Paleoenvironmental History Research Articles

Carbonate ecosystem and environmental evolution during the Valanginian–Barremian: Discussion on possible controlling factors in the Apennine Carbonate Platform record (Italy)

Shallow-water carbonate records are often characterised by low stratigraphic resolution and poor chronostratigraphic calibration despite abundant and diversified fossil content. We present here a stratigraphic study of a Valanginian–Barremian carbonate platform section, exposed in the southern Apennines (Italy). In the San Lorenzello section, we produced a high-resolution dataset integrating sedimentology, biostratigraphy, cyclostratigraphy and sequence stratigraphy to investigate how neritic biofacies responded to palaeonvironmental and palaeoclimatic changes in the time interval after the Weissert event. Fossil assemblages and lithofacies characteristics allowed the reconstruction of the paleoenvironmental history of the section, which is part of a shallow carbonate platform influenced by waves activity, storm events and sea-level changes. The latter induced cyclic emersions of this flat-topped subtropical platform, witnessed by karstification and pedogenesis. Investigations lead to a refinement of the previous biostratigraphy, also producing a close agreement between the biostratigraphic and C-isotope position of the Valanginian–Hauterivian boundary. Numerous green algae and benthic foraminifera bioevents have been identified and six biozones have been defined and anchored to the southern Tethys biozonal schemes.We used biostratigraphy and previous C-isotope stratigraphy to correlate local to global stratigraphic events and to discuss controlling factors influenced this carbonate platform system. An eustatic control on the hierarchical organization of the superbundles, also interpreted in terms of depositional sequences, is evidenced. Most Trangressive/Regressive Facies Trends (T/RFTs) boundaries have been correlated with the “global” Sequence Boundaries and to the Cretaceous eustatic curve. A correspondence between calcareous algae and benthic foraminiferal turnover phases and long-term eustatic events is also shown.

The Bouse Formation, a controversial Neogene archive of the evolving Colorado River: a scientific drilling workshop report (28 February–3 March 2019 – BlueWater Resort & Casino, Parker, AZ, USA)

Abstract. Neogene deposits of the lower Colorado River valley, especially the Miocene(?) and early Pliocene Bouse Formation, have been the focus of intense debate regarding the early paleoenvironmental history of this important continental-scale river system in southwestern North America and its integration with the proto-Gulf of California. Fine-grained units within these Neogene deposits also hold a promising archive of Pliocene paleoclimate history for this part of the world. Because the depocenter deposits of the Bouse Formation and the deposits that overlie and underlie it are poorly exposed and highly weathered, the formation is ripe for study through collection of drill cores. A workshop was held 28 February–3 March 2019 in Parker, AZ, USA, to discuss how scientific drilling might be employed to help resolve the Bouse controversies and improve our understanding of paleoclimate history in the region.

High-resolution climatic (monsoonal) variability reconstructed from a continuous ~2700-year sediment record from Northwest Himalaya (Ladakh)

A chronologically well-constrained sedimentary archive from Upshi (Ladakh) was studied using a multi-proxy approach namely palynology, environmental magnetism, total organic carbon (TOC), total nitrogen (TN), stable isotopes of carbon and nitrogen providing a continuous vegetation, and paleoenvironmental history spanning the last ~2700 years with a temporal resolution of ~43 years. Pollen assemblage shows non-arboreal pollen (NAP) and non-pollen palynomorph (NPP) were dominant around the Upshi from ~2646 to 2431 cal. yr BP, indicating warmer conditions. Arboreal pollen (AP) and NAP gradually increased from 2431 to 1860 cal. yr BP in the study area, under warm and wet conditions, corresponding to the Roman Warm Period (RWP). This phase also witnessed enhanced sediment δ15N and χlf values. From ~1860 to ~1154 cal. yr BP increased Chenopodiaceae/Amaranthaceae and substantial spread of NPP suggest decreased temperature and prevalence of cold-dry climate. This period also records declining trends of χlf, δ15N, δ13Corg, TOC, and TN contents. From ~1154 to 293 cal. yr BP, the vegetation type reversed to mixed conifer and broad-leaved forest with significant increase in herbaceous taxa, rising δ15N, δ13Corg, TOC, and TN suggesting warm and wet conditions in the study area. This period broadly corresponds to the ‘Medieval Warm Period’ (MWP). Among all the proxies employed, depth profiles of TOC and TN (wt%) appear to respond best against external climate forcing showing remarkable correlation(s) with residual Δ14C in atmosphere, indicating dominance of intrinsic solar variability on regional climate/environment. The reconstructed recorded is well connected with established historical events and cultural activities of the Eurasian region.

