The evolution of a tropical rainforest/grassland mosaic in southeastern Brazil since 28,000 C yr BP based on carbon isotopes and pollen records

The lack of paleoecological records from the montane Atlantic Rainforest of coastal Brazil, a hotspot of biological diversity, has been a major obstacle to our understanding of the vegetational changes since the last glacial cycle. We present carbon isotope and pollen records to assess the impact of the glaciation on the native vegetation of the Serra do Mar rainforest in São Paulo, Brazil. From ca. 28,000 to  22,000 ¹⁴C yr BP, a subtropical forest with conifer trees is indicative of cool and humid conditions. In agreement carbon isotopic data on soil organic matter suggest the presence of C₃ plants and perhaps C₄ plants from  28,000 to  19,000 ¹⁴C yr BP. The significant increase in the sedimentation rate and algal spores from  19,450 to  19,000 ¹⁴C yr BP indicates increasing humidity, associated to an erosion process between  19,000 and  15,600 ¹⁴C yr BP. From  15,600 ¹⁴C yr BP to present there is a substantial increase in arboreal elements and herbs, indicating more humid and warmer climate. From  19,000 to  1000 ¹⁴C yr BP, δ¹³C values indicated the predominance of C₃ plants. These results are in agreement with studies in speleothems of caves, which suggest humid conditions during the last glacial maximum.     

Holocene Relative Sea Level Changes along the Seattle Fault at Restoration Point, Washington

At a marsh on the hanging wall of the Seattle fault, fossil brackish water diatom and plant seed assemblages show that the marsh lay near sea level between 7500 and 1000 cal yr B.P. This marsh is uniquely situated for recording environmental changes associated with past earthquakes on the Seattle fault. Since 7500 cal yr B.P., changes in fossil diatoms and seeds record several rapid environmental changes. In the earliest of these, brackish conditions changed to freshwater 6900 cal yr B.P., possibly because of coseismic uplift or beach berm accretion. If coseismic uplift produced the freshening 6900 cal yr B.P., that uplift probably did not exceed 2 m. During another event about 1700 cal yr B.P., brackish plant and diatom assemblages changed rapidly to a tidal flat assemblage because of either tectonic subsidence or berm erosion. The site then remained a tideflat until the most recent event, when an abrupt shift from tideflat diatoms to freshwater taxa resulted from 7 m of uplift during an earthquake on the Seattle fault 1000 cal yr B.P. Regardless of the earlier events, no Seattle fault earthquake similar to the one 1000 cal yr B.P. occurred at any other time in the past 7500 years.     

Archean Granitoids at the Contact of Eastern Ghat Granulite Belt and Singhbhum-Orissa Craton, in Bhuban-Rengali Sector, Orissa, India

The small granite plutons occurring at the contact of the Singhbhum-Orissa Iron Ore craton (IOC) to the north and the Eastern Ghat Granulite Belt (EGGB) to the south in eastern Indian shield are characterised by the presence of enclaves of the granulites of EGGB and the greenschist facies rocks of IOC. These granites also bear the imprints of later cataclastic deformation which is present at the contact of the IOC and the EGGB. In situ Pb-Pb zircon dating of these granites gives minimum age of their formation 2.80 Ga. A whole-rock three point Rb-Sr isochron age of this rock is found to be 2.90 Ga. Therefore, the true age of formation of these granites will be around 2.90–2.80 Ga. These granitic rocks also contain xenocrystic zircon components of 3.50 Ga and show a later metasomatic or metamorphic effect 2.48 Ga obtained from the analyses on overgrowths developed on 2.80 Ga old zircon cores. The presence of granulitic enclaves within these contact zone granite indicates that the granulite facies metamorphism of the EGGB is 2.80 Ga or still older in age. The cataclastic deformations observed at the contact zone of the two adjacent cratons is definitely younger than 2.80 Ga and possibly related to 2.48 Ga event observed from the overgrowths. As 2.80 Ga granite plutons of small dimensions are also observed at the western margin of the IOC; it can be concluded that a geologic event occurred 2.80 Ga over the IOC when small granite bodies evolved at the marginal part of this craton after its stabilisation at 3.09 Ga.     

