Beach Ridges Research Articles

The Accretional Beach Ridge System of Tongoy Bay: An Example of a Regressive Barrier Developed in the Semiarid Region of Chile

The Accretional Beach Ridge System of Tongoy Bay: An Example of a Regressive Barrier Developed in the Semiarid Region of Chile

Riverine influence in Sr isotope ratio of mollusk shells and relationship with foraminiferal assemblages in a Late Quaternary succession of the Po River Delta (Northern Italy)

The freshwater influence in the 87Sr/86Sr ratio of mollusk shells were analyzed within a Late Quaternary subsurface succession of the Po River Delta (core 187-S1). Sr isotope ratios of the Po and others rivers' (Brenta, Adige and Reno) waters, discharging in the Adriatic Sea, at about 30 km North and South of the Po Delta, show a domi¬nant contribution in the core area of fluvial water with isotope ratios remarkably lower than seawater values. Core 187-S1 consists of continental deposits formed during cold-climate periods, with intercalated two paralic to shallow-marine intervals indicative of warm-climate conditions and attributed to the last interglacial (Eemian) and to the Holocene period. Foraminiferal assemblages of these intervals reveal a comparable transgressive-re¬gressive palaeoenvironmental evolution and great variation in river discharge, with highest influence of freshwater observed in the Hol¬ocene prodelta.The new Sr isotope ratios from marine and deltaic mollusks are commonly comparable with those of seawater and are not influenced by freshwater dilution, also in beach ridge samples, deposited at very shallow water depth. Excluding two anomalous ratios from the trans¬gressive part of the Holocene succession, deviation from marine val¬ues toward lower ratios (consistent with remarkable influx of river water) are observed in samples with foraminiferal assemblages indic-ative of inner prodelta and great proximity of the river mouth. This work shows that combining foraminiferal micropalaeon¬tology and Sr isotope data of freshwater draining the analyzed are¬as, it is possible to recognize conditions (i.e. deltaic settings greatly influenced by fluvial water with low 87Sr/86Sr ratio) that hamper the application of the Sr isotope ratios as dating tool for shallow marine fossils.

Tracing climate-driven water level fluctuations of Lake Prespa (Greece) to lacustrine beach ridge sediments: a modern case study to facilitate past lake level reconstruction

The Prespa Lake Basin (southwestern Balkans) contains a unique Holocene beach ridge record, which offers the opportunity to reliably reconstruct past water-level fluctuations based on absolute geomorphic stage index points. Such lake-level records are of great value for generating robust (quantified) hydro-climatic interpretations. These are urgently required for the Balkans, located at the juncture of contrasting Mediterranean climate and hydrological domains, as the few regional lake-proxy records covering the past millennium lack chronological resolution and appear to show different timing of wet-dry episodes. In order to use lake stage records for past climate change reconstructions, it is vital to understand modern lake-level sensitivity to specific hydro-climatic events and to track this signal to the landform-sediment archive. Accordingly, this paper analyses the impact of recent hydro-climate variability on the level of Lake Megali Prespa and traces this water-level signal to modern beach ridge sediments to facilitate future lake-level reconstructions. Annual lake fluctuations are strongly related to cumulative wet season precipitation which is highly correlated to the North Atlantic Oscillation. Lake Prespa reacts to sustained water balance changes by adjusting its lake surface area and thus surface evaporation. Historical water levels fluctuated between 853 and 842 m. Within this height range, lake surface areas change abruptly at 853–852, 847–846 and < 842 m. At stage levels in between these thresholds, set by the bathymetry, lake surface area only changes marginally and hydro-climatic conditions are approximately stable. This study finds that lake-level fluctuations are reliably registered by lacustrine beach sediment facies. Major lake level movements, which cross bathymetric thresholds, are clearly registered in the sediment-stratigraphic record by characteristic truncation surfaces and deposits. The chronological resolution of this lake-level record, and therefore the hydro-climatic signal it contains, is up to decadal timescales. Establishing quantified hydrological change estimates from the Prespa beach-ridge record requires knowledge of lake surface areas at specific lake stage index points. Modern analogues will give the difference in annually evaporated lake water volume between key stages. These differences are approximately equivalent to the change in water input (precipitation and discharge) and/or water loss (evaporation).

