This review focuses on the development of the 'Little Ice Age' as a glaciological and climatic concept, and evaluates its current usefulness in the light of new data on the glacier and climatic ...variations of the last millennium and of the Holocene. 'Little Ice Age' glacierization occurred over about 650 years and can be defined most precisely in the European Alps (c. AD 1300-1950) when extended glaciers were larger than before or since. 'Little Ice Age' climate is defined as a shorter time interval of about 330 years (c. AD 1570-1900) when Northern Hemisphere summer temperatures (land areas north of 20°N) fell significantly below the AD 1961-1990 mean. This climatic definition overlaps the times when the Alpine glaciers attained their latest two highstands (AD 1650 and 1850). It is emphasized, however, that 'Little Ice Age' glacierization was highly dependent on winter precipitation and that 'Little Ice Age' climate was not simply a matter of summer temperatures. Both the glacier-centred and the climate-centred concepts necessarily encompass considerable spatial and temporal variability, which are investigated using maps of mean summer temperature variations over the Northern Hemisphere at 30-year intervals from AD 1571 to 1900. 'Little Ice Age'-type events occurred earlier in the Holocene as exemplified by at least seven glacier expansion episodes that have been identified in southern Norway. Such events provide a broader context and renewed relevance for the 'Little Ice Age', which may be viewed as a 'modern analogue' for the earlier events; and the likelihood that similar events will occur in the future has implications for climatic change in the twenty-first century. It is concluded that the concept of a 'Little Ice Age' will remain useful only by (1) continuing to incorporate the temporal and spatial complexities of glacier and climatic variations as they become better known, and (2) by reflecting improved understanding of the Earth-atmosphere-ocean system and its forcing factors through the interaction of palaeoclimatic reconstruction with climate modelling.
U radu je prikazano istraživanje u podmorju sjevernog Jadrana i priobalja južne Dalmacije unutar naslaga pliocena, pleistocena i holocena. Njime su opisane postojeće litostratigrafske jedinice u ...taložinama rijeke Po u Hrvatskoj i određene takve jedinice u prostoru taloženja rijeke Neretve. Oba taložna prostora bila su pod utjecajem promjena razina mora, posebice tijekom kvartara, što se znatno odrazilo u smanjivanju dubine mora i povećanju površine kopna tijekom oledaba, posebice u sjevernom Jadranu. U hrvatskom dijelu Padske depresije navedene su dvije formacije – Istra (pliocen) i Ivana (pleistocen, holocen). U formaciji Ivana opisana su tri člana, poimence Anamarija, Katarina i Izabela. Dalje prema jugu, u priobalju južne Dalmacije, imenovana je nova formacija Neretvanski kanal (za taložine pliocena, pleistocena i holocena). Ona je zatim podijeljena u pijeske Neretva (koji mogu biti ekvivalent i cijele formacije) te član Malostonski zaljev (kvartarne starosti). Isključivo pliocenski tipski litotip nije opisan.
During the last stages of the Weichselian glaciation (ca. 9,000-15,000 years B.P.), reduced ice loads and glacially affected stress fields resulted in active faulting in Fennoscandia with fault ...scarps up to 160 km long and up to 30 m high. These postglacial (PG) faults are usually SE dipping, SW-NE oriented thrusts, and represent reactivated, pre-existing crustal discontinuities. Postglacial faulting indicates that the glacio-isostatic compensation is not only a gradual viscoelastic phenomenon, but also includes unexpected violent earthquakes, suggestively larger than other known earthquakes in stable continental regions. We explore here possibilities and benefits for investigating, via scientific drilling, the characteristics of postglacial faults in northern Fennoscandia, including their structure and rock properties, present and past seismic activity and state of stress, as well as hydrogeology and associated deep biosphere. The research is anticipated to advance science in neotectonics, hydrogeology and deep biosphere studies, and provide important information for nuclear waste disposal, petroleum exploration on the Norwegian continental shelf and studies of mineral resources in PG fault areas.
Ljubljansko barje je izjemna pokrajina. Vlažne hidrološke razmere omogočajo dobro ohranjenost arheoloških najdišč in paleoekološkega zapisa. Vendar pa je Ljubljansko barje za paleoekološke ...raziskave hkrati tudi izjemno zahtevna regija. Razvoj holocenske pokrajine in vegetacije je bil namreč zelo dinamičen, posledica tega pa spremenljive tafonomske razmere in, zaradi kompleksne hidrološke mreže in človekovega vpliva (rezanje šote), pogosto fragmentiran paleoekološki zapis. Kljub številnim raziskavam v zadnjih desetletjih, podrobne raziskave nekdanje hidrologije niso bile opravljene, čeprav je za arheologijo in paleoekologijo to očitno pomembna tema, saj se je v zadnjih letih razvila živahna diskusija o tem, ali je območje Ljubljanskega barja nekoč pokrivalo jezero ali rečna poplavna ravnica. S tem prispevkom se želim vključiti v razpravo in predstaviti svoj pogled na hidrološko problematiko. Moje mnenje je, da so bile paleoekološke razmere na področju Ljubljanskega barja preveč kompleksne, da bi jih lahko zreducirali samo na polemiko “jezero ali poplavna ravnica?”, moj glavni očitek raziskovalcem, ki so dozdaj razpravljali o tej temi pa, da je njihova interpretacija hidrološkega dogajanja preveč ambiciozna, ker temelji na rezultatih premalo ob-sežnih paleoekoloških raziskav, pa najsi gre za rezultate njihovih lastnih raziskav ali interpretiranje rezultatov drugih raziskovalcev.