Experimental frictional heating of coal gouge at seismic slip rates: Evidence for devolatilization and thermal pressurization of gouge fluids

High velocity (1 m/s) friction experiments on bituminous coal gouge display several earthquake-related phenomena, including devolatilization by frictional heating, gas pressurization, and slip weakening. Stage I is characterized by sample shortening and reduction in the coefficient of friction (μ) from  1 to 0.6. Stage II is characterized by high frequency ( 5 Hz) oscillations in stress and strain records and by gas emissions. Stage III is marked by rapid weakening (μ  0.1 to 0.35) and sample shortening, together with continued gas emissions. Stage IV produces stable stress records and continued weakness (μ  0.2), but without gas emission. Stage I shortening is due to compaction of the gouge and the weakening is attributed to mechanical or thermal effects. Stage II behavior is interpreted as due to coal gasification and fluctuations in fluid pressure, resulting in high frequency stick-slip type behavior. Dramatic reduction in shear stress in stage III is attributed to gas pressurization by pore collapse and corresponds to a frictional instability, analogous to nucleation of an earthquake. Microstructural observations indicate the deformation was brittle during stages I and II but ductile during stages III and IV. Time dependent finite element frictional heat models indicate the center of the samples became hot ( 900 °C) during stage II, whereas the edge of samples remained relatively cold (< 300 °C). Vitrinite reflectance of coal samples shows an increase in reflectance from  0.5 to  0.8% over the displacement interval 20–40 m (20–40 s), indicating that the reflectance responds to frictional heating on a short time scale. The energy expended per unit area in these low stress, large displacement experiments is similar to that of higher stress ( 50 MPa), short displacement ( 1 m) earthquakes ( 10⁷ J/m²).     

A late Quaternary paleotemperature record from Hanging Lake, northern Yukon Territory, eastern Beringia

The late Quaternary paleoclimate of eastern Beringia has primarily been studied by drawing qualitative inferences from vegetation shifts. To quantitatively reconstruct summer temperatures, we analyzed lake sediments for fossil chironomids, and additionally we analyzed the sediments for fossil pollen and organic carbon content. A comparison with the δ¹⁸O record from Greenland indicates that the general climatic development of the region throughout the last glaciation–Holocene transition differed from that of the North Atlantic region. Between  17 and 15 ka, mean July air temperature was on average 5°C colder than modern, albeit a period of near-modern temperature at  16.5 ka. Total pollen accumulation rates ranged between  180 and 1200 grains cm^− 2 yr^− 1. At  15 ka, approximately coeval with the Bølling interstadial, temperatures again reached modern values. At  14 ka, nearly 1000 yr after warming began, Betula pollen percentages increased substantially and mark the transition to shrub-dominated pollen contributors. Chironomid-based inferences suggest no evidence of the Younger Dryas stade and only subtle evidence of an early Holocene thermal maximum, as temperatures from  15 ka to the late Holocene were relatively stable. The most recognizable climatic oscillation of the Holocene occurred from  4.5 to 2 ka.     

Evolution of mineralizing fluids in the Zn–Pb–Cu(–Ag ± Au) skarn and epithermal deposits of the world-class San Martín district, Zacatecas, Mexico

