Environmental Archives Research Articles

Combining Inorganic and Organic Carbon Stable Isotope Signatures in the Schwalbenberg Loess-Palaeosol-Sequence Near Remagen (Middle Rhine Valley, Germany)

Western Central European Loess-Palaeosol-Sequences (LPS) provide valuable terrestrial records of palaeoenvironmental conditions, which formed in response to variability in the North Atlantic climate systems. Over the last full glacial cycle (~130 ka), climate oscillations within these systems are best documented in deep sea and ice cores; the responses of terrestrial systems are not yet fully understood. A better understanding of metabolism governing input and output variables of organic- and inorganic C pools is, however, crucial for investigating landscape-atmospheric feedback processes and in particularly, for understanding the formation of calcareous LPS as environmental archives. Here we quantify the contributions of primary carbonates (PC) and secondary carbonates (SC) to the overall inorganic carbon pool down a LPS at the Schwalbenberg site, based on the natural abundance ratio of stable carbon isotopes (δ13C). This facilitates detailed insights into the carbonate metabolism and hence, loessification and percolation processes. PC accumulate predominantly in cold phases during periods of reduced biological activity and become leached during wetter and warmer periods contemporary with higher rates of SC re-precipitation and total organic carbon (TOC) increases due to enhanced biomass production. We find that mineral dust input is most significant during stadials, as well as towards the end of warmer interstadials, characterised by gradual cooling back to stadial conditions. Pedogenesis in the Schwalbenberg LPS kept pace with surface accumulation of mineral dust. This indicates that palaeosols are of accretionary nature, which gives raise to the idea of incorporation of former topsoils in preserved subsoil horizons. Our study decodes fundamental aspects of the link between atmospheric dust circulation and terrestrial records in western Central Europe. In addition, interdependencies between factors governing the regional moisture budged and LPS can be reconstructed in a more holistic way than before.

Multi-tracer analysis to estimate the historical evolution of pollution in riverbed sediment of subtropical watershed, the lower course of the Piracicaba River, São Paulo, Brazil

The main land use/land cover changes (LULCC) have been associated with population growth and energy policies in the São Paulo State, Brazil, since 1970. The LULCC can alter the behavior of trace elements in different environmental systems, with the riverbed sediments being the main reservoirs or sinks for trace elements, and thus become a valuable environmental archive on temporal changes. Thus, the main purpose of the study was to apply a multi-tracer analysis to estimate the historical evolution of pollution in riverbed sediment of a subtropical watershed, the lower course of the Piracicaba River, São Paulo, Brazil. 210Pb measurements done on river sediment core samples allowed estimating a sedimentation rate of 9 mm yr−1 between 1971 and 2001. Zn was the most abundant trace element in the sediment core, followed by Cr, Cu, Ni, Pb, Sc and Cd. The total concentrations of Cd, Cr, Ni, Sc and Pb presented practically no variations in the sediment core, with a continuous excess of ca. 0.27 μg g−1 yr−1 of Cu and of ca. 0.54 μg g−1 yr−1 of Zn between 1971 and 2001. The excess of Cu and Zn was associated with labile fractions, in particular with carbonate bound to Zn and organic matter bound to Cu. The assessment of trace metal pollution indicated that most of the trace elements were of geogenic origin, except for Cu and Zn. According to the sediment quality guidelines used in Brazil, Pb showed no potential toxic effect, Cu, Cr and Zn were intermediate to Threshold Effect Level (TEL) and Probable Effect Level (PEL) and the Cd and Ni concentrations were above the PEL limits. The elemental and isotopic analysis of C and N and the C/N ratio indicated that the anthropogenic origin of POM found in the sediment core is related mainly to domestic sewage.

Hekla 1947, 1845, 1510 and 1158 tephra in Finland: challenges of tracing tephra from moderate eruptions

ABSTRACTSeveral cryptotephra layers that originate from Icelandic volcanic eruptions with a volcanic explosivity index (VEI) of ≤ 4 and tephra volumes of < 1 km3 have previously been identified in Northern Europe, albeit within a restricted geographical area. One of these is the Hekla 1947 tephra that formed a visible fall‐out in southern Finland. We searched for the Hekla 1947 tephra from peat archives within the previously inferred fall‐out zone but found no evidence of its presence. Instead, we report the first identification of Hekla 1845 and Hekla 1510 cryptotephra layers outside of Iceland, the Faroe Islands, Ireland and the UK. Additionally, Hekla 1158 tephra was found in Finland for the first time. Our results confirm that Icelandic eruptions of moderate size can form cryptotephra deposits that are extensive enough to be used in inter‐regional correlations of environmental archives and carry a great potential for refining regional tephrochronological frameworks. Our results also reveal that Icelandic tephra has been dispersed into Finnish airspace at least seven times during the past millennium and in addition to a direct eastward route the ash clouds can travel either via a northerly or a southerly transport pathway.

