palaeoceanography of lower cretaceous alpine platform carbonates shallow water carbonate platforms evolve in an interplay of local regional and global dynamics thereby generating a detailed record of environmental conditions platform sediments constitute important archives of past environmental change and as such they are increasingly analysed for the information they contain on wider scale patterns the integration of this information with palaeoceanographic data obtained from deeper water sediments provides a powerful tool to develop a more diverse and complete image of past environmental change in this contribution the remains of the northern tethyan carbonate platform of early cretaceous age cropping out in the western swiss jura and the helvetic alps are used to illustrate the advantage of a palaeoceanographic approach in their interpretation the tools applied are biostratigraphy and chemostratigraphy carbon and strontium isotopes in order to obtain a precise age model for correlation with hemi pelagic sediments in adjacent basins sequence stratigraphy as a means to reconstruct the impact of sea level change phosphorus stratigraphy as a proxy for trophic levels facies and microfacies analyses as a gateway to gain better insight into the carbonate factory and the detailed analysis of platform drowning unconformities as an indicator of wider scale palaeoenvironmental change it is shown that changes from periods of predominantly photozoan to predominantly heterozoan carbonate production near the berriasian valanginian boundary and middle early aptian coincided with substantial increases in phosphorus burial rates and major carbon isotope excursions furthermore the majority of the platform drowning episodes occurred just prior to and during episodes of major palaeoenvironmental change and last but not least the platform itself may have influenced the chemistry of adjacent basins and the carbon isotope composition of associated carbonates by the export of periplatform ooze

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

postglacial paleoecology and inferred paleoclimate in the engelmann spruce subalpine fir forest of south central british columbia canada abstract pollen charcoal and plant macrofossil analyses reveal five postglacial vegetation periods at crater lake crater mountain british columbia the first period beginning ca 11 400 14c yr bp was characterized by artemisia steppe tundra at 9700 14c yr bp pinus parkland developed and by 6700 14c yr bp was replaced by fire successional pinus dominated engelmann spruce and subalpine fir forest essf at 3800 14c yr bp picea became a more important element of the forest and modern forest structure and composition developed by 1600 14c yr bp comparison of the fossil vegetation and fossil midge data derived from several essf sites in the southern interior reveals 1 similar late pleistocene vegetation and climate at all sites 2 three distinct holocene climatic stages warm dry warm moist and cool moist 3 confirmation of the warm moist period as a distinct climatic period and 4 distinct differences in holocene vegetation change among the sites the driest and warmest site was most sensitive to climatic change whereas cooler moister sites were less sensitive the present east west climate gradient originated with postglacial warming at the beginning of the holocene vegetation response to climate change and natural disturbance in these sites is strongly controlled by local site characteristics these characteristics may have implications for forest environment and resource management

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

evaluation of proposed early holocene advances of alpine glaciers in the north cascade range washington state usa constraints provided by palaeoenvironmental reconstructions many palaeoenvironmental reconstructions from across western north america indicate that the early to mid holocene was warmer and drier than present the wide distribution of these records suggests that relatively mild and arid conditions were regionally ubiquitous during the early holocene in contrast two recently proposed advances of alpine glaciers in the cascade range of washington state corresponding to equilibrium line altitude depressions of 350 to 450 m are placed in the early holocene the juxtaposition of the proposed major expansion of early holocene alpine glaciers with the constraint provided by a number of palaeoenvironmental reconstructions from directly adjacent areas results in palaeoclimatic gradients that are untenable the apparent diachronous behaviour of adjacent palaeoenvironmental records may be an artifact of dating errors

chemostratigraphy of the posidonia black shale sw germany ii assessment of extent and persistence of photic zone anoxia using aryl isoprenoid distributions aquatic depositional environments where anoxic conditions extend from bottom waters into the photic zone occurred frequently during the geologic past periods of photic zone anoxia pza can be recognized by the presence of specific lipids produced exclusively by the green sulphur bacteria chlorobiaceae that are preserved in the sedimentary record chlorobiaceae perform anoxygenic photosynthesis that requires light penetration into h2s saturated waters sediment samples integrate paleoenvironmental conditions over time intervals ranging from at best a few decades to more commonly several millennia photic zone anoxia recognized in paleoenvironmental analyses is thus defined as episodic with no further interpretation on the duration and persistence of the anoxic events we provide here a high resolution multiproxy chemostratigraphy study for the toarcian posidonia black shale from the dotternhausen section in sw germany in order to assess duration and seasonal fluctuation of photic zone anoxia based on the relative abundance of derivatives of chlorobiaceae lipids we assess the variability in the degree and persistence of photic zone anoxia using an aryl isoprenoid ratio air obtained by calculating the proportion of the short chain c13 17 versus the intermediate chain c18 22 aryl isoprenoids higher relative abundance of the short chain analogues is interpreted as indicating more intensive aerobic degradation of aryl isoprenoids air varies between values of 0 5 indicative of persistent pza phases and 3 0 for short termed episodic pza events absolute concentration of aryl isoprenoids is negatively correlated with the air which is in agreement with a progressive diagenetic breakdown of aryl isoprenoids the air decreases are validated using independent palecological and geochemical redox indicators for the posidonia shale in sw germany d 2004 elsevier b v all rights reserved

8000 year old wood from the athabasca glacier alberta several wood fragments of pinus sp dated at 8230 80 and 8000 90 years bp and abies sp were recovered from the snout of the athabasca glacier this wood derived from an unknown source up valley indicates that the glacier was less extensive than at present during the hypsithermal and that an area up valley of the present snout was tree covered ca 8000 8300 years bp

holocene vegetational history of the kootenai river valley montana abstract pollen records in the kootenai and fisher river drainages in western montana reveal a fivezone sequence of holocene vegetation change deposition of glacier peak ash layer g ca 10 540 660 yr b p in the lowermost sediments clay intermixed with pebbles at tepee lake gives a minimum date for the initiation of sedimentation initial vegetation on the newly deglaciated terrain was dominated by pinus probably white bark pine with small amounts of gramineae picea and abies reflecting a relatively cool moist macroclimate two vegetation units appear to contribute to pollen zone ii ca 11 000 7100 yr b p arboreal communities with pines along with pseudotsuga or larix or both and treeless vegetation dominated by artemisia pollen zone ii represents an overall warmer macroclimate than occurred upon ice withdrawal after ca 7100 yr b p pollen zone iii diploxylon pines became a major pollen contributor near both tepee lake and mckillop creek pond indicating an expansion of xerophytic forest p contorta and p ponderosa along with an increase in the prominence of pseudotsuga menziesii or larix occidentalis or both artemisia briefly expanded coverage near tepee lake concomitant with the mazama ashfall ca 6700 yr b p a short term climatic trend with more available water began after ca 4000 yr b p as abies probably a grandis along with picea engelmannii became a more regular component of the forest surrounding both sites emergence of the modern macroclimate is indicated primarily with the first regular appearance of tsuga heterophylla in the pollen record by ca 2700 yr b p synchronous with the development of western hemlock forest within the same latitudes in northern idaho and northeastern washington

reactivated basement structures affecting the sedimentary facies in a tectonically quiescent epicontinental basin an example from nw switzerland abstract the jurassic deposits in the southern part of central europe accumulated in a shallow epicontinental sea and their deposition has usually been believed to have corresponded to a phase of tectonic quiescence neither on conventional seismic records nor in outcrops obvious indications of synsedimentary tectonics were found nonetheless subtle variations in lithofacies and thickness occur above faults in the crystalline basement in fact preexisting structures became reactivated in the jurassic during major extensional phases when the tethys and the north atlantic opened this reactivation led to differential subsidence and or to rotation of fault bounded blocks but the sediments were deformed mainly flexurally as vertical movements in the basement were dissipated by triassic salt thus the depositional area was morphologically differentiated into swells and depressions in siliciclastic muddy environments swells were characterized by hardbottoms and hiatus beds depressions were filled by distal tempestites and gravity deposits in carbonate settings reefs nucleated on swells marls and muds were deposited in depressions many of them gravity deposits reactivation of faults occurred only during short episodes and was not synchronous throughout the study area and reactivation of individual faults was episodic and probably controlled by the palaeostress field and the faults orientation reactivation of deep rooted faults is also documented by hydrothermal activity which led to vein mineralization and alteration of minerals today exposed in nearby basement units the chronostratigraphic ages of the hydrothermal processes coincide with phases of enhanced subsidence during the sinemurian aalenian bajocian bathonian and oxfordian in turn facies changes of the sedimentary cover should be useful to predict basement structures when no seismic records are available

an 18 000 year palynological record from the southern alberta segment of the classical wisconsinan ice free corridor radiocarbon dates of 18 300 380 years bp gsc 2668 and 18 400 1090 years bp gsc 2670 on moss fragments from the clay near the base of a core from chalmers bog alberta indicate that the classical wisconsinan ice free corridor was in existence in the foothills of southern alberta by this time palynological studies show sparse herbaceous tundra like vegetation probably prevailed at this time in the area surrounding the small lake formed in the abandoned glacial spillway later shrubs became more prominent to form a shrub tundra environment sometime before 8220 years bp gsc 2851 trees began to invade the area and the pinus contorta dominated coniferous forest extant in the area today began to form bog and fen vegetation invaded the shallow lake basin about this time as well to form the bog that occupies the basin to the present day