The 1997 Kronotsky earthquake and tsunami and their predecessors, Kamchatka, Russia

Abstract. The northern part of the Kamchatka subduction zone (KSZ) experienced three tsunamigenic earthquakes in the 20th century – February 1923, April 1923, December 1997 – events that help us better understand the behavior of this segment. A particular focus of this study is the nature and location of the 5 December 1997 Kronotsky rupture (Mw ∼ 7.8) as elucidated by tsunami runup north of Kronotsky Peninsula in southern to central Kamchatsky Bay. Some studies have characterized the subduction zone off Kronotsky Peninsula as either more locked or more smoothly slipping than surrounding areas and have placed the 1997 rupture south of this promontory. However, 1997 tsunami runup north of the peninsula, as evidenced by our mapping of tsunami deposits, requires the rupture to extend farther north. Previously reported runup (1997 tsunami) on Kronotsky Peninsula was no more than 2–3 m, but our studies indicate tsunami heights for at least 50 km north of Kronotsky Peninsula in Kamchatsky Bay, ranging from 3.4 to 9.5 m (average 6.1 m), exceeding beach ridge heights of 5.3 to 8.3 m (average 7.1 m). For the two 1923 tsunamis, we cannot distinguish among their deposits in southern to central Kamchatsky Bay, but the deposits are more extensive than the 1997 deposit. A reevaluation of the April 1923 historical tsunami suggests that its moment magnitude could be revised upward, and that the 1997 earthquake filled a gap between the two 1923 earthquake ruptures. Characterizing these historical earthquakes and tsunamis in turn contributes to interpreting the prehistoric record, which is necessary to evaluate recurrence intervals for such events. Deeper in time, the prehistoric record back to ∼ AD 300 in southern to central Kamchatsky Bay indicates that during this interval, there were no local events significantly larger than those of the 20th century. Together, the historic and prehistoric tsunami record suggests a more northerly location of the 1997 rupture compared to most other analyses, a revision of the size of the April 1923 earthquake, and agreement with previous work suggesting the northern KSZ ruptures in smaller sections than the southern KSZ. The final suggestion should be considered with caution, however, as we continue to learn that our historic and even prehistoric records of earthquakes and tsunamis are limited, in particular as applied to hazard analysis. This study is a contribution to our continued efforts to understand tectonic behavior around the northern Pacific and in subduction zones, in general.

Mid- to late-Holocene marine inundations inferred from coastal deposits facing the Nankai Trough in Nankoku, Kochi Prefecture, southern Japan

This study investigates the Holocene sedimentary history of a small coastal lowland in Nankoku, Kochi Prefecture, on the coast of southern Japan facing the Nankai Trough. The sedimentary fill of the lowland area consists mainly of marine-brackish clay overlain by beds of freshwater clay and peat. We found four laterally extensive sand sheets, one directly underlying the freshwater deposits and the other three interbedded with them. Radiocarbon dates show that these sand sheets were deposited between 5970 and 2440 cal. BP. Although the sand sheets contained few marine-brackish diatoms, they were concentrated in the seaward part of the study site, suggesting that they were deposited by marine inundations. These sand sheets were formed as a result of tsunamis or unusually large storm surges. The apparent frequency of marine inundations during 5970–2440 cal. BP was much lower than that of megathrust earthquakes along the Nankai Trough recorded during the last 1300 years. Event deposits were absent between 2440 and 960 cal. BP, a gap that we attribute to the development of beach ridges. The new marine inundation records reported here will aid efforts to reconstruct the timing and recurrence intervals of megathrust earthquakes in the western Nankai Trough.

Geomorphic origin of Merritt Island-Cape Canaveral, Florida, USA: A paleodelta of the reversed St. Johns River?

