Recent Sedimentation Rates Research Articles

Estimating Recent Sedimentation Rates Using Lead-210 in Tropical Estuarine Systems: Case Study of Volta and Pra Estuaries in Ghana, West Africa

The Volta River and its basin form about one-third of Ghana's total land area and contributes significantly to the hydrological network of the country’s river system while River Pra basin is noted for large and small scale mining activities within it. Both river systems are important for sediment delivery for beach nourishment along Ghana’s coast. This work presents the first ever estimates of the sedimentation rates at the estuaries of these rivers using 40 cm long sediment cores. Sediment accumulation rates were estimated using the 210Pb sediment dating technique which is based on alpha and gamma emitting radionuclides. The total 210Pb concentration in the sediment was measured with an alpha spectrometer while the activities of supported 210Pb and 137Cs were measured with a gamma spectrometer with high germanium n-type detector. The unsupported 210Pb was determined by subtraction of the supported from the total at each core sediment level. Irregularities in the 210Pb activity versus depth profile, indicated variation in the net sedimentation accumulation rate during the past 96 and 182 years at the Volta and Pra estuaries, respectively. From the CRS model calculations, sedimentation rates varied markedly before (1.1 gcm-2y-1) and after (0.5 gcm-2y-1) construction of the Akosombo dam resulting in about 50% drop in sedimentation rate at the Volta estuary. Sediment accumulation rates were relatively low at the Pra estuary compared to the Volta estuary. Depositional fluxes of 210Pb were 190.1 ± 15.9 Bqcm-1y-1 and 217.8 ± 11.8 Bqcm-1y-1 in Pra and Volta estuaries respectively. 137Cs profile did not show defined peaks. However, the ages and sedimentation rates were better explained using historical events and anthropogenic activities that occurred within the catchment areas, providing a better understanding of deficit in sediment budget caused by hydric erosion processes prevailing in the Ada and Keta beaches in Ghana, due to reduction of sediment input from the Volta estuary.

Aquatic effects of peat extraction and peatland forest drainage: a comparative sediment study of two adjacent lakes in Central Finland

The aquatic effects of forestry practices and peat extraction continue to cause serious concerns. The effect mechanisms of peat extraction on water quality and aquatic ecology of the receiving surface waters are well known, but the impacts are often difficult to differentiate from those of forest management. A pairwise temporal sediment study was conducted on two adjacent lakes in Central Finland to study whether the unique effects of peat extraction can be detected in an area of intensive forest drainage. Both lakes are affected by forestry, but the reference lake has no history of peat extraction in its watershed. The deepest parts of the lakes were cored through the lacustrine sediments, and the recent carbon and dry matter sedimentation rates were compared to their site-specific reference values. Recent changes in benthic macroinvertebrates (chironomids) and diatom algae were studied to assess the ecological effects of these practices in the lakes. No significant differences in recent increases in carbon accumulation were found between the peat extraction-impacted lake and the reference lake. The pairwise comparison allowed identification of a regional pattern of impacts that is closely related to the history of land use, particularly forestry, in the region. The approach also allowed identification of the transient signs of peat extraction in the chemical and chironomid records of the impacted lake. The recent changes in chironomids and diatoms suggest eutrophication and deterioration in benthic conditions likely caused by drainage ditch network maintenance activities in the catchments.

Reconstruction of the conditions of Late Holocene sedimentation by integrated analysis of a core of the bottom sediments from the Chukchi Sea

Integrated studies were performed on bottom sediments collected in the Chukchi Sea in the northern part of the Gerald Canyon 150 km northeast from Wrangel Island. The recent sedimentation rate amounted to 0.9 mm/year by 210Pb at the sampling site. The concentrations of biogenic components (SiO2bio, Сorg, Ntot, and Br) were minimum at the lower part of the core, where an increase of Thalassiosira antarctica antarctica, probably results from low biological productivity during the Maunder Minimum. The increased concentrations of biogenic components, as well as the decreased values of magnetic susceptibility and X-ray density, in the upper part of the core (1–2 cm) correspond to the last decade of recent of global warming.