tidal circulation in an ancient epicontinental sea the early jurassic laurasian seaway we model tides and associated bed shear stress in the early jurassic laurasian seaway of northwest europe sensitivity tests with different water depths highlight those regions that are least affected by paleobathymetric uncertainty results show that although the vast seaway was largely microtidal the tides were still capable of affecting sediment transport more than 2000 km from the open ocean flow constriction associated with shallow platforms and straits produced elevated bed shear stresses a direct proxy for the entrainment and transport of sediment that were decoupled from tidal range and were capable of transporting sand areas of increased bed shear stress broadly correlate with published geological data varying the water depth in the basin provides an insight into the effects of an idealized transgression increasing the water level leads to a net reduction in the bed shear stress at the shelf edge but promotes further penetration of tidal energy into the basin interior although it is still focused into areas of flow constriction further drowning of the seaway eventually widens the straits to the point that they fail to constrict the flow and bed shear stress is reduced increasing water level counterintuitively leads to an increase in bed shear stress in a small number of locations

holocene treeline dynamics in the mountains of northeastern british columbia canada inferred from fossil pollen and stomata changes in pollen and stomata assemblages in sediment cores recovered from tundra and forest tundra lakes in alpine regions of northeastern british columbia ree ect vegetation and inferred climatic change throughoutthe holocene pollen and stomata records are presented from two lakes bc2 located in the alpine tundra zone and dead spruce lake at the present elevation of subalpine treeline the pollen and stomata records from bc2 indicate that an ephemeral shrub and herb assemblage was rapidly replaced by an aspen populus spruce picea birch betula woodland at 10600 cal yr bp the occurrence of stomata suggests that treeline was at least 235 m higher than present from 10 600 until 7500 cal yr bp and temperatures were at least 1 4 c warmer than at present analyses from dead spruce lake indicate that the density of trees was also higher between 9000 and 4800 cal yr bp high concentrations of macroscopic charcoal between 9800 and 8000 cal yr bp suggest that conditions were also drier at this time changes in the position of treeline during the early to mid holocene appear to track closely shifts in climate while forest development at our forest tundra site ree ects a combination of both heightened summer insolation and increased e re activity the fossil stomata record from bc2 suggests that a rapid cooling event at 8200 cal yr bp may have been the trigger that resulted in the downslopemovement of treeline to its present elevation increased picea percent ages pollen accumulation rates pars and concentration of stomata between 3600 and 2700 cal yr bp provide evidence for a late holocene increase in forest tundra density in response to warmer temperatures

hydrogen sulphide poisoning of shallow seas following the end triassic extinction the end of the triassic period was marked by a mass extinction biomarkers in black shales that formed at the time suggest that the repeated poisoning of shallow seas by hydrogen sulphide delayed the early jurassic recovery

postglacial history of subalpine forests olympic peninsula washington usa to investigate subalpine vegetation history on the olympic peninsula washington usa two pol len macrofossil and charcoal records were studied in climatically distinct zones martins lake 1415 m in the moist tsuga mertensianazone and moose lake 1508 m in the drier abies lasiocarpa zone the interpret ation of fossil pollen assemblages was aided by comparisons with 308 modern assemblages from the olympic peninsula and western north america both pollen records show a cold dry period following deglaciation 10 000 radiocarbon years bp with sparse tundra and little similarity to any modern pollen assemblage in the early holocene when summer temperatures are thought to have been higher than present high percentages of alnus sinuata type pollen at both lakes suggest increased avalanche activity at martins lake warmer summers were not accompanied by forest establishment possibly because persistent spring snow pack snow avalanches and or edaphic constraints limited tree establishment at this site the martins lake record shows a steplike shift in vegetation to modern tsuga mertensiana abies amabilis parkland across the mazama tephra 6730 bp in contrast to martins lake abies lasiocarpa forest quickly established at moose lake in the early holocene though forests were probably initially open and fires may have been frequent from 7800 to 5100 bp forests near moose lake shifted gradually to cooler and moister species composition with the addition of chamaecyparis nootkatensis tsuga mertensianaand pinus though abies lasiocarpa remained dominant for est cover was probably greatest during this transition with parklike conditions at moose lake beginning at c 5100 bp the major differences in the records between the two sites may be due to differences in the local expression of regional climatic change and or differences in soil development and stabilization

c16 c29 homologous series of monomethylalkanes in the pyrolysis products of a holocene microbial mat preparative open pyrolysis products of kerogen isolated from a holocene microbial mat collected in abu dhabi united arab emirates contain homologous series of monomethylalkanes mmas c16 c29 the isomer and carbon number distributions of these branched alkanes closely match those of mmas in ancient sediments and oils it is proposed that monomethylalkanes in oils and in thermally mature ancient sediments derive from non extractable organic matter produced by one or more members of the cyanobacterial assemblage eubacterial primary producers and or heterotrophic bacteria 2000 elsevier science ltd all rights reserved

identification and significance of tephras encountered in a core from mary lake yoho national park british columbia mary lake is a small subalpine lake located proximal 3 km to the continental divide near lake o hara in yoho national park british columbia a 1 25 m core recovered from surficial bottom sediments was found to contain both bridge river tephra 2350 years bp and mazama tephra 6800 years bp identification of the tephras was initially based on distinctive colour texture phenocryst assemblages and glass shard habits and was confirmed by electron microprobe analysis of the constituent glass shards the microprobe technique employed backscattered and secondary electron imagery and both energy dispersive and wavelength dispersive analyses mean annual sedimentation rates calculated from tephra depths in the mary lake core were found to be of the order of 0 15 mm year for the post bridge river time period and 0 02 mm year for the mazama bridge river interval the preservation of mazama tephra in mary lake lacustrine sediments indicates that deglaciation had proceeded upvalley from the mary lake basin

molecular organic matter in speleothems and its potential as an environmental proxy abstract organic matter preserved in speleothems has considerable potential to record changes in the surrounding environment particularly in the overlying vegetation here we review three types of organic matter analysis relevant to speleothems organic fluorescence lipid biomarker analysis and amino acid racemisation organic matter luminescence provides a useful non destructive and rapid method for assessing dissolved organic matter quantity and quality while biomarker analysis amino acids and lipids has the potential to provide a more detailed signal related to specific parts of the surrounding ecosystem such as the dominant vegetation regime and bacterial activity amino acid analysis has yet to prove demonstrably useful in stalagmites due to the inability to characterise the sources of proteinaceous matter however the small but increasing body of work on lipid biomarker analysis in stalagmites has shown that a wide variety of recognisable biomarkers are preserved over long periods of time 100 ka can be recovered at temporal resolutions of

reconstructing millennial scale regional paleoclimates of boreal canada during the holocene abstract regional paleoclimate reconstructions for northern canada quantify holocene climate variability on orbital and millennial time scales and provide a context to better understand the current global warming the reconstructions are based on available pollen diagrams from the boreal and low arctic zones of canada and use the modern analog technique mat four regional reconstructions document the space time evolution of the climate during the holocene highest summer and winter temperatures anomalies are found in central canada during the early holocene eastern canada was relatively cool in the early holocene whereas central canada was warmest at that time labrador was relatively dry in the early to mid holocene during which time western canada was relatively moist millennial scale temperature variations especially the medieval warm period and little ice age are seen across the continent with some suggestion of time transgressive changes from west to east at the millennial scale precipitatio

terminal proterozoic mid shelf benthic microbial mats in the centralian superbasin and their environmental significance abstract a combined sedimentological and biogeochemical study has been conducted on several terminal proterozoic mid shelf microbial mat facies from the centralian super basin isotopic and organic geochemical analysis of the bitumen and kerogen indicated that two sources of organic matter from planktonic and benthic microbial mat populations contributed to the sediment the planktonic source provided a suite of n alkanes with c20 whereas the benthic source contributed an overlay of n alkanes c20 with a strong even preference together with mid chain methyl alkanes kerogen and biomarkers derived from the microbial mat were found to be depleted in 13c relative to planktonic material pyrite in the micorbial mats was also found to be depleted in 34s compared to surrounding facies the combination of these observations suggested that the mats may have been at least partly composed of sulfide oxidising bacteria these organisms have specific environmental tolerances that set limits on palaeo environment their requirement for oxygen indicates that the water column above the mid shelf could not have been anoxic accordingly from the results and age determinations reported here it would appear that mid shelf environments of the centralian superbasin of australia were seeing significant levels of oxygen through the ediacarian

carbon isotopic compositions of prokaryotic lipids as tracers of carbon cycling in diverse settings recent work has highlighted the ubiquity of bacteria and archaea and continues to affirm their significance in diverse biogeochemical processes the 13c values and distributions of diagnostic lipids derived from such microorganisms can provide insights into prokaryotic processes in modern settings and are one of the few means by which past prokaryotic processes in depositional settings can be elucidated here we present a brief review of prokaryotic lipids commonly observed in sediments and the controls on their carbon isotopic compositions we then present two case studies one of mediterranean cold seeps at which anaerobic oxidation of methane occurs and one of a holocene peat deposit in which a variety of aerobic and anaerobic microorganisms govern the degradation of organic matter these two studies illustrate the potential utility of compound specific carbon isotope analyses to deconvolute pathways of carbon flow in microbial communities