A relictual troglomorphic harvestman discovered in a volcanic cave of western Argentina: Otilioleptes marcelae, new genus, new species, and Otilioleptidae, new family (Arachnida, Opiliones, Gonyleptoidea).

The troglomorphic harvestman Otilioleptes marcelae gen. nov., sp. nov. from the basaltic cave Doña Otilia, Payunia region, Mendoza Province, Argentina, is described. Its systematic affinities were studied through cladistic and Bayesian analyses that included representatives of Gonyleptoidea; it was determined to represent a new monotypic family, Otilioleptidae fam. nov., occupying a basal position within the clade Laminata. This species shows accentuated troglomorphic traits, typical for troglobitic harvestmen: elongated appendages, depigmentation, reduction of eyes and fading of scutal sulci. Additionally, it almost lacks sexual dimorphism, the distal portion of coxa IV is not completely fused to the stigmatic segment, and penis morphology is remarkably divergent with other Laminata; these features cannot be attributed to cave adaptation and may reflect early lineage divergence. Otilioleptes marcelae is the first troglobitic gonyleptoid known from a lava tube. The xeric environments around the cave (Patagonian ecoregion) and the paleoenvironmental history of the area suggest the relictual character of O. marcelae. Scattered evidence supports a long time evolutionary scenario and a presumable relationship with the Chilean opiliofauna (especially with genus Osornogyndes). A comparative overview of all known troglobitic gonyleptoids is provided. The urgent need to protect this new species and its unique cave environment is emphasized.

Cyclostratigraphic age constraining for Quaternary sediments in the Makarov Basin of the western Arctic Ocean using manganese variability

Abstract The Quaternary paleoenvironmental history of the Arctic Ocean remains uncertain, mainly due to the limited chronological constraints, especially beyond the 14C dating limits of accelerator mass spectrometry (AMS). The difficulty in establishing reliable chronostratigraphies is mainly attributed to low sedimentation rates and diagenetic sediment changes, resulting in very poor preservation of microfossils and altered paleomagnetic records. In the absence of independent chronostratigraphic data, the age model of Pleistocene sediments from the Arctic Ocean is mainly based on cyclostratigraphy, which relates lithologic changes to climatic variability on orbital time scales. In this study, we used the Mn/Al record measured from the sediment core ARA03B-41GC retrieved from the Makarov Basin in the western Arctic Ocean. The Mn/Al variation was tuned to the global benthic oxygen isotope stack (LR04) curve under different assumptions for computational correlation. Regardless of assumptions, our computational approach led to similar ages of about 600–1,000 ka for the bottom part of the core. These age models were up to about 200 ka older than those derived from lithostratigraphic approaches. Interestingly, our new age models show that the Ca/Al peak, a proxy for a detrital input from the Laurentide Ice Sheet, first occurred about 150 ka earlier than those previously proposed. Therefore, our results suggest that the glaciers in northern North America developed more extensively at about 810 ka than in earlier glacial periods, and influenced the sedimentary and paleoceanographic environments of the Arctic Ocean much earlier than previously thought. In order to establish a more comprehensive age model, more work is needed to validate our findings with different sediment cores recovered from the western Arctic Ocean.