A Continental and Marine-Influenced Tree-Ring Mercury Record in the Old Crow Flats, Yukon, Canada

Gaseous elemental mercury (Hg0) concentrations in the atmosphere have been increasing due to anthropogenic activities since the onset of colonial mining in the 17th century. However, accurate measurements of atmospheric Hg, including temporal trends, are mostly limited to recent decades. Natural environmental archives including tree rings show promise for reconstructing atmospheric concentrations of Hg0. In this paper, we present a new white spruce (Picea glauca) tree-ring Hg record (1696–2005) from the Old Crow Flats in northern Yukon. The record we present shows an increase in tree-ring Hg concentration (a proxy for gaseous Hg0 concentration) between 1748 and 1990 at a rate of +3.3% per year. A decrease in measured Hg is observed at the end of the record between 1990 and 2005, which may reflect the success of international regulations to reduce emissions including Hg. When compared with two other sites (a continental and marine location) in northwest Canada, there is not only some coherence in Hg trends at the regional scale but also some unique differences, suggesting that the location may influence atmospheric Hg0 available for assimilation. Further local factors within a site, such as soil moisture, may also affect the efficiency of this uptake. Results from this study highlight the need to better understand intra-site and inter-site differences in measured tree-ring Hg, and we recommend the continued development of a spatially resolved tree-ring Hg network in the northern boreal forest. Such records will be useful for developing better atmospheric Hg and global Hg models.

Revisiting afro-alpine Lake Garba Guracha in the Bale Mountains of Ethiopia: rationale, chronology, geochemistry, and paleoenvironmental implications

Previous paleolimnological studies demonstrated that the sediments of Garba Guracha, situated at 3950 m asl in the afro-alpine zone of the Bale Mountains of Ethiopia, provide a complete Late Glacial and Holocene paleoclimate and environmental archive. We revisited Garba Guracha in order to retrieve new sediment cores and to apply new environmental proxies, e.g. charcoal, diatoms, biomarkers, and stable isotopes. Our chronology is established using 210Pb dating and radiocarbon dating of bulk sedimentary organic matter, bulk n-alkanes, and charcoal. Although bedrock was not reached during coring, basal ages confirm that sedimentation started at the earliest ~ 16 cal kyr BP. The absence of a systematic age offset for the n-alkanes suggests that “pre-aging” is not a prominent issue in this lake, which is characterised by a very small afro-alpine catchment. X-ray fluorescence scans and total organic carbon contents show a prominent transition from minerogenic to organic-rich sediments around 11 cal kyr BP coinciding with the Holocene onset. While an unambiguous terrestrial versus aquatic source identification seems challenging, the n-alkane-based Paq proxy, TOC/N ratios, δ13C values, and the sugar biomarker patterns suggest a predominantly autochthonous organic matter source. Supraregional climate events, such as the African Humid Period, the Younger Dryas (YD), a 6.5 cal kyr BP short drying event, and the 4.2 cal kyr BP transition to overall drier climate are recorded in our archive. The Garba Guracha record suggests that northern hemisphere forcings played a role in the Eastern African highland paleoclimate.

Atmospheric mercury pollution deciphered through archaeological bones

Mercury is a major environmental pollutant extensively used by humans, whose pollution dates back at least to c. 3250 BCE (South Iberian Peninsula). As it happens today, past populations were mostly affected by low dose chronic mercury exposure, with levels that varied with the intensity of some anthropogenic activities (mining and metallurgy in particular). Despite its toxic nature, mercury impact in humans themselves has been hardly addressed by Archaeology. The aim of this research is to increase our knowledge on mercury levels in past populations by 1) analysing human (cortical) bone from skeletons recovered in a necropolis from NW Iberia covering contrasting periods of atmospheric pollution: Roman, AD 1st to 4th centuries, and post-Roman, AD 5th to 7th centuries; 2) considering bone type variability; 3) contextualizing our findings with previous works. Samples from 3 types of bone (n = 143) as well as soils/sediments associated to the burials (n = 34) were analysed. Mercury concentrations in soil were below 5 ng g−1, while the average in bone was 36 ± 52 ng g−1, making post-depositional incorporation unlikely. We found significant differences between the two periods (Romans: 54 ± 60 ng g−1, post-Romans: 21 ± 23 ng g−1), but no effect of type of bone, sex, age, social status or diet of the individuals. Our results agree with the chronology of mercury pollution reconstructed from a local peatland, which suggests a predominant atmospheric source. This fact contrasts with previous research in which high mercury concentrations were mainly related to post-mortem burial customs and pre-mortem medical treatment and poisoning. Thus, mercury distribution in past communities was possibly more complex than previously thought, with different pre- and post-mortem sources interacting. Furthermore, our research also supports the use of archaeological bone as environmental archive of metal pollution, when metal cultural exposure is low.