midge inferred holocene climate history of two subalpine lakes in southern british columbia canada to investigate postglacial environmental changes in both the coastal and interior wet belts of british columbia fossil midges were analysed from two subalpine lakes one adjacent to the lower fraser canyon frozen lake and the other in mount revelstoke national park eagle lake the midge stratigraphy for frozen lake revealed an abundance of rheophilous chironomid taxa and simuliidae larvae refecting the presence of an inflowing stream an abundance of chaoborus mandibles and microtendipes during the early holocene c 10100 7700 14c years bp c 11500 8500 cal years bp suggests warmer temperatures a subsequent decline in the warm indicators and relative increases in cold stenotherms heterotrissocladius and diamesa indicate cooling until present day this climate reconstruction is consistent with other quantitative and qualitative evidence for past climatic change in southern british columbia at eagle lake the warm indicators dicrotendipes and polypedilum are seen in the early holocene c 85

infrared satellite observations of hydrogen sulfide in the volcanic plume of the august 2008 kasatochi eruption 1 hydrogen sulphide h2s is one of the main trace gases released from volcanoes with yearly global emissions estimated between 1 and 37 tg with sulfur dioxide so2 15 21 tg year it dominates the volcanic sulfur budget and the emission ratio h2s so2 is an important geochemical probe for studying source conditions sulfur chemistry and magma water interactions contrary to so2 measurements of h2s are sparse and difficult here we report the first measurements of a large h2s plume from space observations were made with the infrared sounder iasi of the volcanic plume released after the 7 8 august 2008 eruption of kasatochi volcano the eruption was characterized by 5 consecutive explosive events the first events were phreatomagmatic producing a plume rich in water vapor and poor in ash and so2 we show that the observed h2s plume calculated at 29 10 kt with integrated columns exceeding 140 25 dobson units du is likely associated with these first explosions h2s so2 ratios with maximum values of 12 2 are found representative of redox conditions in the hydrothermal envelop with a detection threshold of 25 du future space observations of h2s plumes are certain these will be important for improving the atmospheric sulfur budget and characterizing the h2s so2 fingerprint of different eruptions

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

molecular and isotopic characterization of biomarkers in the frick swiss jura sediments a palaeoenvironmental reconstruction on the northern tethys margin abstract molecular and stable carbon isotope compositions of source specific hydrocarbons have been used to reconstruct palaeoenvironmental conditions during deposition of the middle hettangian to upper sinemurian sediments on the northern epicontinental tethys margin frick swiss jura increasing algal cyanobacterial and phytoplanktonic i e dinoflagellate contributions associated with the 13 c enrichment of cyanobacteria derivatives i e hopanes and monomethylalkanes suggest enhanced primary productivity upsection this is related to the 13 c enrichment of dissolved co 2 in the upper layers and the progressive increase of depth and oxygenation of the water column in the middle hettangian shallow water environments lagoon the occurrence of green sulfur bacteria chlorobiaceae derivatives indicates that the lower part of the water column was strictly anoxic and rich in h 2 s since these bacteria require very low light intensity to grow these euxinic conditions may be extended up to the photic zone allowing for anaerobic photosynthesis light penetration depth is most likely reduced by high productivity and or turbidity in the photic zone in these sediments 13 c depleted hopanoids 39 5 are most likely associated with phototrophic purple sulfur bacteria utilizing isotopically light organic carbon at the base of the aerobic zone these purple sulfur bacteria may have consumed the h 2 s used by chlorobiaceae in the deeper layers and thus sustained the algae and cyanobacteria productivity in the upper layers the 13 c depleted carbonate 13 3 may be partially related to the anaerobic oxidation of the organic matter during bacterial sulfate reduction

postglacial vegetational history of tonquin pass british columbia a pollen and macrofossil study of peat sediments in tonquin pass british columbia provides the oldest dated record of vegetational and climatic changes in the middle canadian rockies paleoecological interpretation of these events dated by tephrochronology and radiocarbon dating is facilitated by comparisons with other regional pollen profiles late wisconsin ice receded from tonquin pass prior to 10 000 years bp by 9700 years bp a pinus contorta forest with an understory dominated by ferns had colonized the area the climate of this period was cool and moist following this interval was a brief episode 9000 8040 years bp of haploxylon pine dominance during which the climate became colder a long warm period beginning by 8040 years bp was characterized by desiccation of local meadows and fens and invasions of these areas by trees principally picea dated fossil picea and abies logs from alpine bogs within jasper national park document that timberlines had advanced beyond present limits by 8770 years b

occurrence and origin of mono di and trimethylalkanes in modern and holocene cyanobacterial mats from abu dhabi united arab emirates n alkanes highly branched isoprenoids monomethylalkanes mmas dimethylalkanes dmas and trimethylalkanes tmas are the most abundant components in the hydrocarbon fractions of extracts of four modern and two holocene cyanobacterial mats t1500 and 5110 170 y bp collected in abu dhabi united arab emirates the homologous families of mmas dmas and tmas were identified by comparison of mass spectral and relative retention time data with published data dmas were also identified by synthesis of authentic standards 3 9 dimethyltricosane 5 9 dimethyltricosane and 11 15 dimethylheptacosane mmas dmas and tmas of the cyanobacterial mats can be separated into two groups on the basis of their distribution patterns and structures mmas and dmas in the c16 c22 range are characterized by methyl substituents mainly located at c 6 or 6 and c 7 or 7 and are derived from cyanobacteria they are relatively abundant components in the modern cyanobacterial mats but with increasing age of the mats they become much less abundant on the contrary mmas dmas and tmas in the c24 c45 range are exclusively found in the holocene cyanobacterial mats their longest chains mainly contain an odd number of carbon atoms and they always carry the methyl substituents at odd numbered carbon atoms the similarity in composition of this very specific group of branched alkanes with that encountered in insect epicuticular waxes suggests that these sedimentary hydrocarbons originate from insects which probably grazed on the cyanobacterial mats

possible algal origin of long chain odd n alkanes in immature sediments as revealed by distributions and carbon isotope ratios a pliocene oil shale pula hungary a c3 plant triticum aestivum and a c4 plant zea mays were compared using isotopic composition of bulk organic matter along with distributions and individual carbon isotope ratios of n alkanes from organic extracts the microalga botryococcus braunii a race was thus shown to be the main source of the predominant 27 29 and 31 n alkanes of pula sediment therefore the dominance of odd carbon numbered n alkanes in the range c25 35 in extracts from immature sediments shall not be systematically assigned to higher plant contribution but algal input is also possible in fact the long chain n alkanes with an odd predominance previously observed in extracts of various immature sediments are likely to be derived at least partially from algae

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

organic geochemistry of the san vicente zinc lead district eastern pucara basin peru abstract isotopic and chemical studies of organic matter of the san vicente mississippi valley type zn pb district hosted in the dolomitic units of the eastern pucara basin peru provide insight into the source of organic matter and of the organic matter ore relationship a large scatter exists in the 13c and 15n values of the highly mature kerogens these bulk data were combined with 13c covariations of the saturated and aromatic fractions of the rock extracts to indicate a contribution of continental higher plant lipids to the marine algal source of the organic matter disseminated in the host carbonate rocks an enrichment in 15n of the kerogens of mineralized samples compared to barren samples suggests that isotopically heavy nitrogen compounds were introduced to the ore fluid the fluid likely leached these compounds from the underlying clastic rocks and other detrital units of the pucara the extracts from mineralized samples are enriched in 13c compared to the associated kerogens this suggests that the rocks in the mineralized areas were stained by a mixture of extrinsic and indigenous bitumens by the use of novel instrumentation such as a gas chromatograph gc coupled to a stable isotope ratio mass spectrometer irms through a combustion c interface gc c irms stable carbon isotope analyses of individual hydrocarbons were also obtained both the molecular and isotopic signatures of the individual hydrocarbons are related to mineralization the variability in the organic molecular parameters and the 13c values of the individual n alkanes and isoprenoids indicate mixing of indigenous hydrocarbons with extrinsic 13c depleted microbially derived hydrocarbons the extrinsic source hydrocarbons were introduced to the mineralization site by the ore fluid or later fluids using the same porosity network oxidative alteration of the migrating hydrocarbons was involved in the thermochemical reduction of sulfate to h2s and precipitation of pyrobitumen large differences 12 in the carbon isotope compositions of long chain c20 n alkanes can be utilized in distinguishing sources of organics in the barren and mineralized samples

how quick was marine recovery after the end triassic mass extinction and what role did anoxia play oxygen restricted conditions were widespread in european shelf seas after the end triassic mass extinction event and they are reported to have hindered the recovery of marine benthos here we reconstruct the redox history of the early jurassic blue lias formation of southwest britain using pyrite framboid size analysis and compare this with the recovery of bivalves based on field and museum collections results suggest widespread dysoxia punctuated by periods of anoxia in the region with the latter developing frequently in deeper water settings despite these harsh conditions initial benthic recovery occurred rapidly in the british jurassic especially in shallowest settings and shows no relationship with the intensity of dysoxia a stable diversity was reached by the first recognised ammonite zone after the end triassic mass extinction this contrasts with the deeper water more oxygen poor sections where the diversity increase was still continuing in the earliest sinemurian stage considerably longer than previously reported similar recovery rates are seen amongst other groups brachiopods and ammonites oxygen poor conditions have been suggested to delay recovery after the permo triassic mass extinction but this is not the case after the end triassic crisis we suggest that this was because the european dysoxia was only a regional phenomenon and there were plenty of well ventilated regions available to allow an untrammelled bounce back

