The quaternary geomorphology of Scotland: The research contribution of J.B. Sissons

Between 1958 and his retirement in 1982, J.B. Sissons published some 80 articles and two books. The majority of these were devoted to aspects of the Quaternary geomorphology of Scotland, but many of his findings have much wider application. This paper reviews the six main areas in which Sissons made an outstanding research contribution. In approximate chronological order, these were as follows: (i) reassessment of the significance of meltwater channels and related fluvioglacial landforms (1958–1963); (ii) the deciphering of an extremely complex sequence of raised and buried shorelines and associated sea-level changes in eastern Scotland (1962–1972), together with reinterpretation of the age and origin of marine rock-cut platforms in western Scotland (1974–1982); (iii) work on the data banking of borehole records and the relevance of certain aspects of drift stratigraphy to engineering operations (1969–1971); (iv) research on the extent and chronology of the last Scottish ice sheet and associated readvances (1961–1982); (v) the reconstruction of the extent and palaeoclimatic implications of Loch Lomond Stadial glaciers (1972–1982); and (vi) investigation into aspects of landscape evolution in the Glen Roy area, including the formation of former lake shorelines, the catastrophic drainage of former ice dammed lakes and its effects, the interpretation of complex terrace sequences and the discovery of links between deglaciation, unloading, faulting, earthquakes and landslides (1978–1982). This paper also includes a complete list of Sissons' publications.     

Recent research developments on the Isle of Rum,NW Scotland

The appearance in 1997 of the British Geological Survey's memoir on Rum was followed by a period of intense research, leading to upwards of 35 papers, books and other articles. The scope of these publications, and the research progress over the last 15 years since publication of the memoir, is reviewed here. Igneous activity on Rum was short lived, possibly only ca. 500 ka, and, at about 60.5 Ma. The Rum central complex thus pre‐dates the nearby Skye central complex. The earliest, acidic and mixed acidic/basic magmatism on Rum involved both shallow intrusions and ignimbrite eruptions into a collapsing caldera bound by the Main Ring Fault, a structure which probably also exercised a structural influence on subsequent mafic and ultrabasic magmatism. Subsequent emplacement of gabbros and ultrabasic rocks caused only limited thermal metamorphism of the surrounding Torridonian sandstones, contrasting markedly with the intense alteration of uplifted masses of Lewisian gneiss within the ring fault. Detailed textural studies on the gabbroic and ultrabasic rocks allow distinction between intrusive peridotites and peridotite that formed as part of the classic layered units of Rum and, furthermore, this work and that on the chromite seams and veins in these rocks shows that movements of trapped magma and magma derived from later intrusions, may produce textures and structures hitherto regarded as primary features of cumulate rocks. Rare picritic dykes provide an indication of likely parent magma for the mafic and ultrabasic rocks, but these and other magmatic rocks on Rum have all undergone varying degrees of crustal contamination, involving both Lewisian granulite and amphibolite crust but, notably, not Moine rocks as at Ardnamurchan. Sulphides in the chromite seams and ultrabasic rocks show possible influences from assimilated Jurassic sediments. From recent apatite fission track studies it seems likely that Rum, in common with other Palaeogene centres, underwent a brief, but significantly younger (Mesozoic) heating event.     

Pollen analysis of fossil packrat middens from the Sonoran Desert

Pollen contained in 22 fossil packrat middens from the Sonoran Desert provides a complementary, but differing, view of the paleoenvironment from that derived by analysis of the associated plant macrofossils. The regional component of the pollen data is in sharp contrast to the locally oriented macrofossils. A total of 84 macrofossil taxa and 47 pollen taxa were identified; only 18 taxa were common to both. The low Index of Similarity, 0.4, indicates that the two sources of fossil information are providing different sets of paleobotanical data. When combined with plant macrofossils and good radiocarbon dating control, the pollen spectra derived from fossil middens are compatable with other paleoenvironmental sequences.     

Tectonic landforms and quaternary tectonics in Japan

The study of tectonic landforms is one of the main themes of geomophological research in Japan, characterized as a tectonically active area along the subducting oceanic plates. The recent trends in the studies of tectonic landforms which include an arrangement or distribution of major ranges and plains, vertical displacement of low-relief erosion surfaces and of marine terraces, and various kinds of deformed features due to active faulting or folding, are introduced here with special reference to the Quaternary geomorphic development. A regionality of each tectonic landforms is also summarized. Further, some fundamental concept of the Quaternary tectonics, for instance, an accumulative character of each type of deformation and sequence of rate of tectonic movement, reconstruction of former stress field as well as a relation between the Quaternary tectonic movement and seismic deformation in present and historic time are discussed on the basis of analysis of the tectonic landforms. The Quaternary tectonics of the Japanese Islands are essentially characterized by the compressional stress, originated from the subduction of oceanic plates, and regionality can be interpreted as the result of the different response of each tectonic region to island arc tectonics.     

