High‐grade localized metasomatic alteration of the granitic gneiss surrounding a clinopyroxene‐rich pegmatoid dyke: Söndrum stenhuggeriet,Halmstad, SW Sweden

The Söndrum stone quarry (Halmstad, SW Sweden) exposes a transition from migmatized granitic gneissic country rock into a foliated clinopyroxene‐free granitic gneiss, and then a central pegmatoid dyke dominated by clinopyroxene megacrysts. This transition zone represents a fracture‐controlled, fluid‐alteration zone that developed under conditions of 650–700 °C and 790 MPa. Mineral chemical trends in F, Cl, Fe, Ti, Mn and Y are interpreted as documenting a fluid infiltration event associated with the formation of the pegmatoid dyke. Fluid inclusions from the pegmatoid dyke are CO₂ dominant, whereas in the surrounding country rock they are dominated by H₂O‐NaCl‐CaCl₂. Fluid inclusions from the intermediate foliated clinopyroxene‐free granitic gneiss are a mixture of the two types. The pegmatoid dyke appears to have originated from a high Ca activity, Fe‐Mg enriched, fluid‐rich granitic melt with a CO₂ component, which was emplaced along a tectonic fracture in a regionally migmatized granitic gneiss in the lower crust. This was accompanied by limited partial melting of the surrounding granitic gneiss. The Ca activity of the melt was high enough to allow for the formation of clinopyroxene megacrysts as opposed to orthopyroxene. H₂O‐enriched fluids expelled from the crystallizing pegmatoid dyke, which retained the majority of the CO₂ helping to stabilize the clinopyroxene. The expelled fluids coarsened and chemically affected the surrounding country rock resulting in trends in the mineral and fluid inclusion chemistry seen today in the foliated and regional granitic gneiss.     

Climatic and environmental changes during the Weichselian Lateglacial Interstadial in the Weerterbos region,the Netherlands

Lake sediment records from the Weerterbos region, in the southern Netherlands, were studied to reconstruct summer temperature and environmental changes during the Weichselian Lateglacial Interstadial. A sediment core obtained from a small lacustrine basin was analysed for multiple proxies, including lithological changes, oxygen isotopes of bulk carbonates, pollen and chironomids. It was found that the oxygen isotope record differed strongly from the other proxies. Based on a comparison with three additional lake sediment records from the same region, it emerged that the oxygen isotope records were strongly affected by local environmental conditions, impeding the distinction of a regional palaeoclimate signal. The chironomid‐inferred July air temperature reconstruction produced inferred interstadial temperatures ranging between ～15° and 18°C, largely consistent with previously published results from the northern part of the Netherlands. A temporary regressive phase in the pollen record, which can be tentatively correlated with the Older Dryas, preceded the expansion of birch woodland. Despite differences between the four pollen records from the Weerterbos region, a comparable regressive vegetation phase that was possibly the result of a shift to drier conditions could be discerned in all of the profiles. In addition, a temporary temperature decline of ～1.5°C was inferred from the chironomid record during this regressive phase. The multi‐proxy approach used here enabled a direct comparison of inferred changes in temperature, vegetation and environmental conditions at an individual site, while the multi‐site approach provided insight into the factors influencing the pollen and isotope records from these small‐scale depressions.     

The younger dryas cooling in northeast Germany: summer temperature and environmental changes in the Friedländer Groβe Wiese region

A lake sediment record from the Friedländer Groβe Wiese in northeast Germany was studied to reconstruct summer temperature changes associated with changes in vegetation development during the Weichselian Lateglacial. The record was analysed for pollen, chironomids, and oxygen and carbon isotopes of lake marl. The combination of radiocarbon dates, the presence of the Laacher See Tephra and correlation of lithological and palynological changes with other records from the region indicated that the record encompassed the Allerød to the early Holocene. Pollen assemblages reflect development of birch and later pine‐dominated forests during the Allerød, comparable to other sites in the region. Chironomid‐inferred mean July air temperatures (C‐IT) for this period range between ～14.0 and 14.8°C. A temporary decrease in C‐IT of ～1°C, a negative shift in the isotope records, and a minor decline of birch may correspond to Greenland Interstadial 1b. Even though the transition to the Younger Dryas appears to be affected by reworking and redeposition processes, a drop in C‐IT to ～11.1°C is reconstructed for the later part of the Younger Dryas, while it appears that pine locally persisted in the region. Comparison with a nearby pollen record further indicates a local expansion of wetland grasses during this period. At the transition to the Holocene, C‐IT increased to ～15.7°C, while birch and pine forests re‐expanded. Copyright © 2012 John Wiley & Sons, Ltd.     

