Boulder Beaches Research Articles

A Boulder Beach Formed by Waves From a Calving Glacier Revisited: Multidecadal Tsunami–Controlled Coastal Changes in Front of Eqip Sermia, West Greenland

ABSTRACTThe calving of glaciers regularly produces tsunami‐like waves that pose a serious threat to coastal environments. Those strong waves are not only able to move ice mélange and redistribute icebergs, growlers, or sea ice across a fjord but also flood and remodel neighbouring cliffs and beaches. Here, we analyze over 90 years (1929–2023) of coastal zone changes that occurred in front of Eqip Sermia. We show that calving waves play a dominant role in transforming the lateral moraine and forming a beach and spit system south of the glacier front. Part of the former moraine has transformed into a boulder‐dominated spit, which closed the lagoon over the years. By multidecadal analysis, we also detected a significant erosion of unconsolidated cliffs located on the opposite side of the bay (~0.53 m per year between 1985 and 2023). In addition, we demonstrate that even a single event (one calving wave) can remodel a beach surface by entrainment of up to 1.8‐m‐diameter boulders and the erosion of the beach surface by washing away sand and gravel from rocky outcrops. Our study constitutes important progress toward modes of paraglacial coastal evolution in regions characterized by rapidly retreating calving glaciers.

Fantastic Flatworms and Where to Find Them: Insights into Intertidal Polyclad Flatworm Distribution in Southeastern Australian Boulder Beaches

There is a rapid and extensive decline of our marine biodiversity due to human impacts. However, our ability to understand the extent of these effects is hindered by our lack of knowledge of the occurrence and ecology of some species groups. One such group of understudied organisms are marine flatworms of the order Polycladida, a conspicuous component of southeastern Australia’s marine ecosystems that has received little attention over the years. Intertidal boulder beaches support a diverse range of polyclad flatworms in other countries, but the role of these environments in maintaining biodiversity is not well understood. In this study, we identified hotspots of flatworm occurrence by assessing the diversity and overall abundance of flatworms at boulder beaches along the southeast Australian coast. Bottle and Glass, Sydney Harbour, was found to be the most diverse site for flatworms. We also identified a higher occurrence of flatworms under large boulders and less exposed beaches and noted an increased presence of flatworms at higher latitudes. Probable influences on these patterns such as the requirement for shelter and protection are discussed. This study contributes to our knowledge of Australia’s coastal biodiversity and can be used to assist in the management and conservation of our marine environments.

Propuesta metodológica para la caracterización y tipificación de las costas españolas. Aplicación a las costas de Galicia.

Hay varias clasificaciones costeras. La mayoría de ellas han sido elaboradas a nivel mundial utilizando criterios tectónicos, climáticos, topográficos u oceanográficos. Otras clasificaciones han sido elaboradas a mayor escala y han sido enfocadas a catalogar las formas costeras: acantilados, playas, estuarios, lagunas o complejos dunares.Este trabajo analiza los tipos de litoral, entendiendo como tal cada sector que presenta determinadas condiciones topográficas marcadas por la elevación y pendiente, y que se modeló sobre un tipo concreto de roca en un entorno climático y marino específico. Se describe un enfoque metodológico para una clasificación a escala detallada. Este enfoque se basa en la delimitación de los diferentes sistemas costeros, ejemplificados en acantilados y playas de cantos rodados, playas de arena y dunas. En este caso las plataformas costeras, marismas y lagunas no han sido consideradas por los problemas técnicos derivados de la fuente de datos LiDAR, de la cual se derivan los modelos digitales del terreno (MDT) de resolución espacial de 2 m.El primer paso en la clasificación fue una delimitación manual que combinaba MDT y ortofotografías. Posteriormente, se realizó otra tipificación mediante la creación automática de Unidades Topográficas Litorales (UTC). Este índice es la combinación de dos variables: elevación costera y pendiente. La posible integración de otras, como la orientación o la litología, es posible, pero generan un número muy elevado de unidades y dificultan su interpretación. Por esta razón, este estudio no consideró más variables.En este proyecto se generaron 30 UTC, y luego se seleccionaron solo aquellas que aparecen en los sectores de acantilados, playas de cantos rodados, playas de arena y dunas costeras. La posibilidad de visualizar una o varias UTC en cualquier sector de la costa permite conocer con mayor precisión las condiciones de cada sector y estas categorías podrían mejorar los planes de gestión costera.

