Abstract This Special Publication presents 23 papers that examine comparable, predominantly siliciclastic coastal zones of low-lying passive trailing-continental margins (primarily east Americas) from polar areas to the equator. The objective is to establish similarities and major differences among them. This introductory paper outlines major contributions of the various papers, but will also highlight coastal differences and briefly add information not fully treated by others. This is done in three parts: (a) some basic concepts are stressed, such as the importance of ‘coastal zone’ (total landscape) in the north–south comparison and the variable climates; (b) a review is made of the component materials of the coasts, such as difference in sediments owing to source rocks, weathering and geological history (glaciations), and in flora and fauna such as burrowing organisms; and (c) a few classical examples are reported from warm zones, such as Galveston Island and the Sapelo Island marshes, but the focus is on less well-known environments of cold areas – those most impacted by climate change. Each component of the coastal zone can develop diagnostic characteristics, but the entire assemblage of sedimentary and biological features is what uniquely defines present environments and allows identification of ancient coastal zones.

Abstract From a geographical point of view, the general pattern of coastal zones (or geographical coastal zonality) is arranged along latitudinal gradients and gradations from the Equator to the poles, caused by the spherical shape of our planet and the distribution of heat according to the angle of incoming radiation. As the distribution of land and oceans differs between hemispheres and along latitudes, and atmospheric and oceanic circulation moves energy in all directions, the global pattern of coastal forms and processes due to climate-triggered conditions is very complex. Moreover, each single pattern is dynamic and subject to revision by changes in the climate. Some coastal zones (e.g. humid tropics or high polar zones) can be delimited rather easily, while others (e.g. temperate cool or those with alternating tropical climate) are more difficult to define. This paper provides a short overview of the state of the art in geographical zonality of coastal environments (not only of coastlines) from the poles to the Equator, with the main emphasis on cold and warm zones, pointing to climate-induced differences in the context of Quaternary climate change or those occurring over the last centuries and decades.

Abstract The term meiobenthos refers to a group of invertebrate organisms that are intermediate in size between macro- and microfauna, and inhabit all sediment types in all marine environments and in all climatic zones. They may occur at enormously high densities of millions of individuals per square metre; this means that 10 cm 3 of sediment in any given habitat may contain thousands of these organisms. Although meiobenthos in some extreme arctic habitats is uncommonly poor, the abundance and composition of the polar or subpolar meiobenthic assemblages are not essentially different from those found in boreal–tropical locations at corresponding sediments and depths.

Abstract Indigenous peoples occupy many of the world's coastal zones, and have used and managed coastal and marine resources for millennia. As a result they have accumulated extensive knowledge about these environments that supported their ability to colonize new territories in the past and informs their on-going adaptive responses to environmental, climatic and socio-cultural changes. This paper examines the adaptive capacity of Indigenous peoples over time and across a range of coastal settings. It begins with a discussion of some reasons for the relative neglect, until recently, of cultural adaptations in coastal settings. The experiences of a selection of Indigenous groups in each of three coastal zones – Arctic, Temperate and Tropical – are then explored in relation to various adaptive mechanisms they have employed traditionally as well as in contemporary contexts. Comparison across these experiences indicates that Indigenous peoples regard the coast as an integral component of a land–sea continuum that provides enhanced food security, important cultural and spiritual attachments, and valuable opportunities for social interaction and learning. Coastal science and policy initiatives stand to benefit from greater consideration of the adaptive strategies of Indigenous coastal peoples.

Abstract The arctic environment is changing: air temperatures, major river discharges and open water season length have increased, and storm intensities and tracks are changing. Thirteen quantitative studies of the rates of coastline position change throughout the Arctic show that recently observed environmental changes have not led to ubiquitously or continuously increasing coastal erosion rates, which currently range between 0 and 2 m/yr when averaged for the arctic shelf seas. Current data is probably insufficient, both spatially and temporally, however, to capture change at decadal to sub-decadal time scales. In this context, we describe the current understanding of arctic coastal geomorphodynamics with an emphasis on erosional regimes of coasts with ice-rich sedimentary deposits in the Laptev, East Siberian and Beaufort seas, where local coastal erosion can exceed 20 m/yr. We also examine coasts with lithified (rocky) substrates where geomorphodynamics are intensified by rapid glacial retreat. Coastlines of Svalbard, Greenland and the Canadian Archipelago are less frequently studied than ice-rich continental coasts of North America and Siberia, and studies often focus on coastal sections composed of unlithified material. As air temperature and sea ice duration and extent change, longer thaw and wave seasons will intensify coastal dynamics in the Arctic.