molecular and isotopic biogeochemistry of the miocene clarkia formation hydrocarbons and alcohols the miocene lacustrine deposit at clarkia northern idaho u s a is well known for its rich and exceptionally well preserved higher plant leaf fossils in the present study the distributions abundance and isotopic compositions of aliphatic hydrocarbons and alcohols isolated from two sediment samples and from two associated fossils magnolia latahensis and platanus dissecta are investigated the general similarity of these characteristics in the sediments suggests a relatively uniform depositional environment and consistent terrestrial input the sediment hydrocarbons are comprised mainly of compounds derived from higher plants and bacteria whereas the alcohols reflect contributions from both higher plants and algae a notable feature of the higher plant derived terpenoid hydrocarbons is the prevalence of des a triterpenes largely in the absence of their pentacyclic precursors indicating the dominance of a ring degradation for these pentacyclic triterpenoids the des a triterpenes include several novel compounds namely 19 h and 19 h 28 nor des a lup 17 ene and des a oleana 9 13 18 diene the sediment samples contain high abundances of c24 c32 long chain alkanediols consisting of a series of diols 1 diols 1 15 diols and an unusual series of 1 3 diols both fossil leaves show clear differences in their compound distributions and concentrations from the associated sediments which suggests that they retain a composition distinct from the sediment groundmass the 13c values of c25 c33 n alkanes and c24 c32 n alcohols in sediments and fossils are consistent with an origin from terrestrial c3 higher plants algal lipids in the two sediments are represented by dinostanol 24 6 and 25 9 inherited from dinoflagellates and long chain 1 15 alkanediols 26 4 to 29 7 derived from microalgae the long chain 1 and 1 3 alkanediols are more enriched in 13c 21 8 to 26 4 suggesting an origin from sources other than higher plants probably aquatic photoautotrophic organisms the 13c depletion of some hopanoids 35 9 to 61 0 attests to contributions from methanotrophic bacteria and suggests an active methane cycle at the time of deposition

postglacial palaeoecology of the subalpine forest grassland ecotone of southwestern alberta new insights on vegetation and climate change in the canadian rocky mountains and adjacent foothills postglacial vegetation change at the subalpine forest grassland ecotone in the foothills of southwestern alberta is reconstructed from fossil pollen plant macrofossils and fossil charcoal the fossils were obtained from the sediments of a small lake chronological control for the record is provided by tephra analysis and the 14c dating of terrestrial plant macrofossils the fossil record is compared with the results from similar studies at sites in the rocky mountains and foothills of alberta and british columbia the comparison of vegetation change at the upper and lower elevational limits of the subalpine forest provides a record of changes in temperature and aridity over the holocene at 10 000 yr b p the study site supported a shrub and herb dominated vegetation picea pinus abies forests were present at mid to high elevations in the mountains and in the northern foothills by this time the climate in the southern foothills was likely arid but not severely cold a relatively open picea and pinus forest was established in the study area between 9400 yr b p and 8000 yr b p fire activity in the region was at a postglacial maximum during this period the transition to forest suggests moister conditions by 8000 yr b p the importance of members of the chenopodiaceae amaranthaceae and typha latifolia increased suggesting an onset of arid conditions characterised by low and fluctuating water levels in lakes between 8000 yr b p and 5000 yr b p the picea and pinus contorta forest at the study site was largely replaced by grassland and pinus flexilis at high elevation sites treeline was located above its modern position during this period little vegetation change is recorded at sites in the northern foothills and at mid elevations at this time the vegetation change in the southern foothills and at high elevations suggests both an elevational and latitudinal displacement of vegetation zones during the mid holocene warm and arid conditions were prevalent in southwestern alberta picea glauca pinus contorta populus tremuloides forest has occupied the site since 5000 yr b p when cooler and moister conditions were established

late pleistocene and holocene deglaciation and environments of the southern chugach mountains alaska the description of late pleistocene and holocene deglaciation and environments in the copper river chugach mountains region is based on surficial geology as well as on pollen analysis and radiocarbon dating of core samples the results of this study indicate that late pleistocene glaciers extended well beyond the present coastal plain deglaciation began in the lower copper river valley prior to 14 000 yr b p and in the bremner and tasnuna river valleys about 10 000 and 9000 yr b p respectively cirque glaciers formed marginal moraines at an elevation of 560 m in the tasnuna valley 8800 yr b p on the basis of the pollen record shrub herb tundra characterized the initial late wisconsinan vegetation tundra was succeeded first by alder dominated vegetation and then by spruce forest the late glacial pollen zones indicate a time transgressive colonization of the river valleys and mountain slopes inland from the coast

dinoflagellate origin for sedimentary 4α methylsteroids and 5α h stanols biological marker compounds provide useful tools for evaluating the depositional environments of recent and ancient sediments and petroleums1 largely through established relationships between the organic matter of sediments and source organisms1 2 such relationships are best tested and explored by investigating the lipid components of natural populations of autochthonous biota that can be clearly recognized as contributors to underlying bottom sediments in this context we have studied the lipids of the freshwater dinoflagellate peridinlum lomnickii woloszynska order peridiniales class dinophyceae collected from the waters of priest pot3 a eutrophic lake in the english lake district its distributions of both 4 methylsterols and 4 methylstanones closely resemble those of the underlying bottom sediments demonstrating that dinoflagellates are important contributors of these sedimentary compounds the 4 methylsteroidal hydrocarbons found in ancient sediments and petroleums4 6 are presumably diagenetic products of such 4 methylsteroids and therefore reflect dino flagellate inputs to the original depositional environments furthermore the prominence of 5 h cholestan 3 ol in p lomnickii suggests that dinoflagellates may be the long sought direct biological source of sedimentary 5 h stanols

the significance of hiatus beds in shallow water mudstones an example from the middle jurassic of switzerland abstract limestone beds formed in nearly carbonate free shallow water mudstones by discontinuous sedimentation and erosion are called hiatus beds anaerobic oxidation of organic matter by microbes provided excess alkalinity inducing carbonate precipitation a multiphase history of such beds is documented from the swiss jurassic by several cementation and dissolution phases four cement types occur micrite as earliest cement 13c 10 to 20o oo stellate calcite between micrite cemented parts 13c 5 to 10o oo fibrous calcite cement in dissolution cavities 13c 30o oo and blocky calcite in remaining pores 13c 5o oo except for the late blocky cement all cements contain pyrite indicating carbonate precipitation within the sulfate reduction zone after early cementation by micrite the beds moved relatively upwards into a shallower geochemical zone and some even to the seafloor because of erosion cavities formed during reburial by dissolution in the upper part of the sulfate reduction zone and in the upper part of the methanogenic zone strongly reduced sedimentation rates provided the requisite stable geochemical conditions for at least several thousands of years which permitted precipitation and dissolution of carbonate by biochemical processes and diffusion this happened on short lived swells caused by differential subsidence and rotation along listric faults when basement structures became reactivated during the extensional stress regime from opening of the tethys during the jurassic and cretaceous breakup of pangea the shelf area increased and differential subsidence on these newly formed shelves was the main factor responsible for the observed post paleozoic maximum in hiatus beds and hiatus concretions

late quaternary history of the lake o hara region british columbia an evaluation of sedimentation rates and bulk amino acid ratios in lacustrine records lake o hara subalpine and opabin lake alpine are situated directly adjacent to a high section of the continental divide in the central canadian rocky mountains core samples recovered from the lakes show a consistent stratigraphy comprising gyttja and underlying inorganic clastic sediments the gyttja contains bridge river 2350 years bp and mazama 6800 years bp tephras and is separated from the lower clastic sediments by a sharp conformable contact radiocarbon dates obtained from conifer needles extracted from directly above the contact indicate that deglaciation had proceeded upvalley from the o hara basin priorto ca 10 100 years bp preliminary palaeobotanical and macrofossil data suggest that a pinus abies forest with lesser picea was established in the vicinity of lake o hara by this time consequently the minimum age of moraine systems situated downvalley from lake o hara is late wisconsinan mean annual sedimentation rates were derived from sediment thickness data from 14 lake o hara an

mid chain branched mono and dimethyl alkanes in hot spring cyanobacterial mats a direct biogenic source for branched alkanes in ancient sediments hot spring cyanobacterial mats from yellowstone national park u s a and the orakei korako thermal area new zealand have been found to contain suites of monomethyl alkanes compounds frequently reported in cultured and natural populations of cyanobacteria the complete range of possible structural isomers for mid chain branching for c17 c18 and c16 c18 alkanes occurs in the two mats respectively several c19 dimethyl and c20 multibranched alkanes were also observed as major hydrocarbons of the orakei korako mat the recognition of series of mid chain branched alkanes in modern cyanobacterial mats suggests that their occurrence in ancient sediments may reflect direct biogenic contributions rather than formation by diagenetic processes

holocene paleohydrology of central alberta testing the general circulation model climate simulations paleoecological investigations of 28 lakes and bogs provide the basis for a holocene paleohydrological record for central alberta shallow basins empty during the early holocene began flooding shortly after 8000 years ago most filled from 6500 to 4500 years ago and none filled later than 3000 years ago pollen of a hypersaline indicator genus ruppia was found in cores of lakes where the plant does not presently grow indicating lower lake levels evaporation stress and increased salinity from 8000 to 3000 years ago moore lake 54 30 n 100 30 w may have dropped 15 m from 9200 to 5900 years ago and lofty lake 54 44 n 112 29 w largely dried up between 8700 and 6300 years ago lower water levels are suggested for several lakes by shifts in fossil diatom populations from planktonic to benthic particularly epipelic species including pioneering taxa these shallow warm lakes were highly productive and sedimentary pigment levels reached maximum values between about 9000 and 4000 years ago the pale