Microbialites of modern siliciclastic rock coasts

ABSTRACT Contemporary microbialite formation has been documented on rock coasts in a variety of geomorphic, oceanographic, and climatic settings. Based on a synthesis of these diverse occurrences plus new observations, a generalized model is presented. At each locality microbialite development is associated with discharge of mineralized freshwater in the coastal zone. Microbialite formation in the high intertidal and supratidal zones of rock coasts occurs in a variety of sub-environments (cliff face, shore platform surface, platform surface pools, boulder beach, and sand beach) and forms a variety of laminated rock encrustations and oncoids. Allochthonous microbialites occur on the backshore as breccias of reworked microbialite clasts, oncoids transported from rock pools, and partly encrusted boulders. The microbialite-influenced rock coast is a distinct type of siliciclastic environment that offers potential comparison for ancient microbialite occurrences. It has preservation potential in both transgressive and regressive settings. Potential ancient examples are suggested.

The Use of UAVs for the Characterization and Analysis of Rocky Coasts

Rocky coasts represent three quarters of all coastlines worldwide. These areas are part of ecosystems of great ecological value, but their steep configuration and their elevation make field surveys difficult. This fact, together with their lower variation rates, explains the lower numbers of publications about cliffs and rocky coasts in general compared with those about beach-dune systems. The introduction of UAVs in research, has enormously expanded the possibilities for the study of rocky coasts. Their relative low costs allow for the generation of information with a high level of detail. This information, combined with GIS tools, enables coastal analysis based on Digital Models and high spatial resolution images. This investigation summarizes the main results obtained with the help of UAVs between 2012 and the present day in rocky coastline sections in the northwest of the Iberian Peninsula. These investigations have particularly focused on monitoring the dynamics of boulder beaches, cliffs, and shore platforms, as well as the structure and function of ecosystems. This work demonstrates the importance of unmanned aerial vehicles (UAVs) for coastal studies and their usefulness for improving coastal management. The Galician case was used to explain their importance and the advances in the UAVs’ techniques.

Tracking clast mobility using RFID sensors on a boulder beach in Galicia, NW Spain

Previous studies using unmanned aerial vehicles and remote sensing techniques have provided data on group sediment dynamics and overall mobility of a boulder beach at Oia in Galicia, northwestern Spain. They recorded changes in the location and disposition of hundreds of clasts but were unable to trace the intermittent movement of individual boulders. Radio Frequency IDentification (RFID) sensors were used in the present study to identify and record the long-term trajectories of boulders in this area. Sensors were installed in 80 boulders (mean intermediate axes approximately 55 cm) in September 2016 and were used to locate and record their displacement on five occasions, terminating in December 2019. Although burial and other factors prevented data being collected from every tagged boulder during these periods, recovery rates ranged from approximately 50%–75% of the original population. There was considerable variability in the displacement of the boulders, with maxima of >20 m and mean values >5 m. The distance of travel tended to decrease during the course of this study, despite a corresponding increase in storm frequency and intensity. Patterns of movement, including transport distance and direction were essentially chaotic in nature, reflecting the complex interaction and compound effect of a multitude of controls related to such factors as the location of boulders on the beach, their relationship to surrounding boulders, including the effects of sheltering, interlocking, and burial, and their size, shape, and other physical characteristics. The unpredictable behaviour and high transport thresholds of boulder beaches are in contrast to sand and gravel beaches that are characterized by more uniform and predictable patterns of sediment transport and morphological change.

