Quaternary history of vultures in Bulgaria – fossil and subfossil records

The papers presented at this meeting have two essential features in common, (i) They are based on detailed subsurface investigations of slopes, using boreholes, trial pits or sections; (ii) the stages of development of the slopes or, more generally, of the valleys or escarpments, have been correlated so far as possible with Quaternary history. In addition, some unity derives from the facts (iii) that the slopes are all in clay strata (Jurassic, Cretaceous or Eocene), whether or not there is a capping of rock; and (iv) the sites all lie outside the ice limits of the Last (Devensian) Glaciation. The inland sites have therefore been subjected to a complex cycle of climatic changes, including the rigour of one or more glacial periods; and it is evident that no attempt to elucidate the history and mechanics of these slopes, without taking the climatic factors into account, can have any hope of success.

The Geological History of Cenozoic Polar Oceans: Arctic Versus Antarctic - An Introduction.- Physiography and Plate Tectonics of the Polar Deep-Sea Basins and Their Continental Margins.- Morphology and Plate Tectonics: The Modern Polar Oceans.- The Opening of the Arctic Ocean.- On the Tectonic Evolution and Paleoceanographic Significance of the Fram Strait Gateway.- The Evolution of the Svalbard Margins: Synthesis and New Results.- The Western Barents Sea During the Cenozoic.- Structures in Rift-Basin Sediments on the Conjugate Margins of Western Tasmania, South Tasman Rise, and Ross Sea, Antarctica.- A Fine-Scale Seismic Stratigraphy of the Eastern Margin of the Weddell Sea.- Some Speculations Regarding the Nature of the Explora-Andenes Escarpment, Weddell Sea.- Polar Ice - Covers as Geological Agents.- A Comparison of Arctic and Antarctic Sea Ice and the Effects of Different Properties on Sea Ice Biota.- Sea Ice Characteristics and the Role of Sediment Inclusions in Deep-Sea Deposition: Arctic - Antarctic Comparisons.- Cycles, Rhythms, and Events in Quaternary Arctic and Antarctic Glaciomarine Deposits.- Cenozoic Glacier Fluctuations in Polar Regions - Terrestrial Records From Antarctica and the North Atlantic Sector of the Arctic.- Past Changes in Precipitation Rate and Ice Thickness as Derived From Age - Depth Profiles in Ice-Sheets Application to Greenland and Canadian Arctic Ice Core Records.- Stability of the Arctic Ocean Ice-Cover and Pleistocene Warming Events: Outlining the Problem.- Late Weichselian Ice Recession in the Central Barents Sea.- Modern Depositional Environments of Polar Oceans.- Distribution Patterns of Calcareous Foraminifers in Arctic Ocean Sediments.- Physiographic and Biologic Factors Controlling Surface Sediment Distribution in the Fram Strait.- Norwegian - Iceland Seas: Transfer Functions Between Marine Planktic Diatoms and Surface Water Temperature.- Particle Sedimentation and Productivity in Antarctic Waters of the Atlantic Sector.- Sediment Patterns in the Southern Weddell Sea: Filchner Shelf and Filchner Depression.- Quaternary History and Paleoceanography of Polar Oceans.- The Last Deglaciation in the Southern and Northern Hemispheres: A Comparison Based on Oxygen Isotope, Sea Surface Temperature Estimates, and Accelerator 14C Dating From Deep-Sea Sediments.- Synthesis of Arctic and Sub-Arctic Coccolith Biochronology and History of North Atlantic Drift Water Influx During the Last 500.000 Years.- Coccoliths in Sediments of the Eastern Arctic Basin.- Foraminiferal Assemblages in Sediments From Mendeleev Ridge, Arctic Ocean.- Physical and Acoustic Properties of Arctic Ocean Deep-Sea Sediments: Paleoclimatic Implications.- High Resolution 10Be and 230Th Stratigraphy of Late Quaternary Sediments From the Fram Strait (Core 23235).- The Enigma of Oxygen Isotope Stage 5 in the Central Fram Strait.- Dropstones in the Norwegian-Greenland Sea - Indications of Late Quaternary Circulation Patterns?.- Glacial to Interglacial Changes in the Isotopic Gradients of Southern Ocean Surface Water.- Stable Isotope Record and Late Quaternary Sedimentation Rates at the Antarctic Continental Margin.- Pre-Quaternary Records of Polar Ocean History.- Evolution of Biosiliceous Sedimentation Patterns - Eocene through Quaternary: Paleoceanographic Response to Polar Cooling.- Neogene to Recent Palynostratigraphy of Circum-Arctic Basins: Results of ODP Leg 104, Norwegian Sea, Leg 105, Baffin Bay, and DSDP Site 611, Irminger Sea.- Miocene to Quaternary Paleoceanography in the Northern North Atlantic: Variability in Carbonate and Biogenic Opal Accumulation.- Neogene and Pleistocene Glaciations in the Northern Hemisphere and Late Miocene - Pliocene Global Ice Volume Fluctuations: Evidence From the Norwegian Sea.- Southern Ocean Response to the Intensification of Northern Hemisphere Glaciation at 2.4 Ma.- Pliocene - Pleistocene Paleoceanography in the Weddell Sea - Siliceous Microfossil Evidence.- Polar Front Fluctuations and the Upper Gauss to Brunhes Paleoceanographic Record in the Southeast Atlantic Ocean.- Authors Index.