A consideration of polychlorinated biphenyls as a chemostratigraphic marker of the Anthropocene

Polychlorinated biphenyls, organic pollutants of anthropogenic origin, were widely used in many industrial applications worldwide roughly from the 1930s to the 1970s. Both the use and disposal of polychlorinated biphenyls contributed to their ubiquity in different environmental compartments, and they show extremely high persistence because of their high physical and chemical stability. Concentrations of polychlorinated biphenyls in environmental archives located in different parts of the world usually show an initial increase in the 1940s–1950s and maxima in the 1960s–1970s followed by a sharp decline following the ban in their use. Thus, the increase in polychlorinated biphenyl concentrations would appear to be suitable as a chronostratigraphic marker in Anthropocene strata. This manuscript discusses the polychlorinated biphenyls record in different environmental archives in the context of temporal and spatial trends in production and application of these compounds as well as the advantages and disadvantages of the use of polychlorinated biphenyls in the chemostratigraphy of the Anthropocene series.

Oxygen isotope disequilibrium in the juvenile portion of oyster shells biases seawater temperature reconstructions

For decades, bivalve shells have constituted one of the most common supports for paleoclimatic archives based on stable isotope approaches. In this work, we conducted chemical marking and recapture techniques to study the fluctuation of δ18O values of oyster shells of the species Magallana gigas reared in natural environment in Normandy (France) for two years. The results were compared to the continuous monitoring of temperature and salinity and monthly records of seawater δ18O. Isotopic measurements were performed on the hinge area that regroups the whole life of the oysters. Here we demonstrate that oysters mineralized their shells with no significant growth breaks during the two-years experiment, even at temperatures below 6 °C. The results confirm that adult oysters (i.e. > 1 yr) mineralized their shells at equilibrium. However, juvenile specimens exhibit a strong isotopic disequilibrium, with a maximum shift of the δ18O values of 3‰ in winter, likely due to kinetic isotope effects. This corresponds to a reconstructed temperature up to 13 °C warmer than expected. This work indicates that although these oyster shells can be used as an accurate archive of (paleo)environmental conditions, the shell portion mineralized during the juvenile stage (i.e. < 1 yr) should be avoided for paleotemperature reconstructions. Given the wide use of bivalve shells as environmental archives, similar studies on others species are required.

Improving the paleoceanographic proxy tool kit – On the biogeography and ecology of the sea ice-associated species Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica in the northern North Atlantic

Abstract A long-term perspective is essential for understanding environmental change. To be able to access the past, environmental archives such as marine and lake sediments that store information in the form of diverse proxy records are used. Whilst many analytical techniques exist to extract the information stored in these proxy records, the critical assessment and refinement of current methods in addition to developing new methods is crucial to improving our understanding. This study aims to improve our knowledge on diatom species used for reconstructing ocean surface conditions, especially temperature and sea ice variability over time. We define the distribution and the relationship to sea surface temperature (SST) and sea ice concentrations (SIC) of the species Fragilariopsis oceanica, Fragilariopsis reginae-jahniae and Fossula arctica using diatom training sets from the northern North Atlantic. We further assess the effect of separating these species compared to grouping them under F. oceanica, as has been done in the past. Our results suggest that while these three species share similarities such as the preference for stratified waters induced by sea ice or glacier meltwater, they also exhibit heterogeneous distributions across the northern North Atlantic, with individual optima for SST and SIC. This also affects quantitative reconstructions based on our data, resulting in lower SST and higher SIC estimates when the species are separated in the surface sediment and down-core diatom assemblages.