Mineralizing fluids at the San Martín skarn show an evolution characterized by prograde and retrograde associations. The prograde mineral associations consist of (1) a massive garnet zone, (2) a tremolite ± garnet zone, and (3) a late association of quartz, sphalerite, calcite and fluorite lining the vugs in the garnet zone. The fluids of the prograde associations exhibit decreasing temperatures of homogenization (Th) and variable salinities. The fluids of the massive garnet zone have salinities of 36 wt.% NaCl equiv. and Th of 645 to 570 °C, corresponding to pressures of 1055 bar. At the tremolite ± garnet zone, Th range from 438 to 354 °C. In the late association at the endoskarn, the following evolution can be drawn: (a) salinities of 50 to 42 wt.% NaCl equiv., and Th of 455 to 346 °C in quartz, (b) salinities of 46 wt.% NaCl equiv., and Th of 415 to 410 °C in sphalerite, (c) salinities of 50 to 37 wt.% NaCl equiv., and Th of 479 to 310 °C in calcite, (d) salinities of 33 to 28 wt.% NaCl equiv. and of 24 to 22 wt.% KCl in fluorite, and (e) two types of fluids with salinities of 2 and 39 wt.% NaCl equiv. and Th 344 and 300 °C, respectively, in later saccharoidal quartz segregations. The retrograde mineral associations comprise pervasive propylitic alteration to carbonization, and mantos with sulfides. Fluids in epidote have salinities of 7.6 wt.% NaCl equiv. and Th of 287 to 252 °C, and in calcite have salinities of 9.2 to 1 wt.% NaCl equiv. and Th of 188 to 112 °C. Fluids in the sulfide assemblages in the mantos have salinities of 8 to 3 wt.% NaCl equiv. and Th 300 °C, with corresponding pressures of 94 bar. Fluids in late epithermal veins close to the intrusive body have salinities of 10 to 5 wt.% NaCl equiv. and Th of 275 to 200 °C, and distal veins show salinities of 2 to 1 wt.% NaCl equiv. and Th of 160 °C.     

Cretaceous and Cenozoic cooling history across the ultrahigh pressure Tongbai–Dabie belt, central China, from apatite fission-track thermochronology

The crystalline terrane of the Tongbai–Dabie region, central China, comprising the Earth's largest ultrahigh-pressure (UHP) exposure was formed during Triassic collision between the Sino–Korean and Yangtze cratons. New apatite fission-track (AFT) data presented here from the UHP terrane, extends over a significantly greater area than reported in previous studies, and includes the (eastern) Dabie, the Hong'an (northwestern Dabie) and Tongbai regions. The new data yield ages ranging from 44 ± 3 to 142 ± 36 Ma and mean track lengths between 10 and 14.4 μm. Thermal history models based on the AFT data taken together with published ⁴⁰Ar/³⁹Ar, K–Ar, apatite and zircon (U–Th)/He and U–Pb data, exhibit a three-stage cooling pattern that is similar across the study region, commencing with an Early Cretaceous rapid cooling event, followed by a period of relative thermal stability during which rocks remained at temperatures within the AFT partial annealing zone (60–110 °C) and ending with a possible renewed phase of accelerated cooling during Pliocene to Recent time. The first cooling phase followed large-scale transtensional deformation between 140 and 110 Ma and is related to Early Cretaceous eastward tectonic escape and Pacific back arc extension. Between this phase and the subsequent slow cooling phase, a transition period from 120 to 80 Ma (to 70 to 45 Ma along the Tan–Lu fault) was characterised by a relatively low cooling rate (3–5 °C/Ma). This transition is likely related to a tectonic response associated with the mid-Cretaceous subduction of the Izanagi–Pacific plate as well as lithospheric extension and thinning in eastern Asia. The present regional AFT age pattern is therefore basically controlled by the Early Cretaceous rapid cooling event, but finally shaped through active Cenozoic faulting. Following the transition phase the subsequent slow cooling phase pattern implies a net reduction in horizontal compressional stress corresponding to increased extension rates along the continental margin due to the decrease in plate convergence. Modelling of the AFT data suggests a possible Pliocene–Recent cooling episode, which may be supported by increased rates of sedimentation observed in adjacent basins. This cooling phase may be interpreted as a response to the far-field effects of the frontal India–Eurasia collision to the west. Approximate estimates suggest that the total amount of post 120 Ma denudation across the UHP orogen ranged from 2.4 to 13.2 km for different tectonic blocks and ranged from 0.8 to 9.7 km during the Cretaceous to between 1.7 and 3.8 km during the Cenozoic.     

