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The natural variability of Holocene climate defines the baseline to assess ongoing climate change. Greenland ice-core records indicate warming superimposed by abrupt climate oscillations in the early Holocene, followed by a general cooling trend throughout the middle and late Holocene that culminated during the Little Ice Age (LIA). Tropical precipitation changes correlate with these patterns throughout the Holocene. Here we use mountain glaciers in the European Alps to reconstruct the regional Holocene climate evolution and to test for a link between mid-latitude, North Atlantic, and tropical climate. Our precise 10Be chronology from Tsidjiore Nouve Glacier, western Swiss Alps, indicates a glacier culmination during the earliest Holocene ~11.4 k.y. ago, likely related to the Preboreal Oscillation. Based on our data, no Holocene glacier advance of similar amplitude occurred until ~3.8 k.y. ago, when the glacier reached LIA limits. The 10Be ages between 500 and 170 yr correspond to the LIA, while the youngest 10Be ages overlap with the historically recorded post-LIA glacier positions. Integrating our data with existing records, we propose a hemispheric climate link between the Alps, North Atlantic temperature, and tropical precipitation patterns for the Holocene, supporting the concept of a pervasive climate driver. These findings from northern mid-latitudes are consistent with the hypothesis formulated for the tropics that the Earth's thermal equator, responding to North Atlantic temperature changes, might have migrated southward throughout the Holocene, reaching the southern turning point toward the end of the LIA. [ABSTRACT FROM AUTHOR]

The existence of narrow axial volcanic zones of mid-oceanic ridges testifies of the underlying concentration of both melt distribution and tectonic strain. As a result of repeated diking and faulting, axial volcanic zones therefore represent a spectacular topographic expression of plate divergence. However, the submarine location of oceanic ridges makes it difficult to constrain the interplay between tectonic and magmatic processes in time and space. In this study, we use the Dabbahu–Manda Hararo (DMH) magmatic rift segment (Afar, Ethiopia) to provide quantitative constraints on the response of tectonic processes to variations in magma supply at divergent plate boundaries. The DMH magmatic rift segment is considered an analogue of an oceanic ridge, exhibiting a fault pattern, extension rate and topographic relief comparable to intermediate- to slow-spreading ridges. Here, we focus on the northern and central parts of DMH rift, where we present quantitative slip rates for the past 40 kyr for major and minor normal fault scarps in the vicinity of a recent (September 2005) dike intrusion. The data obtained show that the axial valley topography has been created by enhanced slip rates that occurred during periods of limited volcanism, suggestive of reduced magmatic activity, probably in association with changes in strain distribution in the crust. Our results indicate that the development of the axial valley topography has been regulated by the lifetimes of the magma reservoirs and their spatial distribution along the segment, and thus to the magmatic cycles of replenishment/differentiation (<100 kyr). Our findings are also consistent with magma-induced deformation in magma-rich rift segments. The record of two tectonic events of metric vertical amplitude on the fault that accommodated the most part of surface displacement during the 2005 dike intrusion suggests that the latter type of intrusion occurs roughly every 10 kyr in the northern part of the DMH segment. [ABSTRACT FROM AUTHOR]

The hydrological conditions during the Last Glacial Maximum in the Eastern Mediterranean have long been debated. In particular, very little is known about the development of high-altitude glaciers in this region. In the present study, morphological and sedimentological evidence, such as U-shape valleys, glacial cirques, and morainic ridges, are used to identify past glaciers on the western slopes of Mount Lebanon, which is by far the highest topography along the eastern Mediterranean coast (3088 m a.s.l.). The geometry of three paleo-glaciers is reconstructed: one 8-km-long glacial tongue stretching from the highest peak down to an elevation of about 2000 m a.s.l., and two small glacial cirques located at about 2300 m a.s.l. The age of maximum glacier advance is constrained from a 10-m-deep 36Cl depth-profile within the diamicton of one terminal moraine, and yields an early LGM timing (between 25.4 ± 3.1 ka and 31.2 ± 4.5 ka), which agrees with the chronology of the last maximum glacier extension in the Eastern Mediterranean. The three glaciers together form a consistent group, compatible with an Equilibrium Line Altitude (ELA) at 2400 m estimated using the Accumulation Area Ratio method. A degree-day model is further used to infer the temperature and precipitation conditions required to depress the LGM ELA to 2400 m. Our results suggest that the observed glacier extent is compatible with early LGM paleo-temperature records of the area only under the condition of decreased precipitation relative to modern times. These findings thus support an early LGM climate of the Levant region that was drier than today. • First evidence of LGM glaciers in the southeastern Mediterranean (Mount Lebanon; 34.25°N) are provided. • The geometry of three glaciers is reconstructed and constrains the LGM Equilibrium Line Altitude at about 2400 m a.s.l. • Glacial and climate modeling indicates a drier LGM climate than today. [ABSTRACT FROM AUTHOR]

