Professor,dr. phil. et scient. Axel Schou 70 år 18.8.1972

Prior, D. D. &; Eve, R. M. 1975: Coastal landslide morphology at Røsnæs, Denmark. Geografisk Tidsskrift 74: 12–20. København, Juni, 1, 1975.

Based on the field studies the coastal landslide morphology and the moss movement types in the Røsnæs area are described and classified, followed by a general discussion of the factors which promote slope instability.     

Millennial‐scale stratigraphy of a tide‐dominated incised valley during the last 14 kyr: Spatial and quantitative reconstruction in the Tokyo Lowland,central Japan

Spatial and quantitative analysis of infilling processes of the tide‐dominated incised valleys beneath the Tokyo Lowland during the last 14 kyr was undertaken by using data from 18 sediment cores, 467 radiocarbon dates and 6100 borehole logs. The post‐Last Glacial Maximum valley fills consist of braided river, meandering river, estuary, spit and delta systems in ascending order. The boundary between the estuary and delta systems is regarded as the maximum flooding surface. The maximum flooding surface beneath the Tokyo Lowland is dated at 8 ka in the Arakawa Valley and 7 ka in the Nakagawa Valley. This age difference is due to the migration of the Tone River from the Arakawa Valley to the Nakagawa Valley at 5 ka, and suggests that the widely held view that the global initiation of deltas coincided with the abrupt rise of sea‐level at 9 to 8 ka is true only where there has been steady sediment supply from major rivers. The meandering river system is dominated by sheet‐like sands that were deposited during lateral migration of channels during the Younger Dryas and isolated vertical sands within muds that reflect vertical aggradation of channels before and after the Younger Dryas. The transition between these channel geometries is controlled by a threshold sea‐level rise of 4 to 7 mm yr^?1. Before migration of the Tone River at 5 ka, the tide‐dominated bay in the Nakagawa Valley was filled by upward‐fining laterally accreting muds. The muds accreted from the margin to the axis of the bay. Such lateral accretion of suspended particles derived from outside the bay has been documented in other tide‐dominated coastal environments and is probably common in other similar settings. After the migration of the Tone River, the bay was filled by upward‐coarsening deltaic sediments.     

南黄海第四纪轨道事件与非轨道事件的探讨

南黄海陆架区,作为地球轨道事件的代表,最明显的表现是海侵—海退序列。其中海侵层HⅠ、HⅣ、HⅤ、HⅥ、HⅦ分别与氧同位素1、5、7、13、23等温暖阶段相对应。主要的海侵周期受控于地球轨道要素所引起的全球变化进程。 关于非轨道事件,在南黄海发现了新仙女木事件(Younger Dryas)的证据,在~(14)C测年11100±260aB.P.至10340±110aB.P.这一时段,出现了海平面短时期下落;孢扮资料发现11100aB.P.以前的植被由栎树落叶阔叶林—草原突变为干旱草原植被,持续到11340aB.P.再度变为栎树落叶阔叶林植被,证明这段时间发生了突然变旱及降温事件。从碳氧同位素资料还发现14100±810aB.P.(~(14)C)之后的冰消期在新仙女木期之前有两期更短时间的降温,可对应于老仙女木期(Older Dryas)和最老仙女木期(Oldest Dryas)。     

A late-glacial transition from Picea glauca to Picea mariana in southern New England

Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at  14,500–14,000 cal yr BP, followed by a transition to Picea mariana between  14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO₂ levels.     

Climate change, patch choice, and intensification at Pont d'Ambon (Dordogne, France) during the Younger Dryas

This paper considers the impact of the Younger Dryas on the prehistoric inhabitants of Pont d'Ambon, a site in the Dordogne region of southwestern France, through an examination of the zooarchaeological remains from this site. An investigation of patch choice indicates that patch choice evenness declines during the Younger Dryas due to increasing local dominance of the grassland patch. Analyses of demographic composition, cutmark frequency, and marrow processing in the wild European rabbit (Oryctolagus cuniculus) assemblage suggest intensified rabbit use during this period. This study thus supports the hypothesis that changing climate had significant impacts on the prehistoric inhabitants of Pont d'Ambon. However, the traditional climate hypothesis—that changing climate negatively impacted the availability of larger fauna, forcing a switch to smaller, lower-ranked prey items—is not supported here. The inhabitants of Pont d'Ambon seem to have adapted to changing climate by efficiently exploiting the new species available to them, and possibly, during the Younger Dryas, by intensifying their use of one of these new species, the European rabbit.     

A second tephra isochron for the Younger Dryas period in northern Europe: The Abernethy Tephra

Visible and non-visible (cryptotephra) volcanic ash layers are increasingly being used to underpin the chronology and high-precision correlation of sequences dating to the last glacial–interglacial transition (LGIT). As the number of sediment records analysed for tephra content rises, and methodological developments permit the detection, extraction and chemical analysis of increasingly scantily represented glass shard concentrations, greater complexity in shard count profiles is revealed. Here we present new evidence from sites in Scotland, and review published evidence from sites elsewhere in NW Europe, that indicate complexity in the eruptive history of Katla volcano during the mid-Younger Dryas and Early Holocene. We propose evidence for a previously-overlooked tephra isochron, here named the Abernethy Tephra, which is consistently found to lie close to the Younger Dryas/Holocene transition. It has a major-element chemical composition indistinguishable from that of the Vedde Ash, which was erupted from the Katla volcano at 12,121 ± 114 cal a BP. The new data suggest that Katla may have erupted again between 11,720–11,230 cal a BP and the subsequent ash fall increases the potential to assess environmental response to Holocene warming across north and west Europe.     