Annually Laminated Lake Sediments—Recent Progress

The collection of papers entitled “Annually Laminated Lake Sediments” illustrates the recent progress made in varved sediment research and highlights the variety of methodological approaches and research directions used. The contributions cover the monitoring of modern sediment fluxes using sediment traps, geochronological and sedimentological analyses of varves, multi-proxy investigations, including geochemical and biological proxies, as well as spatiotemporal analyses based on multi-core studies supported by satellite images. The scientific issues discussed the influences of hydroclimatological phenomena on short-term changes in sediment flux, the relationships between biogeochemical processes in the water column and the formation of varves, the preservation of environmental signals in varves, and possibilities of synchronizing varved records with other high-resolution environmental archives.

The quest for AMS of 182Hf – why poor gas gives pure beams

The long-lived radioisotope 182Hf (T1/2 = 8.9 Ma) is of high astrophysical interest as its potential abundance in environmental archives would provide insight into recent r-process nucleosynthesis in the vicinity of our solar system. Despite substantial efforts, it could not be measured at natural abundances with conventional AMS so far due to strong isobaric interference from stable 182W. Equally important is an increase in ion source efficiency for the anions of interest. The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at VERA tackles the problem of elemental selectivity in AMS with a novel approach. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio-frequency quadrupole (RFQ) ion cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas. We present first results with this approach on AMS-detection of 182Hf. With He +O2 mixtures as buffer gas in the RFQ, suppression of 182WF5− vs 180HfF 5− by &gt;105 has been demonstrated. Mass analysis of the ejected anion beam identified the formation of oxyfluorides as an important reaction channel. The overall Hf-detection efficiency at VERA presently is 1.4% and the W-corrected blank value is 182Hf/180Hf = (3.4 ± 2.1)×10−14. In addition, a survey of different sample materials for highest negative ion yields of HfF 5− with Cs-sputtering has been conducted.

Small paleolakes of the Southern Kurils, as Holocene environmental archives

Investigations of the environmental changes on the Southern Kurils was based on multi-proxy studies of sediments from several paleolakes. Stages of the lake development have been identified. Our study revealed climatic and palaeolandscape changes, ages and ecological effect of volcanic ash falls on Kunashir Island since the end of the Late Pleistocene, and manifestation of strong tsunami during the Middle to Late Holocene in Urup and Shikotan Islands.

Swift evolutionary response of microbes to a rise in anthropogenic mercury in the Northern Hemisphere

Anthropogenic mercury remobilization has considerably increased since the Industrial Revolution in the late 1700s. The Minamata Convention on Mercury is a United Nations treaty (2017) aiming at curbing mercury emissions. Unfortunately, evaluating the effectiveness of such a global treaty is hampered by our inability to determine the lag in aquatic ecosystem responses to a change in atmospheric mercury deposition. Whereas past metal concentrations are obtained from core samples, there are currently no means of tracking historical metal bioavailability or toxicity. Here, we recovered DNA from nine dated sediment cores collected in Canada and Finland, and reconstructed the past demographics of microbes carrying genes coding for the mercuric reductase (MerA)—an enzyme involved in Hg detoxification—using Bayesian relaxed molecular clocks. We found that the evolutionary dynamics of merA exhibited a dramatic increase in effective population size starting from 1783.8 ± 3.9 CE, which coincides with both the Industrial Revolution, and with independent measurements of atmospheric Hg concentrations. We show that even low levels of anthropogenic mercury affected the evolutionary trajectory of microbes in the Northern Hemisphere, and that microbial DNA encoding for detoxification determinants stored in environmental archives can be used to track historical pollutant toxicity.

Environmental archives of atmospheric Hg deposition – A review

Environmental archives offer an opportunity to reconstruct temporal trends in atmospheric Hg deposition at various timescales. Lake sediment and peat have been the most widely used archives; however, new records from ice, tree rings, and the measurement of Hg stable isotopes, are offering new insights into past Hg cycling. Preindustrial Hg deposition has been studied over decadal to millennial timescales extending as far back as the late Pleistocene. Exploitation of mercury deposits (mainly cinnabar) first began during the mid to late Holocene in South America, Europe, and Asia, but increased dramatically during the Colonial era (1532–1900) for silver production. However, evidence for preindustrial Hg pollution is restricted to regions directly downwind or downstream of cinnabar or precious metal mining centers. Excluding these areas, there has been an approximately four-fold increase in atmospheric deposition globally over the industrial era (i.e., since 1800–1850), though regional differences exist, especially during the early 20th Century. Lake sediments, peat, ice, and tree rings are all influenced by (and integrate) a range of processes. For example, lake sediments are influenced by atmospheric deposition, sediment focusing, and the input of allochthonous material from the watershed, peat records reflect atmospheric deposition and biotic uptake, ice cores are a record of Hg scrubbed during precipitation, and tree rings record atmospheric concentrations. No archive represents an absolute record of past Hg deposition or concentrations, and post-depositional transformation of Hg profiles remains an important topic of research. However, natural archives continue to provide important insight into atmospheric Hg cycling over various timescales.