Kinematic variations across Eastern Cordillera at 24°S (Central Andes): Tectonic and magmatic implications

The Eastern Cordillera (Central Andes,  24°S) consists of a basement-involved thrust system, resulting from Miocene–Quaternary eastward migrating compression, separating the Puna plateau from the Santa Barbara System foreland. The inferred Tertiary strains arising from shortening in the Eastern Cordillera and Santa Barbara System are similar, higher than in the Puna. Slip data collected on the major  N–S trending faults of Eastern Cordillera show a westward progression from dip-slip (contraction) to dextral and sinistral motions. This, consistently with established tectonic models, may result from partitioning due to the oblique Mio-Quaternary underthrusting of the Brazilian Shield north of 24°S. This strain partitioning has three main implications. (1) As the dextral and sinistral shear in the Eastern Cordillera are  62% and 29% of the compressive strain respectively, the Eastern Cordillera results more strained than Santa Barbara System foreland, contrary to previous estimates. (2) The partitioning in the Eastern Cordillera may find its counterpart in that to the west of the Central Andes, giving a possible structural symmetry to the Central Andes. (3) The easternmost N–S strike-slip structures in the Eastern Cordillera coincide with the easternmost Mio-Pliocene magmatic centres in the Central Andes, at  24°S. Provided that, further to the east, the crust is partially molten, the absence of magmatic centres may be explained by the presence of pure compressive structures in this portion of the Eastern Cordillera.     

Holocene activity of the Scilla Fault, Southern Calabria: Insights from coastal morphological and structural investigations

Integration of on-land and offshore geomorphological and structural investigations coupled to extensive radiometric dating of co-seismically uplifted Holocene beaches allows characterization of the geometry, kinematics and seismotectonics of the Scilla Fault, which borders the eastern side of the Messina Strait in Calabria, Southern Italy. This region has been struck by destructive historical earthquakes, but knowledge of geologically-based source parameters for active faults is relatively poor, particularly for those running mostly offshore, as the Scilla Fault does. The  30 km-long normal fault may be divided into three segments of  10 km individual length, with the central and southern segments split in at least two strands. The central and northern segments are submerged, and in this area marine geophysical data indicate a youthful morphology and locally evidence for active faulting. The on-land strand of the western segment displaces marine terraces of the last interglacial (124 to 83 ka), but seismic reflection profiles suggest a full Quaternary activity. Structural data collected on bedrock faults exposed along the on-land segment provide evidence for normal slip and  NW-SE extension, which is consistent with focal mechanisms of large earthquakes and GPS velocity fields in the region. Detailed mapping of raised Holocene marine deposits exposed at the coastline straddling of the northern and central segments supplies evidence for two co-seismic displacements at  1.9 and  3.5 ka, and a possible previous event at  5 ka. Co-seismic displacements show a consistent site value and pattern of along-strike variation, suggestive of characteristic-type behaviour for the fault. The  1.5–2.0 m average co-seismic slips during these events document M_e  6.9–7.0 earthquakes with  1.6–1.7 ka recurrence time. Because hanging-wall subsidence cannot be included into slip magnitude computation, these slips reflect footwall uplift, and represent minimum average estimates. The palaeoseismological record based on the palaeo-shorelines suggests that the last rupture on the Scilla Fault during the February 6, 1783 M_w = 5.9–6.3 earthquake was at the expected time but it may have not entirely released the loaded stress since the last great event at  1.9 ka. Comparison of the estimated co-seismic extension rate based on the Holocene shoreline record with available GPS velocities indicates that the Scilla Fault accounts for at least  15–20% of the contemporary geodetic extension across the Messina Strait.     