Humans, fire, and ecology in the southern Missouri Ozarks, USA

A multiproxy study from Sweeton Pond, Ozark County, Missouri, USA, provides a high-resolution 1900-year-long history of vegetation and fire in the southern Missouri Ozarks, where the modern vegetation is oak-hickory ( Quercus-Carya) forest. Pollen and charcoal data are compared with dendroecological data to assess how climate and fire shaped local vegetation history. Land use, particularly by the Osage tribe of Native Americans, is assessed from historical and archaeological records. Three cultural periods are superimposed on the paleoenvironmental history: (1) The Pre-Osage period, ending ~1500 CE, was characterized by open oak-hickory forest and frequent low-severity fires, suggesting interannual climate variability as a driver of vegetation and fire occurrence. At ~1360 CE, mesic tree species began to expand, while fire frequency remained low. (2) The Osage period (~1500–1820 CE) was characterized by the continued expansion of mesic, fire-sensitive species, especially elm ( Ulmus), in conjunction with cool, effectively wet conditions in the southern Missouri Ozarks. Despite climate conditions less favorable for fire, Osage expansion in the region was accompanied by increased fire and fire-dependent shortleaf pine ( Pinus echinata). The expansion of both fire-sensitive and fire-dependent taxa coincident with Osage occupation suggests that anthropogenic fire and land use was local in nature and increased landscape heterogeneity prior to Euro-American settlement. (3) The Euro-American period (since ~1820 CE) was characterized by increased disturbance pollen types (e.g. Ambrosia-type) at the expense of shortleaf pine pollen, resulting from increased settlement size and extensive agricultural and logging activities. During this period, forest clearance led to fuel fragmentation, reducing fire activity; after 1920 CE, fire was actively suppressed.

Geoarchaeology of the Water Canyon Paleoindian site, west‐central New Mexico

AbstractWater Canyon is a rare buried, multicomponent, stratified Paleoindian site in west‐central New Mexico. This paper presents a geoarchaeological assessment of the site as part of a broader interdisciplinary investigation of its paleoenvironmental history and archaeology. The archaeology is associated with ancient wetland deposits (Stratum 6) within an alluvial fan. The fan formed initially through the late Pleistocene. Formation of the fan stopped and wetland deposition began ~11,310 14C yr BP (~13,170 cal yr BP). Stratum 6 evolved via wetland deposition and cut‐and‐fill cycles. The bulk of Stratum 6 dates <10,300 14C yr BP (<12,200 cal yr BP). One, or possibly two, beds of bison bone, likely processing‐stations, were found on the margin of the paleowetland and date to ~9,200 14C yr BP (~10,400 cal yr BP) (lower bone bed) and ~8,200 14C yr BP (~9,150 cal yr BP) (upper bone bed). Farther out in the paleo‐wetland a probable kill site was discovered with an in situ Eden projectile point dated to at least ~8,955 14C yr BP (~10,070 cal yr BP). The wetland landscape returned to an alluvial fan system <8,000 14C yr BP (<8,900 cal yr BP) with two more cycles of fan deposition by ~6,500 cal yr.

Ichnology, paleosols and palimpsests surfaces in the Tinat Member of the Nuayyim Formation (Unayzah Group), subsurface Saudi Arabia: Trace fossils and genetic stratigraphy in continental settings

The Nuayyim Formation of the Unayzah Group is widespread in subsurface central Saudi Arabia and constitutes a laterally variable stratigraphic unit with a complex mosaic of facies. Sedimentation for the Tinat Member took place majorly in a continental setting dominated by aeolian processes that resulted in dunes, interdunes, ephemeral stream deposits terminating with regional development of paleosols. Facies, ichnofacies and palynological analysis, suggest an arid to semi-arid setting with biogenic activity in the form of continental fauna and plants in deposits associated with pedogenetical alteration in paleosol horizons. Therein, burrowing exhibits elements of the Scoyenia Ichnofacies in beds with sparse to abundant bioturbation. Tectonic uplift and subaerial exposure resulted in the exhumation of previously buried substrates, leading to the formation of burrowed palimpsests surfaces associated with paleosols at the end of Unayzah deposition prior to the onset of the Khuff Formation. Progressive thermal updoming is interpreted to have occurred during the latest portion of the Unayzah Group sedimentation cycle in the Arabian Plate culminating in the regional “Pre-Khuff unconformity” at the top of this megacycle recognized in this study by biogenically-demarcated diastems.Ichnological and sedimentological observations outlined in this study are significant because they: (i) refine existing interpretations of the paleoenvironmental history in the study area; (ii) document diastems marking breaks in sedimentation; and (iii) outline several soil-forming cycles that allowed the establishment of a trace fossil suite with continental affinities, thus demarcating the end of an entire sedimentation cycle. The recognition and delineation of burrowed horizons associated with paleosols provides a tool to understand the tectono-stratigraphic evolution of similar successions in the rock record.