A bat guano deposit in Jamaica recorded agricultural changes and metal exposure over the last >4300 years

Bats are excellent ecological indicators because they are long-lived, globally distributed, and show predictable responses to environmental stressors. Unaltered bat guano deposits, although rare, can serve as environmental archives to reveal changes in dietary patterns over millennial time scales. We inferred changes in agricultural and industrial practices using a continuous 4300-year-old bat guano deposit from Jamaica. Cadmium, mercury, lead, and zinc increased during the Industrial Revolution, (which began in ca. 1760), a period characterized by elevated emissions of metals to the atmosphere. Beginning in the early 20th century, decreases in 206Pb/207Pb isotopes tracked the history of leaded gasoline use. Metal concentrations in the bat guano deposit exceeded those recorded in two nearby lake sediment cores from Jamaica. Carbon, nitrogen, and sulfur stable isotope profiles in bat guano tracked the agricultural history of Jamaica, specifically the introduction of nitrogen fertilizers, sugarcane, and possibly fungicides. Bat populations are under stress globally, and such intact guano deposits provide potentially critical information on long-term changes in their food source and exposure to metals.

Complementarity, completeness and quality of long-term faunal archives in an Asian biodiversity hotspot.

Long-term baselines on biodiversity change through time are crucial to inform conservation decision-making in biodiversity hotspots, but environmental archives remain unavailable for many regions. Extensive palaeontological, zooarchaeological and historical records and indigenous knowledge about past environmental conditions exist for China, a megadiverse country experiencing large-scale biodiversity loss, but their potential to understand past human-caused faunal turnover is not fully assessed. We investigate a series of complementary environmental archives to evaluate the quality of the Holocene-historical faunal record of Hainan Island, China's southernmost province, for establishing new baselines on postglacial mammalian diversity and extinction dynamics. Synthesis of multiple archives provides an integrated model of long-term biodiversity change, revealing that Hainan has experienced protracted and ongoing human-caused depletion of its mammal fauna from prehistory to the present, and that past baselines can inform practical conservation management. However, China's Holocene-historical archives exhibit substantial incompleteness and bias at regional and country-wide scales, with limited taxonomic representation especially for small-bodied species, and poor sampling of high-elevation landscapes facing current-day climate change risks. Establishing a clearer understanding of the quality of environmental archives in threatened ecoregions, and their ability to provide a meaningful understanding of the past, is needed to identify future conservation-relevant historical research priorities. This article is part of a discussion meeting issue 'The past is a foreign country: how much can the fossil record actually inform conservation?'

Extinction in the Anthropocene.

Samuel Turvey and Jennifer Crees introduce the effects of humans on biodiversity.

The transboundary transport of air pollutants and their environmental impacts on Tibetan Plateau