Two detailed valley side sections are described. Both are of landslipped slopes cut in Upper Lias at the point where the Inferior Oolite escarpment is breached by the east­ ward flowing river Gwash, a few kilometres east of Oakham, Rutland. Field mapping suggests that the slopes were cut in Ipswichian times either shortly before or during the deposition of the Second Terrace of the river Welland, of which the Gwash is a tribu- tary. One of the slopes (Barnsdale) was oversteepened by fluvial erosion which stripped the cambered Inferior Oolite and frost-disturbed Lias from the escarpment face, leaving, at the slope foot, a prominent erosion surface (the £Hambleton Surface’). After cessation of erosion Head accumulated on the Surface and the slope degraded, much of the degradation possibly occurring in the Middle Devensian, though land­ slide movement continued to the end of the Late Devensian. The other slope (Hambleton) which had formerly been cambered, suffered only slight steepening contemporaneously with the Barnsdale slope and the large, shallow rotational landslide that developed in the frost-disturbed Lias clay was subsequently partly obscured by Late Devensian solifluction. Stability analyses of these two landslides, together with three other previously pub­ lished case records, show that the field values of residual strength of Upper Lias clay are strongly stress dependent, with the magnitude of p'T (4 = 0)falling to 10° as the normal stress increases. Laboratory measurements of residual strength using the ring-shear apparatus are similarly stress dependent, but show considerable strength variations between different samples with similar index properties. The ring-shear strengths underestimate the field strengths by up to 11%.

In the neighbourhood, of Sevenoaks Weald many of the small hills and ridges standing up to 20 or 30 m above the streams in the clay vale south of the Lower Greensand escarpment are capped by Head deposits consisting of angular chert fragments, and other stones derived from the Greensand, set in a clay matrix. These deposits extend for a distance of at least 2 km from the escarpment, forming dissected remnants of what were originally extensive sheets, inclined at gradients of about 1.5°. The available evidence suggests they are periglacial solifluction deposits of Wol- stonian age. Probably at about the same period large-scale structural disturbances occurred in what are now spurs of the escarpment; massive blocks of the Hythe Beds subsided into the underlying Atherfield and Weald Clays, and the clays were forced up at the foot of the scarp in the form of bulges. Following this stage considerable erosion took place in the vale, accompanied by re­ treat of the escarpment within embayments between the spurs. On the eroded land­ scape solifluction debris moved up to 1 km from the scarp face during the Devensian period. This deposit again consists predominantly of clay with embedded angular chert fragments. It is about 2 m thick, with a minimum gradient of a little more than 2°, and overlies brecciated Weald Clay which typically contains several slip surfaces in its uppermost layers. Landslips in the escarpment within the embay­ ments probably occurred at about the same time. Not long afterwards, in the Late-Devensian Interstadial, around 12000 radiocarbon years b.p., a soil formed of which traces can be found buried beneath a lobate soli­ fluction sheet. The lobes extend over the lower sheet for distances of 300 m from the scarp foot at an average slope of about 7°. In the subsequent Postglacial period only minor changes have taken place; some escarpment landslips have been reactivated and the streams in the vale have eroded small channels or valleys not more than 4 m deep. Based on thaw-consolidation theory, and by using measured properties of the clays, calculations are presented which provide a reasonable explanation, in terms of soil mechanics principles, for solifluction movements of the active layer above perma­ frost on slopes inclined at angles as low as 1.5 or 2°. Under temperate conditions, mass movements are possible only on slopes steeper than about 8°. The paper includes an account of the longitudinal profiles and stratigraphy of the Eden and Medway river terraces.