Holocene Boulder Beach Eroded from Chromite and Dunite Sea Cliffs at Støypet on Leka Island (Northern Norway)

This project examines the role of high-latitude storms degrading a Holocene coast formed by igneous rocks composed of low-grade chromite ore and dunite that originated within the Earth’s crust near the upper mantle. Such rocks are dense and rarely exposed at the surface by tectonic events in the reconfiguration of old ocean basins. An unconsolidated boulder beach occupies Støypet valley on Leka Island in northern Norway, formerly an open channel 10,000 years ago when glacial ice was in retreat and rebound of the land surface was about to commence. Sea cliffs exposing a stratiform ore body dissected by fractures was subject to wave erosion that shed large cobbles and small boulders into the channel. Competing mathematical equations are applied to estimate the height of storm waves impacting the channel floor and cliffs, and the results are compared with observations on wave heights generated by recent storms striking the Norwegian coast with the intensity of an orkan (Norwegian for hurricane). Lateral size variations in beach clasts suggest that Holocene storms struck Leka Island from the southwest with wave heights between 5 and 7.5 m based on the largest beach boulders. This result compares favorably with recent high-latitude storm tracks in the Norwegian Sea and their recorded wave heights. The density of low-grade chromite ore (3.32 g/cm3) sampled from the beach deposit exceeds that of rocks like limestone or other igneous rocks such as rhyolite, andesite, and basalt taken into consideration regarding coastal boulder deposits associated with classic hurricanes in more tropical settings.

Comparison of Modern and Pleistocene (MIS 5e) Coastal Boulder Deposits from Santa Maria Island (Azores Archipelago, NE Atlantic Ocean)

Modern and palaeo-shores from Pleistocene Marine Isotope Substage 5e (MIS 5e) featuring prominent cobble/boulder deposits from three locations, on the southern and eastern coast of Santa Maria Island in the Azores Archipelago, were compared, in order to test the idea of higher storminess during the Last Interglacial. A total of 175 basalt clasts from seven transects were measured manually in three dimensions perpendicular to one another. Boulders that exceeded the minimum definitional diameter of 25 cm contributed to 45% of the clasts, with the remainder falling into the category of large cobbles. These were sorted for variations in shape, size, and weight pertinent to the application of two mathematical formulas to estimate wave heights necessary for traction. Both equations were based on the “Nott-Approach”, one of them being sensitive to the longest axis, the other to the shortest axis. The preponderance of data derived from the Pleistocene deposits, which included an intertidal invertebrate fauna for accurate dating. The island’s east coast at Ponta do Cedro lacked a modern boulder beach due to steep rocky shores, whereas raised Pleistocene palaeo-shores along the same coast reflect surged from an average wave height of 5.6 m and 6.5 m. Direct comparison between modern and Pleistocene deposits at Ponta do Castelo to the southeast and Prainha on the island’s south shore produced contrasting results, with higher wave heights during MIS 5e at Ponta do Castelo and higher wave heights for the modern boulder beach at Prainha. Thus, our results did not yield a clear conclusion about higher storminess during the Last Interglacial compared to the present day. Historical meteorological records pit the seasonal activity of winter storms arriving from the WNW-NW against the scant record of hurricanes arriving from the ESE-SE. The disparity in the width of the marine shelf around Santa Maria Island with broad shelves to the north and narrow shelves to the south and east suggested that periodic winter storms had a more regular role in coastal erosion, whereas the rare episodic recurrence of hurricanes had a greater impact on southern and southeastern rocky shores, where the studied coastal boulder deposits were located.

Effects of unregulated visitor access on chick fledging mass and survival in yellow-eyed penguins

Abstract Context Wildlife tourism is expanding and can detrimentally affect taxa such as penguins, if not managed carefully. The yellow-eyed penguin (Megadyptes antipodes) is an endangered species, with mainland populations projected to decline to extinction in the next 40 years, despite conservation interventions. Their nesting sites are exposed to increasing numbers of human visitors, which contributes to reduced reproductive success. AimsWe evaluated the effectiveness of a breeding colony (Boulder Beach) closure to the public, which was implemented to reduce visitor disturbance. MethodsWe compared reproductive success 5 years before and 5 years during the closure with success at an adjacent site (Sandfly Bay) that experiences high human disturbance, over the same time periods. Key resultsBeach closure did not result in an increase in chick mass or survival at Boulder Beach; however, trends at adjacent Sandfly Bay suggested that, without the closure, chick survival at Boulder Beach would likely have declined. Chick survival decreased at Sandfly Bay across the two 5-year periods, whereas chick survival at Boulder Beach did not decline, but remained constant during the closure years. ConclusionsThe beach closure was beneficial because it appeared to buffer environmental factors, so that mean chick survival remained constant rather than declining. Implications Beach closures might be difficult to implement because of public expectations regarding free access to coastal land in New Zealand, but they should be considered at sites where increasing numbers of visitors are likely to have detrimental impacts on wildlife. Without urgent action, these culturally important animals will likely be extinct on mainland New Zealand within the next few decades. Beach closures may represent an effective management measure to increase population resilience by decreasing the detrimental impacts of visitors on breeding success.