Recent sedimentation rates in the Caravelas estuary (Bahia, Brazil) using unsupported 210Pb and 137Cs modeling

Abstract The Caravelas estuary is located in a zone of the Brazilian coast (Southern Bahia State) which has been submitted to different kinds of land uses during the last 50 years. This zone has an important ecological role, due to its mangroves and its location next to Abrolhos coral reef, the most important in the Southern Atlantic Ocean. 210Pb and 137Cs dating methods, accompanied by a sedimentological study, were applied to sediment cores in order to establish sedimentation rates and identify historical trends of land use and erosive processes. Sedimentation rates were established according to the “Constant Rate of Supply” (CRS) 210Pb dating model, which was preferred rather than the “Constant Initial Concentration” (CIC) model. Corrected sedimentation rates obtained from 210Pb dating were corroborated through a second independent radionuclide tracer such as 137Cs. The sedimentation rates obtained according to the CRS model for the cores were 1.07 ± 0.13 cm yr –1 for T#2 (inner sector), 0.65 ± 0.06 cm yr –1 for T#5 and 0.85 ± 0.09 cm yr –1 for T#8 (outer sector). The difference in sedimentation rates among the sampling sites could be due to hydrodynamic processes and could be related to the tendency of increase of erosive processes, conditioned by the changes in the landscape and land use to, which this region has been submitted.

Influence of lake basin morphology on recent sedimentation rates based on the example of Lake Raduńskie Górne, N Poland

Abstract The study relates to the use of the 210Pb method for determining sedimentation rates, sedimentation accumulation rates and identifying post-depositional processes. The analysis was based on seven cores of recent sediments collected from different parts of Lake Raduńskie Górne, which is a typical channel lake with diverse bottom morphology. We used alpha spectrometry to determine 210Pb activities in sediment samples and a CF:CS dating model to obtain mean sediment accumulation rates. The results show significant differences between coring sites with highest values in the deepest part of the lake and lowest within the shallow and flat bottom areas. The reason for such a large diversity is the lake basin morphology, e.g. steep slopes and complex configuration of the lake bottom, most probably responsible for the post-depositional sediment replacements.

Sediment dynamics and heavy metal pollution history of the Cruhlig Lake (Danube Delta, Romania)

This is the first study reporting recent sedimentation rates data (e.g. the past 120–150 years) for the Cruhlig Lake situated in the Danube Delta. The aim of this study is to analyse the recent sedimentation rates using the 210Pb dating method and identifying the heavy metal pollutants and their variability in time. Five sediment cores were taken with a gravity corer and – after drying the sliced samples–physical parameters, organic material and inorganic carbon content were determined. The total 210Pb content was measured via 210Po by alpha spectrometry, while supported 210Pb was measured by 226Ra (trough short life 222Rn daughters) with HPGe detectors. Heavy metals were determined by ICP-MS; from the 64 measured elements, only exceeding values of Al, As, Cd, Co, Cs, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Ni, Pb and Zn are discussed. After applying the CRS model, ages and sedimentation rates were calculated. The average sedimentation rate of the Cruhlig Lake is 0.21 ± 0.02 g/cm2y, Minimum values (0.05 ± 0.003 g/cm2y) are registered along the eastern shoreline of the lake before 1913, while maximum values are recorded due to the flooding in 2006 in the western side (1.34 ± 0.12 g/cm2y). Recent sedimentation rates divide the lake into three areas: the secluded eastern near shore part (0.63 ± 0.07 g/cm2y), the centre of the lake (0.92 ± 0.05 g/cm2y) and the dynamic western area, where most sediment transport takes place (1.13 ± 0.01 g/cm2y). The sedimentation pattern proves this lake to be very sensitive to fluvial discharge fluctuations. The building of the Iron Gate dams (1972 and 1985) had a negative impact on the sedimentation decreasing it with 58.74%, while after 1989 these values grew 2.25 times. The lake received a quantity of sediment rich in heavy metals in 1992 ± 3 y, which settled mostly on the eastern part. Values for Cd, Co, Cr, Hg, Pb and Zn are up to five times higher in 1980 ± 5 y in the eastern part of the lake, while Cd, Co, Cr and Ni are twice as high as the values measured for the marine substrate. Values of As show increasing of up to 150% in 2006 ± 2 y throughout the whole surface of the lake.