Strain analysis and strain path modelling in the Loch Tollie gneisses,Gairloch, NW Scotland

A quantitative structural analysis is presented for the Loch Tullie gneisses of the Lewisian complex outcropping at Gairloch. The gneisses and the dykes they contain are folded into a large antiformal structure known as the Tollic Antiform. Quartz aggregates in quartzo-feldspathic gneisses have been used as finite strain markers in eleven specimens across the antiform. Two models, using rotational strain (simple shear) and irrotational strain (pure shear), are used to reconstruct the strain path. Results show that only the rotational strain model satisfies the strain data and the field evidence, and indicates a steeply northeast (75°) dipping shear plane and moderately northwest (55°) plunging shear direction, with a southwest-side-down sense of shear. A strain profile is constructed for the Tollie gneisses using the model and the attitude of gneissose layering. This shows increasing shear strain to the southwest to a maximum gamma value of approximately 8. The strain profile indicates a horizontal dextral displacement of 4.7 km and a vertical displacement of 6.8 km for the Tollie gneisses. The Tollie Antiform thus lies on the northeast margin of a large-scale shear zone, the main zone of deformation of which can be traced southwestwards some 4 km. Such a shear zone presents a major tectonic boundary within the Lewisian of northwest Scotland.     

Pollen analysis of some mid-Pleistocene interglacial lagoonal sediments from southern Delaware

Results of pollen analysis on lagoonal sediments from southern Delaware, dated at 500,000–1,000,000 yr B.P. by amino acid racemization, are presented. Three pollen zones are identified in sediments that were deposited during the final stage of an interglacial cycle. A closed forest of mixed conifer-deciduous trees dominated by Tsuga, Pinus, Fagus, Liquidambar, and Quercus is recorded in the basal zone (Zone I). The inferred climate at this time was temperate and moist. A probable lowering of sea level during the deposition of Zone II exposed large areas in the surrounding estuaries and tidal flats which were colonized by marsh and bog plant taxa. Zone III is characterized by Pinus, Quercus, and Picea pollen. A scrub oak-pine association may have been favored on the coarse sandy soils of the Delmarva Peninsula at this time because of a drop in the local water table. The inferred climate during this interval was colder and probably drier than in Zone I.     

Access rights in Scotland and geological fieldwork

Perhaps you may have always assumed that there was no law of trespass in Scotland, as is sometimes said. The legal profession assert that this is not the case, but there remains a strong popular belief in the existence of some kind of common law right of access to land in Scotland, especially in exercising traditional freedoms of access to the hills. This article sets out the position in Scotland since the enactment of new legislation in 2005 for access to land, relevant to geological fieldwork.     

Lateglacial and postglacial shorelines in western Scotland

Some recent studies of raised shorelines in western Scotland, which are gaining international acceptance, are assessed in the light of subsequent criticisms. Fieldwork has revealed that there are differences in altitude measurements, interpretations, and conclusions between these studies and the present one in Lorn and eastern Mull. Two short lateglacial shorelines are tentatively suggested, but there is a general abesence of clear, widespread shorelines of this age. The Main Postglacial Shoreline has a gradient of 0.05 m/km, considerably less than found in previous studies in both western and south-cast Scotland. Subsequently, as relative sea level fell to its present level, two fairly clear shorelines with low gradients were formed together with traces of intermediate ones. The influences of the. Falls of Lora rock bar and of exposure on showline altitude are also examined.     

Pre-Cambrian landscapes in Northwest Scotland

An old land surface carved out of basement gneisses is extensively preserved beneath Torridon Group sandstones (deposited ca. 750 m.y. B.P.). Contoured reconstructions show that relief declines westward from 2000 ft (600 m) to almost nothing over a distance of 25 km. North-northeast trending zones of similar dissection can be traced for 160 km. Weathering up to 2 m deep is locally present in the flat zone. The essentially unweathered land surface forming the mountains probably originated by dissection of a palaeoplain. The flat zone is probably, but not certainly, a relatively young pediplain. All land forms are thought to have developed before, not during, deposition of the overlying sediments.     

Late-glacial marine erosion in Scotland

A pronouaced raised reck platform and cliff that occur on part of the west coast of Scotland ale generally considered to have been formed before the last glaciation. It is argued in this paper that they were formed in late-glacial times, mainly during the Loch Lomond (Upper Dryas) Readvance. The features arc correlated with an extensive buried and/or submerged marine erosion feature in South-East Scotland. It is also suggested that the Scottish features correlate with the 'Main line' (P₁₂ shoreline) of northern Norway.     

Late quaternary uplift in eastern Indonesia

Radiocarbon dates of fifteen samples representing raised shorelines on various islands of the tectonically mobile region of eastern Indonesia suggest rates of tectonic uplift ranging up to 12.5 mm/year. Low rates of 0.35–1.2 mm/year are from Biak Island and are averages for the last 31,000–36,000 years. The low rates may be explained to indicate subsidence alternating with uplift, both of which occurring under influence of the large Irian fault zone that passes to the immediate south of the island. Very young elevated strandlines (250 years BP) indicate rates of uplift between 8 and 12.5 mm/year which seem to demonstrate the episodic character of vertical diastrophic movements. Intermediate rates of uplift are in the order of 5 mm/year and may represent averages for eastern Indonesia.     