Paleoenvironment of Jawa basalt plateau, Jordan, inferred from calcite speleothems from a lava tube

This paper explores the environmental conditions that faced the people of ancient Jawa during the Holocene, as well as previous prehistoric periods of the mid-late Pleistocene. Calcite speleothems in a lava tube are dated using the U-Th method, to marine oxygen isotope stage 7 from  250 to 240 ka and from  230 to  220 ka; and the stage 5/4 transition between  80 and 70 ka. The available evidence indicates general aridity of the Black Desert during most of the mid-late Quaternary, punctuated by short wetter periods, when the Mediterranean cyclonic systems intensified and penetrated the north Arabian Desert. These Mediterranean systems had a longer and more intense effect on the desert fringe closer to the Mediterranean and only rarely penetrated the Black Desert of Jawa. The results do not exclude some increase of rainfall which did not change water availability dramatically during the warm Holocene. The ancient Jawa city appears to have depended on technological ability to build elaborate runoff-collection systems, which became the prime condition for success.     

Reconstruction of climatic and environmental changes in NW Romania during the early part of the last deglaciation (15,000–13,600 cal yr BP)

High resolution pollen, plant macrofossil, charcoal, mineral magnetic and sedimentary analyses, combined with AMS ¹⁴C measurements, were performed on multiple sediment sequences along a transect through the former crater lake Preluca iganului in northwestern Romania in order to reconstruct the climatic and environmental changes during the early part of the Last Termination. Lake sediments started to accumulate at 14,700 cal yr BP. Initially the upland vegetation consisted of an open forest with mainly Betula and Salix and few Pinus sp., but from 14,500 cal yr BP onwards, Pinus mugo, P. sylvestris and Populus and later on also Larix became established around the lake. Between 14,150 and 13,950 cal yr BP, Pinus cembra seems to have replaced P. mugo and P. sylvestris. At 13,950 cal yr BP the tree cover increased and Picea appeared for the first time, together with Pinus cembra, P. mugo and Larix. From 13,750 cal yr BP onwards, a Picea forest developed around the site. Based on the combined proxy data the following climatic development may be inferred: 14,700–14,500 cal yr BP, cooler and wet/humid; 14,500–14,400 cal yr BP: gradually warmer temperatures, wet/humid with dry summers; 14,400–14,320 cal yr BP: warm and dry; 14,320–14,150 cal yr BP: cooler and wet/humid; 14,150–14,100 cal yr BP: warm and dry; 14,100–13,850 cal yr BP: warmer and wet/humid; <13,850 cal yr BP: warm and dry. The tentative correlation of this development with the North Atlantic region assumes that the period >14,700 cal yr could correspond to GS-2a, the time span between 14,700 and 14,320 to GI-1e, the phase between 14,320 and 14,150 cal yr BP to GI-1d and the time frame between 14,150 and 13,600 cal yr BP to the lower part of GI-1c.     

Evidence for eukaryotic diversification in the 1800 million-year-old Changzhougou Formation, North China

Shales and silty shales of the 1800 million-year-old Changzhougou Formation (lowermost Changcheng Group) in the Pangjiapu Region of North China contain well-preserved, acritarchs. These microbial body fossils, although sphaeromorphs, have a size and fine-scale morphological complexity that would attribute them to the eukaryotic domain on the tree of life. Sphaeromorphs range in size from 62 μm to 216 μm. Shapes include spheroidal, ellipsoidal, and fusiform. Some have medial splits indicating excystment and others have a complex wall structure with three or more wall layers. Thirteen distinct morphological entities have been identified. These results indicate that eukaryotic microbial life was well established by close of the Paleoproterozoic and had already undergone a moderate amount of diversification.     