Governing community forests and the challenge of solving two-level collective action dilemmas—A large-N perspective

The effectiveness of forest governance practices has consequences that range from the local to the global level. In general, the study of community forest governance relies heavily on case-study materials. The strength of single case and small-N comparative studies is related to the ability to uncover the nuances of time and place specific particularities. A recognized weakness of this approach relates to the fact that results cannot easily be extrapolated. For my analysis, I use a large-N, cross-national dataset instead. What constitutes an effective local forest governance regime? I show that especially monitoring – and to a lesser extent, maintenance – is correlated with improving forest conditions. When are effective governance regimes likely to emerge? I show that social capital, organization, leadership and autonomy contribute to the development of institutions for collective action. How does competition between forest users affect governance? I provide empirical evidence that two-level collective action dilemmas hinder the emergence of effective governance regimes.     

Sequence stratigraphy of coal‐bearing,high‐energy clastic units: The Maitland‐Cessnock‐Greta Coalfield and Cranky Corner Basin

Upper Carboniferous to Lower Permian sedimentary rocks extend along the periphery of the northern Sydney Basin, a sub‐basin of the Sydney‐Gunnedah‐Bowen Basin complex. The basin contains basal basalts and volcanic sediments deposited in a nascent rift zone. This rift zone was created through crustal thinning during trench rollback on the eastern edge of the New England Orogen. Thermal subsidence created accommodation for predominantly marine Dalwood Group sediments. Clastic sedimentation then occurred in the Maitland‐Cessnock‐Greta Coalfield and Cranky Corner Basin during the Early Permian. This occurred on a broad shelf undergoing renewed thermal subsidence on the margin of a rift flank of the Tamworth Belt of the southern New England Orogen. Braidplain fans prograded or aggraded in two depositional sequences. The first sequence commences near the top of the Farley Formation and includes part of the Greta Coal Measures, while the second sequence includes the majority of the Greta Coal Measures and basal Branxton Formation. Thin, areally restricted mires formed during interludes in a high sedimentation regime in the lowstand systems tracts. As base‐level rose, areally extensive mires developed on the transgressive surface of both sequences. A paludal to estuarine facies changed to a shallow‐marine facies as the braidplain was transgressed. The transgressive systems tracts continued to develop with rising relative sea‐level. Renewed uplift in the hinterland resulted in the erosion of part of the transgressive systems tract and all of the highstand systems tract of the lower sequence. In the upper sequence a reduction in relative sea‐level rise saw the development of a deltaic to nearshore shelf highstand systems tract. Extensional dynamics caused a fall in relative base‐level and the development of a sequence boundary in the Branxton Formation. Finally, renewed thermal subsidence created accommodation for the overlying, predominantly marine Maitland Group.     

Geological constraints on glacio-isostatic adjustment models of relative sea-level change during deglaciation of Prince Gustav Channel,Antarctic Peninsula

The recent disintegration of Antarctic Peninsula ice shelves, and the associated accelerated discharge and retreat of continental glaciers, has highlighted the necessity of quantifying the current rate of Antarctic ice mass loss and the regional contributions to future sea-level rise. Observations of present day ice mass change need to be corrected for ongoing glacial isostatic adjustment, a process which must be constrained by geological data. However, there are relatively little geological data on the geometry, volume and melt history of the Antarctic Peninsula Ice Sheet (APIS) after Termination 1, and during the Holocene so the glacial isostatic correction remains poorly constrained. To address this we provide field constraints on the timing and rate of APIS deglaciation, and changes in relative sea-level (RSL) for the north-eastern Antarctic Peninsula based on geomorphological evidence of former marine limits, and radiocarbon-dated marine-freshwater transitions from a series of isolation basins at different altitudes on Beak Island. Relative sea-level fell from a maximum of c. 15 m above present at c. 8000 cal yr BP, at a rate of 3.91 mm yr^?1 declining to c. 2.11 mm yr^?1 between c. 6900–2900 cal yr BP, 1.63 mm yr^?1 between c. 2900–1800 cal yr BP, and finally to 0.29 mm yr^?1 during the last c. 1800 years. The new Beak Island RSL curve improves the spatial coverage of RSL data in the Antarctic. It is in broad agreement with some glacio-isostatic adjustment models applied to this location, and with work undertaken elsewhere on the Antarctic Peninsula. These geological and RSL constraints from Beak Island imply significant thinning of the north-eastern APIS by the early Holocene. Further, they provide key data for the glacial isostatic correction required by satellite-derived gravity measurements of contemporary ice mass loss, which can be used to better assess the future contribution of the APIS to rising sea-levels.     

