Results from genetic and geologic studies can be combined to elucidate some general patterns of the biogeographic and evolutionary history of Central America (CA) and of its biota. Based on an ample review of geologic, biogeographic and genetic studies, our aim was to examine how common genetic patterns can be linked with geologic processes. Considering information about geologic and tectonic evolution of CA, we subdivided the region into four tectonic blocks: Maya, Chortis, Chorotega and Chocó. Species exchange between North/South America and CA encompasses three events: a first migration during the Late Cretaceous–Early Paleocene, a second through a terrestrial corridor preceding the formation of the Isthmus of Panama (IP), and the third involving a major dispersion through the IP. Such events caused similar genetic differentiation patterns and left a signature on the diversification of extant taxa, which we propose as three evolutionary groups: 1) Mayan, characterized by marked genetic structure and divergence, multiple refugia and formation of cryptic species; 2) Mid-CA, defined by high differentiation at the population level and between highland and lowlands, associated with intense volcanic activity; 3) Panamian, distinguished by migration from north to south and vice versa via de IP, with markedly high species divergence and speciation.

Lake high-stand sediments are found in three onshore terraces at Lake Donggi Cona, northeastern Tibetan Plateau, and reveal characteristics of hydrological changes on lake shorelines triggered by climate change, geomorphological processes, and neo-tectonic movements. The terraces consist of fluvial–alluvial to littoral-lacustrine facies. End-member modeling of grain-size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition. Radiocarbon dating revealed higher than modern lake levels during the early and mid Holocene. Lake levels follow the trend of Asian monsoon dynamics, and are modified by local non-climatic drivers. Site-specific impacts explain fluctuations during the initial lake-level rise ~ 11 cal ka BP. Maximum lake extension reached ~ 9.2 cal ka BP, at ~ 16.5 m above present lake level (a.p.l.l.). Littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post-depositional cryoturbations at ~ 8.5 cal ka BP, when the lake level fell to ~ 8 m a.p.l.l. After a second maximum at ~ 7.5 cal ka BP, lake level declined slightly at ~ 6.8 cal ka BP, probably due to a non-climatic pulse that caused lake opening. The level remained high until a transition towards drier conditions ~ 4.7 cal ka BP. Though discontinuous, high-stand sediments provide a unique, high-resolution archive.

Fire-history reconstructions inferred from sedimentary charcoal records are based on measuring sieved charcoal fragment area, estimating fragment volume, or counting fragments. Similar fire histories are reconstructed from these three approaches for boreal lake sediment cores, using locally defined thresholds. Here, we test the same approach for a montane Mediterranean lake in which taphonomical processes might differ from boreal lakes through fragmentation of charcoal particles. The Mediterranean charcoal series are characterized by highly variable charcoal accumulation rates. Results there indicate that the three proxies do not provide comparable fire histories. The differences are attributable to charcoal fragmentation. This could be linked to fire type (crown or surface fires) or taphonomical processes, including charcoal transportation in the catchment area or in the sediment. The lack of correlation between the concentration of charcoal and of mineral matter suggests that fragmentation is not linked to erosion. Reconstructions based on charcoal area are more robust and stable than those based on fragment counts. Area-based reconstructions should therefore be used instead of the particle-counting method when fragmentation may influence the fragment abundance.

Sedimentary records of invertebrate assemblages were obtained from a small lake in the Khibiny Mountains, Kola Peninsula. Together with a quantitative chironomid-based reconstruction of mean July air temperature, these data provide evidence of Holocene climate variability in the western sector of the Russian Subarctic. The results suggest that the amplitude of climate change was more pronounced in the interior mountain area than near the White Sea coast. A chironomid-based temperature reconstruction reflects a warming trend in the early Holocene, interrupted by a transient cooling at ca. 8500–8000 cal yr BP with a maximum drop in temperature (ca. 1°C) around 8200 cal yr BP. The regional Holocene Thermal Maximum, characterized by maximum warmth and dryness occurred at ca. 7900–5400 cal yr BP. During this period, July temperatures were at least 1°C higher than at present. The relatively warm and dry climate persisted until ca. 4000 cal yr BP, when a pronounced neoglacial cooling was initiated. Minimum temperatures, ca. 1–2°C lower than at present, were inferred at ca. 3200–3000 cal yr BP. Faunal shifts in the stratigraphic profile imply also that the late-Holocene cooling was followed by a general increase in effective moisture.

