A sediment core from a lake in the Kap Farvel area on South Greenland was analysed with respect to pollen and microfossil content, loss-on-ignition, magnetic susceptibility and radiocarbon age. The ...aim was to reconstruct the limnic and terrestrial changes taking place at the Pleistocene-Holocene boundary. Organic sedimentation started between 12 200 and 12800 cal yr B.P. Break-up of sea-ice around Kap Farvel, as indicated by the appearance of marine dinoflagellates (Hystrix), took place some hundred years after the transition into Preboreal. The pollen analysis indicates that the area was barren during the Younger Dryas and that the Holocene vegetation establishment was slightly delayed.
Sediment lithology, lithofacies relationships, palynological and diatom analysis indicate that two drill cores extracted from ancient valleys of the Juminda Peninsula, north Estonia, represent a ...previously undetected interglacial sedimentary sequence sandwiched between the Middle and Late Pleistocene glacigenic deposits. Four different coloured major lithofacies associations (units), representing two glacigenic cycles, and deposits with the Late Saalian pollen assemblages zone (LS1), the uppermost Eemian (E9), and Early Weichselian pollen zone (EW) were distinguished at the section. The bottommost depositional unit consists of brownish coloured clay, diamicton and gravel beds. The second depositional unit, correlative to the Eemian Interglacial, consists of a black organic-rich palaeosoil and stratified sand. A thick grey coloured bed of massive and partly stratified Weichselian diamicton, sand, clay and silt comprises the third unit, and the fourth, the topmost depositional unit, consists of yellowish grey sands and silts of the Baltic Sea.
The variation of the magnetic susceptibility recorded in each layer in the Portel cave shows a good correlation with the sedimentological analyses and also with the evolution of the composition of ...the faunal associations and their palaeoenvironmental significance on the northern edge of the Ariege Pyrenees during the Middle Palaeolithic. This study reveals the presence of several layers with different magnetic properties. The high values of magnetic susceptibility and its frequency dependence and the ratio IRM-100/SIRM are the result the abundance of non-detrital iron oxides (produced from primary iron oxides by physico-chemical processes). These oxides are very fine-grained, they have a low coercive field and saturate in a weak magnetic field.
The percentage of supermagnetic grains increases with the clay content (climatic improvement), and decreases in the more sandy, less clayey layers (climatic deterioration).
La variation de la susceptibilité magnétique de la grotte du Portel enregistrée dans chaque couche montre une bonne corrélation avec les résultats des analyses sédimentologiques et aussi avec l'évolution de la composition des associations fauniques et leurs significations paléoenvironnementales sur la frange septentrionale des Pyrénées ariégeoises au paléolithique moyen.
Cette étude a permis d'individualiser plusieurs couches de propriétés magnétiques différentes. Les fortes valeurs de susceptibilité magnétique, et de dépendance en fréquence de la susceptibilité magnétique et du rapport ARI-100/ARI sont le résultat de l'abondance des oxydes de fer non détritiques (issus de la transformation des oxydes de fer primaires par des phénomènes physico-chimiques). Ces oxydes ont une taille très fine, ils ont un faible champ coercitif et se saturent dans un champ magnétique faible. Le pourcentage des grains superparamagnétiques augmente en présence d'argile (amélioration climatique), et diminue dans les couches pauvres en argile et riches en sables et éléments cryoclastiques (dégradation climatique).
