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The volcanic history of Ruapehu during the past 2 millennia based on the record of Tufa Trig tephras (1997)

Donoghue, S. L. ; Neall, V. E. ; Palmer, A. S. ; [et al.]

Springer

Bulletin of volcanology 59 (1997), S. 136-146

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ISSN: 1432-0819

Keywords: Key words Ruapehu ; Tufa Trig Formation ; Holocene ; Tephra ; Hydrovolcanic ; Pyroclast morphology ; Crater Lake ; Marker beds

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract Tufa Trig Formation comprises a sequence of at least 19 andesitic tephras erupted from Mt. Ruapehu (Tongariro Volcanic Centre, New Zealand). Tephras of Tufa Trig Formation are the most recent eruptives from Ruapehu, dated between ca. 1850 years B.P. and the present. Members of the Formation show restricted dispersals, principally to the east of Mt. Ruapehu. Volumes calculated for the most widespread members are all less than 0.1 km3. Compared with other Mt. Ruapehu eruptives, Tufa Trig Formation tephras represent small eruptions that have contributed little tephra to the ring plain. They do, however, show a greater frequency of eruption with one event occurring on average every 100 years. Tufa Trig Formation members Tf3–Tf18 are black to dark grey, vitric, coarse-ash and lapilli-grade tephras which mantle the relief. They contain juvenile vitric particles which exhibit varying degrees of vesicularity, together with free crystals of pyroxene and feldspar, and few lithic fragments. Several morphological types of vitric pyroclasts are recognised in these tephras, the dominant type being of equant blocky morphology with fracture-bound surfaces (type-1 morphology). Field characteristics, tephra distributions, and the morphologies and textures of constituent pyroclasts suggest that these members (Tf3–Tf18) are the products of small-volume hydrovolcanic eruptions resulting from the interaction of fresh magma and meteoric water. We propose that a source of this water was an ancestral crater lake which formed within the late Holocene ca. 3000 years B.P. The morphological, compositional, and chemical (major-element) characteristics of three Tufa Trig Formation Tephras are compared with those of two new tephras erupted from Ruapehu Volcano during the October 1995 eruptions which comprise part of a newly defined member (Tf19) of Tufa Trig Formation. The comparisons support our interpretation that the majority of the Tufa Trig Formation tephras are primarily the products of hydrovolcanic eruptions. Other members of the Formation (Tf1 and Tf2) are coarse-grained scoriaceous tephras and are interpreted to be the products of strombolian events.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004450050181

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2

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Mid-Holocene stable isotope record of corals from the northern Red Sea (2000)

Moustafa, Y. A. ; Pätzold, J. ; Loya, Y. ; [et al.]

Springer

International journal of earth sciences 88 (2000), S. 742-751

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ISSN: 1437-3262

Keywords: Key words African monsoon ; Corals ; Holocene ; Northern Red Sea ; Stable isotopes

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract We present a study based on X-ray chronologies and the stable isotopic composition of fossil Porites spp. corals from the northern Gulf of Aqaba (Red Sea) covering the mid-Holocene period from 5750 to 4450 14C years BP (before present). The stable oxygen and carbon isotopic compositions of five specimens reveal regular annual periodicities. Compared with modern Porites spp. from the same environment, the average seasonal δ 18O amplitude of the fossil corals is higher (by ca. 0.35–0.60‰), whereas annual growth rates are lower (by ca. 3.5 to 2 mm/year). This suggests stronger seasonality of sea surface temperatures and increased variability of the oxygen isotopic composition of the sea water due to changes in the precipitation and evaporation regime during the mid-Holocene. Most likely, summer monsoon rains reached the northern end of the Red Sea at that time. Average annual coral growth rates are diminished probably due to an increased input and resuspension of terrestrial debris to the shallow marine environment during more humid conditions. Our results corroborate published reports of paleodata and model simulations suggesting a northward migration of the African monsoon giving rise to increased seasonalities during the mid-Holocene over northeastern Africa and Arabia.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s005310050302

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3

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Multi-component carbon isotope evidence of early Holocene environmental change and carbon-flow pathways from a hard-water lake in northern Sweden (1997)

Hammarlund, Dan ; Aravena, Ramon ; Barnekow, Lena ; [et al.]