Raised coastal terraces along the Ionian Sea coast of northern Calabria, Italy, suggest space and time variability of tectonic uplift rates

A detailed study of uplifted Middle–Late Pleistocene marine terraces on the eastern side of northern Calabria, southern Italy, provides insights into the temporal and spatial scale variability of vertical displacement rates over a time span of 400 ka. Calabria is located in the frontal orogen of southern Italy above the westerly-plunging Ionian slab, and a combination of lithospheric, crustal, and surface processes concurred to rapid Late Quaternary uplift. Eleven terrace orders and a raised Holocene beach were mapped up to 480 m a.s.l., and were correlated between the coastal slopes of Pollino and Sila mountain ranges across the Sibari Plain, facing the Ionian Sea side of northeastern Calabria. Precise corrections were applied to the measured shoreline angles in order to account for uncertainty in measurement, erosion of marine deposits, recent debris shedding, and bathymetric range of markers. Radiometric (ESR and ¹⁴C) dating of shells provides a crono-stratigraphic scheme, although many samples were found to be resedimented in younger terraces. Terrace T4, whose inner margin stands at elevations of 94–130 m, is assigned to MIS 5.5 (124 ka), based on new ESR dating and previous amino acid racemization estimations. The underlying terraces T3, T2 and T1 are attributed to MIS 5.3 (100 ka), 5.1 (80 ka) and 3 (60 ka), as inferred from their relative position supplemented by ESR and ¹⁴C age determinations. The age of higher terraces is poorly constrained, but conceivably is tracked back to MIS 11 (400 ka). The reconstructed depositional sequence of terraces attributed to MIS 5.5 and 7 reveals two regressive marine cycles separated by an alluvial fanglomerate, which, given the steady uplift regime, points to minor sub-orbital sea-level changes during interstadial highstands. Based on the terrace chronology, uplift in the last 400 ka occurred at an average rate of 1 mm/a, but was characterized by the alternation of more rapid (up to 3.5 mm/a) and slower (down to 0.5 mm/a) periods of displacement. Spatial variability in uplift rates is recorded by the deformation profile of terraces parallel to the coast, which document the growth of local fold structures.     

SHRIMP zircon U–Pb geochronological and whole-rock geochemical evidence for an early Neoproterozoic Sibaoan magmatic arc along the southeastern margin of the Yangtze Block

It has been generally accepted that the South China Block was formed through amalgamation of the Yangtze and Cathaysia Blocks during the Proterozoic Sibaoan orogenesis, but the timing and kinematics of the Sibao orogeny are still not well constrained. We report here SHRIMP U–Pb zircon geochronological and geochemical data for the Taohong and Xiqiu tonalite–granodiorite stocks from northeastern Zhejiang, southeastern margin of the Yangtze Block. Our data demonstrate that these rocks, dated at 913 ± 15 Ma and 905 ± 14 Ma, are typical amphibole-rich calc-alkaline granitoids formed in an active continental margin. Combined with previously reported isotopic dates for the  1.0 Ga ophiolites and  0.97 Ga adakitic rocks from northeastern Jiangxi, the timing of the Sibao orogenesis is thus believed to be between  1.0 and  0.9 Ga in its eastern segment. It is noted that the Sibao orogeny in South China is in general contemporaneous with some other early Neoproterozoic (1.0–0.9 Ga) orogenic belts such as the Eastern Ghats Belt of India and the Rayner Province in East Antarctica, indicating that the assembly of Rodinia was not finally completed until  0.9 Ga.     

Lake Manly(?) Shorelines in the Eastern Mojave Desert, California

Near Mesquite Spring on the southern edge of the Soda Lake basin in the Mojave Desert, there is a shoreline of an ancient lake at an elevation of 340 m above sea level. At present, Soda Lake would overflow at 280 m; a lake surface at 340 m would extend 240 km northward, to the northern end of Death Valley. Shorelines and lacustrine deposits near the Salt Spring and Saddle Peak Hills, 75 km north of Mesquite Spring, are at 180 m; a lake surface at this elevation today would also extend to the northern end of Death Valley. The most prominent shoreline of the pluvial lake that occupied Death Valley during the Pleistocene, Lake Manly, is that of the Blackwelder stand which ended 120,000 yr ago. This shoreline is 90 m above sea level. The Mesquite Spring and Salt Spring Hills shorelines were probably formed by the Blackwelder stand and subsequently displaced with respect to one another, tectonically, due to transpression in the northeastern Mojave Desert and NW–SE extension across Death Valley. This tectonic regime would result in subsidence of Death Valley and the Salt Spring Hills relative to Mesquite Spring. A reconstruction suggests that the topography at the time of the Blackwelder stand would have had a sill near the level of the highest lake, and also one 20 m lower, corresponding to the next most prominent shoreline in Death Valley. Expansion of the lake over these sills would have increased evaporation, thus possibly stabilizing the lake level.     