Timing of massive ‘Fleuve Manche’ discharges over the last 350 kyr: insights into the European ice-sheet oscillations and the European drainage network from MIS 10 to 2

Continuous high-resolution mass accumulation rates (MAR) and X-ray fluorescence (XRF) measurements from marine sediment records in the Bay of Biscay (NE Atlantic) have allowed the determination of the timing and the amplitude of the ‘Fleuve Manche’ (Channel River) discharges during glacial stages MIS 10, MIS 8, MIS 6 and MIS 4–2. These results have yielded detailed insight into the Middle and Late Pleistocene glaciations in Europe and the drainage network of the western and central European rivers over the last 350 kyr. This study provides clear evidence that the ‘Fleuve Manche’ connected the southern North Sea basin with the Bay of Biscay during each glacial period and reveals that ‘Fleuve Manche’ activity during the glaciations MIS 10 and MIS 8 was significantly less than during MIS 6 and MIS 2. We correlate the significant ‘Fleuve Manche’ activity, detected during MIS 6 and MIS 2, with the extensive Saalian (Drenthe Substage) and the Weichselian glaciations, respectively, confirming that the major Elsterian glaciation precedes the glacial MIS 10. In detail, massive ‘Fleuve Manche’ discharges occurred at ca 155 ka (mid-MIS 6) and during Termination I, while no significant discharges are found during Termination II. It is assumed that a substantial retreat of the European ice sheet at ca 155 kyr, followed by the formation of ice-free conditions between the British Isles and Scandinavia until Termination II, allowed meltwater to flow northwards through the North Sea basin during the second part of the MIS 6. We assume that this glacial pattern corresponds to the Warthe Substage glacial maximum, therefore indicating that the data presented here equates to the Drenthe and the Warthe glacial advances at ca 175–160 ka and ca 150–140 ka, respectively. Finally, the correlation of our records with ODP site 980 reveals that massive ‘Fleuve Manche’ discharges, related to partial or complete melting of the European ice masses, were synchronous with strong decreases in both the rate of deep-water formation and the strength of the Atlantic thermohaline circulation. ‘Fleuve Manche’ discharges over the last 350 kyr probably participated, with other meltwater sources, in the collapse of the thermohaline circulation by freshening the northern Atlantic surface water.     

One million years of cultural evolution in a stable environment at Atapuerca (Burgos,Spain)

The present paper analyses the evidence provided by three sites (Sima del Elefante, Gran Dolina, and Galería) located in the Trinchera del Ferrocarril of the Sierra de Atapuerca. These three sites are cave infillings that contain sediments deposited from approximately 1.2 Ma to 200 kyr. Pollen, herpetofauna, and small and large mammal remains are used as proxies to obtain a general picture of the environmental changes that occurred at the Sierra de Atapuerca throughout the one million-year period represented at these sites. Similarly, cultural changes are tracked analyzing the evidence of human behavior obtained from the study of several bone and lithic assemblages from these three sites. At least three periods with different cultural features, involving technology, subsistence and behavior, are determined from the available evidence. The first two periods correspond to the Mode 1 technology and Homo antecessor: the first is dated around 1.2 to 1.0 Ma and reflects opportunistic behavior both in technology and subsistence. The second period is around 800 kyr BP. Mode 1 technology is still maintained, but subsistence strategies include systematic hunting and the use of base camps. The third period is dated between 500 ka and 200 ka and corresponds to the Mode 2 technology and the acquisition of directional hunting and other organizational strategies by Homo heidelbergensis. A transition from Mode 2 to Mode 3 seems to appear at the end of this time-range, and may reflect the early phases of a fourth cultural change. With regard to the environment, our main conclusion is that there was an absence of extremely harsh conditions at Atapuerca throughout this time period. The presence of Mediterranean taxa was constant and the dominant landscape was a savannah-like open environment, probably with small forest patches. An alternation of Mediterranean and mesic species as the dominant component of the tree storey was induced by the climatic cycles, and steppes spread across the landscape during the drier periods. In any case, it is not possible to establish clear cut-off points separating entirely different environmental episodes. Our results show no evidence of any relationship between environmental change and cultural change at the Sierra de Atapuerca.     