Fosilni ostaci žderonje (Gulo gulo) nađeni su u jami Zvonečka II na brdu Lipnik blizu Karlovca, Hrvatska. Ova vrsta porodice Mustelidae obitava na sjeveru Euroazije i u Sjevernoj Americi. Tijekom ...pleistocena njezino područje rasprostranjenosti sezalo je i do južnijih predjela sve do Hrvatske koja je bila južna granica njezine rasprostranjenosti u ovom dijelu Europe. Fosilni ostaci roda Gulo nađeni su na sveukupno deset lokacija: Šandalja II, Pećina u Brini, Vindija, Pećina na Saftici, Pisana stina, Velika pećina, u koštanoj breči iz Pule, u koštanoj breči s Hvara, u koštanoj breči s nepoznate lokacije te u Zvonečkoj II. Morfologija jame, pozicija ulaza i nalaza ne ukazuju na to da je jama funkcionirala kao prirodna klopka u koju je životinja upala. Životinje su u špilju ulazile kroz vrtaču duboku 20-ak metara koja se nalazi otprilike iznad dvorane. Prethodni ulaz u špilju koji se nalazio na dnu vrtače sada je zatvoren, ali znamo da je postojao zbog velike količine sedimenta u dvorani koji su došli kroz njega. Lubanja je nađena na samom kraju padine. Ostaci žderonje sastoje se od frontalnog dijela lubanje s potpuno očuvanim lijevim očnjakom i zubima obraza, klimavim lijevim sjekutićima, fragmentom desne gornje vilice i klimavim desnim očnjakom. Sudeći po veličini gornjeg četvrtog pretkutnjaka i usporedbi s ostalim fosilima i nalazima žderonja, možemo zaključiti kako se u Zvonečkoj II radi o većem mužjaku. Datiranje žderonje odrađeno je u centru Klaus-Tschira-Labor (KTL, Curt Engelhorn-Zentrum Archäometrie) u Mannheimu, te je uzorak datiran na 28,144 ± 101 14C godina prije sadašnjosti (MAMS-11067). Fosilni ostaci žderonje čuvaju se u Gradskom muzeju grada Karlovca.Nedavno istraživanje drevnog mitohondrijskog DNK Pleistocenskog Europskog žderonje ustanovilo je određenu razinu vremenske i prostorne sličnosti među populacijama. Sekvencijskom analizom DNK od otprilike 40 fosiliziranih žderonja pokazalo je kako je izumrla europska populacija imala veću genetsku raznolikost od recentnih populacija na području Skandinavije što upućuje na njezinu dugogodišnju izoliranost. Današnje žderonje nisu potomci onih iz pleistocena koje su bile sekvencirane, isto tako, te životinje početkom holocenskog zagrijavanja nisu migrirale na sjever, nego su izumrle. Navedene analize nisu bile provedene na uzorku žderonje s hrvatskog teritorija tako da je sekvenciranje njenog DNK još uvijek u tijeku.
Based on high resolution seismic reflection profiling, structural and relief maps of the sedimentary bedrock between Gotland and Hiiumaa in the Baltic Sea have been composed and analysed. The general ...structure and relief of the submarine Lower Palaeozoic succession reveal a westward extension of the homoclinal structure distinguished in the Estonian mainland. The main bedrock structures offshore are 1-4 km wide, and several tens of kilometres long, linear zones of disturbances. On the structural map, these disturbances appear as submeridional zones of contour changes, up to several tens of metres in offset. The seismic profiles usually reveal a faint flexure-like bending of the layers through the zone. Locally, this flexure can be intersected by small faults. These bedrock structures are ascribed to fault movements in the crystalline basement. Two different bedrock relief systems were superposed on the region during the Cenozoic uplift and the Pleistocene glaciations. The first event resulted in the formation of a subparallel cuesta-like system of alternating erosional scarps and plains. Glacial erosion created submeridional valleys and troughs. Today three large bedrock forms, namely the Baltic and the Silurian clints and the Ordovician plateau, characterize the area. The outlines of the cuesta relief, and the amount of eroded sediments, advocate a regional increase in erosional activity from the St. Petersburg district to the area of the Baltic-Bothnian mobile zone northeast of Gotland. This zone existed as a subsided meridional lower ground during the Cenozoic, accommodating a main river that collected water both from the craton margins and the inner platform areas.
A clay-sequence from Lake Götesjön in the south-western part of the Lake Vänern basin has been investigated with respect to the foraminiferal and ostracod faunas and δ
18
O
c
and δ
13
C
c
. The ...sequence covers the middle/late Younger Dryas and the early part of the Preboreal chronozones. The conditions were severe during the Younger Dryas due to sea ice cover and a proximal position to the ice. The faunal assemblages indicate arctic glaciomarine conditions with a reduced salinity and the marine conditions ceased at c. 9700
14
C-years BP. In the late Younger Dryas an increased ice retreat raised the salinity of the bottomwater. This was due to the formation of reaction currents with marine water entering the basin at the bottom as a response to a surface freshwater flowing out from the basin. A period with improved marine conditions is recorded in the Early Preboreal. The transition from the Younger Dryas to the Preboreal is recorded as a lowering in the δ
18
O
c
due to increased input of meltwater and higher δ
13
C
c
as a consequence of a more intensive mixing of water masses and a less extensive sea ice cover. The Vedde Ash is found in the lower part of the sequence and AMS radiocarbon datings of bivalves suggest a marine reservoir age in the area of 800-900 years during the Younger Dryas. The final drainage of the Baltic Ice Lake had only limited effects on the marine environment in the south-western part of the Vänern basin.