Abstract Cold climate exerts a clear influence on the processes of marine transgression in mid- and high-latitude coastal-plain settings, but its signature in the depositional record is much clearer at high latitude. Both cases selected for this study are influenced by the legacy of past glaciation and the pervasive effects of ongoing Holocene marine transgression. Both are affected by sea ice. The high-latitude site lies within the zone of continuous permafrost and the abundance of excess ground ice along the Beaufort coast is the dominant factor distinguishing it from the mid-latitude Gulf of St Lawrence (GSL) setting and standard models of transgressive coasts elsewhere. In the southern GSL, the transgressive unconformity (TU) is at the seabed (or buried by a very thin veneer) across the inner shelf; shoreface sand moves landward, keeping pace with the transgressive front through deposition in barriers, dunes and estuaries. The pace of transgression in the Beaufort Sea is influenced by a number of distinctive periglacial erosion processes, including thermal abrasion and thaw subsidence. Marine transgression across this landscape creates intricate breached-lake estuaries and low sandy barrier beaches with limited dunes, leaving distinctive facies suites and geometry, while seaward sediment transport buries the TU on the inner shelf.

Abstract Foxe Basin is a down-faulted arctic basin floored by Palaeozoic carbonates, surrounded by metamorphic Precambrian terrains. Quaternary deposits consist of Pleistocene–Holocene glacial drift, and frost-shattered bedrock-clasts mostly reworked by sea waves during post-glacial emergence during the last 5000–6000 yr. The shallow, primarily micro- to meso-tidal sea is covered by ice for c. 9–10 months each year. This ensures that the overall energy of the coasts is low, although strong storm waves develop during ice-free periods. Puccinellia phryganodes dominated salt marshes occur on muddy and sandy shores and grade into inland sedge-forb wetlands and Dryas -dominated tundra. Cold climate processes active on the emerged land have generated typical features such as frost heaving of bedrock blocks, solifluction lobes on slopes, frost boils in flatter areas, frost shattering and solution of surficial carbonate pebbles, thermokarst lakes, and shallow Cryosols.

Abstract The purpose of this review is to assess if there are any specific processes and morphologies distinguishing coastal dunes developed in cold-climate conditions, in order to illustrate how climate can exert a control on coastal dune morphologies. In the Arctic, availability of sand supply and the duration of winter conditions are limiting factors for the development of large coastal dunes. They are small in size, and embryo dunes including nebkha are the dominant and often only coastal dune type. In milder subarctic settings, characterized by a longer surficial ice-free season, a greater variety of coastal dunes are found, mainly foredunes, blowouts and parabolic dunes. In subarctic areas, as along the SE coast of Hudson Bay, niveo-aeolian processes actively affect coastal dune development. These processes do not generally imprint permanent morphologies, although some distinctive sedimentary structures owing to the melting of snow are observed. The coastal dunes of the arctic regions differ from the dunes of subarctic and temperate regions mainly because of their limited spatial and morphological development. Extreme climatic conditions (low precipitation, extreme cold), and very limited vegetation growing season, combined with low sediment supply, explain the fact that only embryo dunes develop in arctic environments.

Abstract The current temporal and spatial context of water-level change, drivers of change, and possible future scenarios of the Laurentian Great Lakes is controversial. Palaeohydrographs are being constructed from measured subsurface elevations of palaeo-swash zones and modelled ages in strandplains of beach ridges that are preserved in embayments along the lakes’ edge. More than 800 elevations and 200 ages have been collected from 15 strandplains to construct site strandplain palaeohydrographs. Palaeo-beach elevations from whole strandplains or sets of correlative palaeo-beaches within strandplains are then used to establish an outlet palaeohydrograph for each lake. Adjusting strandplain palaeohydrograph elevations to account for glacial isostatic adjustment and refining age models help define the outlet palaeohydrograph. Common basin-wide water-level patterns and changes in outlet location or conveyance can then be interpreted. Systematic patterns of elevation and geomorphic/sedimentologic properties in individual, groups and sets of beach ridges in strandplains suggest that long-term patterns of water-level change and sediment supply occurred on decadal, centennial and millennial scales. Outlet palaeohydrograph construction for Lake Superior revealed discrepancies between geological and historical rates of glacial isostatic adjustment. These differences are currently being investigated using new data from Lake Huron.

