The Fluvial Archives Group (FLAG) was founded in 1996 to bring together researchers looking at the development of fluvial systems over multiple timescales and global spatial scales. Fluvial archives of various types are important not just because they provide insights into past landscape dynamics, e.g., driven by climate or crustal processes, but also because they frequently contain fossil or archaeological material for which they provide stratigraphic control. Since 1996, FLAG has evolved from a research group of the British Quaternary Research Association into an organisation with around 500 members in over 20 countries. The research group held 12 biennial meetings, comprising both presentations and field excursions, as well as multiple themed sessions at international conferences. These had resulted by 2017 in 19 journal special issues, all fully detailed by Cordier et al. (2017). The goals of FLAG are: provision of a community for discussion of key issues concerning fluvial archives, including organising the aforementioned biennial discussion/field meetings, sessions at relevant international conferences, and special issues of journals; continued promotion of the value of fluvial archives by means of readily accessible published information; and coordination of activity with other research groupings with overlapping interests, e.g., by co-convening sessions and collaborating on publications.

Combined archaeological, ecological, and geologic research on Chuginadak and Carlisle Islands in the Islands of Four Mountains (IFM) probed questions about the sustainability of human settlements over the past 4000 years in the face of geologic, ecological, and social hazards. We use a human ecodynamics approach to frame the investigation and present original archaeological evidence from this poorly known region of the remote Aleutian Islands. Several village sites occupied during the last four millennia are clustered in locations that were not damaged by earthquake-induced tsunamis; however, new geologic evidence indicates that at least one volcanic eruption forced humans to abandon one or more prehistoric village sites. Combined archaeological, ecological, and geologic analyses demonstrate resilient Unangax̂ occupations of the IFM through long-term climate change as well as earthquakes, tsunamis, and volcanic eruptions with occasional community vulnerability to volcanic eruptions.

Formerly closed drainage basins provide exceptional settings for quantifying fluvial incision and landscape dissection at different time scales. Endorheic basins trap all the sediment eroded within the watershed, which allows estimates of post–basin opening erosion patterns. The Duero Basin was a former closed basin and is presently drained by the Duero River into the Atlantic Ocean. During the Cenozoic, the basin experienced a long endorheic period, marked by the formation of continental carbonates and evaporites. The retrogressive erosion of the Atlantic drainage coming from the Portuguese coast subsequently captured the internal drainage, and significant fluvial dissection occurred. Presently, the basin contains a relatively well-preserved sedimentary fill. Gridding and surface fitting in this paper provide the first attempt to reconstruct the surface of the top of the former endorheic sedimentary sequence to quantify the erosional impact of the basin opening. At least 2251±524 km3 of sediment was removed from the formerly closed basin following the start of exorheism. This volume represents a mean basin-surface lowering of 65±13 m. Erosion estimates and landscape dissection patterns are consistent with geologic evidence of progressive establishment of an outward drainage system.

We present the results of multiproxy study of a peat deposit from Carlisle Island (the Islands of Four Mountains, Aleutians). Vegetation on the initial stage of the peat is characterized by heath vegetation dominated by Ericales indicating cold conditions at 7300–6100 cal yr BP. The appearance of Betula and Alnus is the result of long-distance transportation attributable to strong winds at this time. Sedge-grass (Cyperaceae and Poaceae) communities began replacing heath vegetation at 6100 cal yr BP because of the climatic amelioration. C/N ratios and pollen spectra remain relatively stable at 6100–2450 cal yr BP. For the CR-03 peatland, volcanic tephra contributed significantly to the Fourier transform infrared spectroscopy spectral data. Volcanic input created overlap of an aluminosilicate signal with carbohydrate vibrations. Significant changes occurred at approximately 2450 cal yr BP when there is the some evidence of cooler and wetter conditions of the Neoglacial. High values of δ15N observed at 7100–7000 cal yr BP reflect the fertilizing effect of seabird nesting colonies. A decrease in δ15N ca. 6900 cal yr BP may indicate initial settlement on Carlisle Island corresponding with harvesting seabirds. Human predation continued until a series of volcanic eruptions, which deposited Okmok II and CR-02 tephra layers at ca. 2000 and 1050 cal yr BP, respectively.

