Najat Bhiry

Palaeoecology of a palsa and a filled thermokarst pond in a permafrost peatland, subarctic Québec, Canada

Radiocarbon dating and macrofossil data from a palsa and a filled thermokarst pond within a subarctic permafrost peatland were used to reconstruct their evolution and to distinguish between allogenic and autogenic processes that had been involved in their development. Peat began to accumulate in the peatland basin shortly after 6000 cal. BR The initial stage was a shallow bay or a salty marsh, followed by a wet marsh triggered by a relatively rapid drop in sea level related to a rapid isostatic uplift of land. By 5640 cal. BP, the site had transformed into a rich fen. A high rate of peat accumulation led to the establishment of a short-lived intermediate fen by 4610 cal. BP and to a poor fen from 4200 cal. BP until 1760 cal. BP. Low water-tables associated with decreased precipitation occurred between 5170 and 4610 cal. BP, and 3100 and 1760 cal. BP Between 1760 and the Little Ice Age, there was ombrotrophication of the site largely as a result of a thick peat accumulation. During this period, autogenic processes had controlled the general hydrosere, while allogenic processes, mainly precipitation, had influenced species composition. Permafrost established during the Little Ice Age leading to palsa formation and it has been melting in response to recent climate warming and precipitation increases. Macrofossil results from the filled thermokarst pond show that plant succession used the followed hydrosere: Calliergon giganteum and Sphagnum riparium when the ponds depth was at a maximum, S. riparium and C. giganteum when the pond was partly filled in, and S. lindbergii and S. riparium since the pond has been completely filled in.

Isolation and water-level fluctuations of Lake Kachishayoot, Northern Québec, Canada

This study combines different methods, including grain size, macrofossil, and pollen analyses, to reconstruct paleogeographical and paleoclimatological conditions for periods before, during, and after the isolation of a small lake (Lake Kachishayoot) in northern Quebec. After the retreat of the Laurentide Ice Sheet around 8000 14C yr B.P., the area was submerged by the Tyrrell Sea. The transition from marine to lacustrine environment occurred about 5400 yr B.P. Two major periods of water-level fluctuations were inferred from organic and mineral sediments: a high water level that occurred after 3200 yr B.P. and a low water level that started before 2200 yr B.P. Our chronological data for the first period are consistent with those from nearby Lac des Pluviers and from other lakes in east central Canada and in the northeastern United States. During the low-water-level period, however, there is no evidence for minor fluctuations, whereas other lakes in northern Quebec and east-central Canada underwent several brief lowerings. Long-term changes in atmospheric circulation caused by changing global boundary conditions likely explained long-term water-level fluctuations of Lake Kachishayoot.

Holocene plant succession in a dune-swale environment of southern Québec: A macrofossil analysis

Abstract:Macrofossil data allowed the reconstruction of the developmental history of a paludified dunefield site in the Central St. Lawrence Lowland, Quebec. Peat accumulation started between dunes around 7000 years BP after a period of free drainage reflected by podzolized sands. In interdune depressions, the vegetation developed from aquatic communities to damp forests, fen and bog communities. Between ca 7000-4100 years BP, slow peat accumulation reflected effective plant decomposition in the depressions while free drainage prevailed on the dune ridges. After 4100 years BP, wetness increased, and beaver occupied the site until ca 3800-3750 years BP. After 3750 years BP, the contrast between dunes and swales was attenuated by the vertical expansion and lateral spread of peat and the overall ombrotrophication of the site. Peat accumulation resulted from regional climatic changes toward moister conditions after 7000 (peat initiation), 4100 (beaver occupation), 3000 (larch establishment on slopes) and 1500...

Reconstruction of changes in vegetation and trophic conditions of a palsa in a permafrost peatland, subarctic Québec, Canada

Abstract Macrofossil and chronostratigraphic data of a peat monolith extracted from a palsa within a subarctic permafrost peatland were used to reconstruct changes in vegetation and trophic conditions of the study site during the last 4500 cal y BP. The vegetation cover developed from Carex marsh or wet meadow to poor fen, bog, and to palsa peatland communities. The ombrotrophication was favoured by late-Holocene cooling and by the high peat accumulation. Permafrost inception began about 1660–1630 calibrated y BP, at the end of the Sphagnum accumulation stage. A comparison of the late-Holocene development of two peatlands in the same region (Arlen-Pouliot & Bhiry, 2005, and this study) suggests that permafrost initiation was due to a cool, dry climate associated with the Little Ice Age. However, Sphagnum cover prevented the permafrost from melting.