Climate and vegetation history from a 14,000-year peatland record, Kenai Peninsula, Alaska

Analysis of pollen, spores, macrofossils, and lithology of an AMS ¹⁴C-dated core from a subarctic fen on the Kenai Peninsula, Alaska reveals changes in vegetation and climate beginning 14,200 cal yr BP. Betula expansion and contraction of herb tundra vegetation characterize the Younger Dryas on the Kenai, suggesting increased winter snowfall concurrent with cool, sunny summers. Remarkable Polypodiaceae (fern) abundance between 11,500 and 8500 cal yr BP implies a significant change in climate. Enhanced peat preservation and the occurrence of wet meadow species suggest high moisture from 11,500 to 10,700 cal yr BP, in contrast to drier conditions in southeastern Alaska; this pattern may indicate an intensification and repositioning of the Aleutian Low (AL). Drier conditions on the Kenai Peninsula from 10,700 to 8500 cal yr BP may signify a weaker AL, but elevated fern abundance may have been sustained by high seasonality with substantial snowfall and enhanced glacial melt. Decreased insolation-induced seasonality resulted in climatic cooling after 8500 cal yr BP, with increased humidity from 8000 to 5000 cal yr BP. A dry interval punctuated by volcanic activity occurred between 5000 and 3500 cal yr BP, followed by cool, moist climate, coincident with Neoglaciation. Tsuga mertensiana expanded after ~ 1500 cal yr BP in response to the shift to cooler conditions.     

Late Pleistocene and late Holocene lake highstands in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA

Shoreline geomorphology, shoreline stratigraphy, and radiocarbon dates of organic material incorporated in constructional beach ridges record large lakes during the late Pleistocene and late Holocene in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA. During the late Holocene, a transgression began at or after 3595 ± 35 ¹⁴C yr B.P. and continued, perhaps in pulses, through 2635 ± 40 ¹⁴C yr B.P., resulting in a lake as high as 1199 m. During the latest Pleistocene and overlapping with the earliest part of the Younger Dryas interval, a lake stood at approximately 1212 m at 10,820 ± 35 ¹⁴C yr B.P. and a geomorphically and stratigraphically distinct suite of constructional shorelines associated with this lake can be traced to 1230 m. These two lake highstands correspond to periods of elevated regional wetness in the western Basin and Range that are not clearly represented in existing northern Sierra Nevada climate proxy records.     

Younger Dryas事件与北黄海泥炭层的形成

形成于海平面变化处于停滞阶段和湿润气候条件下的泥炭层是古环境变化信息的重要载体。对北黄海4个含泥炭层的沉积剖面进行研究后发现,其均集中在渤海海峡入口处,水深变化在50～54m。泥炭层的AMS14C年龄在10650～1010014 CaBP,与发生在11000～1000014 CaBP间的末次冰消气候回冷事件——Younger Dryas(YD)事件在年代上非常吻合,表明北黄海泥炭层的形成可能与YD事件的全球效应密切相关,可作为YD事件在北黄海陆架响应的一个重要证据。泥炭层在北黄海的集中出现说明,冰后期的海平面上升过程中在YD事件期间存在停滞阶段,这一时期海面已经达到渤海海峡外侧,并可能在此徘徊了近千年。此外,泥炭层的大量出现和孢粉记录表明YD事件发生期间约为10600～1020014 CaBP,此时北黄海可能处在寒冷而湿润的环境。这一发现与全球范围内大部分YD事件的海陆记录存在明显差异,说明不同地区对YD事件的响应存在差异,不能简单地利用单一的干冷模式来分析YD事件在区域上的响应特征和过程。     

末次冰期及全新世冲绳海槽东部Z14-6孔的10Be记录

文章讨论了末次冰期及全新世以来冲绳海槽中部偏东处的沉积物岩芯Z14-6中10Be的历史记录,并与冲绳海槽北部钻孔DGKS9603的10Be记录进行对比.重力柱状岩芯Z14-6取于冲绳海槽水下739m( 27°07'N,127°27′E),全长8.96m.选取了晚更新世末次冰期和全新世的层段(2～175cm,年代跨度为0.37 ～29.3kaB.P.)中12个层位,利用加速器质谱法测定了10Be的含量.Z14-6孔10Be的平均含量为6.10×108atoms/g,最高值(8.71×108atoms/g)出现在6.3kaB.P.层位,末次冰期10Be含量总体上处于低值.与DGKS9603孔(28°08.869′N,127°16.238′E;永深1100m,岩芯长585cm)的数据比较,Z14-6孔中10Be含量普遍较低.Z14-6孔的10Be沉积通量平均值为1.04×109 atoms/cm2 · ka.最高值(1.36× 109atoms/cm2·ka)出现在6.3kaB.P.层位,最低值(6.45×10s atoms/cm2·ka)出现在9.27kaB.P.层位.Z14-6孔所处水深较浅,黑潮流在末次冰期时并未流经Z14-6孔海区,所以其10Be沉积通量只相当于10Be的大气平均生产率( 1.21 ×109 atoms/cm2 ·ka).Z14-6孔中10Be沉积通量降低可能与几个低温事件有关,Z14-6孔在约3kaB.P.和9kaB.P.存在10Be通最减弱现象,因此推测黑潮产生较大变动.Z14-6孔在全新世一些时段的10Be沉积通量峰值显著高于末次冰期时的沉积通量峰值,表明当时黑潮对该海域已发生影响.