Biogeochemical evidence of eutrophication and metal contamination of Frame Lake, City of Yellowknife, Northwest Territories, Canada

The sediments of Frame Lake, Yellowknife, NWT were examined to evaluate human impact due to urbanization and mining and provide background information for potential remediation efforts. Physical and geochemical analyses were carried out on cores from two sites targeting the lake’s deep basins. Pb-210 analysis was used to establish chronological control and determine recent sedimentation rates. Frame Lake contains sediments spanning the whole of the Holocene from the time of deglaciation to the present. With the development of the city and increasing human population over the last ~80 years Frame Lake has become increasingly eutrophic. The source of nutrient loading is generalized and probably not exceptionally high; however, due to its limited depth, extensive winter ice cover and low turnover rates, the lake appears to be sensitive to the resulting biological oxygen demand. Frame Lake sediments were found to contain elevated concentrations of metals attributable to gasoline combustion (Pb), mining and ore processing (e.g. As, Cu) and other sources (Zn). While most of these elements peak below the sediment surface and contamination has decreased in recent years, concentrations remain above levels recommended for the protection of aquatic life. It is apparent that contaminants previously deposited within the catchment are still supplying the lake and in the case of As, that post-depositional translocation within the sediments is taking place.

Holocene paleoclimate history of Fallen Leaf Lake, CA., from geochemistry and sedimentology of well-dated sediment cores

Millennial-scale shifts in aridity patterns have been documented during the Holocene in the western United States, yet the precise timing, severity, and regional extent of these shifts prompts further study. We present lake sediment core data from Fallen Leaf Lake, a subalpine system at the southern end of the Lake Tahoe basin for which 80% of the contemporary inflow is derived from snowpack delivered by Pacific frontal storm systems. A high quality age model has been constructed using 14C ages on plant macrofossils, 210Pb, and the Tsoyowata tephra datum (7.74–7.95 cal kyr BP). One core captures the transition from the Late Tioga-younger Dryas glaciolacustrine package to laminated opaline clay at 11.48 cal kyr BP. Early Holocene sedimentation rates are relatively high (∼1.9 mm/year) and cooler winter temperatures are inferred by the presence of pebbles interpreted to be transported out into the lake via shore ice. There is a geochemically distinct interval from ∼4.71 to 3.65 cal kyr BP that is interpreted as a late Holocene neopluvial, characterized by depleted δ13C and lower C:N that point to reduced runoff of terrigenous organic matter, increased winter precipitation, and increased algal productivity. The largest Holocene signal in the cores occurs at the end of the neopluvial, at 3.65 cal kyr BP, and marks a shift into a climate state with variable precipitation, yet is overall more arid than the neopluvial. This new climate state persists for ∼3 ka, until the Little Ice Age. Low sedimentation rates (0.5 mm/year), the homogeneous opaline sediment, and steadily increasing contributions of terrestrial vs. algal organic matter in these cores suggest that the lowstand state of Fallen Leaf Lake may have been the norm from 3.65 to 0.55 cal kyr BP, punctuated by short term high precipitation years or multi-year intervals capable of rapid short duration lake level rise. Fallen Leaf Lake is strongly influenced by changes in winter precipitation and temperature, manifested largely by the geochemical proxies, and highlights unique advantages of subalpine lakes in regional paleoclimate reconstructions.

Variability of the 14 C reservoir effects in Lake Tangra Yumco, Central Tibet (China), determined from recent sedimentation rates and dating of plant fossils

Abstract Sediments from lakes provide one of the most important archives for past environmental changes on the Tibetan Plateau. The recent sedimentation rate of modern lakes is widely used as an independent method to calibrate 14 C-derived chronologies because 14 C values are often affected by a reservoir effect. Terrestrial plant residues in lake sediments are believed to be the ideal material for 14 C dating because they normally provide the true ages of the sediments. In this study, we present the spatial and temporal variations in modern sedimentation rates over the past ∼150 years and evaluate the reservoir effects of 14 C ages determined from bulk sediments and plant residues from Lake Tangra Yumco on the central Tibetan Plateau. The results show that ages determined from plant residues are systematically younger than those of the bulk sediments. However, the reservoir effects associated with the bulk sediments are much more constant than those of the plant residues, highlighting the complicated composition of these macro-remains and the fact that they might not be the best dating materials in Tangra Yumco, especially in southern part. A similar reservoir effect of ∼2200 years is observed in the southern and northern parts of Tangra Yumco, based on the dating of modern surface sediments and aquatic plants. This study demonstrates the complexity of the reservoir effect in a closed lake on the Tibetan Plateau, and careful consideration must be paid to the use of different approaches to date different materials in order to establish a reliable chronology.