Istraživanje u hrvatskom dijelu Sjevernog Jadrana započelo je 1970. godine snimanjem 2D seizmike te istraživačkim bušenjem. Do 1995. načinjeno je više od 16 000 km 2D seizmičkih profila te 80 ...bušotina. Tijekom ranih 80-ih godina XX. stoljeća otkriveno je nekoliko plinskih polja koja su kasnije postigla značajnu proizvodnju ugljikovodika. Ležišta plina nalaze se u nekonsolidiranim ili tek slabo konsolidiranim pijescima pleistocenske starosti taloženim u Padskoj depresiji (litostratigrafski pripadaju formaciji Ivana prema hrvatskoj, odnosno formacijama Ravenna i Carola po talijanskoj podjeli). Zamke su strukturnog i strukturno-stratigrafskog tipa, uglavnom oblikovane procesom diferencijalne kompakcije te, manjim dijelom, boranjem, nasljeđivanjem oblika mezozojskog paleoreljefa te bočnom promjenom facijesa. Plin je biogenog podrijetla, nastao i nakupljen uglavnom „in situ“, a sastavljen prevladavajuće od metana s vrlo malim udjelom dušika.
Zbog nedostatka infrastrukture u početku proizvodnje te tehnoloških problema zbog kontrole kretanja pijeska u ležištu, razrada sjevernojadranskih polja započela je 1996., kada je, za to vrijeme, primijenjena vrlo napredna kontrola proizvodnje iz pijesaka. Većina proizvodnih bušotina tako je opremljena dvostruko, tj. opremom za visoki protok vode (engl. high rate water pack) i/ili kontrolu kretanja pijeska (engl. FracPack sand control technique). Ta tehnologija se pokazalo vrlo uspješnom kod crpljenja iz nekonsolidiranih ležišta. Primjena kontrole pijeska potaknula je partnere (INA i ENI) da zajednički ulože (preko tvrtke INAgip) u novi ciklus istraživanja i proizvodnje. Tako je od 1996. snimljeno približno 5000 km2 3D seizmike, izbušeno 12 novih istraživačkih bušotina te otkriveno dodatnih 7 plinskih polja. Radom tvrtke INAgip otkriveno je ukupno 105 plinskih ležišta u 9 plinskih polja, načinjeno preko 40 proizvodnih bušotina, instalirano 19 proizvodnih platformi te dosegnuta prosječna proizvodnja oko 30 000 boe/day.
A local varve chronology from southeast Sweden between the town of Karlskrona in the province of Blekinge and Hultsfred in the province of Småland is presented. The chronology covers approximately ...800 varve-years. The glaciolacustrine varves were deposited in the Baltic Ice Lake during the Late Weichselian deglaciation. The study includes 60 connected and 56 unconnected varve series and shows that the ice recession rates vary between 75-125 m/year and 250-340 m/year in the southern and northern parts of the area, respectively. An abrupt change from thin to thick clay varves was found in the northern part of the area. The change has been correlated with a similar change of silty varves in the bottom bed of one of the delta plains close to the highest shoreline. This change in the meltwater deposition has been hypothetically correlated with the transition between the Older Dryas (GI-1d) and Alleröd (GI-1c) chronozones, or around 13,750 GRIP years.
This thesis presents palaeoenvironmental data from equatorial Africa covering two important time intervals; i) the warming period forming the Pleistocene/Holocene transition and ii) the last ...millennium. The Empakaai Crater, in northern Tanzania contains a lake from where sediment cores, spanning two time-slices 14.8-9.3 ka and 800-2000 AD, have been studied. Palaeoecological and palaeohydrological reconstruction is based on a multitude of proxies from the sediments, representing both catchment environment and the lakes aquatic ecosystem response. Between 14.8 and 10 ka the catchment vegetation and lake hydrology responded to both regional climate changes and local environment, but with different amplitude and frequency, reflecting temporal and spatial lags between the two systems. However, at c 10 ka both lake conditions and catchment vegetation showed drastic changes towards drier conditions. The record covering the last millennium reveals environmental changes related to climate and human activities. The catchment’s vegetation was affected by frequent fires, most probably human induced, while near shore vegetation responded to lake level fluctuation associated with rainfall variability. About 15 km from Empakaai Crater is an extensive abandoned irrigation system, the Engaruka complex, which was in active use between c 1400 AD and 1840 AD. By comparing a number of social and environmental factors potentially influencing the societal development at Engaruka it is shown that wet climate conditions have had positive effects on the societal development but also that dry climate conditions were not always disastrous to the society. The resemblance of the pollen taxa present is strong between the two time slices and pollen representing catchment conditions respond in similar manner in both records. The lake conditions are however very different between the two periods Thus the lake responds to both long and short term changes of variable amplitude, while the catchment vegetation seems to responds to high amplitude, low frequency changes.