Springer

Journal of paleolimnology 18 (1997), S. 219-233

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ISSN: 1573-0417

Keywords: northern Sweden ; stable carbon isotopes ; carbon isotope fractionation ; limnic sediments ; Holocene ; lake

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract A 9000-year carbonate-rich sediment sequence from a small hard-water lake in northernmost Sweden was studied by means of multi-component stable carbon isotope analysis. Radiocarbon dating of different sediment fractions provides chronologic control and reveals a rather constant hard-water effect through time, suggesting that the lake has remained hydrologically open throughout the Holocene. Successive depletion of 13C in fine-grained calcite and carbonate shells during the early Holocene correlate with a change in catchment vegetation from pioneer herb communities to boreal forest. The vegetational change and associated soil development likely gave rise to an increased supply of 13C-depleted carbon dioxide in groundwater recharging the lake. This process is therefore believed to be the main cause of decreasing values of δ13C in dissolved inorganic carbon of the lake and thereby in limnic carbonates. Strongly 13C-depleted sedimentary organic matter may be related to enhanced kinetic fractionation during photosynthetic assimilation by means of proton pumping in Characean algae. This interpretation is supported by a substantial offset between δ13C of DIC as recorded by mollusc shells and δ13C of fine-grained calcite.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007953614927

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4

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Holocene history of lacustrine and marsh sediments in a dune-blocked drainage, Southwestern Nebraska Sand Hills, U.S.A. (1997)

Mason, Jon P. ; Swinehart, James B. ; Loope, David B.

Springer

Journal of paleolimnology 17 (1997), S. 67-83

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ISSN: 1573-0417

Keywords: paleohydrology ; paleoclimate ; sand dunes ; eolian ; Holocene ; Nebraska

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract As many as 2500 interdune lakes lie within the Nebraska Sand Hills, a 50 000 km stabilized sand sea. The few published data on cores from these lakes indicate they are typically underlain by less than two m of Holocene lacustrine sediments. However, three lakes in the southwestern Sand Hills, Swan, Blue, and Crescent, contain anomalously thick marsh (peat) and lacustrine (gyttja) sediments. Swan Lake basin contains as much as 8 m of peat, which was deposited between about 9000 and 3300 years ago. This peat is conformably overlain by as much as 10.5 m of gyttja. The sediment record in Blue lake, which is 3 km downgradient from Swan lake, dates back to only about 6000 years ago. Less than two m of peat, which was deposited from 6000 to 5000 years ago, is overlain by 12 m of gyttja deposited in the last 4300 years. Crescent Lake basin, one km downgradient from Blue Lake, has a similar sediment history except for a lack of known peat deposits. Recently, a 8-km long segment of a paleovalley was documented running beneath the three lakes and connecting to the head of Blue Creek Valley. Blockage of this paleovalley by dune sand during two arid intervals, one shortly before 10 500 yr BP and one in the mid-Holocene, has resulted in a 25 m rise in the regional water table. This made possible the deposition of organic-rich sediment in all three lakes. Although these lakes, especially Swan, would seem ideal places to look for a nearly complete record of Holocene climatic fluctuations, the paleoclimatic record is confounded by the effect dune dams have on the water table. In Swan Lake, the abrupt conversion from marsh to lacustrine deposition 3300 years ago does not simply record the change to a wetter regional climate; it reflects the complex local hydrologic changes surrounding the emplacement and sealing of dune dams, as well as regional climate.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007917110965

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5

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The plant-macrofossil record of past lake-level changes (1997)

Hannon, Gina E. ; Gaillard, Marie-José

Springer

Journal of paleolimnology 18 (1997), S. 15-28

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ISSN: 1573-0417

Keywords: plant-macrofossils ; palaeoecology ; water-chemistry ; trophic-status ; water-depth ; lake-level changes ; Holocene

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract Plant-macrofossil analysis is one of the most useful biostratigraphical methods for the reconstruction of former lake-level changes. The distribution of submerged, floating-leaved and emergent lake-shore vegetation is mainly dependant on water depth, but water chemistry and nutrient status must also be taken into account when interpreting water-level changes. Lake-level studies should be based on the investigation of several littoral cores along a transect perpendicular to the lake-shore. Multiple cores are essential for separating genuine lake-level changes from other processes influencing the plant-macrofossil record. Physical analyses of sediment stratigraphy provide important additional information to the plant-fossil record, because natural infilling processes and erosion from the catchment must be distinguished from climatic events causing a change in the water level. Here we review several important concepts, including suitability of lakes for lake-level study, the degree of detail required in the analysis, and macrofossil records of lake-level changes, and illustrate those concepts by examples from southern Sweden and Minnesota. We discuss how to reconcile alternative hypotheses for the stratigraphic changes seen in the macrofossil assemblages.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007958511729

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6

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The relationship between glacial activity and sediment production: evidence from a 4450-year varve record of neoglacial sedimentation in Hector Lake, Alberta, Canada (1997)

Leonard, Eric M.