Short-term movement patterns, population estimates and breeding biology of an island endemic bird, the Tristan Thrush

The Tristan Thrush Turdus eremita is the only land bird that survived human colonisation of the main island of Tristan da Cunha and is listed as “Near Threatened”. Population estimates are confounded by the thrushes’ inquisitive and gregarious nature as well as limited information on their movements. We report the first measures of nest densities on Nightingale Island: 6 nests·ha-1 in Phylica arborea woodland and 4–5 nests·ha-1 in tussock habitat, which suggests that the population is approximately double the previous estimate. At Inaccessible Island, we individually color ringed 110 thrushes over two months to track their short-term movements and estimate the local population size. Individuals moved up to 950 m along the coast, but 96% of resightings were < 100 m. A Bayesian data augmentation approach estimated that some 260 thrushes visited the core study area, a 200-m stretch of cobble and boulder beach where birds come to drink, bathe and forage. This result suggests that the population on Inaccessible Island also is substantially larger than reported previously. We estimate the total population to be 8000–15,000 Tristan Thrushes. The main need is a population estimate for the nominate subspecies on the main island of Tristan.

From fine sand to boulders: Examining the relationship between beach-face slope and sediment size

It is a long-standing maxim that coarser sediment sizes are associated with steeper beach-face slopes; but because most work has focused on sandy beaches, few data are available for the pebble, cobble, or boulder size ranges. Little is known, therefore, about how beach morphology and grain size relate at the coarser size grades. We compiled data from the literature—2144 measurements of beach-face slope with associated grain sizes— covering the range from very fine sand to boulders. This meta-analysis shows that beach faces do tend to steepen as average grain size increases, at least up to the cobble size range; but the trend is not simple. Although previous studies suggested a simple power-law relationship between grain size and beach-face slope, in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens (and may trend downward for boulders). Fine and medium sands have the greatest range of reported slopes and the data support the importance of effective-weight modification and boundary layer dynamics as primary controls on beach-face steepness at these fine size grades. Around the very coarse sand size grade, a plateau marks a shift in beach dynamics: as hydraulic conductivity increases, beaches switch to being infiltration-dominated. The trend toward steeper slopes continues, but at a lower and steady rate, from granules through cobbles. There appears to be a falloff in slope for the coarsest boulder deposits (but we note that this is based on very few locations, so should be considered preliminary). The overall data distribution is described by a power-law function: tanβ=a(D50−0.125)b+c. The broadness of each transition zone also shows that a range of factors, other than grain size, governs where that tipping point occurs. In the cobble and boulder size ranges there are two deposit categories: boulder beaches, and supratidal boulder ridges. Although not commonly thought of as beaches, boulder ridges record long-term storm deposition and reworking on the highest energy coasts. Supratidal ridges and boulder beaches seem to show different slope/grain-size relationships, with the steepest slopes occurring in boulder ridges, and with boulder beaches showing more gentle gradients than other coarse clastic beaches; but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum, and invites further work to investigate the sedimentology of cobble- and boulder-dominated systems.