Holocene and Late Glacial sedimentation near steep slopes in southern Lake Baikal

<p>We here present new data on sedimentation at and near the steep north-slopes of southern Lake Baikal. Short sediment cores were taken at 550 m and at 1366 m water depth, within 3600 m offshore Cape Ivanovskii at the station of the <em>Baikal Deep Underwater NEUTRINO</em> <em>Telescope</em>. The sediments within 3600 m off the northern coast of Southern Lake Baikal are dominated by pelagic deposition. Our data reveal surprisingly little influence from terrigenous material from adjacent coastal areas, tributaries and their catchment. At the shallow-water site (at 550 m water depth, 700 m off shore) just 27 cm thick homogenous sediments have accumulated during the Holocene on top of Pleistocene deposits resulting in Holocene sedimentation rates of 0.003 cm a<sup>-1</sup>. The very low rates are caused by long-term persistent winnowing of fine particles caused by week contour currents along the slope. The uppermost sediments are oxidized down to 22 cm. Very low concentrations of C<sub>org</sub>, Si<sub>bio</sub> and N<sub>tot</sub> in Pleistocene sediments increase dramatically within the Holocene. The heavy mineral fraction of the shallow-water sediments contains up to 33.6 % olivine and up to 2.4 % spinel. These rare minerals originate from white marbles of the nearby coastal outcrop <em>Belaya Vyemka</em> of the Early Precambrian <em>Sharyzalgaiskaya</em> <em>Series</em>. At the deep-water site (at 1366 m water depth, 3600 m off shore) Holocene sedimentation rates are 10-times higher (0.036 cm a<sup>-1</sup>). Sediment oxidation occurs just within the uppermost 2 cm. Of the two rare type minerals of the <em>Sharyzalgaiskaya</em> <em>Series</em> spinel does not occur at all and olivine is represented by very diminished concentrations. This indicates insignificant influx of terrestrial material from the nearby shore to the deep-water site . Distal turbidites of far-off sources are intercalated to pelagic sediments at the deep-water site. Breakdown events of deltas at the SE- and S-coast of the basin are suggested to be responsible for the formation of the turbidites. They contain terrestrial (deltaic) material, low amounts of biological material (diatoms, spiculae, chrysophyte cysts), low concentrations of Si<sub>bio</sub>, C<sub>org </sub>and N<sub>tot</sub> and occur at approximate recurrence rates of 300 years. </p>

Using fallout radionuclides to investigate recent overbank sedimentation rates on river floodplains: an overview

Abstract. Information on rates of overbank sedimentation on river floodplains is needed for a variety of purposes. Use of 137Cs and 210Pbex measurements provides an effective means of estimating medium-term floodplain sedimentation rates and that approach has now been successfully used in many areas of the world. This contribution reviews the use of 137Cs and 210Pbex measurements in floodplain sedimentation investigations and discusses some of the important sampling requirements and key issues associated with interpreting the measurements, and subsequently deriving reliable estimates of sedimentation rates. The potential use of other radionuclides, including 241Am, 238,239+240Pu, and 7Be is considered, and the advantages of using two or more radionuclides, in combination, is highlighted.

Statistical validation of the model of diffusion-convection (MDC) of 137Cs for the assessment of recent sedimentation rates in coastal systems

This study aimed the validation of the model of diffusion-convection (MDC) of 137 Cs for the calculation of recent sedimentation rates in 13 sedimentary cores of two Brazilian coastal systems, the Cananeia-Iguape and Santos- Sao Vicente estuarine systems. The MDC covers key fac- tors responsible for 137 Cs vertical migration in sediments: its diffusion to the interstitial water and the vertical con- vection of this water through the sediments. This study successfully validated the MDC use to determine sedi- mentation rates, which was statistically validated not only with 210 Pbxs (unsupported 210 Pb) models, widely used in oceanographic studies, but also by literature values for those regions.

Radionuclides and recent sedimentation and mixing rates in Northern Gulf of Eilat/Aqaba, Red Sea

Natural radionuclides and man-made 137Cs were analyzed in five short sediment cores taken in northern part of the Gulf of Eilat (Gulf of Aqaba) in order to provide information on sedimentation and mixing rates and sediment sources. The maximum estimates of sedimentation rates based on excess 210Pb were found to vary between 0.105±0.020 and 0.35±0.23cm·year−1. Even the lowest estimates are significantly higher than those expected from dust deposition, suggesting other sources and processes being responsible for most of the allochthonous material accumulation, including periodical floods following heavy rain events, internal erosion or triggers, like earthquakes. In 137Cs depth profiles no 1963 related nuclear weapon test maxima were found; instead, the activities decrease monotonically, suggesting that a major process leading to radionuclides' depth distribution might be mixing. The mixing rates calculated from 137Cs, excess 210Pb and excess 228Th reach values up to 2.18±0.69cm2·year−1.