The appearances of palaeosurfaces intercalated into palaeo-dune fields on Fuerteventura are multifaceted. Although reddened layers in these dune sediments might suggest that strong soil-formation processes have taken place, the combination of aridity and parent material, namely biogenic carbonate sand of shelf origin, reveals that strong soil formation seems unlikely. These sediments rather represent de- and recalcification processes only. Solely in the case of admixed material of volcanic origin and dust deposits further soil-forming processes seem to be possible. Hematite-rich Saharan dust contributes to reddish colouration of the palaeosurfaces. In addition, CaCO3-coated iron particles appear to be ingredients of dust being leached after deposition and transformed to hematite. Overall, we propose much weaker soil-forming processes during the Pleistocene than previously postulated. Our findings support the relevance of local environments. Carbonate sands of shelf origin hinder strong soil formation and the reddish layers separating dune generations are palaeosurfaces, which mainly consist of Saharan dust. After deposition of allochthonous material, these layers are overprinted by weak soil-forming processes. The formation of palaeosurfaces primarily depends on morphodynamically stable periods during limited sand supply. Our data suggest a cyclicity of processes in the following order: (1) sand accumulation, (2) dust accumulation and weak soil formation, and (3) water-induced erosion. For the Canary Islands, we support the assumption of glacial maxima being periods of increased levels of moisture. In combination with rising sea level, we propose that favorable conditions of surface stability occur immediately after glacial maxima during periods of starting transgression, whereas regression periods immediately after sea-level high stands seem to yield the highest sand supply for the study area.

Different interpretations of accumulation and preservation of aeolian sediments lead to divergent and sometimes contradictory palaeoclimate reconstructions. Although aeolian transport mainly occurs during dry climate, the preservation of the aeolian sediment is a critical factor in many environments in determining the nature of the aeolian sedimentary archive. Analysis of more than 200 optically stimulated luminescence ages for aeolian sands from Tibet shows four different aeolian phases of accumulation. Strong aeolian activity occurred during the last glacial maximum, but hardly any aeolian sediments are preserved. Consequently, the period with the highest aeolian activity is not recorded in the sedimentary record. A phase of aeolian accumulation occurred in the late glacial and the early Holocene. The duration of deposition for this phase is a consequence of the complex topography and an increase in moisture. This phase was punctuated by exceptionally strong accumulation during the Younger Dryas stade. The mid-Holocene is characterised by weak aeolian accumulation and fluvial erosion caused by greater precipitation during the maximum height of the Asian summer monsoon. Aeolian activity resumed in the late Holocene because of drier conditions. The conceptual model provides an approach that can be applied to other mountain and desert margin regions that have limited sediment availability.

The Ebro catchment includes a continental foreland basin that underwent an endorheic–exorheic transition. Morphometric studies, including hypsometric curves, hypsometric integrals, asymmetry factor, mountain front sinuosity, normalised stream-length gradient, and normalised concavity indices for the Ebro River and 32 of its tributaries, show the signals of transient response to this major drainage change. The Ebro River, its upper catchment tributaries, and the Pyrenean tributaries have concave-up longitudinal profiles, concave hypsometric curves, and low hypsometric integrals, parameters typical of deeply dissected basins. This suggests a mature stage of development, controlled by the shift of the base level to the Mediterranean Sea. Iberian Range tributaries display low concavity profiles with numerous knickpoints and high values of hypsometric integral, indicating a transient state as a response to tectonic uplift, ratified by the values of mountain front sinuosity surrounding the basin.