Reproduction of the anthozoan Anemonia sulcata (Pennant, 1777) in southern Spain: from asexual reproduction to putative maternal care

Anemonia sulcata (Pennant, 1777) is a common shallow water cnidarian from rocky platform and boulder beaches in southern Spain, where it is a popular seafood item with an increasing fishery. To aid in the management of a sustainable fishery, a study on the reproduction of A. sulcata in the littoral of Malaga (southern Spain) was performed from November 2014 to September 2015, using histological methods. A total of 123 specimens were examined, with a size range (as diameter of the pedal disc) from 1.1 to 48.2 mm. The sex ratio was significantly biased to females, with 1.7 females: 1 male (χ2 = 4.45, p < 0.01). The spermatozoids and oocytes arise from the endodermal cells. The mature oocytes receive nutritive filaments (trophonema) from the endoderm cells. There were zooxanthellae in the mesenteries, tentacles and also inside the oocytes. A gastrula was observed in one individual, as well as several planula larvae in different degree of development in others. Asexual reproduction by internal budding was observed in some individuals. The studied population showed an extended reproductive cycle with a peak of spawning in April. The size and weight of sexual maturity of the studied population were 21.5 mm and 16.5 g, respectively. A positive significant correlation was observed between size and weight of individuals. We suggest that the diameter of the pedal disc should be used as the legal parameter for the management of this fishery, as this measurement is easier to take by fishermen at sea than the weight, the current legal parameter.

The prevalence and species richness of spiders associated with marine strandlines on different shore types around Banks Peninsula, New Zealand

ABSTRACTMarine strandlines provide habitat for a variety of littoral and terrestrial invertebrates, including arachnids. In this study we recorded spiders in strandlines at 35 sites on Banks Peninsula, New Zealand. On average, only 1.5 named species were recorded per thirty-minute hand search, and many sample visits (30%) recorded no spiders. Species accumulation curves suggested further species could be recorded with further sampling, but these may be tourist species rather than strandline residents. Thirty-eight species were recorded in total, with the introduced theridiid Steatoda capensis being the most common (30 records) and widespread (17 locations). The New Zealand endemic species Otagoa nova (25 records) (Toxopidae), Anoteropsis litoralis (15) and Anoteropsis hilaris (15) (Lycosidae), and the introduced Tenuiphantes tenuis (24) (Linyphiidae), were also common. Spiders were more frequent in strandlines on boulder beaches compared with shingle beaches, although there was no statistical differences in the numbers of species recorded on the different beach types.

Widespread neonatal infection with phocid herpesvirus 1 in free-ranging and stranded grey seals Halichoerus grypus

Phocid herpesvirus 1 (PhHV-1) is known to infect grey seals Halichoerus grypus but little is known about its pathogenicity or true prevalence in this species. To investigate the prevalence of and risk factors associated with PHV-1 infection, nasal swabs were collected from grey seal pups and yearlings on the Isle of May, a well-studied grey seal breeding colony, and from stranded grey seal pups submitted to a rehabilitation centre. PhHV-1 nucleic acids were detected in nasal swabs from 58% (52/90) of live free-ranging grey seal pups, 62% (18/29) of live stranded grey seal pups and 28% (5/18) of live free-ranging yearlings, suggesting recrudescence in the latter. Location within the colony, pup body mass and stranding were determined to be risk factors for shedding PhHV-1 in live seal pups with a significantly higher prevalence of PhHV-1 in pups born on the tidal boulder beach when compared to other sites; a significantly positive correlation of PhHV-1 shedding and pup body mass and a higher prevalence in stranded grey seal pups compared to their free-ranging conspecifics. The prevalence of PhHV1 in dead pups on the Isle of May was 56% (27/48) with a positive PhHV-1 PCR status significantly associated with hepatic necrosis (p = 0.01), thymic atrophy (p < 0.001) and buccal ulceration (p = 0.027). Results indicate that PhHV1 was widespread in the pups in the Isle of May grey seal breeding colony.