Bottom topography, recent sedimentation and water volume of the Cerro Prieto Dam, NE Mexico

The Cerro Prieto dam, a relatively small water reservoir in NE Mexico, is one of the main resources of potable water for Monterrey, a city with a population of about fourmillion inhabitants. A high resolution seismic study using non-linear parametric sub-bottom echo-sounder SES-2000 was carried out in this water reservoir. High resolution acoustic data interpretation shows that the thickness of recent sediments due to siltation of the reservoir reaches 3.5-4.0m. It shows a high recent sedimentation rate (1-2 up to 14cm/ year). Based on the echo-sounder data, the first bathymetric map and a digital model of recent sediment thickness were designed. A significant (5-12%) difference between the volume capacity value used by National Commission of Water (CNA) and acoustic survey results was revealed. Differences between the CNA and acoustic data indicate storage losses from 12-17 up to 30million cubic meters. The results obtained through study such as this one, could be useful to improve a water resources management.

The Glacial–Interglacial transition and Holocene environmental changes in sediments from the Gulf of Taranto, central Mediterranean

An extensive, high-resolution, sedimentological–geochemical survey was done using geo-acoustics, XRF-core scans, ICP-AES, AMS 14 C-dating and grain size analyses of sediments in 11 cores from the Gulf of Taranto, the southern Adriatic Sea, and the central Ionian Sea spanning the last 16 cal. ka BP. Comparable results were obtained for cores from the Gallipoli Shelf (eastern Gulf of Taranto), and the southern Adriatic Sea suggesting that the dominant provenance of Gallipoli Shelf sediments is from the western Adriatic mud belt. The 210 Pb and 14 C-dated high-accumulation-rate sediments permit a detailed reconstruction of climate variability over the last 16 cal. ka BP. Although, the Glacial–Interglacial transition is generally dry and stable these conditions are interrupted by two phases of increased detrital input during the Bølling–Allerød and the late Younger Dryas. The event during the Younger Dryas period is characterized by increased sediment inputs from southern Italian sources. This suggests that run-off was higher in southern- compared to northern Italy. At approximately ~ 7 cal. ka BP, increased detrital input from the Adriatic mud belt, related to sea level rise and the onset of deep water formation in the Adriatic Sea, is observed and is coincident with the end of sapropel S1 formation in the southern Adriatic Sea. During the mid-to-late Holocene we observed millennial-scale events of increased detrital input, e.g. during the Roman Humid Period, and of decreased detrital input, e.g., Medieval Warm Period. These dry/wet spells are consistent with variability in the North Atlantic Oscillation (NAO). A negative state of the NAO and thus a more advanced penetration of the westerlies into the central Mediterranean, that result in wet conditions in the research area concord with events of high detrital input e.g., during the Roman Humid Period. In contrast, a positive state of the NAO, resulting in dry conditions in the Mediterranean, dominated during events of rapid climate change such as the Medieval Warm Period and the Bronze Age. • A sedimentological–geochemical, basin-wide survey in the Gulf of Taranto • High Holocene sedimentation rates (~ 0.5 mm/yr) • A humid Younger Dryas in southern Italy, in contrast with northern Italy • Millennial-scale events of increased detrital input (e.g., Roman Humid Period) • Dry/wet spells reflecting the North Atlantic Oscillation (NAO)

Radioanalytical assessment of sedimentation rates in Guajará Bay (Amazon Estuary, N Brazil): a study with unsupported 210Pb and 137Cs modeling

Guajara Bay is an integral part of the Amazon Estuary system, and functions as the main receiver of urban and industrial wastes from the city of Belem, capital city of PA State (N Brazil). There is a lack of knowledge regarding quantitative measures of sedimentation, such as sedimentation rates, in the literature for this area of the Amazon Estuary. This study aimed the evaluation of recent (time range of 100 years) sedimentation rates in three sediment profiles collected in the coastal system of Guajara Bay with a radioanalytical approach of unsupported 210Pb and 137Cs modeling. The mean sedimentation rates for the cores obtained were 0.85 ± 0.12 cm year−1 for Anadim core, 1.02 ± 0.17 cm year−1 for Outeiro core and 0.53 ± 0.04 cm year−1 for Tucunduba core. With the use of three models of sedimentation rate models, it was observed that Anadim and Outeiro core presented constant sedimentation rates for the evaluated time range, but Tucunduba did not. This difference in sedimentation rates was probably due to their different sampling locations that present diverse hydrodynamic regime, with deposition of fine sediments in the upper area of the bay and stronger fluvial currents in the southernmost region.