The form and evolution of Fairy Dell, an active landslide complex on the Dorset coast, is described using a combination of cartographic, air photograph and field survey techniques. Erosion rates for the main landslide scars, undercliffs and sea cliffs are calculated and the spatial patterns of landslide evolution demonstrated by the use of sequences of maps and geological cross sections. Two dominant mechanisms are identified and described: (1) rotational landsliding and (2) block disruption, the breakup of originally large landslide units as they move downslope and over time. The role of small-scale erosion, in combination with the infilling of depressions by scree, wash debris and mudslides so as to produce an increasingly subdued topography as the landslides degrade, is emphasized and simple evolutionary models are proposed. The active landslide complex is then compared with the now stable, degraded landslide slopes inland. It is shown how the spatial patterns of landforms recognized in these areas on morphological maps and the complex subsurface forms revealed in sections can be better understood by reference to the suggested evolutionary sequence developed for the active complex. The sections in the stable but degraded slopes clearly support the idea of retrogressive rotational landsliding followed by block disruption, infilling and the downslope reduction of topographic expression of landslide units. Finally, it is suggested that this evolutionary interpretation might assist in the understanding of similar areas elsewhere and, if used in conjunction with geomorphological surveys, could result in the planning of more efficient site investigations.

Hadleigh Cliff forms part of a line of abandoned London Clay slopes, rising to a height of generally + 40 m o.d. or more, which extends westwards from Southend-on- Sea. The cliff, with its toe level originally at about —19 m o.d., was formed by strong fluvial erosion in the Middle and Late Devensian. By the latter part of the Late Devensian erosion had virtually ceased and since then the cliff has degraded in an episodic manner, largely in response to climatic changes. Four main stages of degradation, with intermediate periods of relative stability, have been recognized and dated, as follows: (1) Late-glacial, periglacial mudsliding, associated with a toe level of —19 m o.d. (2) Early Atlantic, temperate mudsliding, associated with a toe level which was rising with the continuing Flandrian aggradation, but lay on average at about —9m o.d. (3) Early Sub-Atlantic, temperate mudsliding, taking place to the present toe level of about + 3 m o.d. (4) A late 19th century, moderately deep-seated landslide in the crest of the slope, possibly caused in part by human interference. The times at which the first three of these stages of degradation occurred are believed to represent periods of generally increased mass movement activity in much of Britain and Europe. The present morphology of Hadleigh Cliff comprises a straight 20 scarp at the crest, an irregular and actively unstable 11° degradation zone, fronted by a smoother, quasi-stable accumulation zone inclined at about 8°. From a knowledge of the volumes and dates of the various colluvial units mantling the slope, reconstructions of earlier positions of the cliff profile are made. These indicate that during the last 10 000 years the inclination of the combined degradation zone and crest scarp has declined from about 19° to 13°, while that of the accumulation zone has remained relatively constant. The accompanying recession of the cliff crest has been approximately 50 m. From the pattern and dating of the various stages of colluviation, which increase both in age and in degree of fabric breakdown from crest to toe of the slope, it is clear that the cliff is degrading from the top. This is also reflected in the fact that the zone of weathered, in situ London Clay beneath the colluvium diminishes in thickness, in general, from bottom to top of the slope and is entirely absent beneath the late 19th century landslide. In an average year the potential evaporation at Hadleigh exceeds the rainfall. As a result soil moisture deficits are unusually high and appreciable pore-water tensions in the capillary zone probably exist even at times of maximum seasonal piezometric levels. Account is taken of these in the stability analyses that are carried out, which indicate that the accumulation zone has a factor of safety of around 1.05 in com­ parison with the value of unity obtaining in the currently unstable degradation zone. A comparison between the values of (pT indicated by the back analyses and those measured on the Hadleigh colluvium in ring shear shows the latter to be appreciably the lower: the discrepancy is reduced if the effects of pore-water tensions in the capillary zone are allowed for.