Mesozoic plutons of the Yidun Arc, SW China: U/Pb geochronology and Hf isotopic signature

The Yidun Arc is a Triassic volcanic arc located between the Songpan Garzê Fold Belt and the Qiangtang Block, southwest China. To constrain the age of a number of the major granitic plutons from the Yidun Arc, laser ablation ICP-MS U/Pb analysis of zircon was conducted. Hafnium isotope data was also acquired through laser-ablation multicollector ICPMS analysis of zircon, with the aim of gaining insight into the age and nature of the source region of the plutons. Three age groups have been identified from seven granite samples: Early–Middle Triassic ( 245 to 229 Ma), Late Triassic ( 219 to 216 Ma) and Cretaceous ( 105 to 95 Ma). Hafnium analysis shows the Triassic granites to have negative and variable ε_Hf values and Mesoproterozoic ( 1.6 Ga) depleted-mantle model ages, which is interpreted to reflect derivation from an isotopically heterogeneous, largely crustal source. The Cretaceous granite shows higher and less variable ε_Hf values and slightly younger model ages ( 1.3 Ga), and is interpreted to be derived from melting of a more homogeneous crustal source. A depleted-mantle model age of  1.5 Ga is calculated from the pooled Triassic and Cretaceous samples. The source region for these magmas may be tentatively correlated with Mesoproterozoic material of the Yangtze Craton, which has been suggested to underlie the Yidun Arc; however, further work is necessary to demonstrate this suggestion.     

Latest Pleistocene and Holocene glaciation of Baffin Island, Arctic Canada: key patterns and chronologies

Melting glaciers and ice caps on Baffin Island contribute roughly half of the sea-level rise from all ice in Arctic Canada, although they comprise only one-fourth of the total ice in the region. The uncertain future response of arctic glaciers and ice caps to climate change motivates the use of paleodata to evaluate the sensitivity of glaciers to past warm intervals and to constrain mechanisms that drive glacier change. We review the key patterns and chronologies of latest Pleistocene and Holocene glaciation on Baffin Island. The deglaciation by the Laurentide Ice Sheet occurred generally slowly and steadily throughout the Holocene to its present margin (Barnes Ice Cap) except for two periods of rapid retreat: An early interval 12 to 10 ka when outlet glaciers retreated rapidly through deep fiords and sounds, and a later interval 7 ka when ice over Foxe Basin collapsed. In coastal settings, alpine glaciers were smaller during the Younger Dryas period than during the Little Ice Age. At least some alpine glaciers apparently survived the early Holocene thermal maximum, which was several degrees warmer than today, although data on glacier extent during the early Holocene is extremely sparse. Following the early Holocene thermal maximum, glaciers advanced during Neoglaciation, beginning in some places as early as 6 ka, although most sites do not record near-Little Ice Age positions until 3.5 to 2.5 ka. Alpine glaciers reached their largest Holocene extents during the Little Ice Age, when temperatures were 1–1.5 °C cooler than during the late 20th century. Synchronous advances across Baffin Island throughout Neoglaciation indicate sub-Milankovitch controls on glaciation that could involve major volcanic eruptions and solar variability. Future work should further elucidate the state of glaciers and ice caps during the early Holocene thermal maximum and glacier response to climate forcing mechanisms.     