Abstract In Chignecto Bay, upper Bay of Fundy, Canada, the muddy tidal flats exhibit distinctive sedimentological and ichnological characteristics indicative of winter conditions and the development of ice. From late spring to autumn (May–October: mean temperature +13.6 °C), the mud flats sustain a high infaunal biomass and sediment deposition is dominated by tidal processes. Neap–spring tidal rhythmites, fluid-mud deposition and high levels of bioturbation are all characteristic of summer deposits. During the winter, temperatures remain below zero (December–March: mean temperature −6.3 °C), and ice forms in the bay and periodically on the mud flats. Ice rafts and blocks are common on the tidal-flat surface, and these blocks deform the muddy sediment, cut deep scours and deposit allochthonous sediment (including gravel) across the flats. Intermittent storms in the autumn and winter also contribute to sediment scouring and erosion. Annual die-offs of infauna are reflected by reduced bioturbation in winter deposits. Each spring, renewed larval recruitment and opportunistic colonization results in increasing levels of bioturbation, and the trace suite is dominated by a low-diversity assemblage of diminutive, vertical burrows. The summer–winter cyclicity in infaunal colonization manifests, ichnologically, as a distinctive bioturbated–non-bioturbated bedset character. Infaunal populations in Chignecto Bay peak in the late spring and in the late summer–early autumn. Both population peaks are exploited by vertebrates, including migrating Atlantic sturgeon (late spring) and migratory shorebirds (late summer–early autumn). In particular, the upper Bay of Fundy, including Chignecto Bay, is a staging ground for approximately 42–74% of the world’s Semipalmated sandpipers ( Calidris pusilla ) on their annual migration from the Arctic to South America. Fortunately, anthropogenic modification of Chignecto Bay, and its associated bays and rivers (e.g. construction and dismantling of a causeway over the Petitcodiac River), has not had a significant effect, to date, on the mud-flat habitat or the infaunal biomass.

Abstract Paraglacial coastal systems are formed on or proximal to formerly ice-covered terrain from sediments with direct or indirect glacial origin. This review addresses the roles of tectonic controls, glacial advances and retreats, sea-level changes, and coastal processes in sediment production, delivery and redistribution along the paraglacial Gulf of Maine coast (USA and Canada). Coastal accumulation forms are compositionally heterogeneous and found primarily at the seaward edge of the Gulf's largest estuaries; their existence is directly attributable to the availability of glacial sediments derived from erosion of weathered plutons within coastal river basins. Multiple post-glacial sea-level fluctuations drove the redistribution of these sediments across the modern lowland and inner shelf. Central to the formation of barrier systems was the paraglacial sand maximum, a time-transgressive phase of relative sea-level fall and enhanced fluvial sand export c. 2000–4000 years following deglaciation. Vast quantities of sand and gravel were reworked landward during the subsequent transgression and combined with additional riverine sediments to form the modern barrier systems. Today, reduced fluvial sediment loads, anthropogenic modifications of barrier and river systems, and sea-level rise have combined to exacerbate long-term coastal erosion and may eventually force these barriers toward a state of rapid landward migration.

Abstract Holocene coastal environments in the Tierra del Fuego archipelago, southernmost South America, evolved in a temperate cold climate characterized by strong and persistent mid-latitude westerly winds, and under stable to falling relative sea-level. Southern and western coasts are rocky, microtidal and generally devoid of Holocene accretionary coastal landforms. They are young, having originated from flooding by the early Holocene. Northern and eastern coasts are lined by receding cliffs that supply abundant sediment to macro/mesotidal embayments lodging extensive accretionary coastal landforms. Spit growth on the Atlantic shore played a major part in modifying the development of other landforms by barring the shoreline from wave attack. Sediment was mainly supplied from Pleistocene glacial deposits exposed at eroding headlands and, more locally, obtained by cannibalization and from elevated Pleistocene beaches. In places, westerly winds combined with Atlantic swell to foster spit growth under high-energy wave power on both bay and ocean flanks – a unique occurrence. In addition, the westerlies caused widespread deflation on supratidal marshes and delivered fine-grained sediment inland and to the sea. Recent acceleration of glacio-eustatic rise is gradually changing the coastal zone to a condition of relative sea-level rise. The generally high and steep coastlines will not be greatly affected. A few gently-dipping lowlands might be flooded and biodiversity will be negatively affected.