The construction of a dam at Empingham, Rutland has provided an opportunity to investigate the nature and effect of cambering and valley bulging. A detailed lithostratigraphic sequence has been established and the Upper Lias has been divided into a series of micropalaeontological zones. These features have enabled the internal structure of the Upper Lias to be determined in boreholes and at outcrop. The cambering process results in a progressive valley ward thinning which affects almost the entire Upper Lias sequence. The valley bulges are complex anticlinal structures developed in the valley floors. At depth the steeply inclined strata caught up in the valley bulge gives way along a possible decollement plane to largely undisturbed strata. The valley bulge structures occur throughout the valley and their courses are reminiscent of the trends of the modern valley system. This suggests that they may have been developed in the floors of the ancestral drainage system. The superficial structures were developed at the time of the Chalky Boulder Clay glaciation. Subsequent development of the valley has been a process of continued downcutting with landslipping and solifluxion being the dominant processes since the last glaciation. Possible mechanisms for the development of the superficial structures are discussed in the Appendix.

The valleys of the river Avon and its tributaries in the Bath area are characterized by steep slopes, up to 15°, and high relief, typically up to 160 m. The considerable down­ cutting of the river during the Devensian period, amounting to about 27 m, caused several large landslips, but cambering and valley-bulging appear to have been com­ pleted before the Last (Ipswichian) Interglacial, probably in the Wolstonian glacial period. Cambering is associated with disturbance of the strata to depths of 30-40 m and is present in the more gentle slopes which have been left essentially undisturbed by subsequent erosion. Conversely, the steepest and most actively eroding slopes are not cambered, the disturbed material probably having been removed by landslides and mudflows. The slopes are mostly blanketed by colluvium or Head, ranging from 1 to 5 m in thickness. In general the Head is only marginally stable under present climatic condi­ tions and the angle of limiting equilibrium seems to be related to the thickness of colluvium, in response to the variations of pore pressure and shear strength with depth. The observed lower bound of 9° in the Fuller’s Earth clay slopes, with 5 m of Head, may well be at or close to the angle of ultimate stability.

Reply to the comment on “Late Quaternary depositional history of the North Evvoikos Gulf, Aegean Sea, Greece” Marine Geology, 232, 157–172, 2006