The Islands of Four Mountains island group of the Aleutian island arc is remote and difficult to access. Consequently, little fieldwork has focused on geomorphic processes and their relationship to island morphology, climatic change, and human settlement. We investigated glacial, fluvial, and slope processes on the morphologically different Carlisle, Cleveland, and Tana volcanoes. The islands were extensively glaciated at the last glacial maximum (LGM), and there is evidence for a Neoglacial advance. On the highly dissected Tana volcano, a large basin is likely the result of a pre-LGM sector collapse and subsequent glacial erosion into weak hydrothermally altered rock. Valley and moraine morphology is also influenced by hydrothermal alteration. On both Tana and Carlisle, there are sediment fans composed dominantly of thick debris flow deposits mantled by ~3 m of layered tephras, fine-grained alluvium, and anthropogenic deposits. Debris flow deposition was favored during the unstable paraglacial landscape of the early Holocene–latest Pleistocene. The earliest direct archaeological evidence for settlement is 3.8 cal ka BP, but soil geochemical evidence suggests that the islands were inhabited by 7.3 cal ka BP. This discrepancy in the archaeological record may be explained by geomorphic processes including coastal erosion and unstable geomorphic surfaces.

Detailed study of subsurface deposits in the Polish Sudeten Foreland, particularly with reference to provenance data, has revealed that an extensive preglacial drainage system developed there in the Pliocene–Early Pleistocene, with both similarities and differences in comparison with the present-day Odra (Oder) system. This foreland is at the northern edge of an intensely deformed upland, metamorphosed during the Variscan orogeny, with faulted horsts and grabens reactivated in the Late Cenozoic. The main arm of preglacial drainage of this area, at least until the early Middle Pleistocene, was the Palaeo–Nysa Kłodzka, precursor of the Odra left-bank tributary of that name. Significant preglacial evolution of this drainage system can be demonstrated, including incision into the landscape, prior to its disruption by glaciation in the Elsterian (Sanian) and again in the early Saalian (Odranian), which resulted in burial of the preglacial fluvial archives by glacial and fluvioglacial deposits. No later ice sheets reached the area, in which the modern drainage pattern became established, the rivers incising afresh into the landscape and forming post-Saalian terrace systems. Issues of compatibility of this record with the progressive uplift implicit in the formation of conventional terrace systems are examined, with particular reference to crustal properties, which are shown to have had an important influence on landscape and drainage evolution in the region.

The island of Gran Canaria is regularly affected by dust falls due to its proximity to the Saharan desert. Climatic oscillations may affect the Saharan dust input to the island. Geochemical, mineralogical, and textural analysis was performed on a well-developed and representative early Pleistocene paleosol to examine Saharan dust contribution to Gran Canaria. Significant and variable Saharan dust content was identified in addition to weathering products such as iron oxides and clay minerals. Variations in quartz and iron oxide concentrations in the paleosol likely reflect different Saharan dust input in more/less-contrasted rhexistasic/biostatic climatic conditions. Linking the quartz content in Canarian soils, the Ingenio paleosol, and two Canarian loess-like deposits to different ages from the Quaternary, we hypothesized that the dust input should be lower (about 33–38%) throughout the early to middle Pleistocene than during the late Quaternary. The Saharan dust input to the Gran Canaria profile in the Pleistocene persisted in spite of climatic variations.

Using six paired terrestrial and marine organics collected in the Islands of Four Mountains, Alaska, we present a new regional correction factor, ΔR (495±20 yr), for the eastern Aleutians. We compare our ΔR with previous North Pacific marine corrections. Using the ΔR for the eastern Aleutians, we calibrated the radiocarbon dates of 80 human skeletons recovered from village site Chaluka and cave burials at Ship Rock and Kagamil Islands. These burial places contain two morphologically and genetically distinct humans—an early form called Paleo-Aleut and a later form called Neo-Aleut. Researchers have contested (1) the timing of Neo-Aleut movements into the Aleutians, and (2) Neo-Aleut interactions with Paleo-Aleuts. Our recalibrations indicate that the oldest Paleo-Aleut burial (1135 BC) occurred at Chaluka and the youngest Paleo-Aleut cave burial occurred at Kagamil during the fourteenth century (AD 1305). Neo-Aleuts buried their dead at Chaluka by AD 1375. The oldest definitive Neo-Aleut cave burial occurred during the fifteenth century (AD 1420) at Ship Rock. Eastern Aleuts buried their dead in caves for centuries, with the youngest Neo-Aleut buried at Kagamil circa AD 1865.