Recording inter‐annual changes on a boulder beach in Galicia, NW Spain using an unmanned aerial vehicle

AbstractAn unmanned aerial vehicle (UAV) was flown over a boulder beach (area 20 000 m2) on the southern coast of Galicia (northwestern Spain) in May 2016, continuing earlier work based on flights over the same beach in July 2012, May 2013, and late March 2014. Digital surface models (DSMs) with 1.8 cm resolution were constructed from the 2014 and 2016 data to identify changes in beach morphology over the intervening period. Analyses were conducted using a Limit of Detection (LoD) of 0 cm and 3.71 cm. In both cases, the analyses showed that erosion dominated over 19% of the beach area. Accretion occurred over the rest of the beach, which acquired an additional 1500 m3 of material over the study period. Re‐analysis of the data from earlier flights suggested that erosion dominated on the beach in 2012–2013 and deposition in 2013–2014. Without any clear relationship between beach behaviour and storm severity during each winter period, it is proposed that gravitationally induced erosion and storm‐wave induced deposition are the result of perturbations about an equilibrium beach gradient. The UAV data also suggested that an essentially random component modulates regional patterns of movement. © 2018 John Wiley &amp; Sons, Ltd.

Amino acid racemisation and uranium-series dating of a last interglacial raised beach, Kingscote, Kangaroo Island, southern Australia

ABSTRACTThe extent to which scleractinian coral inhabited southern Australia during the warm intervals of the Quaternary is poorly understood because identifiable corals from interglacial sedimentary records are scarce. Here we document the presence of a sub-tropical coral, Goniopora lobata, recovered together with warm water mollusc species from a raised cobble and boulder beach conglomerate at Kingscote, Kangaroo Island, dated by uranium-series and amino acid racemisation methods respectively to the last interglacial (MIS 5e). The presence of this assemblage preserved within the Glanville Formation at Kingscote suggests a 2–3° C higher than present last interglacial coastal water temperature for northern Kangaroo Island. The height of the last interglacial shoreline deposit was measured by theodolite, and points to a mean last interglacial sea level 3.1 ± 0.4 m higher than present.

Increase of sub-Antarctic fur seals at the Tristan da Cunha Islands

Sub-Antarctic fur seal, Arctocephalus tropicalis, pups were counted on some of the beaches on all four Tristan da Cunha (TdC) islands, in January 2017, to determine the status of the population, in the face of climate change that is magnified in polar regions. Compared to counts done 40 years earlier on Gough, the breeding population increased markedly on some beaches, although negligibly on the largely open boulder beaches on the leeward northeastern sector of the island. Similarly, on the northern group of the TdC islands, the breeding population had increased markedly (including the very first pup counts at Inaccessible and Nightingale), despite fur seal females currently selecting only certain beaches for pupping (at Inaccessible and Tristan). At Tristan da Cunha, only one small breeding colony occurs which is remote from the human settlement, probably the result of anthropogenic disturbance.

Distribution, Habitat, and Population Size of Island Night Lizards on San Nicolas Island, California

The Island Night Lizard (Xantusia riversiana) was removed from the federal list of threatened species in May 2014. This strongly differentiated species is endemic to 3 of the southern California Channel Islands—San Clemente, San Nicolas, and Santa Barbara. Suitable habitat for Island Night Lizards is extensive on San Clemente Island, and the species is abundant there. Habitat is limited and fragmented, however, on San Nicolas Island and small Santa Barbara Island. Bringing together extensive field surveys and mark-recapture sampling, we synthesize available data for Island Night Lizards on San Nicolas Island and calculate population and density estimates for the species in major habitats on the island. Island Night Lizards are widely distributed across most of the eastern half of San Nicolas Island. In contrast, they are nearly absent over the western third of the island except for isolated populations in boulder beach habitats. We combined mark-recapture population estimates with comprehensive measurements of the extent of cactus, boxthorn, and other habitat types on the island to arrive at a more accurate assessment of the status of Island Night Lizards on San Nicolas Island. High densities of Island Night Lizards on the island are found in small areas of cholla cactus (Cylindropuntia prolifera; mean of 4100 lizards/ha), boulder beach habitat (mean of 3400 lizards/ha), and prickly pear cactus (Opuntia spp.; mean of 1700 lizards/ha); low numbers are found in more extensive mixed-shrub habitat (mean of 250 lizards/ha). The U.S. Fish and Wildlife Service requires a post-delisting program for “monitoring the overall health of the Island Night Lizard” to assure the continued long-term viability of the species in its restricted distribution. The information on population size and habitat presented here will inform and guide conservation and management efforts by the U.S. Navy on San Nicolas Island over the coming years.