Abstract The emerged part of the Río de la Plata estuary is characterized by striking coastal geomorphic features. Aerial and satellite images, field observations of the outcrops, shallow boreholes, radiometric dating of sand and shells and Ground Penetrating Radar surveys were analysed. The main sedimentary features are: a large coastal barrier (up of 220 km long), old coastal lagoons, attached beach ridge (about 210) sets distributed along 170 km, the Ibicuy sand body variously interpreted as a reworked shoal/island or delta, and cheniers. The tidal flats and the modern Paraná Delta are located in the centre and on the right side of the inner estuary. The height of the estuarine coastal barrier represents the maximum flooding surface (MFS) of the last transgression at about 6000 aBP. Other main sedimentary forms developed as a falling stage systems tract (FSST) during the sea-level drop between the aforementioned date and the present. The sea surface was about 5 m above sea-level in the inner part of the estuary during the middle-Holocene. This MFS was subsequently followed by a continuous and slow sea-level fall that controlled the generation of the large sedimentary forms developed in the innermost part of the Río de la Plata Estuary.

Abstract The Holocene barrier along the southern Brazilian coast is most likely the most continuous barrier structure in the world. This coast is characterized by a Holocene barrier extending for 760 km, interrupted by only six discontinuities, which are associated with narrow lagoonal inlets and river mouths. This coast is marked by a huge availability of sand, a gently sloping continental shelf, and incident waves of moderate to high energy. Together, these factors constitute ideal conditions for the formation of coastal barriers. During periods of low sea-levels, the continental shelf in front of the La Plata estuary was fed by immature fluvial sands delivered by the Paraná River, which were transported to the southern Brazilian coast by a predominantly northward littoral drift. Based on forecasts of sea-level rise, it will take decades or centuries for change to occur in the progradation of the regressive barriers along the coastal embayments. During the last centuries and millennia (Middle to Late Holocene), the evolution of this coast has been controlled by the variations in wave energy along the coast.

Abstract Dune systems along the South African coast are sensitive barometers of fluctuations in palaeoenvironments, as archived in their orientation, geometry, internal architecture, composition, granulometry, diagenesis, palaeontology and archaeological content. Presently, the pronounced climatic/oceanographic gradients around the southern African coastline, including the west coast Mediterranean climate type, with cold upwelling to progressively warmer in terms of climate and sea temperatures eastwards, are mirrored by variations in these parameters. Here, we review and contribute new information concerning their fluctuations from the Miocene to the present to track changes in the bio-, hydro- and geospheres through time. West coast dunes take the form of dune plumes, which have an orientation since the Miocene that mirrors the southerlies of the South Atlantic Anticyclone (SAA), muted during the warm Pliocene, as reflected by intense bioturbation. Shoreline-parallel, vertically aggraded dune cordons dominate along the southern and eastern coasts, formed by (winter) polar westerlies since the Miocene. The contrasting dunefield morphologies relate to seasonality of wind strength and precipitation. Subtropical east coast dunes are profoundly weathered – on the shelf, glacial-period dunes indicate different atmospheric circulations. The long-term stability of the warm Agulhas Current contrasts with variability in the Benguela. The aeolianites host a rich human and faunal archive, including human ichnofossils. Supplementary material: Tables S1 and S2, which provide details of the data and data sources for Figure 9 in the text, are available at http://www.geolsoc.org.uk/SUP18711 .