Kubischta, F., Knudsen, K.L., Ojala, A.E.K. and Salonen, V.-P., 2011. Holocene benthic foraminiferal record from a high-arctic fjord, Nordaustlandet, Svalbard. Geografiska Annaler: Series A, Physical ...Geography, 93, 227-242. DOI: 10.1111/j.1468-0459.2011.00434.x
This study presents the results of benthic foraminiferal analyses of a marine core record from about 100 m water depth in the fjord environment of Isvika bay, Nordaustlandet, Svalbard. During the Last Glacial Maximum, the bay was glaciated by the north-western sector of the Svalbard-Barents Sea Ice Sheet. The foraminiferal assemblages reflect glaciomarine conditions during deglaciation and early Holocene (about 11-250-9640 cal. yr bp) followed by glacier-distal environment in an open fjord with relatively high influence of Atlantic waters from the open ocean (9640-7430-cal. yr bp). A subsequent foraminiferal indication of a glacial advance was followed by deposition of a diamicton unit within a short time period at 5800-5700 cal. yr bp. The mid- and late Holocene were characterized by assemblages indicating restricted open-ocean connection and gradually more severe conditions, which are considered to be caused partly by a gradual cooling and freshening of the Atlantic water inflow to the shelf area and partly by a continuous isostatic uplift of the area. The foraminiferal record shows that the environmental changes in Murchisonfjorden are not just an effect of changes in solar insolation but are also influenced by local processes, as well as changes in the Atlantic water inflow to the northern Svalbard shelf and to the fjord via Hinlopenstretet.
The retreat record of the tabre lacier into the orra torfjället mountains, after separation from the massive ärnaån lacier at some undetermined time in the tlantic hron, is documented by recessional ...moraines in the foreland. While poorly constrained by radiometric dating, the age of the middle group of moraines averages out to less than 4000 cal
14
yr , the older moraine group probably of ate tlantic age, with the youngest deposits of ittle ce ge. Soils/paleosols range from ntisols (youngest) and nceptisols (middle group) to mature podosols (outer group), existing either as single-story profiles or within pedostratigraphic columns, buried pedons either surfaced with weathered glacial or mass wasted deposits. Some profiles exhibit convoluted properties which could place them in the ryosolic order. The physico-mineral-chemical properties of soils/paleosols in recessional deposits across this sequence provide weathering indices over the mid to ate olocene in the wedish sub-rctic climate. It is likely the middle group of deposits represents stillstand of the retreating glacier offset by climatic deterioration with the onset of Early eoglacial climate which altered the glacial mass balance, at least until termination of the . Correlation to other alpine areas in the middle and tropical latitudes with similar records is attempted and discussed. While the tabre lacier disappeared after the , the nearby ärna lacier remains extant on the land surface, a presumed result of slight elevation differences between the two cirques which affects storm tracks and resultant variations in glacial mass balances.
In Alaska, lichenometry continues to be an important technique for dating late Holocene moraines. Research completed during the 1970s through the early 1990s developed lichen dating curves for five ...regions in the Arctic and subarctic mountain ranges beyond altitudinal and latitudinal treelines. Although these dating curves are still in use across Alaska, little progress has been made in the past decade in updating or extending them or in developing new curves. Comparison of results from recent moraine-dating studies based on these five lichen dating curves with tree-ring based glacier histories from southern Alaska shows generally good agreement, albeit with greater scatter in the lichen-based ages. Cosmogenic surface-exposure dating of Holocene moraines has the potential to test some of the assumptions of the lichenometric technique and to facilitate the development of a new set of improved lichen dating curves for Alaska.
A chain of east-west elongated lakes fringes the eastern flank of the Andes Mountains between 39 and 52°S in southern Chile and Argentina. These deep lakes fill valleys left by the retreat of outlet ...glaciers of the Patagonian Icefield about 16000 years ago. Two of the lakes, Lago General Carrera/Buenos Aires and Lago Cochrane, represent the shrunken remnants of a much larger lake (called here the predecessor lake) that developed in a moat alongside the icefield.
A series of seven stepped lacustrine braid deltas on the southeastern shore of Lago General Carrera/Buenos Aires mark the progressive, punctuated drainage of the predecessor lake. The deltas were formed by the build-out of fans of sand and gravel into the lake. They have the form of Gilbert deltas, with virtually flat subaerial topset beds and steeply inclined subaqueous foreset beds. The exposed delta fronts are marked by a series of small terraces produced by wave erosion during falling lake levels. On either side of the fans are embayments with beaches formed by deposition in the lee of the pro-grading fans. These embayments are filled with ridges of well-sorted gravel deposited by wave-driven long-shore drift.
About 13 000 years ago the regional drainage underwent a remarkable change. Rivers flowing eastwards into the Atlantic reversed their direction to flow westwards through the Andes Mountains and into the Pacific Ocean. The watershed moved some 200 km to the east. The cause of this change, and the falling lake levels, was melting of the Patagonian Icefield. As the ice retreated the icefield split into north and south components. This broke the ice dam that impounded the western end of the predecessor lake. The stepped, progressive fall of the lake level suggests that as the ice melted a series of lower overflow sills of hard rock were exposed. Each of the major episodes of sudden drop in lake level was followed by a long period of up to thousands of years when lake level remained constant. Terraces on the delta fronts indicate that each major episode of fall in the lake level was punctuated by up to ten minor episodes possibly representing major storm events or annual cycles of freezing and melting, blocking the overflow sills.
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