The Merritt Island-Cape Canaveral (MICCSC) sedimentary complex consists of a series of adjacent, non-conformable, beach ridge sets that suggest a multi-phase constructional history, but the feature's geomorphic and sedimentary origins are not well-understood. In spite of its notable sedimentary volume (surface area = 1200 km2), the MICCSC lacks a clear sediment source, or supply mechanism, to explain its presence today. Previously published U/Th, radiocarbon and OSL dates indicate that beach ridge deposition was active during MIS 5 (130–80 ka) on Merritt Island, but has occurred over a shorter, younger time interval on Cape Canaveral proper (6 ka to present). In this paper, it is proposed that the MICCSC is an abandoned paleodelta whose fluvial source provided a sediment supply sufficient for coastal progradation. Although the MICCSC, today, does not receive an appreciable sediment supply, the nearly 23,000 km2 drainage basin of the St. Johns River may well have provided such a sediment supply during MIS 5 times. This low-gradient fluvial system currently empties to the Atlantic Ocean some 200 km north of the MICCSC (near Jacksonville, Florida) but may have flowed southward during the time of MICCSC sedimentary construction, then experienced flow reversal since MIS 5 times. Three possible uplift mechanisms are proposed to explain the northward down-tilting that may have reversed the flow direction of the St. Johns, abandoning deltaic construction of the MICCSC: (1) karst-driven, flexural isostatic uplift in response to carbonate rock dissolution in central Florida, (2) glacio-hydro-isostatic tilting/back-tilting cycles during loading and unloading of the Laurentide ice sheet during the Pleistocene, and (3) mantle convection-driven dynamic topography operating within southeastern North America since the Pliocene. This example testifies to the sensitivity of low-gradient, low-relief landscapes to various sources of uplift, be they isostatic or otherwise.

The Po di Adria, Frattesina and the Po Delta between the Middle-Recent Bronze Age and the Early Iron Age

The Po di Adria, Frattesina and the Po Delta between the Middle-Recent Bronze Age and the Early Iron Age

Diversity of Bats in Contrasting Habitats of Hulu Terengganu Dipterocarp Forest and Setiu Wetland BRIS Forest with a Note on Preliminary Study of Vertical Stratification of Pteropodid Bats.

A study of the bat diversity was conducted in Hulu Terengganu dipterocarp forest and Setiu Wetland Beach Ridges Interspersed with Swales (BRIS) forest in Terengganu, to study the species diversity, composition and stratification of fruit bats from the understorey to the forest canopy. Mist nets were set up at the understorey, sub-canopy and canopy layer while harp traps were set up at the understorey layer. We recorded 170 individuals from six families’ compromised 21 species from Hulu Terengganu dipterocarp forests and four species from Setiu Wetland BRIS forests throughout the sampling period. Megaerops ecaudatus and Cynopterus brachyotis were the most dominant species in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forests. Our study also recorded two species with new distributional records for the east coast of Peninsular Malaysia, namely, Rhinolophus chiewkweeae and Chaerephon johorensis in Hulu Terengganu dipterocarp forests. Potential factors that might influence the results were in terms of the canopy covers, the structural complexity of canopy, food availability and spatial characteristics. This study was able to increase the knowledge on the species diversity and composition of bats in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forest, thus, further aid in the effort of bat conservation in both areas.

Luminescence dating of Holocene beach-ridge sands on the Yumigahama Peninsula, western Japan

Abstract We applied infrared stimulated luminescence (IRSL50) and post-infrared (post-IR) IRSL150 dating to K-feldspar sand obtained from Holocene beach ridges on the Yumigahama Peninsula, Japan, to investigate the rate of progradation of the beach, which has been affected by 17–18th century iron mining in a local river catchment. All samples showed higher equivalent doses for the post-IR IRSL signal. Fading tests indicated that IRSL yielded relatively high g-values (11–13%/decade), while post-IR IRSL yielded negative g-values (–5 to –8%/decade). The corrected IRSL age of the oldest sample, 8.1 ± 1.3 ka, was slightly overestimated with respect to its expected age of 5–6.7 ka. The corrected age is highly dependent on the g-value, which if slightly inaccurate would have caused the overestimate. The uncorrected post-IR IRSL ages were underestimated, and we consider that the post-IR IRSL signal faded. However, given the negative g-values, application of an appropriate fading correction was not feasible. The corrected IRSL ages of the younger samples, coupled with an assumption of residual dose, roughly agreed with the historical shoreline changes, indicating that the rate of shoreline progradation increased markedly during the recent period of mining-related enhanced sediment discharge.