We explored the middle-Holocene decline of Tsuga canadensis by measuring the diameters of pollen grains in two lake-sediment cores from New England. We hypothesized that a drop in pollen size at the time of the decline followed by an increase in pollen diameters as Tsuga recovered during the late Holocene might indicate reduced abundance of Tsuga in the vicinity of the lake during the decline, as smaller pollen grains travel farther than larger ones. To provide context for this hypothesis, we also measured the diameters of Tsuga pollen grains in the surface sediments of sites spanning the modern-day gradient of Tsuga in New England. Both fossil records exhibited a reduction in pollen size during the interval of the middle-Holocene decline, with diameters similar to those observed in the upper sediments of those sites, yet larger than Tsuga pollen grains in the surface sediments of coastal sites beyond the modern range of Tsuga. This pattern suggests that Tsuga persisted in scattered, low-density populations during the middle Holocene, as it has remained on the landscape since European settlement.

Pollen analysis of a 9.03-m-long lake sediment core from Pender Island on the south coast of British Columbia was used to reconstruct the island's vegetation history over the last 10,000 years. The early Holocene was characterized by open mixed woodlands with abundant Pseudotsuga menziesii and a diverse understory including Salix and Rosaceae shrubs and Pteridium aquilinum ferns. The establishment of Quercus garryana savanna-woodland with P. menziesii and Acer macrophyllum followed deposition of the Mazama tephra until ~ 5500 cal yr BP, when these communities gave way to modern mixed P. menziesii forest. Charcoal analyses of the uppermost sediments revealed low charcoal accumulation over the last 1300 years with a mean fire return interval (mFRI) of 88 years. Fires were more frequent (mFRI = 50 yr) during the Medieval Climate Anomaly (MCA) with warm, dry conditions facilitating a higher fire frequency than during the Little Ice Age, when fires were infrequent. Given the projected warming for the next 50–100 years, land managers considering the reintroduction of fire to the Gulf Islands National Park Reserve may want to consider using the mFRI of the MCA as a baseline reference in prescribed burning strategies.

A paleoenvironmental time-series spanning the Holocene was constructed using 29 radiocarbon ages and 149 standardized δ13Csom values from alluvial terrace profiles along the middle Delaware River valley. There is good agreement between increasing δ13Csom and Panicoideae phytolith concentrations, suggesting that variations in C4 biomass are a major contributor to changes in the soil δ13C. A measurement error deconvolution curve over time reveals two isotope stages (II–I), with nine sub-stages exhibiting variations in average δ13Csom (average %C4). Stage II, ~ 10.7–4.3 ka, shows above-average δ13Csom (increase %C4) values with evidence of an early Holocene warming and dry interval (sub-stage IIb, 9.8–8.3 ka) that coincides with rapid warming and cool-dry abrupt climate-change events. Sub-stage IId, 7.0–4.3 ka, is an above average δ13Csom (increase %C4) interval associated with the mid-Holocene warm-dry hypsithermal. The Stage II–I shift at 4.3 ka documents a transition toward below average δ13Csom (decrease %C4) values and coincides with decreasing insolation and hydroclimatic change. Sub-stages Ib and Id (above average %C4) coincide with the first documented occurrence of maize in the northeastern USA and a substantial increase in human population during the Late Woodland. These associations suggest that people influenced δ13Csom during the late Holocene.

A series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.

Aeolian deposits at four sites in the Gonghe Basin were used to reconstruct the history of aeolian activity over the late Quaternary. These deposits include well-sorted aeolian sand, paleosols and/or loess. Aeolian sand represents dune-field expansion and/or dune buildup, whereas paleosols indicate stabilization of dunes, accompanying ameliorated vegetation cover. On the basis of 25 dates by optically stimulated luminescence (OSL), it appears that aeolian activities occurred episodically at 33.5, 20.3, 13.9, 11.8–11.0, 9.4, 7.8, and 5.7 (5.5) ka, which is largely consistent with the recent findings from the adjacent semi-arid areas. Aeolian sand mobility occurring during the early to mid Holocene conflicts with a climatic optimum inferred from lacustrine records in the northeastern Qinghai-Tibetan Plateau. This inconsistency may be resolved by interpreting aeolian activity as a response to decreased effective moisture due to enhanced evaporation, induced by higher summer insolation at that time, together with local terrain and its effects on moisture. Our results suggest that aeolian sand and paleosol cannot be simply ascribed to regional dry and wet climates, respectively, and they most likely reflect changes in effective moisture.