Abstract The 30 000 km-long Australian open coast is located between tropical and temperate latitudes (9°–42°S), with humid north and east coasts, and generally semi-arid–arid south and west coasts. The 9000 km-long temperate arid coast is dominated by carbonate shelf and inshore sediments that have supplied contemporary carbonate beach and dune systems, as well as very extensive Pleistocene calcarenite barrier systems that dominate much of the inner shelf, coast and near interior, and which, in places, have contributed to a blanketing of the downwind interior with calcareous loess deposits. Much of the contemporary coastal landscape and, to varying degrees, the adjacent interior is therefore dominated by a legacy of carbonate marine sediments. This paper reviews the reasons for the dominance of carbonate along this section of coast. It begins by examining the sources, followed by the transport and depositional mechanisms, the nature of the onshore carbonate deposits, including their diagenesis, and their longer-term impact on the coast.

Abstract Here, we explore the evolution of the coastal stretch between Mira Beach and Quiaios Beach in Portugal to understand how it adapted to climatic oscillations. To accomplish this, we integrate subsurface radar images, and sedimentological and chronological data, of the emerged coastal barrier. Our results show the installation and progradation of a stable barrier anchored to transgressive dunes 400 years ago. This is just the last pulse of barrier growth within a complex approximately 5000 year-long history of shoreline stability/instability. Episodes of inland dune mobility have been related to instabilities in the beach sediment budget driven by enhanced storminess and wave rotation around 4.25 and 1.14 ka ago. Conversely, lagoonal deposits documented in the literature suggest periods of relative barrier stability and growth around 4.3 and 2.7 cal ka BP. Wave and wind climate variability are driven by shifts in one of the major modes of atmospheric circulation in the North Atlantic, the North Atlantic Oscillation (NAO). Episodes of persistent positive mode of the NAO related to barrier growth and enhanced longshore sediment transport; those of persistent negative mode contributed to instabilities in the beach sediment budget and aeolian activity by enhancing storminess, but reduced effective longshore sediment transport.

Abstract Seven borehole cores were analysed to reconstruct the Pleistocene evolution of the Pego-Oliva Basin (Mediterranean coast, Iberian Peninsula). A total of 295 samples were recovered for amino acid racemization (AAR) dating, and 77 samples for sedimentological, palaeontological and biomarker determination, with two objectives: (1) to establish a chronological framework (especially for Middle Pleistocene); and (2) to obtain data on the palaeoenvironment. AAR proved that the record covers approximately 650 ka in which no important hiatuses occurred, although minor ones cannot be discarded. AAR provided valuable information on differential subsidence rates, and Marine Isotope Stages (MISs) 15–1 were identified. Litho- and biofacies allowed the identification of distinct palaeoenvironments through time, with the constant presence of a marsh/lagoonal environment with brackish or saline water with continental or marine influence. Remains of marine molluscs allowed the determination of periods of highstand sea level. Biomarkers indicated a constant input from terrestrial plants, and allowed definitions of periods with variable water mass and environmental moisture. As in other Mediterranean littoral areas, facies with a marine influence occurred mainly during odd MISs, indicating periods of highstand sea level. In contrast, alluvial-fan progradation and continental brackish wetlands developed during even MISs.

Abstract The Mediterranean basin is an important area of the Earth for studying the interplay between geodynamic processes and landscape evolution affected by tectonic, glacio-hydro-isostatic and eustatic factors. We focus on determining vertical deformations and relative sea-level change of the coastal zone utilizing geological, archaeological, historical and instrumental data, and modelling. For deformation determinations on recent decadal to centennial time scales, seismic strain analysis based on about 6000 focal mechanisms, surface deformation analysis based on some 850 continuous GPS stations, and 57 tide gauge records were used. Utilizing data from tectonically stable areas, reference surfaces were established to separate tectonic and climate (eustatic) signals throughout the basin for the last 20 000 years. Predominant Holocene subsidence (west coast of Italy, northern Adriatic sea, most of Greece and Turkey are areas at risk of flooding owing to relative sea-level rise), uplift (local areas in southwestern Italy and southern Greece) or stability (northwestern and central western Mediterranean and Levant area) were determined. Superimposed on the long trends, the coasts are also impacted by sudden extreme events such as recurring large storms and numerous, but unpredictable tsunamis caused by the high seismicity of parts of the basins. Supplementary material: A table of locations and timings of the largest tsunamis in the Mediterranean during the last 5660 years BP is available at http://www.geolsoc.org.uk/SUP18757 .