Effects of sediment burial on tropical ruderal seagrasses are moderated by clonal integration

Seagrasses are clonal plants that grow submerged in dynamic sedimentary environments where burial is a common occurrence. Clonal organisms may respond to burial in very different ways depending on how strongly integrated they are through horizontal rhizomes, but the effect of clonal integration under conditions of stress such as burial is poorly studied for seagrasses. We test the effect of burial on tropical seagrasses that occur in multispecific meadows by subjecting plants in mixed stands to burial of 0, 2, 4, 8 and 16 cm for 27 days. Treatments were divided into those where rhizomes were severed and those where rhizomes were left intact. We hypothesize that species withstand burial better if clonal integration is maintained (intact rhizomes). Results showed that all species tolerated burial of up to 4 cm without adverse effects but significant reductions in shoot density and biomass become evident at 8 cm of burial. Furthermore, Cymodocea serrulata and Syringodium isoetifolium were strong integrators, i.e. they provide support for buried shoots, whereas Halophila ovalis and Halodule uninervis were weak integrators that did not show evidence of subsidizing buried shoots. Vertical elongation was observed for C. serrulata and H. uninervis as a response to burial only when rhizomes were severed, leading us to speculate on whether species rely on vertical elongation as an escape strategy only in the absence of resource translocation. Our distinction between the responses of treatments with intact rhizomes from those with severed rhizomes may be extended to an interpretation of burial scale (intact rhizomes=broad spatial?scale burial; severed rhizomes=fine spatial?scale burial). We concluded that broad spatial?scale burial exceeding 4 cm leads to rapid loss or reduction of all species. However, fine spatial–scale burial exceeding 4 cm, such as those caused by shrimp mounds (bioturbation), is expected to favor C. serrulata and S. isoetifolium, while H. ovalis and H. uninervis are disadvantaged. Clonal integration is an important trait in moderating the response of seagrasses to sediment burial and in this way, helps them to cope in high-stress habitats.     

Co-seismic and cumulative offsets of the recent earthquakes along the Karakax left-lateral strike-slip fault in western Tibet

The 400 km-long Karakax left-lateral strike-slip fault is the westernmost segment of the Altyn Tagh fault. It separates northwestern Tibet to the south from the Tarim basin to the north. The western section of the Karakax fault exhibits clear co-seismic surface ruptures of past large earthquakes. Geomorphic offset measurements from the field and high-resolution Ikonos images along 1.5 km across the Sanshiliyingfang fan and along 55 km of the fault, range from 3 to 28 m, with distinct clusters at 6 ± 2(3), 14 ± 2, 19 ± 2 and 24 ± 3 m. The cluster of the smallest offsets around 6 m (full range from 3 to 10 m) distributed over a minimum length of 55 km, is attributed to the last largest surface rupturing event that testifies of the occurrence of a magnitude Mw 7.4-7.6 earthquake along the Karakax fault. We interpret the other offset clusters as the possible repetition of similarly sized events thus favoring a characteristic slip model for the Karakax fault. In a 3 m-deep trench dug across the active trace of the fault we can identify the main rupture strands of the last and penultimate events. The penultimate event horizon, a silty-sand layer, has been radiocarbon dated at 975-1020 AD (AMS ¹⁴C age). It is proposed that large Mw 7.4-7.6 events with co-seismic slip of about 6 m rupture the Karakax fault with a return time of about 900 years implying an average slip-rate of about 6-7 mm/years during the late Holocene. These results suggest that the Karakax fault is the largest left-lateral strike-slip fault at the rim of northwestern Tibet accommodating eastward movement of Tibet due to the India-Eurasia collision.