Modern sea surface productivity and temperature estimations off Chile as detected by coccolith accumulation rates

Recent coccoliths from 74 surface sediment samples recovered from the southeastern Pacific off Chile were examined quantitatively to investigate modern regional gradients of sea surface productivity and temperature. All findings are based on coccolith accumulation rates. Therefore an approach was designed to estimate recent sedimentation rates based on 210Pb and bulk chemistry analyses of the same set of surface samples. Highest total coccolith accumulation rates were found off north-central Chile, where seasonal upwelling takes place. Based on a multiple linear regression between calculated coccolith accumulation rates and World Ocean Atlas derived sea surface temperatures, a calibration model to reconstruct annual average temperatures of the uppermost 75m of the water column is provided. The model was cross-validated and the SST estimates were compared with SST observed and SST estimates based on diatoms and planktonic foraminifera, showing a good correlation.

Trace metals and organic carbon in sediments of the northeastern Chukchi Sea

Concentrations of Al, Fe and selected trace metals (As, Ba, Be, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Sn, V, Zn) in surface sediments from the northeastern Chukchi Sea (NECS) varied considerably as a function of sediment texture (i.e., grain size); however, essentially all metals, when normalized to Al, were present at natural, background values. Total organic carbon content ranged from 0.06–1.56% with a marine origin for at least two-thirds of the organic matter at each station based on δ13C values and C/N ratios. Recent sedimentation rates from 137Cs and 210Pb dating were 0.03–0.14cmyr−1. Corresponding vertical distributions for most metals in age-dated sediment cores showed >100-yr records of uniform metal/Al ratios, including Pb and Hg. Concentrations of As, Mn and Cd were modified in surface sediments at a few stations by early chemical diagenesis. Surveys around two exploratory oil and gas drilling sites that were occupied in 1989 showed that Ba concentrations were as high as 10,000µgg−1 within 200m of one drilling site relative to background values of ~700µgg−1. Barium enrichment was from barite, a drilling mud additive that was discharged to the seafloor. Above background concentrations of Cu, Hg, Pb and Zn also were found in sediments from 3–4 stations within 200m of the two drilling sites. At present, sediments in the NECS are essentially pristine with respect to trace metals of anthropogenic origin, excluding small areas around drilling sites. These data should be of value for detecting and tracking future chemical changes in the sediments of the NECS, particularly in light of planned oil and gas exploration and production as well as environmental changes that may be associated with climate change.

Recent sedimentation rates in Garaet El Ichkeul Lake, NW Tunisia, as affected by the construction of dams and a regulatory sluice

Purpose Ichkeul National Park, NW Tunisia, is a UNESCO Biosphere Reserve. Garaet El Ichkeul Lake is known for its seasonal variability in water level and salinity. In recent decades, the waterbody has been affected by the construction of new hydraulic structures. To reduce the impacts of dams and to maintain the sustainability of the ecosystem, a sluice was built at the outlet of the lake, and it operated for the first time in 1996. This paper describes an investigation of recent sedimentation dynamics in Ichkeul Lake, determined by radiometric dating of sediment cores.

Could bulk density profiles provide information about recent sedimentation rates?

Independent validation has to be an integral part of the 210Pb-based radiometric dating of recent sediments. The combined use of artificial fallout radionuclides leads to serious problems because only the identification of peaks and their use as time-marks is not sufficiently rigorous to ensure the accuracy of dates. Quantitative modelling of depth profiles requires reliable input functions, which can be substantially different from the atmospheric deposition records. The appropriate treatment of compaction is another source of complexity. Continuum mechanics provide a suitable framework to understand compaction in sedimentary basins with length scales of several km. Nevertheless, early compaction (with length scales of few cm at the sediment surface) takes place under hydrostatic equilibrium conditions, and it can be better understood as a transport phenomenon: a mass flow governed by spatial gradients of a compaction-potential energy, involving a conductivity function. This paper explores some analytical and numerical solutions for these equations to provide insight about the early compaction phenomenon. Given a conductivity function and a constant sedimentation rate, the system will evolve towards a steady-state profile for bulk density. The fingerprint of variable sedimentation rates, among other changes in environmental conditions, will be studied with numerical solutions. Finally, the paper explores the use of bulk density profiles for deriving information on recent sedimentation rates, which could provide independent support for the radiometric dating models.