factors controlling 13c contents of sedimentary organic compounds principles and evidence the carbon isotopic composition of any naturally synthesized organic compound depends on 1 the carbon source utilized 2 isotope effects associated with assimilation of carbon by the producing organism 3 isotope effects associated with metabolism and biosynthesis and 4 cellular carbon budgets these factors are reviewed and quantitative considerations summarized particularly with regard to active and passive modes of carbon assimilation by phytoplankton and the existence of discernible regularities in isotope effects associated with lipid biosynthesis it is concluded that n alkyl lipids are in general depleted in 13c by about 1 5 relative to polyisoprenoid lipids produced by the same organism the effects of biological reworking on isotopic compositions of organic carbon are examined and it is suggested that enrichment of 13c in sedimentary organic carbon may result from loss of ch4 from zooplanktonic gut communities isotopic methods for estimation of ancient co2 levels are considered and a hyperbolic form favored for the relationship between concentrations of dissolved co2 and isotopic fractionation

sensitivity and response time of natural systems to climatic change in the late quaternary abstract although the leading theory for the cause of climatic change the milankovitch perturbations in insolation indicates variable rates of change at different latitudes any discussion of the sensitivity and response time of different natural systems is most practical when the climatic change is considered to be relatively abrupt and global rather than gradual and regional the oxygen isotope record in glacial ice should have the swiftest response time but the stratigraphic record in ice sheets at particular localities may be obscured or confused if the glacier flow is irregular the oxygen isotope stratigraphy of ocean sediment cores is a sensitive reflection primarily of contemporaneous ice volume and to a lesser extent ocean temperature ocean temperature however is recorded more specifically by microfossils in ocean sediments and may reflect global insolation directly except that in the north atlantic the influence of glacial meltwater and various feedbacks may override the insolation factor the differential lags in the response of isotopes and faunas to insolational change are apparent in the ocean sediment stratigraphy ice sheets themselves at their terminus may respond to climatic change only slowly if a change in snow accumulation is the factor because of the time involved in building a thickness sufficient for flow to great distances but if wastage near the margin is the factor then the response may be more rapid some glaciers however may advance rapidly without regard to climatic change as in the case of surging or they may retreat just as rapidly if they terminate in deep water through iceberg formation world sea level is depressed with glacial growth and thus reflects the volume of ice sheets but isostatic changes in the crust complicate the sea level response not only locally beneath the ice load but elsewhere as well the pluvial lakes of the american southwest correlated in their high levels with intervals of glaciation show a direct response to climatic patterns resulting from the expansion of the north american ice sheets and thus may lag with respect to the primary climatic change that causes ice sheet growth north african lakes on the other hand respond to the intensity of monsoonal circulation which is controlled directly by insolational shifts the response of plants and insects to deglaciation can be immediate in the case of pioneers on newly exposed terrain although the deglaciation itself may lag behind climatic change succession can follow rapidly but then more slowly as other plants immigrate from great distances it is heare where the more realistic assumption of continuing climatic change may be necessary to explain the dynamics of long range vegetational change following the last deglaciation the distribution and abundance of vertebrate populations reflect primarily their food resources and the disharmonious faunas of the last glacial period in north america with components that no longer have overlapping ranges perhaps may be explained by vegetational associations that likewise may have no modern analogues the cause may be a different climatic seasonality wastage of the ice sheet itself lagging behind the climatic change may have changed the seasonal climatic patterns sufficiently to bring about the precipitous extinction of many vertebrate species

organic geochemistry across the permian triassic transition at the idrijca valley western slovenia abstract bulk and molecular stable c isotopic compositions and biomarker distributions provide evidence for a diverse community of algal and bacterial organisms in the sedimentary organic matter of a carbonate section throughout the permian triassic p tr transition at the idrijca valley western slovenia the input of algae and bacteria in all the upper permian and lower scythian samples is represented by the predominance of c15 c22 n alkanes odd c number alkylcyclohexanes c27 steranes and substantial contents of c21 c30 acyclic isoprenoids the occurrence of odd long chain n alkanes c22 c30 and c29 steranes in all the samples indicate a contribution of continental material the decrease of corg and ccarb contents increase of rock eval oxygen indices and 13c enrichment of the kerogen suggest a decrease in anoxia of the uppermost permian bottom water the predominance of odd c number alkylcycloalkanes c27 steranes and c17 n alkanes with 13c values 30 and 13c enrichment of the kerogens in the lowermost scythian samples are evidence of greater algal productivity this increased productivity was probably sustained by a high nutrient availability and changes of dissolved co2 speciation associated to the earliest triassic transgression a decrease of corg content in the uppermost scythian samples associated to a 13c depletetion in the carbonates up to 4 and individual n alkanes up to 3 4 compared to the upper permian samples indicate lowering of the primary productivity algae cyanobacteria and or higher degradation of the organic matter

severe drought in the early holocene 10 000 6800 bp interpreted from lake sediment cores southwestern alberta canada abstract six lake sediment vibracores from the foothills and mountain valleys of southwestern alberta were analysed on the basis of ams radiocarbon dates tephrochronology and sediment geochemistry from these results the magnitude timing and duration of the early holocene warm period are presented at about 10 000 bp immediately following the younger dryas cold period climate warmed dramatically precipitation decreased and surface evaporation increased previous research has identified this warm interval but new results have improved resolution of regional scale effects specific timing and severity sedimentation changed from extra basinal clastic to intra basinal organic between 10 000 and 9400 bp changes in subalpine lakes from sand silt deposition to biogenic carbonate precipitation suggest decreases in suspended sediment load caused by complete ablation of glacial sediment sources peat which formed in lakes of less than 4 m present depth indicates climate induced lake level lowering in the foothills water depth and stratigraphic position of the peat suggest that regional water table levels decreased by up to 6 5 m at cartwright lake an erosional unconformity 6 5 m below the modern lake surface indicates the lake had completely dried out either during or immediately after mazama tephra time 6800 bp

varve studies at hector lake alberta canada and the relationship between glacial activity and sedimentation glacial lake sedimentary records from hector lake in banff national park alberta are examined with the aim of clarifying the relationship between glacial activity and outwash sedimentation rhythmic couplets in lake bottom sediments provide a method for accurate documentation and dating of recent sedimentation chronology as analysis of 137cs content indicates that the couplets are of annual periodicity i e varves a comparison of sedimentation rate records with recent regional glacial history indicates that high sedimentation rates of one to a few decades duration occur either during and immediately following periods of moraine deposition ie maximum ice stands or during periods of rapid ice recession comparison of sedimentary records with somewhat longer term glacial and vegetation records indicates that sedimentation rate variations of several centuries duration closely parallel changes in upvalley ice extent over this time scale high sedimentation rates occur during periods of relatively increased ice extent low rates during periods of reduced ice extent within this general pattern however sedimentation rates may remain very high for nearly a century following maximum ice stands due to the exposure of unstable glaciogenic deposits to fluvial reworking during ice recession

late quaternary vegetation in the southwestern columbia basin washington abstract a 33 000 yr pollen record from carp lake provides information on the vegetation history of the forest steppe border in the southwestern columbia basin the site is located in the pinus ponderosa zone but through much of late quaternary time the area was probably treeless pollen assemblages in sediments dating from 33 000 to 23 500 yr b p suggest a period of temperate climate and steppe coinciding with the end of the olympia interglaciation the fraser glaciation ca 25 000 10 000 yr b p was a period of periglacial steppe or tundra vegetation and conditions too dry and cold to support forests at low altitudes aridity is also inferred from the low level of the lake between 21 000 and 8500 yr b p and especially after about 13 500 yr b p about 10 000 yr b p chenopodiineae and other temperate taxa spread locally providing palynological evidence for a shift from cold dry to warm dry conditions pine woodland developed at the site with the onset of humid conditions at 8500 yr b p further cooling is suggested at 4000 yr b p when pseudotsuga and abies were established locally

novel cyclised and aromatised diagenetic products of β carotene in the green river shale abstract a suite of novel diagenetic products of carotene has been identified in an extract of a sample from the green river shale identification is mainly based on comparison of mass spectra with those of diagenetic products of another carotenoid isorenieratene these compounds were formed by i cyclisation and aromatisation of the polyene isoprenoid chain ii explusion of toluene and m xylene from the polyene isoprenoid chain and iii aromatisation of the 1 1 5 trimethylcyclohex 5 enyl moieties resulting in 1 2 dimethylbenzene end groups reduction of the double bonds of carotene is the most important diagenetic process however as judged from the high relative amount of carotane 63 of quantified diagenetic products of carotene these results indicate that the fossilisation potential of carotenoids is greater than previously thought

evidence for a neoglacial advance of the boundary glacier banff national park alberta direct evidence for an early neoglacial advance in the canadian rocky mountains is presented radiocarbon dates from buried peat and tree remains at boundary glacier suggest limiting dates for this advance of between 3800 and 4200 years bp these data from boundary glacier are consistent with previously published dates for the onset of the neoglacial and an early neoglacial advance