ICDP workshop on scientific drilling of Nam Co on the Tibetan Plateau: 1 million years of paleoenvironmental history, geomicrobiology, tectonics and paleomagnetism derived from sediments of a high-altitude lake

Abstract. The Tibetan Plateau is of peculiar societal relevance as it provides freshwater from the so-called “Water Tower of Asia” to a large portion of the Asian population. However, future climate change will affect the hydrological cycle in this area. To define parameters for future climate change scenarios it is necessary to improve the knowledge about thresholds, timing, pace and intensity of past climatic changes and associated environmental impacts. Sedimentary archives reaching far back in time and spanning several glacial–interglacial cycles such as Nam Co provide the unique possibility to extract such information. In order to explore the scientific opportunities that an ICDP drilling effort at Nam Co would provide, 40 scientists from 13 countries representing various scientific disciplines met in Beijing from 22 to 24 May 2018. Besides paleoclimatic investigations, opportunities for paleomagnetic, deep biosphere, tectonic and paleobiological studies were discussed. After having explored the technical and logistical challenges and the scientific opportunities all participants agreed on the great value and need to drill this extraordinary archive, which has a sediment thickness of more than 1 km, likely covering more than 1 Ma.

Ion concentrations in ice wedges: An innovative approach to reconstruct past climate variability

For atmospheric gases and aerosols, snow and ice provide a useful archive of paleoenvironmental history. In the northern hemisphere, this archive has been largely limited to Greenland ice, but promising pioneering work has been done recently using chronology of an ice wedge in Barrow, northern Alaska. Here, we investigate past aerosols at the same ice-wedge sampling site, reconstructing the sea-ice fluctuations in the adjacent Beaufort Sea during the Bølling/Allerød (BA) and Younger Dryas (YD) periods. We confirm the integrity of methanesulfonate ion (MS−) concentrations in the BIWS as marine proxies, and then find that the ice wedge has a high MS− concentration through the beginning (coldest) YD periods. The high MS− concentration indicates that even during the coldest YD periods (12,900–12,700 yrBP), the near-shore region in the Alaskan Beaufort Sea near Barrow may not have been completely filled by permanent sea ice.

A new genus of coccolepidid actinopterygian from the Cretaceous Iguanodon-bearing locality of Bernissart, Belgium

The Barremian–Aptian (Cretaceous) locality of Bernissart, Belgium is mainly known for the Iguanodon skeletons it yielded. Nonetheless, it also delivered a rich actinopterygian fauna. Among these fishes, is the coccolepidid Coccolepis macroptera, named by Traquair at the beginning of the 20th century. The systematic revision of several taxa of the family Coccolepididae during the last two decades, not only led to changes in the taxonomic status of these taxa, but also to a much better knowledge of these fishes in general. In the light of this achievements, C. macroptera is here revised and, as a result, it is placed in its own new genus Barbalepis. Barbalepis is a coccolepidid fish with the following combination of characters: lower jaw long and robust; pectoral fins proportionally much smaller than the pelvic fins; some dermal bones covered with a fingerprint-like thin striation and some others smooth; free area of scales covered with tubercles and overlapped area with a thin striation; fin rays smooth; anal fin inserted at the first modified haemal spine. The present paper contains a complete description of this fish with taxonomic conclusions regarding the family Coccolepididae, and a brief discussion of the paleogeographic and paleoenvironmental history of the group, which indicates that the origin of the family predates its first occurrence in the known fossil record and that coccolepidids became restricted to freshwater environments during the Jurassic.