Late-Holocene palaeoecology of a polygonal peatland on the south shore of Hudson Strait, northern Québec, Canada

In order to document climate fluctuations during the late Holocene in Nunavik (in the Québec Arctic), a 182 cm peat core extracted from a polygonal peatland in the Salluit region was subjected to macrofossil and pollen analysis. Peat accumulation began around 4500 cal. BP in the peatland and 2340 cal. BP in the core site following the formation of frost cracks and ice wedges. Four distinct Holocene climatic changes were identified. Between 1910 and 1100 cal. BP, the climate was clement (similar to today’s climate), which favoured the growth of several species of Sphagnum (from poorly minerotrophic to ombrotrophic conditions). Colder and drier conditions starting around 1100 cal. BP are evidenced by the disappearance of Sphagnum and aeolian sedimentation. A short return to more clement conditions occurred around 870 cal. BP and lasted until 670 cal. BP. Subsequently, the climate once again became colder and drier, which induced significant aeolian activity. Late-Holocene local vegetation changes recorded in the peat core were probably induced by permafrost degradation and aggradation, associated with regional warming and a subsequent cooling trend.

Differential Development of Two Palsa Fields in a Peatland Located Near Whapmagoostui-Kuujjuarapik, Northern Québec, Canada

Abstract Macrofossil analysis of the peat and topographic surveys of two palsa fields (Fields 3 and 4) within a permafrost peatland located in subarctic Québec was conducted to trace the factors that contributed to their differential development. The two palsa fields are visibly different in terms of their geomorphology, ecology, and hydrology. According to our results, the evolution of the two fields was largely synchronous in terms of the respective trophic conditions. Moreover, the climate certainly played a significant role in the evolution of this ecosystem. For example, the cooling of the Neoglacial period would have favored the ombrotrophication of both sites, whereas the Little Ice Age conditions would have contributed to palsa formation. Despite the synchronous changes within the two fields, significant differences were also noted. These include the rate of peat accumulation, the number of species found in the peat monoliths, and the presence or absence of forest cover during the ombrotrophic phase. The topography of the underlying substrate would also have influenced the hydrological conditions. For example, a light slope toward the northwest engendered a faster trophic impoverishment in Field 4. In addition, streaming water in Field 3 favored the preservation of wet and rich conditions that triggered the following changes: more diverse vegetation, the significant accumulation of peat, and the formation of higher palsas.

The Qijurittuq site (IbGk-3), Eastern Hudson Bay: An IPY Interdisciplinary Study

Abstract Geografisk Tidsskrift—Danish Journal of Geography 110(2):227–243, 2010 An interdisciplinary study was conducted at Qijurittuq (IbGk-3), an archaeological site located on Drayton Island along the eastern shore of Hudson Bay, Nunavik. Local Inuit made important contributions to the research. High school students participated in the field school, and elders shared their traditional knowledge. The elders expressed an interest in the source of the wood used to construct Qijurittuqs semi-subterranean dwellings, and this inspired us to expand our research in that direction. This interdisciplinary study included a reconstruction of the geomorphological and environmental history of Drayton Island, wood provenance and dendrochronology studies, research on house architecture and settlement patterns, and a zooarchaeological analysis. This paper synthesizes the preliminary results of this interdisciplinary investigation within the context of climate change. We discuss the persistence of semi-subterranean dwellings in eastern Hudson Bay long after they had been abandoned elsewhere. At Qijurittuq, their abandonment corresponds with the end of Little Ice Age. However, at the same time, the development of more permanent contact with Euro-Canadians was having a strong impact upon Inuit culture.