Could tsunami risk be underestimated using core‐based reconstructions? Lessons from ground penetrating radar

AbstractWhere should we take cores for palaeotsunami research? It is generally considered that local depressions with low energy environments such as wetlands are one of the best places. However, it is also recognized that the presence or absence of palaeotsunami deposits (and their relative thickness) is highly dependent upon subsoil microtopography. In the beach ridge system of Ishinomaki Plain, Japan, several palaeotsunami deposits linked to past Japan Trench earthquakes have been reported. However, the number of palaeotsunami deposits reported at individual sites varies considerably. This study used ground penetrating radar (GPR) combined with geological evidence to better understand the relationship between palaeotopography and palaeotsunami deposit characteristics. The subsurface topography of the ~3000–4000 bp beach ridge was reconstructed using GPR data coupled with core surveys of the underlying sediments. We noted that the number (and thickness) of the palaeotsunami deposits inferred from the cores was controlled by the palaeotopography. Namely, a larger number of events and thicker palaeotsunami deposits were observed in depressions in the subsurface microtopography. We noted a total of three palaeotsunami deposits dated to between 1700 and 3000 cal bp, but they were only observed together in 11% of the core sites. This result is important for tsunami risk assessments that use the sedimentary evidence of past events because we may well be underestimating the number of tsunamis that have occurred. We suggest that GPR is an efficient and invaluable tool to help researchers identify the most appropriate places to carry out geological fieldwork in order to provide a more comprehensive understanding of past tsunami activity. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Depositional settings and history of the Lower Miocene Fleming Group, Refugio County, Texas, as defined using seismic geomorphology

Abstract A study of the Lower Miocene Fleming Group in Refugio County, Texas from 3-D seismic and wireline-log data documents continuous strandplain and associated lower-coastal-plain fluvial systems along a wave-dominated shoreline. This study delineates and characterizes, through the interpretation of seismic attributes and seismic geomorphology maps from 15 horizons, three principal styles of stratal patterns: (1) parallel and subparallel, strike-continuous sets of beach ridge and swale deposits within a strandplain system that prograded at least 12 km, (2) sinuous channel belts in a coeval mixed-load meanderbelt system, and (3) acoustically dim, nearly featureless seismic attribute patterns that record homogenous and topographically subdued, shallow-marine mudstones associated with transgressive marine deposits and flooding surfaces. Holocene depositional analogs for these Lower Miocene sandy strandplain deposits include the Nayarit coastline in Mexico, whereas the lower coastal plain between Galveston and Corpus Christi, Texas serves as an appropriate analog for mixed-load meanderbelt systems. The Lower Miocene coastline in Refugio County consists of a regressive phase that was punctuated by two transgressive phases. These episodes of marine transgression correspond to the Anahuac Formation and the Marginulina A shale, respectively. Succeeding events record complex, amalgamated beach-ridge deposits and coeval fluvial-channel systems that exhibit patterns of channel migration, erosion, incision, and downdip fusion of channel belts. This study concludes that potential reservoir geometries and architectures in the Lower Miocene succession are much more complex than previously inferred, the result of rapidly fluctuating and evolving strike-fed shoreline systems and contemporaneous fluvial dip-dispersal systems, some manifested by shore-parallel trends confined in swales. Improved reservoir-development strategies in this prolific hydrocarbon-bearing play should be guided by distribution of sandy depositional elements and the paleogeographic setting.