Springer

Journal of paleolimnology 17 (1997), S. 319-330

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ISSN: 1573-0417

Keywords: varves ; glacial history ; Canadian Rocky Mountains ; Holocene ; Neoglaciation ; glaciolacustrine sediments

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract A 4450-year sequence of varves, spanning the entire Neoglacialinterval, has been recovered from Hector Lake, Alberta. The varve record is compared to records of regional glacial history toevaluate therelationship between alpine glacial activity and sediment production. Glacial controls on sediment production vary with the timescale considered. Long-term variations in sedimentation rate, of centuries to millennial duration, reflect changes in ice extent of the same timescale. Superimposed on these long-term changes is decadal-scale variability that is complexly related to upvalley ice extent. Over the short term, high sedimentation rates may be associated with glacier maximum stands, or with periods of glacier advance or recession. Overthe last millennium at least, highest sedimentation rates appear to have been associated with transitional periods, preceding or post-dating maximum ice stands, rather than with times of maximum ice extent.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1007948327654

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7

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Holocene environmental history of thermokarst lakes on Richards Island, Northwest Territories, Canada: Theocamoebians as paleolimnological indicators (2000)

Dallimore, Audrey ; Schröder-Adams, Claudia J. ; Dallimore, Scott R.

Springer

Journal of paleolimnology 23 (2000), S. 261-283

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ISSN: 1573-0417

Keywords: thecamoebians ; paleolimnology ; Holocene ; thermokarst lakes ; Arctic

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract Richards Island, Northwest Territories, Canada, is characterized by thermokarst lakes which record Holocene limnological change. This study is the first report of thecamoebian assemblages and continuous annual lake water temperatures from these Arctic lakes. Ecological environments on Richards Island are influenced by a climatic gradient resulting from the contrasting influences of the cold Beaufort Sea to the north and the warm waters of the Mackenzie Delta to the east and west. This climatic gradient in turn influences modern thecamoebian assemblages, and is an indication of the complexity involved in interpreting past conditions from core material in this area. Population abundance and species diversity of thecamoebian assemblages on Richards Island are not significantly different from those reported from temperate and semi-tropical latitudes. However, certain assemblage characteristics, such as large and coarse agglutinated tests, dominance of assemblages by one or two species and low morphological variation are interpreted to be diagnostic of Arctic conditions. Thecamoebian assemblages in core material from the area indicate that the local paleolimnological conditions may have changed within the last 3 ka, and this is unrecorded in previously reported pollen data. Paleoenvironmental interpretations in a permafrost landscape have to take into account morphological instability of thermokarst lakes, which can be the cause of paleolimnological and consequently faunal change. In this area ecosystem development is clearly related to geomorphology and local climatic effects and is not exclusively controlled by regional climate change.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008184522637

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8

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Holocene regional and local vegetation history and lake-level changes in the Torneträsk area, northern Sweden (2000)

Barnekow, Lena

Springer

Journal of paleolimnology 23 (2000), S. 399-420

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ISSN: 1573-0417

Keywords: Holocene ; lake-level changes ; climate changes ; vegetation history ; tree-line ; northern Sweden