This report is an overview of limits of glaciations and glacial history in, and east and southeast of, Glacier National Park, Mont., and on the Northern Plains farther east in Montana and northwestern North Dakota (lat 47–49 N., long 102–114 W.). Glacial limits east of long 102 W., in the United States and also in adjacent Canada, are shown on published maps of the U.S. Geological Survey Quaternary Geologic Atlas of the United States (I–1420) (for example, Fullerton and others, 1995, 2000). The glacial-advance limits shown on this map are from data compiled for the Lethbridge, Regina, Yellowstone, and Big Horn Mountains 4 × 6 quadrangles. Limits of Laurentide glaciations shown on the map supersede those mapped by Colton and others (196l, 1963) and Soller (1993, 1994). An abbreviated version of this report is presented in Fullerton and others (2004). This pamphlet is an expanded explanation of the map and supplemental illustrations. Reference to the map is required to follow this discussion. However, the reader can visualize spatial and temporal relations of the glacial limits and patterns of regional ice flow simply by study of the map and figures 1 and 2. The map and figures 1 and 2 depict ice-flow patterns and selected glacial limits in a very large geographic region. Comprehensive discussion of data from this region is beyond the scope of this report. In this pamphlet, we discuss selected glacial limits and selected stratigraphic, geomorphic, and sedimentologic data in a spatial and temporal context. In general, discussion of specific areas under a temporal subheading (for example, “Illinoian Glaciation”) proceeds from west to east. This pamphlet is a summary of published and unpublished information from field studies in Montana and northwestern North Dakota by D.S. Fullerton and R.B. Colton. Discussions of stratigraphic, spatial, and temporal relations of tills in Montana and North Dakota are primarily based on field observations, secondarily on regional synthesis. Discussion of these complex relations is intended for a scientific audience. Descriptions of physical characteristics of tills, discussion of stratigraphic, spatial, and temporal relations of specific till units, and discussion of the history of glaciation are provided for the reader who is interested in the glacial deposits and history in one or more specific geographic or physiographic areas and who also has some prior knowledge of Quaternary deposits and history in the region. We summarize distinguishing field characteristics of Laurentide tills on the plains in Montana in the appendix. Depiction and discussion of selected glacial limits in adjacent Canada is necessary to summarize the history of glaciation in Montana and North Dakota. Discussion of geologic relations in Canada is restricted to topics relevant to interpretation of Quaternary stratigraphy, chronology, and history in Montana and North Dakota. The term “Laurentide glacier” was applied by Chamberlin (1895) to a continental ice sheet east of the Rocky Mountains in North America. Flint (1943) referred to the same body of ice as the “Laurentide ice sheet.” Fulton and Prest (1987) and Dyke and others (1989) proposed that the name “Laurentide ice sheet” be applied only to the ice sheet of Wisconsin age. Dyke and others (1989, p. 184) suggested that ice sheets of Illinoian and pre-Illinoian ages be referred to as “Laurentide ice,” but not “Laurentide ice sheets.” “Laurentide ice sheet” here refers to any Quaternary continental ice sheet east of the Rocky Mountains in the United States and Canada. “Laurentide till” refers to till deposited by a Laurentide ice sheet. A Laurentide ice sheet here is distinguished from a Cordilleran ice sheet (Chamberlin and Salisbury, 1906) in the Cordilleran region in parts of Washington, Idaho, and Montana in the United States and in adjacent Canada. Clague (1989) indicated that Cordilleran ice sheets formed several times during the Pleistocene. He did not restrict the term “Cordilleran ice sheet” to an ice sheet of Wisconsin age. Numerical ages cited in reference to the astronomically tuned marine oxygen isotope time scale are from Martinson and others (1987), Bassinot and others (1994), Berger and others (1994), and Chen and others (1995). Most of the conventional radiocarbon (C) ages cited also are given as calibrated ages (CAL ages). The CAL ages (Bard and others, 1990a,b) cited were calculated by using the simple linear equation for calibration in Bard and others (1998):

In the unglaciated areas of Antarctica, lake sediments act as archives of the regional environmental and climatic history. In most cases, the records are restricted to the Holocene. Amongst the few exceptions are lakes in the McMurdo Dry Valleys, southern Victoria Land, which are known to have remained mostly ice-free during the Last Glacial Maximum. Within the scope of an U.S.-American-German expedition in austral summer 2002/2003, several sediment cores were recovered from the three major lakes in the Taylor Valley: lakes Fryxell, Hoare, and Bonney. In order to reconstruct the late Quaternary regional environmental and climate history, sedimentological, biogeochemical, mineralogical, and chronological investigations were conducted on the sediment sequences recovered from Lake Hoare (core Lz1020) and East Lake Bonney (core Lz1023) within the scope of this thesis. Sediment cores from Lake Hoare with a maximum length of 2.3 m mainly consist of coarse-grained material and penetrate back into the late Weichselian, when Taylor Valley was occupied by the large proglacial Lake Washburn. This lake was dammed by the advanced Ross Sea ice sheet at the valley outlet and was mainly fed by meltwater of the ice sheet. During the Pleistocene-Holocene transition, enhanced evaporation led to a significant lake level drop of Lake Washburn. The Lake Hoare record additionally shows that in course of this event, Lake Washburn desiccated to a very low level, with subaerial conditions at the coring site of Lz1020. After the final retreat of the Ross Sea ice sheet during the early Holocene, Taylor Valley was occupied by remnants of Lake Washburn. Environmental conditions comparable to those of today, with an advanced Canada Glacier separating lakes Hoare and Fryxell, established during the Mid-Holocene. A 2.7 m long core recovered from East Lake Bonney mainly consists of a halite crust. Variations in the properties of the salt crystals and of clastic components embedded in the salts imply environmental changes over time. New paleoenvironmental insights provided by this record are the evidence for enhanced evaporation in the late Holocene, which led to the precipitation of the more than 2 m thick salt crust. This event was followed by a lake level rise, caused by inflowing meltwaters refilling the basin. As a result of the establishment of a freshwater lense at the top of East Lake Bonney, a perennial ice cover was formed in the recent past. This study shows that the investigated lake sediment records provide crucial information about the late Quaternary environmental history of Taylor Valley, but should be interpreted in context with ice core records, terrestrial, and marine archives for a better understanding of the regional paleoenvironment, and paleoclimate.