OSL dating of late Holocene coastal sediments and its implication for sea-level eustacy in Hainan Island, Southern China

Since the sea-level rise is not geographically homogeneous but rather shows great regional differences, optically simulated luminescence using quartz as a natural dosimeter has proved to be a powerful and reliable dating technique to determine depositional ages of young coastal sediments around the world. The samples acquired from one beach ridge and two marine terraces in coastal Hainan Island, southern China are detected OSL dating for the investigation of sea-level changes. The results show: (1) coastal sands in Hainan Island were well bleached before deposition, and the quartz OSL can date coastal sediments younger than 200 years, which could be one of good indicators for paleo relative sea-level highstand records; (2) three coastal sediments with 4 m, 3.7 m, and 2 m higher than present sea-level were deposited at 2.40 ± 0.05 ka, 2.92 ± 0.17 ka, and 4.26 ± 0.10 ka, respectively, which indicate that the height of highstand relative sea-level are higher than both mean global sea-level eustacy and those records offshore southern China; (3) Comparisons with tropical cyclones observations around South China Sea indicates that the late Holocene coastal sediments of Hainan Island might have been reformed by tropical cyclones with a highstand sea-level.

Soil morphology related to hydrology and degradation in tropical coastal podzols (SE Brazil)

Morphology of podzol profiles can be used to improve our understanding of soil formation and degradation processes. The morphology of a podzol chronosequence was studied for a 1800m long cliff perpendicular to the coastline at the southern coast of the Island Ilha Comprida (São Paulo, Brazil). The large variation in hydrological conditions with time (surfaces with ages from 6000 to 300yrs BP) and space (topography) allowed studying the relation between podzol morphology and drainage conditions, both during soil formation and degradation. On the oldest two surfaces, the podzols formed under poorly drained circumstances. Uplift during their formation resulted in (1) very deep Bh horizons and (2) degradation of the upper B horizon as a result of improved drainage. On the younger surface most podzols were poorly drained, but well-drained podzols and transitions occurred in beach ridges. In the cliffs on the southern coast of the island, improved drainage of the poorly drained podzols resulted in degradation of the B horizon. This degradation exhibits various forms, including (1) complete removal of the B horizon down to an underlying clay layer, (2) degradation of the B horizon along root channels with preferential vertical water transport, (3) degradation of the upper B horizon resulting in a diffuse EB transition, and (4) areas of organic matter (OM) depletion related to microbial activity, sometimes combined with burrowing. Type (2) degradation may result in a convoluted EB transition, the formation of islands of B horizon in the deepening E horizon, and formation of E horizon tongues into the Bh. Recent (post degradation) OM bands were found in E and B horizons. A thorough study of podzol morphology can be used to reconstruct several stages of their formation and degradation in relation to drainage conditions.

Exploring for heavy minerals on Cape York Peninsula, Queensland, Australia

ABSTRACT This paper describes the results of a preliminary study of the heavy mineral (HM) potential of the northwest coast of Cape York Peninsula in far north Queensland that was funded by the Queensland Government's Future Resources Program Industry Priorities Initiative. The study found that the northwest coast may have the potential to host world-class HM deposits. All the essential ingredients in a HM mineral system are present: fertile source rocks, effective transport mechanisms and abundant potential trap sites, particularly along the well-preserved Pleistocene coast. The source rocks are Proterozoic metamorphic and Paleozoic granitic rocks of the Coen Inlier and Mesozoic sedimentary rocks of the Laura and Carpentaria basins, all of which crop out along the spine of the Peninsula. These rocks were exposed in the early Cenozoic and were vigorously eroded by seasonally active rivers throughout the Quaternary. Most of these rivers are currently carrying HM, and the zircon content in river sediments in the region is comparatively high. It is speculated that in the late Pleistocene HM delivered by rivers to the northwest coast were transported predominantly in a southwesterly direction, and trapped in the swash zone of prograding beaches. It is further speculated that at this time the coastline was deeply embayed with cliffs and headlands formed in bauxite, and that structural trap sites formed on the northeastern side of prominent headlands. Pleistocene coastal sediments were partially reworked by Holocene coastal processes, and HM liberated by these processes may have been captured by prograding Holocene beach ridges. These Holocene beach ridges are not as extensive as the Pleistocene beach ridges but are more prominent, partly because they are less well vegetated. The Holocene coastline was probably more regular than the Pleistocene coastline, with fewer headlands to create structural traps. The modern coastline is relatively starved of river sediment because the Holocene and Pleistocene coastal sediments act as barriers to river flow. It is recommended that ongoing exploration for HM in the region should focus on potential trap sites on the Pleistocene coast and that two sites, Vrilya Point and Jackson River, where structural traps may have been formed by coastal promontories, should be priority targets. It is also noted that if the exploration of Cape York Peninsula for HM deposits is to be effective, further research needs to be carried out into the geomorphological evolution of the west coast and, in particular, the role of cyclones in forming HM deposits in tropical climates.