Use of high-resolution seismic reflection data for paleogeographical reconstruction of shallow Lake Yamanaka (Fuji Five Lakes, Japan)

High-resolution seismic profiles, combined with the integration of published drilling data, provide a detailed paleoenvironmental history of Lake Yamanaka (Fuji Five Lakes, Japan). This study presents a detailed analysis of the different depositional stages of the area currently occupied by Lake Yamanaka (floodplain wetland, river and lake). From ca. 5500 cal yr BP to ca. 5050 cal yr BP, the Yamanaka basin was occupied by floodplain wetlands. During that period, the landscape was very stable and erosion on northeastern flank of Mt. Fuji was relatively limited. From ca. 5050 cal yr BP to ca. 3050 cal yr BP, the water level increased and the floodplain wetlands became a lake. From ca. 3050 cal yr BP to ca. 2050 cal yr BP, the water level progressively decreased, leading to a reduction in lake extent. During this lowering of the lake's water level, a 1 km2 mass-transport deposit modified the physiography of the lake floor. From ca. 2050 cal yr BP to ca. 1050 cal yr BP, the lake disappeared and a river flowing towards the northwest occupied the depression. Ponds occupied morphological lows formed by mass-transport deposits. From ca. 1050 cal yr BP to the present day, the lake water level rose again, connecting the ponds with the main lake. Since then, the lake water level has continued to rise to the current level. Lake water level fluctuations are the results of several factors that could be interconnected: (i) changes in precipitation rates; (ii) margin destabilization (the Yamanaka mass-transport deposit), (iii) changes in river inlets and therefore variation in water supplies, (iv) volcanic eruptions (scoria fall-out and lava flows) and (v) changes in vegetation cover. This study highlights the importance of coupling sediment cores and high-resolution seismic reflection profiling to identify lateral variation and modification of sedimentary inputs through time.

Late Holocene climate changes from diatom records in the historical Reservoir Gonggeomji, Korea

The paleoenvironmental history of the artificial Reservoir Gonggeomji in Sangju City, Korea, was reconstructed using fossil diatom analysis of four sediment cores: GG01, 02, 03, and 04. Accelerator mass spectrometer (AMS) radiocarbon dating results suggest that Reservoir Gonggeomji was maintained from ca. 1350 to 150 cal year BP, and the diatom record in core sediment samples revealed well-defined hydrological changes and paleoenvironmental conditions during this period. The fossil diatom assemblages were predominantly benthic freshwater diatoms. The highest diatom concentrations in all cores were in diatom zone II, in which species richness and diversity were also very high. Cymbella, Eunotia, Gomphonema, Gyrosigma, Navicula, and Pinnularia were the dominant genera in all core sediments. The long-term trend in diatom species abundance and species diversity showed a stronger relationship to temperature anomalies in the northern hemisphere during the past 2000 years with changes in precipitation. These diatom changes could have been controlled by natural climate change, despite anthropogenic activities linked to construction of the dyke in the artificial reservoir.

Soils of Agricultural Terraces with Retaining Walls in the Mountains of Dagestan

Soil-archeological studies of agricultural terraces with retaining walls in the area of construction of the Gotsatlinskaya Hydroelectric Power Station in Khunzakh district of the Republic of Dagestan have been performed. The morphogenetic and chemical properties of the anthropogenic soils (Anthrosols) in different parts of the terrace complex are analyzed. It is argued that slope terracing in the mountains ensures the development of thicker soil profiles with pronounced genetic horizons. The soils of agricultural terraces store important information of the paleoenvironmental history and land use. A characteristic feature of the Anthrosols of agricultural terraces is a relatively even distribution of gravelly material of up to 5 cm in diameter in the plow layer. The soils of terraces are characterized by the high variability in their properties within the entire terrace complex and within the particular terraces.

The Holocene paleo-environmental history of the Gangkou River estuary, Hengchun Peninsula, Taiwan

The Holocene paleo-environmental history of the Gangkou River estuary, Hengchun Peninsula, Taiwan

Middle Bronze Age humidity and temperature variations, and societal changes in East-Central Europe