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract A combination of pollen and macrofossil analyses from six lakes at altitudes between 370 and 999 m above sea level (a.s.l.) in the Torneträsk area reflect the Holocene vegetation history. The main field study area has been the Abisko valley at altitudes around 400 m a.s.l. The largest lake, Vuolep Njakajaure has annually laminated (varved) sediments. The chronology and sedimentation rates in the pollen-influx calculations are based on varve yrs in this lake and on radiocarbon dated terrestrial plant macrofossils in the other lakes. A strong increase of mountain birch (Betula pubescens ssp. tortuosa) during the early Holocene with a tree-line c. 300 m above the present, indicates that the summer temperature was c. 1.5 °C higher than today, assuming that the land uplift has been 100 m since then. Scattered stands of pine (Pinus sylvestris) may have been growing in the area immediately after the deglaciation but a forest consisting of pine and mountain birch expanded first at low elevations and reached the eastern parts of the Torneträsk area at c. 8300 cal BP and the western parts at c. 7600 cal BP. The highest pine-birch forest limit was not reached until 6300 cal BP (110 m above present pine limit). Warm and dry conditions during the pine forest maximum led to lowering of the water level documented in Lake Badsjön in the Abisko valley about 1-1.5 m lower than today. Pine and mountain birch were growing at the maximum altitude until c. 4500 cal BP. Assuming that land uplift has been in the range of 20-40 m since the mid-Holocene, this implies that the temperature was then c. 1.5-2 °C higher than today. Rising lake-levels and lowering limits of pine and mountain birch since c. 4500 cal BP indicate a more humid and cool climate during the late Holocene.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008171418429

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9

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Holocene lake sediment records of Arctic hydrology (2000)

MacDonald, Glen ; Felzer, Benjamin ; Finney, Bruce ; [et al.]

Springer

Journal of paleolimnology 24 (2000), S. 1-13

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ISSN: 1573-0417

Keywords: Arctic ; Holocene ; paleohydrology ; paleolimnology ; climate change

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract Although paleoclimatic research in the Arctic has most often focused on variations in temperature, the Arctic has also experienced changes in hydrologic balance. Changes in Arctic precipitation and evaporation rates affects soils, permafrost, lakes, wetlands, rivers, ice and vegetation. Changes in Arctic soils, permafrost, runoff, and vegetation can influence global climate by changing atmospheric methane and carbon dioxide concentrations, thermohaline circulation, and high latitude albedo. Documenting past variations in Arctic hydrological conditions is important for understanding Arctic climate and the potential response and role of the Arctic in regards to future climate change. Methods for reconstructing past changes in Arctic hydrology from the stratigraphic, isotopic, geochemical and fossil records of lake sediments are being developed, refined and applied in a number of regions. These records suggest that hydrological variations in the Arctic have been regionally asynchronous, reflecting the impacts of different forcing factors including orbitally controlled insolation changes, changes in geography related to coastal emergence, ocean currents, sea ice extent, and atmospheric circulation. Despite considerable progress, much work remains to be done on the development of paleohydrological proxies and their application to the Arctic.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008100714795

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10

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GCM-simulated hydrology in the Arctic duringn the past 21,000 years (2000)

Felzer, Benjamin ; Thompson, Starley ; Pollard, David ; [et al.]

Springer

Journal of paleolimnology 24 (2000), S. 15-28

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ISSN: 1573-0417

Keywords: Last Glacial Maximum ; Arctic ; paleoclimatology ; Holocene ; climate modeling ; hydrology

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences

Notes: Abstract The Paleoclimates from Arctic Lakes and Estuaries (PALE) project has chosen to conduct high resolution data-model comparisons for the Arctic region at 21 and 10 (calendar) ka BP. The model simulations for 21, 10, and 0 ka BP were conducted with the GENESIS 2.0 GCM. The 10 ka BP simulation was coupled to the EVE vegetation model. The primary boundary conditions differing from present at 21 ka BP were the northern hemisphere ice sheets and lower CO2, and at 10 ka BP were the orbital insolation and smaller northern hemisphere ice sheets. The purpose of this article is to discuss the hydrological consequences of these simulations. At the Last Glacial Maximum (21 ka BP) the large ice sheets over North America and Eurasia and the lower CO2 levels produced a colder climate than present, with less precipitation throughout the Arctic, except where circulation was altered by the ice sheets. At 10 ka BP greater summer insolation resulted in a warmer and wetter Beringia, but conditions remained cold and dry in the north Atlantic sector, in the vicinity of the remnant ice sheets. Less winter insolation at 10 ka BP resulted in colder and drier conditions throughout the Arctic. Precipitation - evaporation generally correlated with precipitation except where changes in the surface type (ice sheets, vegetation at 10 ka BP, or sea level at 21 ka BP) caused large changes in the evaporation rate. The primary hydrological differences (from present) at 21 and 10 ka BP correlated with the temperature differences, which were a direct result of the large-scale boundary condition changes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008161631633

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