Land use and landscape pattern changes driven by land reclamation in a coastal area: the case of Volturno delta plain, Campania Region, southern Italy

The paper provides documentary evidence of the direct impacts on the coastal setting in the northern Campania (southern Italy) region, crossed by the Volturno River, that have led to dramatic alterations of alluvial channels, floodplain and the deltaic environment, aside from the coastline retreat following four centuries of land reclamation. The Volturno delta plain is characterized by an outer delta formed mainly by beach ridges, and an inner plain containing several depressions of drained marsh regions. Until the beginning of the last century, this area was the site of swamps and ponds bearing a high incidence of malaria. Historical analysis coupled with a cartographic restitution in a geographic information system environment has produced documentary evidence of the geomorphological evolution of the coastal sector and has allowed the reconstruction of relevant landscape and hydrographic changes since the end of the seventeenth century, when—during the Spanish vice-kingdom—it was subjected to major land reclamation. The availability of reclaimed lands along the coastal alluvial plain promoted the development of agriculture and farming, as well as a strong coastal urbanization. As a consequence, a landscape fragmentation increased significantly between the 1960s and the 1990s; built-up land area increased as well, overgrowing to the sea. An overall reduction in high-quality ecosystems (humid coastal setting, lacustrine/marshy back-dune area and beach-dune system) is recorded, resulting in biodiversity loss and a dramatic reduction in environmental quality. The outcomes of this research will be beneficial to society for better decision-making over these coastal area applications, in a sustainable manner, especially in these countries that are still experiencing land reclamation.

Proxy records of Holocene storm events in coastal barrier systems: Storm-wave induced markers

Extreme storm events in the coastal zone are one of the main forcing agents of short-term coastal system behavior. As such, storms represent a major threat to human activities concentrated along the coasts worldwide. In order to better understand the frequency of extreme events like storms, climate science must rely on longer-time records than the century-scale records of instrumental weather data. Proxy records of storm-wave or storm-wind induced activity in coastal barrier systems deposits have been widely used worldwide in recent years to document past storm events during the last millennia.This review provides a detailed state-of-the-art compilation of the proxies available from coastal barrier systems to reconstruct Holocene storm chronologies (paleotempestology). The present paper aims (I) to describe the erosional and depositional processes caused by storm-wave action in barrier and back-barrier systems (i.e. beach ridges, storm scarps and washover deposits), (ii) to understand how storm records can be extracted from barrier and back-barrier sedimentary bodies using stratigraphical, sedimentological, micro-paleontological and geochemical proxies and (iii) to show how to obtain chronological control on past storm events recorded in the sedimentary successions. The challenges that paleotempestology studies still face in the reconstruction of representative and reliable storm-chronologies using these various proxies are discussed, and future research prospects are outlined.

Coarse‐sand beach ridges at Cowley Beach, north‐eastern Australia: Their formative processes and potential as records of tropical cyclone history