late quaternary paleoenvironments of the morley flats and kananaskis valley of southwestern alberta a 3 1 m section of limnic sediment and peat from a bog on the morley flats and a 2 8 m section of limnic sediment from wedge lake in the kananaskis valley have yielded the first comprehensive late quaternary biostratigraphic record from south western alberta both sections were analyzed for subfossil pollen molluscs and several sedimentary indices two distinct pollen zones were recognised the basal zone characterized by high relative abundancy of artemisia salix juniperus suggests that the morley flats were dominated by a sparse vegetation composed of aggressive pioneer species following deglaciation until prior to approximately 10 000 bp similarly the mollusc fauna from this zone is dominated by northern ranging species the second zone is typified by a predominance of pinus and picea this reflects the expansion of coniferous forest into the region both the relative abundance of southern ranging mollusc species and the total carbonate concentration in the sediment increase in this zone the veg

late quaternary landscape history and archaeology in the ice free corridor some recent results from alberta abstract multidisciplinary research programs conducted within the alberta portion of the ice free corridor since 1986 as part of the archaeological survey s first albertans project have used studies of palaeogeography and palaeoenvironments to formulate archaeological search strategies this approach has resulted in the discovery of two new important sites saskatoon mountain ghqt 4 and the james pass meadow complex ekpu 3 to 9 that are yielding information on terminal late wisconsinan early holocene human occupation of the corridor both sites are dated by ams or conventional radiocarbon dates to the millennium 10 000 9 000 bp in the fifteen years since the 1978 amqua conference on the corridor other researchers have identified four additional significant paleo indian sites in this region so far none confirm human occupation of the ice free corridor region before about 11 000 bp

composition and sources of lipid compounds in speleothem calcite from southwestern oregon and their paleoenvironmental implications we analyzed speleothem calcite from the oregon caves national monument southwestern oregon to determine the preservation distribution concentrations and sources of aliphatic lipid compounds preserved in the calcite maximum speleothem growth rate occurs during interglaciations and minimum during glacial intervals concentrations of the total lipid compounds range from 0 5 to 12 9 g g 1 they increase at times of low speleothem growth rate suggesting dilution whereas the apparent accumulation rate of lipid compounds tends to be highest during times of fastest speleothem growth rate such increased accumulation generally corresponds to times of warm interglacial climate suggesting either a greater source of organic materials during interglacial times and or greater efficiency of compound capture during more rapid calcite growth aliphatic lipid compounds include homologous n alkanoic acids n alkanols and methyl n alkanoates and sterols with concentrations ranging from 0 3 to 7 8 g g 1 0 4 to 1 1 g g 1 0 5 to 9 6 g g 1 and 0 1 to 2 7 g g 1 respectively minor amounts of branched methyl n alkanoates and dimethyl n alkanedioates are also present the high concentrations of methyl n alkanoates are the result of esterification reactions of free fatty acids in alkaline solutions with high ph values associated with the dripping cave waters the distribution patterns and geochemical parameters and indices indicate that the major sources of the aliphatic lipids involved leaching from higher plants and microbial residues derived from the soil zone above the cave system the estimated percentage of microbial inputs ranged from 42 to 90 of the total lipids and also showed an increase in accumulation during warm climates these well preserved lipid compounds in speleothem calcite could be used as biomarkers for paleoenvironmental study

reconstruction of holocene changes in alpine vegetation and climate in the maligne range jasper national park alberta abstract pollen macrofossil logs and needles and oxygen isotope data from tree rings are presented for three alpine bog sites in the maligne range of the canadian rockies organic sedimentation at the watchtower site began prior to ca 9500 14 c yr b p and by 8770 yr b p timberlines were at least 100 m above present levels the two pollen records are dominated by pinus and subsequent changes in timberlines are inferred from pollen ratio data abies pinus and from macrofossils the recovered records indicate two periods of high hypsithermal timberlines ca 8800 7500 and 7200 5200 yr b p separated by a short interval ca 7300 7400 yr b p when timberline approached modern levels after ca 4500 yr b p timberlines have been similar to or lower than present reaching minimum values in the last 500 yr 18 o determinations from the cellulose of samples of 5 or 10 annual rings cut from contemporary picea englemannii at timberline show strong correlations with mean annual temperatures at jasper isotopic determinations from hypsithermal age logs recovered from sites above present timberline indicate mean annual temperatures were at least 0 5 c warmer ca 8060 and 8770 yr b p than at present at the watchtower site data from logs at the maligne pass site suggest that temperatures were about 1 2 and 1 6 c warmer ca 6000 and 5300 yr b p estimates of temperature from the pollen ratio data are more conservative and suggest maximum differences of ca 1 0 c in july temperatures over the last 8000 yr

chemical and carbon isotopic evolution of hydrocarbons during prograde metamorphism from 100 c to 550 c case study in the liassic black shale formation of central swiss alps abstract hydrocarbon distributions and stable isotope ratios of carbonates 13ccar 18ocar kerogen 13cker extractable organic matter 13ceom and individual hydrocarbons of liassic black shale samples from a prograde metamorphic sequence in the swiss alps were used to identify the major organic reactions with increasing metamorphic grade the studied samples range from the diagenetic zone 17 n alkanes suggests the occurrence of cracking reactions of high molecular weight compounds the isotopically heavier up to 5 6 c 13 n alkanes with metamorphism suggests progressive thermal release of kerogen linked fatty acid precursors and degradation of n alkanes changes of the steroid and terpenoid distributions are clearly related to increasing metamorphic temperatures the absence of 18 h 22 29 30 trisnorneohopane ts the occurrence of 17 h trisnorhopane 17 h 21 h hopanes in the c29 to c31 range and 5 h 14 h 17 h 20r c27 c29 steranes in the low diagenetic samples the occurrence of specific hydrocarbons e g n alkylcyclopentanes cadalene hydrogenated aromatic compounds in metamorphic samples points to kerogen degradation reactions most probably occurring in the presence of water and under reducing conditions the changes of hydrocarbon distributions and carbon isotopic compositions of n alkanes related to metamorphism suggest that the organic geochemistry may help to evaluate the lowest grades of prograde metamorphism

new high resolution geochemistry of lower jurassic marine sections in western north america a global positive carbon isotope excursion in the sinemurian abstract recognising variations in the carbon isotope compositions of marine organic rich sedimentary rocks can provide insight into changes in ocean chemistry throughout geological time further identification of global excursions in the carbon isotope record has proved to be valuable as a chronostratigraphic correlation tool this investigation presents new high resolution organic carbon isotope data c org 13 for marine sediments from 2 regions in north america last creek british columbia canada and five card draw nevada usa the carbon isotope profiles demonstrate that there were significant differences between the carbon reservoirs at five card draw and last creek notably in the upper part of the leslei zone the c org 13 values show a gradual positive cie 2 at last creek in the upper part of the leslei zone this corresponds to a coeval positive cie of similar duration in dorset uk upper turneri zone jenkyns and weedon 2013 suggesting that this may be a global marine carbon isotope signature and likely reflects a widespread increase in primary productivity during the early sinemurian in addition a brief negative cie is observed in the uppermost lower sinemurian at last creek this negative excursion is not recorded in the dorset section suggesting localised upwelling of 12c rich bottom waters at last creek further the signals identified at last creek are not present in coeval sections at five card draw thus highlighting a significant difference between these localities osmium os isotope data initial 187os 188os values provide a quantitative determination of the contrasting depositional environments of five card draw and last creek at least partially restricted with high levels of continental inundation and open ocean respectively this demonstrates that basinal restriction may act as a major factor that controls isotopic stratigraphic signatures thus preventing the identification of global or widespread regional excursions

chlorine isotope behavior during prograde metamorphism of sedimentary rocks abstract chlorine stable isotope compositions of two sedimentary sequences and their metamorphic equivalents were measured in order to study fractionation effects during prograde metamorphism and devolatilization protoliths n 25 were collected from a 50 m section of triassic fluvial and playa lake strata and jurassic liassic marine black shales in a well characterized quarry low greenschist to middle amphibolite facies equivalents n 80 were collected from the glarus alps urseren zone and lucomagno region bulk 37 cl values are constant within individual sedimentary layers but vary from 2 0 to 2 4 in triassic rocks and from 3 0 to 0 in the black shales dolomitic and gypsiferous samples have positive 37 cl values but marls and shales are isotopically negative bulk cl contents show only small declines during the earliest stages of metamorphism metamorphic equivalents of the triassic and liassic protoliths record the same overall ranges in 37 cl as their protoliths samples with highly correlated bulk compositions but different metamorphic grade show no statistically significant difference in 37 cl these data lead to the following conclusions 1 terrestrial and marine sedimentary rocks display large primary heterogeneities in chlorine isotope composition as a result an unambiguous sedimentary signature does not exist in the chlorine stable isotope system 2 no isotopic fractionation is discernable during metamorphic devolatilization even at low temperatures alpine style metamorphism thus has little to no effect on bulk chlorine isotopic compositions despite significant devolatilization 3 cl is largely retained in the rocks during devolatilization contrary to the normally assumed hydrophilic behavior of chlorine continuous release of mixed volatile c o h fluids likely affected cl partitioning between fluid and minerals and allowed chlorine to remain in the rocks 4 there is no evidence for fluid communication across meta sedimentary layers except within the urseren shear zone these data contribute to a relatively closed system view of metamorphic devolatilization from anchizone through mid amphibolite facies conditions