Archaeological evidence points to substantial changes in Bronze Age societies in the European-Mediterranean region. Isotope geochemical proxies have been compiled to provide independent ancillary data to improve the paleoenvironmental history for the period of interest and support the interpretation of the archaeological observations. In addition to published compositions, in this study we gathered new H isotope data from fluid inclusion hosted water from a stalagmite of the Trió Cave, Southern Hungary, and compared the H isotope data with existing stable isotope and trace element compositions reported for the stalagmite. Additionally, animal bones and freshwater bivalve shells (Unio sp.) were collected from Bronze Age archaeological excavations around Lake Balaton and their stable C and O isotope compositions were measured in order to investigate climate changes and lake evolution processes during this period. The data indicate warm and humid conditions with elevated summer precipitation around 3.7 cal ka BP (Before Present, where present is 1950 CE), followed by a short-term deterioration in environmental conditions at about 3.5 cal ka BP. The environment became humid and cold with winter precipitation dominance around 3.5 to 3.4 cal ka BP, then gradually changed to drier conditions at ∼3.2 cal ka BP. Significant cultural changes have been inferred for this period on the basis of observations during archaeological excavations. The most straightforward consequences of environmental variations have been found in changes of settlement structure. The paleoclimatological picture is well in line with other East-Central European climate records, indicating that the climate fluctuations took place on a regional scale.

Petrographic characteristics and paleoenvironmental history of Eocene lignites of Cambay basin, Western India

Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin (Gujarat) were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group (71.6%–86.3%) followed by liptinite (10.1%–19.3%) and inertinite (3.6%–11.0%) maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index (GI) and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxygenated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin.

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

Paleontology and stratigraphy of Middle Eocene rock units in the southern Green River and Uinta Basins, Wyoming and Utah

The Bridger Formation is restricted to the Green River Basin in southwest Wyoming, and the Uinta and Duchesne River Formations are located in the Uinta Basin in Utah. These three rock units and their diverse fossil assemblages are of great scientific importance and historic interest to vertebrate paleontologists. Notably, they are also the stratotypes from oldest to youngest for the three middle Eocene North American Land Mammal Ages—the Bridgerian, Uintan, and Duchesnean. The fossils and sediments of these formations provide a critically important record of biotic, environmental, and climatic history spanning approximately 10 million years (49 to 39 Ma). This article provides a detailed field excursion through portions of the Green River and Uinta Basins that focuses on locations of geologic, paleontologic, and historical interest. In support of the field excursion, we also provide a review of current knowledge of these formations with emphasis on lithostratigraphy, biochronology, depositional, and paleoenvironmental history, and the history of scientific exploration.

Holocene evolution of lakes in the forest-tundra biome of northern Manitoba, Canada

The late-Quaternary paleoenvironmental history of the western Hudson Bay region of Subarctic Canada is poorly constrained. Here, we present a regional overview of the post-glacial history of eight lakes which span the forest-tundra biome in northern Manitoba. We show that during the penultimate drainage phase of Lake Agassiz the lake water had an estimated pH of ∼6.0, with abundant quillwort (Isöetes spp.) along the lakeshore and littoral zone and some floating green algae (Botryococcus spp. and Pediastrum sp.). Based on multiple sediment proxies, modern lake ontogeny in the region commenced at ∼7500 cal yrs BP. Pioneering diatom communities were shaped by the turbid, higher alkalinity lake waters which were influenced by base cation weathering of the surrounding till following Lake Agassiz drainage. By ∼7000 cal yrs BP, soil development and Picea spp. establish and the lakes began a slow trajectory of acidification over the remaining Holocene epoch. The natural acidification of the lakes in this region is slow, on the order of several millennia for one pH unit. Each of the study lakes exhibit relatively stable aquatic communities during the Holocene Thermal Maximum, suggesting this period is a poor analogue for modern climatic changes. During the Neoglacial, the beginning of the post-Little Ice Age period represents the most significant climatic event to impact the lakes of N. Manitoba. In the context of regional lake histories, the rate of diatom floristic change in the last 200–300 years is unprecedented, with the exception of post-glacial lake ontogeny in some of the lakes. For nearly the entire history of the lakes in this region, there is a strong linkage between landscape development and the aquatic ecosystems; however this relationship appears to become decoupled or less strong in the post-LIA period. Significant 20th century changes in the aquatic ecosystem cannot be explained wholly by changes in the terrestrial ecosystem, suggesting that future changes to the lakes of N. Manitoba will be strongly influenced by direct climatic effects to the lakes.