Advance in Pollen Source Area

The conception of pollen source area has attracted broadly attention since it was proposed in the 1960s. In this paper,it can be subdivided into Normal Source Area of Pollen (NSAP) and Relevant Source Area of Pollen (RSAP) based on reviewing former studies and our recent work of vegetation survey and pollen analysis in the Northern China. The NSAP means a source area of pollen input a sedimentary basin,indicating a distance area beyond where the pollen contents of major pollen types do not show evident increase with increased distance. The RSAP means a source area of pollen assemblages in a basin has the closest relationship with surrounding plants,indicating a distance area beyond where the relationship between pollen assemblage and surrounding vegetation do not show obvious increase with increased distance. The changes of sedimentary basins radii and pollen grain size influence the NSAP and RSAP evidently. Wind speed also changes the NSAP, but does not significantly affect RSAP. The pollen of a sedimentary basin is composed of local pollen,regional pollen and extra regional pollen,which usually account for 30%~45%,25%~60% and 10%~30%,respectively. Local pollen which refers to the pollen coming within the RSAP range,is a reflection of the surrounding vegetation,and has important implications to the reconstruction and succession of local vegetation. Regional pollen which refers to the pollen coming from within the range of NSAP and excluding the range of local pollen,is the important carrier of studies for vegetation restoration and climate change. The pollen that comes outside the range of NSAP is called Extra regional pollen,which is mainly from greater distance by upper air flow,and has no indicator significance to the regional vegetation.     

Ancient dna from pleistocene fossils: Preservation, recovery, and utility of ancient genetic information for quaternary research

Until recently, recovery and analysis of genetic information encoded in ancient DNA sequences from Pleistocene fossils were impossible. Recent advances in molecular biology offered technical tools to obtain ancient DNA sequences from well-preserved Quaternary fossils and opened the possibilities to directly study genetic changes in fossil species to address various biological and paleontological questions. Ancient DNA studies involving Pleistocene fossil material and ancient DNA degradation and preservation in Quaternary deposits are reviewed. The molecular technology applied to isolate, amplify, and sequence ancient DNA is also presented. Authentication of ancient DNA sequences and technical problems associated with modern and ancient DNA contamination are discussed. As illustrated in recent studies on ancient DNA from proboscideans, it is apparent that fossil DNA sequence data can shed light on many aspects of Quaternary research such as systematics and phylogeny. conservation biology, evolutionary theory, molecular taphonomy, and forensic sciences. Improvement of molecular techniques and a better understanding of DNA degradation during fossilization are likely to build on current strengths and to overcome existing problems, making fossil DNA data a unique source of information for Quaternary scientists.     

Geochemistry characterizes provenance in southern Scotland

An understanding of the Ordovician—Silurian development of the Southern Uplands accretionary thrust belt is an essential precursor to reconstructing the British sector of the Appalachian—Caledonian orogen. The British Geological Survey (BGS) has now extended its regional geochemical database to cover this controversial area. Integration of the new geochemical data with results from the current geological resurvey allows fresh insights into the provenance patterns of the Southern Uplands' greywacke sequences and constrains the extrapolation of geological boundaries.     

Windows下的土坡稳定性分析研究

利用CAD二次开发技术,对边坡进行稳定性分析,采用的计算方法为瑞典圆弧滑面条分法。通过编程计算,能得到该边坡的任意滑面的安全系数和最危险滑面位置及其安全系数,该程序有良好的Windows风格的用户界面,直观、形象的计算过程,简单明了的输出结果,是进行边坡稳定分析的新选择     

Toward a comprehensive upper quaternary tephra and ignimbrite stratigraphy in New Zealand using electron microprobe analysis of glass shards

New Zealand Quaternary marine and terrestrial sequences contain numerous tephras, or volcanic-ash horizons, that are the distal correlatives of voluminous welded ignimbrite sheets, erupted from central North Island. Electron microprobe analyses of glass shards from the distal tephras demonstrate their homogeneity and are shown to identify each tephra examined. By matching tephras from stratigraphically controlled sequences, the first comprehensive tephra stratigraphy spanning from 50,000 to 700,000 yr ago and covering the New Zealand region is advanced.Analyses on glass shards from the unwelded base of ignimbrite sheets are comparable to the distal tephra analyses and allow correlation between ignimbrites and to the distal tephras. The better exposed tephra record constrains the number of separate eruptive events and the stratigraphy of the ignimbrites, both of which were previously confused by lack of outcrop.Samples from pumiceous marine sediments were found to contain two or more chemically distinct populations of glass. The pumice is in cross-bedded sands or sand lenses within conglomerate, attesting to a shallow high-energy environment where reworking could occur. However, each glass population could be matched to older, known tephras.