evidence for cirque glaciation in the colorado front range during the younger dryas chronozone abstract late pleistocene glacial chronologies developed for the front range mountains of colorado include two or more cirque glacier advances locally known as the satanta peak advances sediment cores were recovered from sky pond an alpine lake 3320 m located less than 100 m downvalley from a moraine that exhibits late pleistocene to early holocene relative age features and appears to correlate to the satanta peak deposits one of the cores penetrated 0 5 m of basal diamict and recovered 3 3 m of overlying sediments that are predominantly gyttja an accelerator mass spectrometry ams age of 12 040 60 yr14c b p was obtained from directly above the basal diamict and is similar to other reported ages for cirque deglaciation in the front range mountains the lower portion of the gyttja contains an interval of clastic sediments that show characteristics consistent with glacial activity in alpine catchments radiocarbon ages obtained from below and near the upper contact of this clastic interval are 11 070 50 and 9970 8014c yr b p respectively an additional ams age of 10 410 9014c yr b p was obtained from within the clastic interval in a second core the most likely source for this interval of clastic sediments is a moraine situated directly upvalley from sky pond and consequently it appears that the deposition of this moraine was coeval with the european younger dryas event 11 000 10 00014c yr b p similarities in soil development weathering features and altitude between this moraine and the type satanta peak moraines suggest that the moraines are correlative these findings are in agreement with a growing body of evidence that suggests a relatively minor advance of alpine glaciers occurred in the north american rockies during the younger dryas chron

late pleistocene and early holocene environmental history of southwestern washington state u s a a comparison of pollen records and associated plant remains from sites along a major precipitation gradient in southwestern washington enables reconstruction of the late quaternary environment during glacial and early holocene time during the evans creek stade 25 000 17 000 years bp little moisture reached lowlands east of the olympic mountains and as a result both the puget trough and the columbia basin featured a cold dry climate and parkland tundra vegetation in glacial time greatest aridity seems to have occurred between 19 000 and 17 000 years bp after 17 000 years bp the development of mesophytic subalpine parkland suggests that maritime conditions extended farther east into the puget trough and the cascade range became an important precipitation divide conditions warmer and or drier than today developed throughout western washington between 10 000 and 8000 6000 years bp vegetation on opposite sides of the cascade range became dissimilar as early as 17 000 years bp but this trend was ac

carbon isotope evidence for unusual plankton blooms and fluctuations of surface water co2 in strangelove ocean after terminal cretaceous event abstract a decrease in 13c kerogen by 3 and increase in 13c carbonate kerogen by 1 2 has been observed in sediments at the k t boundary substantiating the occurrence of a strangelove ocean wherein dissolved co2 was enriched in 12c because of mass mortality or reduced plankton production a subsequent increase in 13c kerogen by 7 and decrease in 13c carbonate kerogen by 5 4 indicate a dramatic reduction in pco2 this decrease could be the consequence of depletion of co2 in surface waters because of unusual plankton blooms these environmental changes which characterize the strangelove ocean occurred after the terminal cretaceous event during this time rapid fluctuations in dissolved co2 of ocean surface waters may have caused significant perturbations in atmospheric pco2 levels and consequently major instability of the global climate

chlorobiaceae in palaeozoic seas revealed by biological markers isotopes and geology biomarker hydrocarbons in oils and sediments have considerable potential for assessing the nature of biological processes in the past but only a few can be uniquely related to particular organisms reef hosted oils in the silurian of the michigan basin canada and the devonian of western canada have high abundances of 1 alkyl 2 3 6 trimethylbenzenes their precise structures suggest that they are diagenetic products of aromatic carotenoids of the green sulphur bacteria individual components are enriched in 13c by 7 8 relative to the saturated hydrocarbons of the same oil an isotopic anomaly of this magnitude and direction correlates with a component of photosynthetic carbon assimilation by the reductive tricarboxylic acid cycle these results together with data on palaeoenvironments provide compelling evidence for the existence in ancient restricted seas of microbial communities containing chlorobiaceae organisms with distinctive biochemistry which leave morphologically identifiable remains

deglaciation and postglacial timberline in the san juan mountains colorado abstract lake emma which no longer exists because of a mining accident was a tarn in a south facing cirque near the headwaters of the animas river in the san juan mountains of southwestern colorado during the pinedale glaciation this area was covered by a large transection glacier centered over the lake emma region three radiocarbon dates on basal organic sediment from lake emma indicate that by ca 15 000 yr b p this glacier one of the largest in the southern rocky mountains no longer existed twenty two radiocarbon dates on picea and abies krummholz fragments in the lake emma deposits indicate that from ca 9600 to 7800 yr b p from 6700 to 5600 yr b p and at 3100 yr b p the krummholz limit was at least 70 m higher than present these data in conjunction with picea pinus pollen ratios from both the lake emma site and the hurricane basin site of j t andrews p e carrara f b king and r struckenrath 1975 quaternary research 5 173 197 suggest than from ca 9600 to 3000 yr b p timberline in the san juan mountains was higher than present cooling apparently began ca 3000 yr b p as indicated by decreases in both the percentage of picea pollen and picea pinus pollen ratios at the hurricane basin site andrews et al 1975 cooling is also suggested by the lack of picea or abies fragments younger than 3000 yr b p at either the lake emma or the hurricane basin site

organic matter sources and early diagenetic alterations in arctic surface sediments lena river delta and laptev sea eastern siberia ii molecular and isotopic studies of hydrocarbons abstract the hydrocarbons extracted from three surface sediment samples from the delta of the lena river and adjacent areas of the laptev sea were examined to derive information on their source s natural vs anthropogenic terrestrial vs marine the abundance nature distribution and individual stable carbon isotope ratios of these hydrocarbons were determined it thus appeared that the laptev samples are characterized by i a negligible level of oil pollution due to anthropogenic and or natural petrogenic inputs ii an almost exclusive occurrence of long chain predominantly odd carbon numbered n alkanes and iii some differences in the level of bacterial alteration with a relatively higher degradation of the n alkanes in the seaward sediment a non terrestrial origin is proposed for these n alkanes based on the present results and on previous observations on carboxylic acid moieties and the pyrolysis products of the three surface sediments such hydrocarbons are probably not derived from the epicuticular waxes of higher plants but chiefly correspond to autochthonous products likely of algal origin these observations added to recent results on samples from other types of marine environments stress that an abundance of long chain predominantly odd n alkanes in extracts should not be systematically considered alone as evidence for a major contribution of higher plant waxes the relatively low contribution of terrestrial n alkanes in the laptev sediments should result from the combination of i a major dilution of the terrestrial input due to high primary productivity in summer promoted both by a large influx of nutrients provided by the lena river and by the specific conditions in such an arctic environment and ii the high level of degradation of the organic material transported by the lena river thus the latter probably provided a low input of lipids from terrestrial sources to the laptev samples

late quaternary vegetation history of wilcox pass jasper national park alberta five pollen zones are recognized in a radiocarbon and tephra dated core from an alpine site at an elevation of ca 2355 masl in wilcox pass jasper national park and record late quaternary vegetation history the two lower zones underlie material dated at 9600 305 yr b p gx 8785 and record early postglacial vegetation the basal zone wp1 containing an artemisia dominated assemblage represents tundra vegetation after deglaciation in zone wp2 arboreal pollen mainly diploxylon pine becomes dominant and represents a lodgepole pine forest the pollen assemblage of zone wp3 which initially contains large amounts of haploxylon pine as well as picea and abies pollen shows a transition from a forest with large amounts of whitebarkpine to vegetation resembling present day subalpine forest during this phase temperatures were probably warmer than present zone wp4 beginning after the influx of mazama tephra 6800 yr b p to the site records an expansion of the subalpine forest to higher elevations with a warmer climate in zone wp5 beginning about 2800 yr b p values of the main arboreal components fluctuate indicating cooler temperatures and less favourable environmental conditions probably associated with neoglacial ice advances the environmental trends observed from this record accord with those from other vegetation records in the canadian rockies

provenance and paleoenvironment of organic matter within the fika sediments in chad bornu basin northeastern nigeria an integrated organic geochemical and palynofacies approach abstract the upper cretaceous fika sediments in the chad bornu basin were characterised to define paleoenvironment and source of the organic matter using an integration of organic geochemical analyses and palynofacies observations the present day toc contents of the fika sediments are in the range of 0 41 2 37 wt while the hydrogen index hi values are largely below 200 mg hc g toc suggesting that the sediments generally have fair to good generative potential and contain mainly type iii and type iv kerogens this is supported by palynofacies observations whereby the kerogen is characterised by large amounts aom and phytoclasts the fika sediments have vitrinite reflectance and t max values in the range of 0 70 1 34 and 429 465 c respectively indicating early mature to late mature stage of oil window the level of organic maturation in fika sediments was further supported by the several biomarker maturity indicators biomarker distributions and palynofacies data provide evidence for a mixed aquatic algae and terrigenous organic matter input deposited in a marginally marine moderate salinity proximal setting with a strong influx of terrestrial plant under environmental conditions that were mostly suboxic compound specific isotopic analysis of n alkanes fraction were also used for the paleoenvironmental inferences the flat portion pattern of the n alkane profile between n c 21 and n c 26 in fika samples is an indication of marine environment and it shows that fika sediments consist of both terrestrial and marine organic matter deposited in fluvial deltaic to shallow marine settings

