cores; the contact rises in elevation towards the Cape Lookout High. Fossils and sediment characteristics suggest a subtropical, shallow, high energy marine environment during the Pliocene. Overlying units include incomplete Pleistocene, clastic, transgressive-regressive (T-R) deposits. These have similar ages and stratigraphic signatures as the T-R cycles in the central and north-central Albemarle Embayment, although mid-Pleistocene deposits may be older in the southern region. The bulk of the early and mid-Pleistocene record consists of inner to mid-shelf sand and muddy sand. In contrast, late Pleistocene sands are of inner shelf origin, reflecting the infilling of the basin. Lowstand paleovalleys, with fluvial, wetland and estuarine fill, dissect the early, mid- and late Pleistocene marine units; their locations reflect antecedent topography. Holocene sediments were deposited in shoreface and barrier island environments. Quaternary foraminiferal assemblages in the southern Albemarle Embayment exhibit greater species richness than those in the central and north-central embayment reflecting the presence of a major biogeographic boundary at the same location as the modern biogeographic boundary at Cape Hatteras.
•Foraminifera, diatoms and pollen as paleoenvironmental indicators•Pliocene subtropical high energy, shallow shelf carbonates in the southern Albemarle Embayment•Pleistocene sediments represent incompletely preserved transgressive-regressive cycles.•Pleistocene terrestrial and marginal marine deposits occur only in lowstand paleovalleys.•The late Pleistocene record is thin due to a lack of accommodation space near the Cape Lookout High.
We examined the use of delta super(13)C, TOC and C/N geochemistry of sedimentary organic matter to reconstruct former sea levels and paleoenvironments in the absence of suitable microfossil data. The ...modern distribution of delta super(13)C, TOC and C/N of 33 vegetation and 74 surface sediment samples collected from four coastal wetlands in the Thames Estuary and Norfolk, UK are described. The delta super(13)C, TOC and C/N geochemistry of sediments varied in relation to the input of in situ vascular vegetation versus allochthonous particulate organic matter and algae, which was controlled primarily by tidal inundation. We reviewed published and unpublished studies to produce an English database of vegetation (n=257) and sediment (n=132) delta super(13)C, TOC and C/N geochemistry. Four elevation-dependent environments in the database had statistically distinct delta super(13)C, TOC and C/N values: (1) tidal flat/low marsh ( delta super(13)C: -24.9 plus or minus 1.2ppt; TOC: 3.6 plus or minus 1.7%; C/N: 9.9 plus or minus 0.8); (2) middle marsh/high ( delta super(13)C: -26.2 plus or minus 1.0ppt; TOC: 9.8 plus or minus 6.7%; C/N: 12.1 plus or minus 1.8); (3) reed swamp ( delta super(13)C: -27.9 plus or minus 0.7ppt: TOC: 36.5 plus or minus 11.5%; C/N: 13.9 plus or minus 1.2); and (4) fen carr ( delta super(13)C: -29.0 plus or minus 0.6ppt; TOC: 41.6 plus or minus 5.7%; C/N: 17.4 plus or minus 3.1). The delta super(13)C, TOC and C/N geochemistry database was applied to a Holocene sediment core collected from the Thames Estuary to produce three new sea-level index points and one limiting date, illustrating the utility of delta super(13)C, TOC and C/N values to reconstruct Holocene relative sea levels.
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