One of the enduring questions in the field of paleohydrology is how quickly desert wetland ecosystems responded to past episodes of abrupt climate change. Recent investigations in the Las Vegas Valley of southern Nevada have revealed that wetlands expanded and contracted on millennial and sub-millennial timescales in response to changes in climate during the late Quaternary. Here, we evaluate geologic evidence from multiple localities in the Mojave Desert and southern Great Basin that suggests the response of wetland systems to climate change is even faster, occurring at centennial, and possibly decadal, timescales. Paleowetland deposits at Dove Springs Wash, Mesquite Springs, and Little Dixie Wash, California, contain evidence of multiple wet and dry cycles in the form of organic-rich black mats, representing periods of past groundwater discharge and wet conditions, interbedded with colluvial, alluvial, and aeolian sediments, each representing dry conditions. Many of these wet-dry cycles date to within the Younger Dryas (YD) chronozone (12.9–11.7 ka), marking the first time intra-YD hydrologic variability has been documented in paleowetland deposits. Our results illustrate that desert wetland ecosystems are exceptionally sensitive to climate change and respond to climatic perturbations on timescales that are relevant to human society.

Numerical dating and geomorphic studies on alluvial sediment were undertaken in the uppermost reaches of the Dunajec River catchment in the northern foreland of the Tatra Mountains of Poland. Successions of alluvial deposits in river terraces and alluvial fans are common in this region. In particular, alluvial fans deposited a thick succession of sediment in the intramontane Orawa–Nowy Targ Depression, and terraces are preserved as two cut-and-fill and six strath terraces along the uplifting sections of river courses. We identify several alluviation phases within the alluvial successions that occurred since Marine Oxygen Isotope Stage 6. These sediments show that deposition largely occurred under temperate-climate conditions. This is in spite of a potential strong impact from headwater glaciers under cold-climate conditions. Glacially produced sediments were largely stored within frontal moraines and proglacial floodplains. These glaciogenic sediments were eroded and resedimented during glacier retreat. We therefore conclude that “warm” alluviation is the dominant process forming alluvial successions in this region.

This first zooarchaeological analysis for the Islands of Four Mountains (IFM), Aleutian Islands, Alaska, provides data about local hunter-gatherer resource exploitation over three thousand yr. The majority of zooarchaeological material represents faunal resources that were harvested within several kilometers of villages. Our analysis shows that IFM subsistence system was shaped by the small size of these islands, which is mostly true for all of the Aleutian Islands. The archaeological middens indicate that Aleuts readily exploited new resources when they became available, expanding their dietary niche. Despite human harvesting, most faunal populations remained stable; however, Aleuts overexploited the storm-petrel colony on Carlisle Island.

A key concern regarding current and future climate change is the possibility of sustained droughts that can have profound impacts on societies. As such, multiple paleoclimatic proxies are needed to identify megadroughts, the synoptic climatology responsible for these droughts, and their impacts on past and future societies. In the hyperarid Atacama Desert of northern Chile, many streams are characterized by perennial flow and support dense in-stream wetlands. These streams possess sequences of wetland deposits as fluvial terraces that record past changes in the water table. We mapped and radiocarbon dated a well-preserved sequence of in-stream wetland deposits along a 4.3-km reach of the Río San Salvador in the Calama basin to determine the relationship between regional climate change and the incision of in-stream wetlands. The Río San Salvador supported dense wetlands from 11.1 to 9.8, 6.4 to 3.5, 2.8 to 1.3, and 1.0 to 0.5 ka and incised at the end of each of these intervals. Comparison with other in-stream wetland sequences in the Atacama Desert, and with regional paleoclimatic archives, indicates that in-stream wetlands responded similarly to climatic changes by incising during periods of extended drought at ~9.8, 3.5, 1.3, and 0.5 ka.