the little ice age in the canadian rockies abstract this paper reviews the evidence and history of glacier fluctuations during the little ice age lia in the canadian rockies episodes of synchronous glacier advance occurred in the 12th 13th early 18th and throughout the 19th centuries regional ice cover was probably greatest in the mid 19th century although in places the early 18th century advance was more extensive glaciers have lost over 25 of their area in the 20th century selective preservation of the glacier record furnishes an incomplete chronology of events through the 14th 17th centuries in contrast varve sequences provide continuous annually resolved records of sediments for at least the last millennium in some highly glacierized catchments such records have been used to infer glacier fluctuations evaluation of recent proxy climate reconstructions derived from tree rings provides independent evidence of climate fluctuations over the last millennium most regional glacier advances follow periods of reduced summer temperatures reconstructed from tree rings particularly ca 1190 1250 1280 1340 1690s and the 1800s reconstructed periods of higher precipitation at banff alberta since 1500 are 1515 1550 1585 1610 1660 1680 and the 1880s glacier advances in the early 1700s the late 1800s and in places the 1950 1970s reflect both increased precipitation and reduced summer temperatures negative glacier mass balances from 1976 to 1995 were caused by decreased winter balances the glacier fluctuation record does not contain a simple climate signal it is a complex response to several interacting factors that operate at different timescales evaluation of climate proxies over the last millennium indicates continuous variability at several superimposed timescales dominated by decade century patterns only the 19th century shows a long interval of sustained cold summers this suggests that simplistic concepts of climate over this period should be abandoned and replaced with more realistic records based on continuous proxy data series the use of the term lia should be restricted to describing a period of extended glacier cover rather than being used to define a period with specific climate conditions

use of lacustrine sedimentary sequences as indicators of holocene glacial history banff national park alberta canada abstract bottom sediments from three lakes in the canadian rocky mountains were examined with the aim of evaluating the usefulness of downvalley sediment studies in reconstruction of holocene glacial histories analyses of organic carbon and carbonate contents of core sediments provide information on changing sedimentation rate and changing relative importance of glacial and non glacial sediment sources sedimentary histories of the three lakes are similar suggesting that they record regional glacial climatic forcing rather than localized events and thus that they may be useful in reconstructing holocene glacial history lacustrine sediments indicate a period of high sedimentation rates and relatively large glacial sediment contribution prior to 7500 7000 yr b p with much reduced rates and decreased glacial sediment contribution between about 6000 and 4000 yr b p possibly interrupted by a brief period of increased glacial sediment output shortly after 5000 yr b p sometime after 4000 yr b p sedimentation rates and glacial sediment output began to rise again reaching approximately present levels by 2750 2650 yr b p and have not since returned to low mid holocene levels in detail over the last 3000 yr there is some indication of a slight decrease in sedimentation rate for more than 1000 yr after about 2200 yr b p sedimentation rates and glacial sediment input into all three lakes rose between about 900 and 750 yr b p and have remained very high since if the lake sediments are interpreted as a proxy record of upvalley glacial activity they allow the development of a glacial chronology which is at once generally consistent with and more complete and easily datable than the surficial glacial record

neoglacial glacier fluctuations in the canadian rockies abstract the little ice age was the most extensive neoglacial glacier advance in the canadian rockies evidence of earlier less extensive neoglacial glacier advances is based on wood recovered from several glacier forefields wood flushed out of athabasca glacier 7550 8230 yr b p three dates and dome glacier 6120 6380 yr b p two dates indicates that forests occurred upvalley of present glacier termini during the hypsithermal detrital logs from peyto 14 dates saskatchewan 3 dates robson 3 dates and yoho 1 date glaciers plus in situ slumps at peyto and robson glaciers have yielded 14 c dates between 2490 and 3300 yr b p 12 dates between 2800 and 2990 this wood is derived from sources at or upvalley from present glacier termini and represents forests overridden by glaciers between ca 3100 and 2500 yr b p treeline was higher than present immediately prior to this advance this advance which did not extend beyond the little ice age maximum position is designated the peyto advance and correlated with the tiedemann advance in western british columbia earliest little ice age advances at peyto and robson glaciers are dated ca 800 600 yr b p at positions ca 500 m upvalley from little ice age limits

the sulfur budget of the 2011 grimsvotn eruption iceland 1 sulfur concentrations have been measured in 28 melt inclusions mis in plagioclase clinopyroxene and olivine crystals extracted from tephra produced during the explosive eruption of grimsvotn in may 2011 the results are compared to sulfur concentrations in the groundmass glass in order to estimate the mass of sulfur brought to surface during the eruption satellite measurements yield order of magnitude lower sulfur 0 2 tg in the eruption plume than estimated from the difference between mi and the groundmass glass this sulfur deficit is readily explained by sulfur adhering to tephra grains but principally by sulfide globules caused by basalt sulfide melt exsolution before degassing a mass balance calculation reveals that approximately 0 8 tg of so2 is present as globules representing 50 of the total sulfur budget most of the sulfide globules likely reside at depth due to their elevated density for potential later remobilization by new magma or hydrothermal circulation

oxygen isotope records of holocene climate variability in the pacific northwest abstract oxygen isotope 18o measurements of authigenic carbonate from cleland lake southeastern british columbia paradise lake central british columbia and lime lake eastern washington provide a 9000 year holocene record of precipitation evaporation balance variations in the pacific northwest both cleland lake and paradise lake are small surficially closed basin systems with no active inflows or outflows lime lake is surficially open with a seasonally active overflow water isotope values from cleland and paradise plot along the local evaporation line indicating that precipitation evaporation balance is a strong influence on lake hydrology in contrast lime lake water isotope values plot on the local meteoric water line signifying minimal influence by evaporation to infer past hydrologic balance variations at a high temporal resolution we sampled the cleland paradise and lime lake sediment cores at 1 60 mm intervals 3 33 years per sample on average and measured the isotopic composition of fine grained

a mid holocene vegetational and climatic record from the subalpine zone of the maligne valley jasper national park alberta canada abstract pollen macrofossils and isotopic data 13 c 18 o from gastropod shells are used to reconstruct holocene vegetational and climatic changes for a lower subalpine forest site elevation 1690 m in the maligne valley jasper national park alberta subalpine forest has characterized the site since the inception of the sedimentary record in this small pond ca 8500 yr b p in contrast to the vertical timberline fluctuations recorded at nearby sites above present tree line vegetational changes at the site appear to have been mainly horizontal i e forest cover and tree density expanded or contracted laterally in response to climatic warming or cooling at maligne lake forest cover was probably at its maximum extent about 7500 yr b p when pseudotsuga and other montane elements had migrated to this elevation but did not displace the existing vegetation the modern mosaic of discontinuous subalpine forest and extensive dwarf birch dominated damp meadows and fens emerged only during the last 1300 years a warmer neoglacial episode dated ca 2600 3400 yr b p is indicated by increases in the temperature limited gastropod lymnaea palustris and by progressive enrichment in the 18 o and 13 c contents of their shells summer temperatures during this period which has been tentatively identified elsewhere in the canadian rockies may have risen by as much as 1 8 c

late quaternary environmental change in the lake o hara region yoho national park british columbia abstract palaeoenvironmental reconstructions for the upper cataract brook valley are derived from radiocarbon and tephra dated cores recovered from subalpine lake o hara and alpine opabin lake located near the continental divide in the central canadian rocky mountains late quaternary vegetational and climatic changes are based on pollen and macrofossil data and are supplemented by preliminary diatom data the postglacial colonizing vegetation prior to ca 10 100 yr b p at lake o hara and before ca 8530 yr b p at opabin lake was a shrub herb community dominated by artemisia gramineae and alnus pioneering forests at both sites were composed of pinus cf albicaulis flexilis and abies with lesser abundances of picea and pinus cf contorta timberline remained above the elevation of opabin lake at least 90 m above modern timberline elevation during the period ca 8500 yr b p to ca 3000 yr b p in response to warmer climatic conditions associated with restricted glacial activity forest compositions resembling the modern subalpine picea abies forest had developed by the end of this period the period ca 3000 yr b p to present was marked by deteriorating climatic conditions associated with renewed glacial activity in the opabin cirque and declining timberlines to below the elevation of opabin lake glacigenic sediments in the opabin record from the post bridge river ca 2350 yr b p interval are associated with reduced diatom production and a change in dominant diatom taxa to those characteristic of turbid water conditions and unstable catchment areas

holocene tree line and climate change on the queen charlotte islands canada palynological study of two subalpine ponds on the queen charlotte islands reveals changes in tree line and climate during the holocene the findings agree with previous reconstructions from nearby louise pond on the queen charlotte islands that suggest a warmer than present climate and higher than present tree lines in the early holocene ca 9600 660014c yr b p basal ages at sc1 pond and shangri la bog indicate that the basins did not hold permanent water before 720014c yr b p consistent with a warmer and drier early holocene previously inferred from louise pond pollen and plant macrofossils indicate the initial establishment of subalpine conditions by 6090 9014c yr b p similar to the 5790 13014c yr b p age for cooling inferred from louise pond conditions similar to present were established at sc1 pond by 3460 10014c yr b p confirming the previous estimate of 340014c yr b p at louise pond this 340014c yr b p vegetation shift on the queen charlotte islands corresponds with the beginning of the tiedemann glacial advance in the south coastal mountains of british columbia ca 330014c yr b p the peyto and robson glacial advances between 3300 and 280014c yr b p in the rocky mountains and climatic cooling inferred from palynological studies throughout southern british columbia northern washington and southeast alaska these findings confirm that changes in regional climate influenced changes in vegetation in coastal british columbia