AbstractStorm surges generated by tropical cyclones have been considered a primary process for building coarse‐sand beach ridges along the north‐eastern Queensland coast, Australia. This interpretation has led to the development of palaeotempestology based on the beach ridges. To better identify the sedimentary processes responsible for these ridges, a high‐resolution chronostratigraphic analysis of a series of ridges was carried out at Cowley Beach, Queensland, a meso‐tidal beach system with a &gt;3 m tide range. Optically stimulated luminescence ages indicate that 10 ridges accreted seaward over the last 2500 to 2700 years. The ridge crests sit +3·5 to 5·1 m above Australian Height Datum (ca mean sea‐level). A ground‐penetrating radar profile shows two distinct radar facies, both of which are dissected by truncation surfaces. Hummocky structures in the upper facies indicate that the nucleus of the beach ridge forms as a berm at +2·5 m Australian Height Datum, equivalent to the fair‐weather swash limit during high tide. The lower facies comprises a sequence of seaward‐dipping reflections. Beach progradation thus occurs via fair‐weather‐wave accretion of sand, with erosion by storm waves resulting in a sporadic sedimentary record. The ridge deposits above the fair‐weather swash limit are primarily composed of coarse and medium sands with pumice gravels and are largely emplaced during surge events. Inundation of the ridges is more likely to occur in relation to a cyclone passing during high tide. The ridges may also include an aeolian component as cyclonic winds can transport beach sand inland, especially during low tide, and some layers above +2·5 m Australian Height Datum are finer than aeolian ripples found on the backshore. Coarse‐sand ridges at Cowley Beach are thus products of fair‐weather swash and cyclone inundation modulated by tides. Knowledge of this composite depositional process can better inform the development of robust palaeoenvironmental reconstructions from the ridges.

The Usumacinta–Grijalva beach-ridge plain in southern Mexico: a high-resolution archive of river discharge and precipitation

Abstract. The beach-ridge sequence of the Usumacinta–Grijalva delta borders a 300 km long section of the southern Gulf of Mexico coast. With around 500 beach ridges formed in the last 6500 years, the sequence is unsurpassed in the world in terms of numbers of individual ridges preserved, continuity of the record, and temporal resolution. We mapped and dated the most extensively accreted part of the sequence, linking six phases of accretion to river mouth reconfigurations and constraining their ages with 14C and OSL dating. The geomorphological and sedimentological reconstruction relied on lidar data, coring transects, GPR measurements, grain-size analyses, and chemical fingerprinting of volcanic glass and pumice encountered within the beach and dune deposits. We demonstrate that the beach-ridge complex was formed under ample long-term fluvial sediment supply and shorter-term wave- and aeolian-modulated sediment reworking. The abundance of fluvially supplied sand is explained by the presence of easily weatherable Los Chocoyos ignimbrites from the ca. 84 ka eruption of the Atitlán volcano (Guatemala) in the catchment of the Usumacinta River. Autocyclic processes seem responsible for the formation of ridge–swale couplets. Fluctuations in their periodicity (ranging from 6–19 years) are governed by progradation rate, and are therefore not indicative of sea level fluctuations or variability in storm activity. The fine sandy beach ridges are mainly swash built. Ridge elevation, however, is strongly influenced by aeolian accretion during the time the ridge is located next to the beach. Beach-ridge elevation is negatively correlated with progradation rate, which we relate to the variability in sediment supply to the coastal zone, reflecting decadal-scale precipitation changes within the river catchment. In the southern Mexican delta plain, the coastal beach ridges therefore appear to be excellent recorders of hinterland precipitation.

Progradation of a Beach Ridge Plain between 5000 and 4000 Years BP Inferred from Luminescence Dating, Coquimbo Bay, Chile

ABSTRACT Hart, E.A.; Stapor, F.W.; Enrique Novoa Jerez, J., and Sutherland, C.J., 2017. Progradation of a beach ridge plain between 5000 and 4000 years BP inferred from luminescence dating, Coquimbo Bay, Chile. Luminescence dating was carried out to determine the depositional history of a 2-km-wide, shore-parallel, beach ridge sequence at Coquimbo Bay, Chile, for which no direct dating had previously been done. The beach ridge plain at Coquimbo Bay represents one of the most extensive Holocene depositional features preserved along the Pacific Coast of South America. Both optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) dates indicate a rapid period of beach ridge progradation lasting approximately 1000 years at an average rate of 2 m y−1. However, based on previously reported luminescence deficiencies of geologically “young” quartz, it is proposed that IRSL dates are more representative of the actual depositional age of the beach ridges. These IRSL ages indicate that the...

Late Holocene Geomorphological Development of Beach Ridge Ranges in the Central Part of Ise Plain, Central Japan

Late Holocene Geomorphological Development of Beach Ridge Ranges in the Central Part of Ise Plain, Central Japan