Quaternary history and landscape development of some tributary drainage basins north of Chaco River

This work uses seismic records to document and classify contourite features around the Iberian continental margin to determine their implications for depositional systems and petroleum exploration. Contourites include depositional features (separated, sheeted, plastered and confined drifts), erosional features (abraded surfaces, channels, furrows and moats) and mixed features (contourite terraces). Drifts generally show high- to moderate-amplitude reflectors, which are cyclically intercalated with transparent layers. Transparent layers may represent finer-grained deposits, which can serve as seal rocks. High-amplitude reflectors (HARs) are likely to represent sandier layers, which could form hydrocarbon reservoirs. HARs occur on erosive features (moats and channels), and are clearly developed on contourite terraces and overflow features. Most of the contourite features described here are influenced by Mediterranean water masses throughout their Pliocene and Quaternary history. They specifically record Mediterranean Outflow Water, following its exit through the Gibraltar Strait. This work gives a detailed report on the variation of modern contourite deposits, which can help inform ancient contourite reservoir interpretation. Further research correlating 2D and 3D seismic anomalies with core and well-logging data is needed to develop better diagnostic criteria for contourites. This can help to clarify the role of contourites in petroleum systems.

Quaternary landscape history determines the soil functional characters of terroir

We asked whether assemblages of species with separate evolutionary histories differed in their response to similar human interventions. We assessed this by comparing the response of riparian plant communities to river regulation on two different continents. We compared free-flowing and regulated rivers between boreal parts of North America (Alberta and British Columbia) and Europe (Sweden), using a standardized sampling protocol and the same field staff on both continents. Although the two regions shared few species, both riparian plant-species diversity along free-flowing rivers and the response to different kinds of flow regulation were similar between the continents. The number of riparian-plant species and their amount of cover differed among types of water-level regime, but the continental affiliation of a river-margin site did not statistically explain any of the variation. Within continents, the local flora of the regulated river-margin sites was largely similar in species composition to the free-flowing ones, but the sites along storage reservoirs were more species-poor. The similarity in the response to regulation between the continents suggests that general guidelines for rehabilitation of degraded boreal rivers are a realistic goal. The number of species and genera, plant cover, and species numbers in most trait groups (classified according to growth form and life span) were similar between free-flowing river margins in Europe and North America. Moreover, the regional native species pools of northern Sweden and Alberta were similar in size and composition of species groups, despite the fact that only 27% of the species in Alberta were found in northern Sweden. This is presumably because the floras share a common Tertiary origin and because the regions have had largely similar late-Tertiary and Quaternary histories. The most pronounced difference between the continents was that we found no exotic species on the 183 Swedish river-margin sites, whereas 9% of the species found in all 24 North American plots taken together were exotics. All North American exotics found have occurred in Europe since prehistoric times, and the difference in exotic richness most likely reflects a difference in the number of species humans have transferred from one continent to another, rather than a difference in invasibility between the regions.