The extant shore platform stromatolite (SPS) facies association: a glimpse into the Archean?

Abstract. Shore platform stromatolites (SPS) were first noted at Cape Morgan on the south-east African seaboard. Since then they have been found growing discontinuously in rocky peritidal zones along the entire southern African seaboard. They have also been found on the southwest Australian coast, at Giant's Causeway in Northern Ireland, and more recently at Harris on the Scottish Hebridean Atlantic coast. In this paper SPS occurrence and SPS potential as analogues for Precambrian fossil stromatolites, as well as potential stromatolite occurrences in shore platform regions on Mars, are assessed. Sub-horizontal surfaces promote stromatolite development, while tufa develops on cliffs and steep rocky surfaces. Tufa and stromatolites are end members of a spectrum dictated by coastal topography. Extant SPS occur on well indurated shore platforms in high wave energy settings, often around or near headlands. They can be associated with boulder beaches, boulder ridges, storm swash terraces, coastal dunes, and peat bogs. In contrast to other extant stromatolites, SPS are produced primarily by mineral precipitation, although minor trapping and binding stromatolites do occur. From a geological perspective, SPS develop in mildly transgressive siliciclastic settings in various climatic and tidal regimes. We suggest that SPS could be preserved in the geological record as micritic lenses on palaeo-shore platform surfaces. SPS share many features with Precambrian stromatolites and are a valid modern analogue despite the widely different atmospheric and oceanic conditions of the Archean. We suggest that terraces associated with former oceanic or lacustrine flooding surfaces on Mars are potential targets in the search for palaeo-SPS on Mars.

The last interglacial (MIS 5e) sea level highstand from a tectonically stable far-field setting, Yorke Peninsula, southern Australia

Yorke Peninsula in southern Australia is an important region for reconstructing relative sea-level histories due to its location on the eastern margin of the tectonically stable Gawler Craton and in one of the world's geographically most remote far-field locations from the Pleistocene ice sheets. Richly fossiliferous, skeletal carbonate sands of the last interglacial (125 ka) Glanville Formation crop out in the coastal cliffs along large sectors of southern Yorke Peninsula. Sedimentary facies include deepening-upward intertidal to shallow subtidal facies, relict storm beach facies and cobble and boulder beach deposits in more exposed, higher energy locations. During deposition of the Glanville Formation, southern Yorke Peninsula had a different coastal geography with two prominent marine corridors extending across the southern-most portion of the entire peninsula. In a 3 km long coastal cliff section in southern Hardwicke Bay, the Glanville Formation crops out as an upward-deepening intertidal-subtidal succession capped by supratidal and subaerially-exposed sediments with pervasive calcrete development. The sedimentary succession passes upwards from a basal unit of intertidal sand flat facies with abundant gastropods (Batillaria diemenensis) near the upper bounding (disconformity) surface, upwards into richly fossiliferous shelly sands (coquina) representing a shallow subtidal facies formed by sediment aggradation in response to a relative sea-level rise. The subtidal facies is dominated by the bivalve molluscs Katelysia sp. and Amesodesma angusta, signifying a water deepening event. The subtidal facies is in turn overlain by pedogenically modified skeletal carbonate sands with pervasive calcrete development signifying a relative sea level fall at the end of the Last Interglacial Maximum. The upper-bounding surface of the shallow-water subtidal facies ranges from 2.4 to 3.0 m Australian Height Datum (AHD) and by analogy with modern sedimentary environments suggests a maximum palaeo-sea level of 4.8 ± 1.0 m during the Last Interglacial Maximum. Uranium-series ages of 127.3 ± 2.1 to 115.0 ± 5.4 ka on specimens of the solitary coral Plesiastrea versipora from the subtidal facies confirm that the succession was deposited during the Last Interglacial Maximum, and are consistent with the independent stratigraphical evidence that the highstand event was represented by a single phase of relative sea-level rise. Correlation with other occurrences of the Glanville Formation in southern Australia has also been confirmed by aminostratigraphy.