Late Pleistocene and Holocene palaeogeography of the Lower Tagus Valley (Portugal): effects of relative sea level, valley morphology and sediment supply

Because of the deep glacial incision, the Lower Tagus Valley hosts a sedimentary record since 20 000 cal BP, making this a unique site along the European Atlantic margin with respect to palaeogeographic and sea level changes. Based on nine cross-sections and 55 radiocarbon dates together with a newly created relative sea level curve, we constructed five palaeogeographic maps of the infill of the Lower Tagus Valley since 20 000 cal BP. We illustrate that relative sea level rise and fluvial sediment supply were the prime forcing factors determining the depositional history and palaeogeographic changes. Around 20 000 cal BP a deeply incised braided river existed, which was directly connected to the ocean across the narrow continental shelf. After that (12 000 cal BP) the gradually moister and warmer climate caused a change to a single-channel river. During the following period (12 000–7000 cal BP) relative sea level rise resulted in a transgression in the Lower Tagus Valley and the establishment of extensive tidal environments. After relative sea level rise had ended (7000 cal BP) the valley was progressively filled by a fluvial wedge and tidally influenced bayhead delta. Since 1000 cal BP the valley-fill history was dominated by increased sediment input due to human-induced degradation of catchment slopes. Generally, climate was of subordinate importance during the entire studied period, merely causing a single-channel river resulting from the change from the cold Heinrich event 1 to the temperate Bölling–Allerød interstadial. Despite the tectonic activity in the region, neotectonic uplift or subsidence was limited, as supported by the horizontal relative sea level curve since 7000 cal BP. Neotectonics played a minor role due to the large distance from the Fennoscandian ice sheet and the narrow continental shelf, which prohibited strong glacio- and hydro-isostatic movements.     

Anatolian surface wave evaluated at GEOFON Station ISP Isparta, Turkey

We have studied seismic surface waves of 255 shallow regional earthquakes recently recorded at GEOFON station ISP (Isparta, Turkey) and have selected these 52 recordings with high signal-to-noise ratio for further analysis. An attempt was made by the simultaneous use of the Rayleigh and Love surface wave data to interpret the planar crust and uppermost mantle velocity structure beneath the Anatolian plate using a differential least-square inversion technique. The shear-wave velocities near the surface show a gradational change from approximately 2.2 to 3.6 km s^− 1 in the depth range 0–10 km. The mid-crustal depth range indicating a weakly developed low velocity zone has shear-wave velocities around 3.55 km s^− 1. The Moho discontinuity characterizing the crust–mantle velocity transition appears somewhat gradual between the depth range  25–45 km. The surface waves approaching from the northern Anatolia are estimated to travel a crustal thickness of  33 km whilst those from the southwestern Anatolia and part of east Mediterranean Sea indicate a thicker crust at  37 km. The eastern Anatolia events traveled even thicker crust at  41 km. A low sub-Moho velocity is estimated at  4.27 km s^− 1, although consistent with other similar studies in the region. The current velocities are considerably slower than indicated by the Preliminary Reference Earth Model (PREM) in almost all depth ranges.     

A late Quaternary pollen sequence from Mfabeni Peatland, South Africa: Reconstructing forest history in Maputaland

This paper documents a continuous  44,000-yr pollen record derived from the Mfabeni Peatland on the Maputaland Coastal Plain. A detailed fossil pollen analysis indicates the existence of extensive Podocarpus-abundant coastal forests before  33,000 cal yr BP. The onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions. Conditions during the last glacial maximum ( 21,000 cal yr BP) are inferred to have been colder and drier than the present, as evidenced by forest retreat and replacement of swampy reed/sedge communities by dry grassland. Forest growth and expansion during the Holocene Altithermal ( 8000–6000 cal yr BP) indicates warm, relatively moist conditions. Previous records from Maputaland have suggested a northward migration of Podocarpus forest during the late Holocene. However, we interpret a mid-Holocene decline in Podocarpus at Mfabeni as evidence of deforestation. Forest clearance during the mid-Holocene is supported by the appearance of Morella serrata, suggesting a shift towards more open grassland/savanna, possibly due to burning. These signals of human impact are coupled with an increase in Acacia, indicative of the development of secondary forest and hence disturbance.