Climate and tectonics effect the fluvial evolution of the Mediterranean Mut basin. The basin contains a river terrace staircase of 16 levels (T16–T1) ranging from 365 to 10 m above the current Göksu River in its middle and lower sections. These river terraces records tectonic uplift in the Mut basin. Optically stimulated luminescence (OSL) dating of the fluvial sediments of the youngest terrace (T16) provides a chronology for the assessment of the important impacts of climatic changes. The ages from the youngest river terrace deposits in T16 may be subdivided into two intervals: (1) 239–194.7 ka during the later part of Marine Oxygen Isotope Stage (MIS) 7, implying that the aggradation of T16 started in (the final phase of) this warm period; and (2) 187.9–171 ka during much of MIS 6. Thus, it appears that the Göksu River continued depositing sediment from an interglacial into a glacial time. The differences in climate-driven fluvial evolution between this Mediterranean fluvial system and the classical, well-studied temperate–periglacial river systems in Europe may be the result of different vegetation cover and greater thaw of more intense snowfalls.

The earliest durable cooking technologies found in Alaska are stone bowls and griddle stones recovered from the Aleutian Islands. This article aims to identify the function of these artefacts. Molecular and chemical analyses of carbonised residues found on their surfaces confirm that these artefacts were used to process marine resources. Both artefacts have high lipid content and C:N ratios, suggesting they were used to process oily substances. Stable isotope results of individual lipids suggest that they were used to process different sets of resources within the aquatic spectrum as griddle stones have slightly more 13C-depleted lipids than stone bowls, possibly indicating more variable use. Integration of these results with archaeological and ethnographic data leads us to infer that griddle stones were used for cooking a diversity of aquatic resources, possibly with the addition of plant foods, whereas stone bowls were specifically used to render marine mammal fats. We further hypothesize that a sudden peak in stone bowl frequencies at 4000–3000 cal yr BP was connected to a Neoglacial cold spell bringing sea ice conditions to the Aleutian Islands. This may have led to new subsistence strategies in which the rendering of marine mammal fats played a central role.

Asx̂aana-x̂ Cave in the Islands of the Four Mountains, Alaska, was excavated in 1990. The cave contained the remains of Unangan mummies and their grave goods including textile, wood, bone and stone artifacts. These mummies were buried between AD 1250 and AD 1780-1790. The mummies were distributed in three distinct areas in the front, middle and back of the large cave. The textile and wooden artifacts and their distribution have been described in earlier publications. The stone artifacts include end blades, adzes, ulus and hammerstones plus an oil lamp and a small figurine; among the bone artifacts are whale bone planks and scapulae, rods and shafts, harpoon heads and labrets. These artifacts are typical of artifacts in the Aleutian Islands, while their distribution continues to strengthen the idea of a disjunct distribution of artifacts in the cave, which I interpret as being due to different social groups using the three areas of the cave for their burials.

The Lower Meuse Valley crosses the Roer Valley Rift System and provides an outstanding example of well-preserved late glacial and Holocene river terraces. The formation, preservation, and morphology of these terraces vary due to reach-specific conditions, a phenomenon that has been underappreciated in past studies. A detailed palaeogeographic reconstruction of the terrace series over the full length of the Lower Meuse Valley has been performed. This reconstruction provides improved insight into successive morphological responses to combined climatic and tectonic external forcing, as expressed and preserved in different ways along the river. New field data and data obtained from past studies were integrated using a digital mapping method in GIS. Results show that late glacial river terraces with diverse fluvial styles are best preserved in the Lower Meuse Valley downstream sub-reaches (traversing the Venlo Block and Peel Block), while Holocene terrace remnants are well-developed and preserved in the upstream sub-reaches (traversing the Campine Block and Roer Valley Graben). This reach-to-reach spatial variance in river terrace preservation and morphology can be ascribed to tectonically driven variations in river gradient and subsurface lithology, and to river-driven throughput of sediment supply.