The Tibetan Plateau is the largest high altitude landform on Earth, with an area of over 2.5×106 km2 and an average elevation of ~4000 m above sea level. With a unique multisphere environmental system, the Tibetan Plateau provides an important ecological sheltering function for China and other parts of Asia. The Tibetan Plateau is one of the world’s most pristine regions, benefiting from a sparse population with negligible local influence on its environment. However, it is surrounded by some of the most polluted areas in the world, such as South Asia, East Asia, and Southeast Asia. With the atmospheric circulation, such pollutants may impact the Tibetan Plateau through long-range transport. Clearly, the scientific research on the transboundary transport of pollutants is not only important for the understanding of multisphere interactions on the earth surface, but also could meet the national strategic needs for ecological and environmental protection. Long-term monitoring combined with short-term intensive observation campaigns, were used to comprehensively summarize the latest research progress regarding the spatial-temporal distribution and transport mechanism of air pollutants, as well as their climate and ecological impacts, which were achieved during the Second Tibetan Plateau Scientific Expedition. With respect of historical trends reconstructed from environmental archives, e.g., glacial ice cores and lake sediments, the black carbon and heavy metals like mercury show a dramatic increase since 1950s, which reflect the enhanced emission of air pollutants in Asia. On-line observation data and WRF-Chem modeling indicate that upper air circulation and local mountain-valley breeze system are the main drivers of trans Himalaya air pollution from South Asia. A regional climate-chemistry model coupled with an aerosol-snow/ice feedback module was used to reveal the natural and anthropogenic light-absorbing aerosols’ radiative effects over the Tibetan Plateau. Results indicated that the mineral dust both in the atmosphere and snow induced 0.1−0.5°C warming over the western Tibetan Plateau and Kunlun Mountains in spring. Meanwhile, dust aerosols caused snow water equivalent to decrease by 5−25 mm over the western TP, Himalayas and Pamir Mountains in winter and spring. The radiative effects of BC-in-snow induced surface temperature increased by 0.1− 1.5°C and snow water equivalent decreased by 5−25 mm over the western Tibetan Plateau and Himalayas. According to the observations the black carbon and dust found in the snow and ice on the surfaces of glaciers were responsible for on average 20% of the albedo reduction within the TP region. Those atmospherically transported pollutants also have obvious negative impacts on the ecosystem in Tibetan Plateau. For example, bioaccumulation of DDTs have been found in Tibetan terrestrial and aquatic food chains, and newly emerging compounds such as polyfluoroalkyl substances and hexabromocyclododecanes have been widely detected in wild fish species. Therefore, the corresponding ecological risks are of great concern. In the future, it is necessary to quantify the extent of atmospherically transported pollution and model the pollutant fate under the future environmental scenarios as well as establish environmental and health risk.

A 16,000-yr-long sedimentary sequence from Lakes Peters and Schrader (Neruokpuk Lakes), northeastern Brooks Range, Alaska

AbstractSediments that accumulate in high-latitude lakes serve as valuable environmental archives of changing conditions in a region currently undergoing rapid change. A previously unexplored sedimentary sequence reaching back 16,000 years from Lakes Peters and Schrader (Neruokpuk Lakes) in the northeastern Brooks Range (69°N), Alaska, shows distinct changes in accumulation rates and biophysical properties including bulk density (BD), organic matter (OM) content, and grain-size distribution at five widely distributed core sites. The oldest sediments contain little OM and accumulated rapidly as glaciers retreated around 15 ka. OM peaked between 12 and 10 ka along with Northern Hemisphere summer insolation. BD increased and OM decreased until around 5 ka, possibly reflecting a decrease in river-transported terrestrial OM. From 5–2 ka, OM consistently increased, suggesting a rise in river discharge, or a rise in summer temperatures, which led to higher productivity, or both. After 2 ka, sediments increased in BD and decreased in OM, suggesting glacier growth. Evidence for glacier expansion late during the Little Ice Age is weak, but increased sedimentation rates may reflect glacier retreat during the last century. This study provides a framework for future paleoenvironmental research of a rare archive in a relatively pristine Arctic setting.

Entre La Pedrera y Araracuara: la arqueología del medio río Caquetá

La arqueología del medio río Caquetá, en la Amazonía colombiana, se conoció recién en los 1970s a partir de los resultados de proyectos de investigación pioneros en Araracuara y La Pedrera. Estas investigaciones identificaron secuencias cerámicas diferentes en cada localidad, documentaron una gran cantidad de petroglifos y, por primera vez, registraron suelos antrópicos negros y pardos en el Noroeste Amazónico. Investigaciones posteriores enfatizaron el estudio de archivos ambientales (arqueobotánicos y geoarqueológicos) y registraron ocupaciones pre-cerámicas del Holoceno temprano y medio. Ã?stas son particularmente importantes debido a que los datos arqueobotánicos asociados sugieren que las poblaciones de la región cultivaron tempranamente una variedad de plantas comestibles, varias de ellas domesticadas en otras regiones. Sin embargo, la arqueología del medio río Caquetá todavía presenta una serie de interrogantes importantes respecto de las ocupaciones del pre-cerámico y de los extensos sitios de habitación de grupos alfareros. Con respecto a estos últimos, es particularmente importante evaluar hasta qué punto estas ocupaciones se pueden enmarcar en las grandes tradiciones cerámicas conocidas para la Amazonía y la cuenca del Orinoco. En este artículo resumimos la información existente sobre la arqueología del medio río Caquetá y presentamos nuevos datos preliminares producidos en los últimos años, ello con el objetivo de evaluar el estado de nuestros conocimientos y fomentar el desarrollo de futuras investigaciones arqueológicas en la región.