Paleoecological perspectives on landscape history and anthropogenic impacts at Uivak Point, Labrador, since AD 1400

Archaeological and paleoecological investigations were undertaken at Uivak Point (HjCl-09 located in Okak Bay, Labrador), a site that consists of a winter village comprising the ruins of nine sod houses and a number of tent ring, cache, and other structures. The site was occupied during the late 18th to early 19th centuries, although the immediate area has been used by many cultural groups spanning from Labrador’s early prehistory into the 20th century. Between ca. 3030 and ca. 710 cal. yr BP, cold and dry climate conditions corresponding to the late Neoglacial period generated the abundance of shrub tundra. From ca. 710 to ca. 550 cal. yr BP, conditions became warmer and wetter, triggering the expansion of trees. Since ca. 550 cal. yr BP, there has been an abundance of dry taxa which may reflect the colder conditions of the ‘Little Ice Age’. Subsequent climate warming has allowed the re-expansion of trees and shrubs over the last 200 years. Moreover, our results indicate that the Thule/Inuit harvested many plant species that grew in the vicinity of Uivak Point for food, raw material, and fuel. For example, many anthropogenic remains (burnt fat, burnt moss leaves, and charcoal) were incorporated into the soil. These activities also triggered the establishment of some weeds and apophytes (Montia Fontana and Silene). Furthermore, our chronostratigraphical and paleoecological data suggest that the site was occupied on an irregular basis since approximately AD 1400.

Fluvial sedimentation in a semi-arid region: the fan and interfan system of the Middle Souss Valley, Morocco

The Souss Valley is a structural basin located between the High Atlas Range and the Anti-Atlas Range in southern Morocco. Quaternary deposits in this valley are stacked as torrential piedmont fans, in which coarse deposits are dominant, and as flat gently sloping interfans, in which silty deposits are dominant. The visible part of the deposits, referred to as the Taroudannt Group, is composed of a lower silty unit (S0), three sequences (SI, S2 and S3), and a discontinuous cover of Rharbian (Late Weichselian—Holocene) deposits. Each sequence begins with an erosional disconformity and contains three superimposed members: a torrential cobble unit, lenses of highly calcareous sand, and a silt unit related to piedmont silt fans composed of aeolian deposits reworked by diffuse rain-wash and sheet-wash. A climatic origin is ascribed to this repeated superposition of facies. Calcareous epigenesis has modified all these deposits. Percentages of kaolinite, palygorskite and hornblende decrease from the base to the top of the sections, neogenic palygorskite and silica being observed by scanning electron microscope on quartz grains from the two lower silt units. The upper sequence (Maader Formation) is correlated with the upper sequence of the Atlantic coast of Morocco and represents the interglacial—glacial Ouljian—Soltanian (Eemian—Weichselian) climatic cycle. The older units may range from the Early to the Middle Pleistocene.

A study of the composition, characteristics, and origin of modern driftwood on the western coast of Nunavik (Quebec, Canada)

Data concerning driftwood is of value to researchers in fields as diverse as oceanography, geomorphology, and human occupation. Yet studies on the subject in the Canadian Arctic have only recently been carried out, and the present study is the first in Nunavik (northeastern Canada). This paper documents the composition, characteristics, and origin of modern driftwood pieces on the beaches of the eastern coast of Hudson Bay. A total of 1057 samples from Ivujivik, Akulivik, Inukjuak, and Umiujaq were identified as belonging to four coniferous species (Picea sp., Larix sp., Abies sp. likely balsamea, and Thuja sp. likely occidentalis) and four deciduous species (Salix sp., Populus sp., Alnus sp., and Betula sp., likely papyrifera). Spruce largely predominate; white birch, white cedar, and fir are rare. The presence of the latter species proves that some of the wood originated from south-southeast of James Bay. Driftwood found in the southern area (Umiujaq) are more numerous, larger, and less degraded than driftwood in the north (Ivujivik). However, many large coniferous samples were found as far north as Akulivik, indicating that they likely traveled a great distance, unlike the smaller wood specimens (especially deciduous samples). All of the wood that we analyzed died relatively young, with an average age of 63 years for conifers and 23 years for deciduous. Measurements of ring widths and the cross-dating of samples with existing reference chronologies of living trees along Hudson Bay and James Bay revealed several possible correlations and origins for wood found in same areas.