Unravelling the volcanic history of the Dabbahu/Manda Hararo rift segment in the Afar depression (Ethiopia) using a combination of cosmogenic ( 36 Cl and 3 He) surface exposure dating of basaltic lava-flows, field observations, geological mapping and geochemistry, we show in this paper that magmatic activity in this rift segment alternates between two distinct magma chambers. Recent activity in the Dabbahu rift (notably the 2005–2010 dyking crises) has been fed by a seismically well-identified magma reservoir within the rift axis, and we show here that this magma body has been active over the last 30 kyr. However, in addition to this axial magma reservoir, we highlight in this paper the importance of a second, distinct magma reservoir, located 15 km west of the current axis, which has been the principal focus of magma accumulation from 15 ka to the subrecent. Magma supply to the axial reservoir substantially decreased between 20 ka and the present day, while the flank reservoir appears to have been regularly supplied with magma since 15 ka ago, resulting in less variably differentiated lavas. The trace element characteristics of magmas from both reservoirs were generated by variable degrees of partial melting of a single homogeneous mantle source, but their respective magmas evolved separately in distinct crustal plumbing systems. Magmatism in the Dabbahu/Manda Hararo rift segment is not focussed within the current axial depression but instead is spread out over at least 15 km on the western flank. This is consistent with magneto-telluric observations which show that two magma bodies are present below the segment, with the main accumulation of magma currently located below the western flank, precisely where the most voluminous recent (<15 ka) flank volcanism is observed at the surface. Applying these observations to slow spreading mid-ocean ridges indicates that magma bodies likely have a lifetime of a least 20 ka, and that the continuity of magmatic activity is maintained by a system of separate relaying reservoirs, which could in return control the location of spreading. This long term ( > 10 5 yr ) alternation between distinct crustal reservoirs located broadly at the same location relative to the segment appears to be a key feature for organizing and maintaining active spreading centres over stable soft points in the mantle. [ABSTRACT FROM AUTHOR]

The Greenland Ice Sheet (GrIS) is a key component of the global climate system. However, our current understanding of the spatio-temporal oscillations and landscape transformation of the GrIS margins since the last glacial cycle is still incomplete. The objective of this work is to study the deglaciation of the Zackenberg Valley (74°N, 20°E), NE Greenland, and the origin of the derived landforms. Based on extensive fieldwork and high-detail geomorphological mapping we identified the different types of landforms, from which those of glacial and paraglacial origin were used to understand the processes driving regional environmental evolution. We applied cosmic-ray exposure (CRE) dating to 32 samples taken from erosive and depositional glacial landforms distributed across the valley. Geomorphological evidence shows that >800-m-thick Late Quaternary glacier filled the valleys and fjords and covered mountain summits. In subsequent phases, as ice thickness decreased, the glacier was limited to the interior of the valley, leaving several lateral moraines. The deglaciation of the Zackenberg Valley that started by ~13.7–12.5 ka also accelerated slope paraglacial processes. Many blocks from lateral moraines were remobilized and fell, reaching the valley floor where they covered the thinning glacier tongue; transforming it into a debris-covered glacier that subsequently melted gradually. By ca. 10.5 ka, the last remnants of glacial ice disappeared from the Zackenberg Valley floor, a chronology of deglaciation that is similar to that observed in other sites across NE Greenland. The results of this work must be considered in similar studies, reinforcing the need to support CRE ages of the different geomorphological phases with paleoclimatic data from other sedimentary records. • We reconstruct the deglaciation of the Greenland Ice Sheet in the Zackenberg Valley. • Local summits were ice-free at ca. 80-50 ka, prior to the Last Glacial Maximum. • The long-term GrIS recession was interrupted by short periods of stillstand or glacial advance during T-1 between 13.7 and 11.2 ka. • Since the Early Holocene (ca. 10.5 ka), no glaciers have existed in the Zackenberg Valley. [ABSTRACT FROM AUTHOR]

The Central Pyrenees hosted a large ice cap during the Late Pleistocene. The cirques under relatively low-altitude peaks (2200–2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. Here, we focus on the headwaters of the Garonne River, namely on the low-altitude Bacivèr Cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. We reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. Ice thickness in the Bacivèr Cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the Garonne paleoglacier. However, by ~15 ka, during the Bølling-Allerød (B-A) Interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the Garonne paleoglacier. Glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debris-covered and rock glaciers in their final stages. Climate conditions prevailing at the transition between the B-A and the Younger Dryas (YD) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the B-A or the YD. The melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. These remained active throughout the Early Holocene until at least ~7 ka. Since then, the landscape of the Bacivèr Cirque has seen a period of relative stability. A similar chronological sequence of deglaciation has been also detected in other cirques of the Pyrenees below 3000 m. As in other mid-latitude mountain regions, the B-A triggered the complete deglaciation of the Garonne paleoglacier and promoted the development of the wide variety of glacial and periglacial landforms existing in the Bacivèr cirque. • We reconstruct the deglaciation of the Bacivèr cirque, in the Central Pyrenees. • The cirque hosts a wide range of glacial and periglacial processes and landforms. • A rapid deglaciation occurred during the Bølling-Allerød (B-A) by 15–14 ka. • Paraglacial dynamics subsequently formed debris-covered glaciers and rock glaciers. • As in other mountain regions, the B-A played a major role shaping the landscape. [ABSTRACT FROM AUTHOR]