Data from multiple ice and sediment cores in the North Atlantic show that Marine Oxygen Isotope Stage 3 (MIS 3) was characterized by recurring millennial-scale variations in climate, but the periodic behavior of the well-known millennial-scale variations, Heinrich events and Dansgaard–Oeschger events, is uncertain. We use oxygen isotope values from the Greenland Ice Sheet Project 2 (GISP2) and North Greenland Ice Core Project (NGRIP) ice cores and estimated sea-surface temperature derived from a Bermuda Rise marine sediment core as climate proxies to assess the periodic behavior of Heinrich events and Dansgaard–Oeschger events using Lomb–Scargle spectral decomposition and continuous time autoregressive models. We find that continuous time autoregressive models produce less variable estimates of periodicity for Heinrich events than Lomb–Scargle methods. Heinrich events during MIS 3 are periodic with an estimated periodicity of 6.29–6.49 ka in the GISP 2 ice core, 6.71–6.76 ka in the marine sediment core, and 7.89–8.23 ka in the NGRIP core. There is insufficient evidence from these data to conclude that Dansgaard–Oeschger events exhibit a single periodicity during MIS 3. We also find that the periodic behavior of millennial-scale variations depends on the observational time frame.

The distribution of marine-influenced oxygen isotope stage (OIS) 5 to OIS 1 sediments was examined in several late Quaternary boreholes from the southern Changjiang (Yangtze) delta plain, China, using different dating methods including OSL, U-series, AMS 14C and paleomagnetism. Results demonstrate that coastal and estuarine deposition during OIS 5 and OIS 3 occurred throughout the study area. However, Holocene transgressive sediments were absent on the Taihu block. The burial depth of intertidal to subtidal sediment deposited during OIS 5e records 30–80 m subsidence caused by sediment compaction and tectonic movement since that time. However, coastal sediments formed during the late phase of OIS 3 were buried to a depth of ca. 6–15 m in the Taihu Lake area, while the burial depth increased eastward to ca. 45–60 m on the coastal plain. This phenomenon, combined with the distribution of Holocene marine strata, indicates at least 25–30 m uplift of the Taihu block since the end of OIS 3. We suggest that this uplift was mainly caused by the differential subsidence due to substantial amount of post-glacial deposition by the Changjiang and Huanghe Rivers on the continental shelf of east China marginal sea.

Cosmogenic nuclide (CN) apparent exposure dating has become a widely used method for determining the age of glacial landforms on the Tibetan Plateau with > 1200 published ages. We present the first 10Be exposure ages from the Dalijia Shan, the most northeastern formerly glaciated mountain range on the Tibetan Plateau. The moraine groups identified from field and remote sensing imagery mapping record four glacial events at 37.07 ± 3.70 to 52.96 ± 4.70 ka (MIS 3), 20.17 ± 1.79 to 26.99 ± 2.47 ka (MIS 2), 16.92 ± 1.49 to 18.76 ± 1.88 ka (MIS 2), and 11.56 ± 1.03 to 11.89 ± 1.06 ka (Younger Dryas). These ages indicate that glaciation in the northeastern Tibetan Plateau is much younger than previously thought. In addition, this record is consistent with many other regions on the Tibetan Plateau, with a local last glacial maximum during MIS 3 asynchronous with Northern Hemisphere last glacial maximum during MIS 2. The Dalijia Shan might also include an event of Younger Dryas age, but this needs to be tested in future studies.

We use a numerical dynamic soil–landscape model to study one aspect of the spatio-temporal soil–landscape evolution process, the effect of climatic fluctuations on soil grading distribution in space and time in response to the interplay between physical weathering and surface erosion (soil mineralogical fluxes). We simulate a synthetic soil–landscape system over the middle and late Quaternary (last 400 ka). The results show that (1) soil–landscape response to climate change is non-linear and highly spatially variable, even at hillslope scale; and (2) soil–landscape adjustment to climate change can lag tens of thousands of years and is both spatially and temporally variable. We propose that the legacy of past climatic condition (i.e. last glacial maximum) in modern soil–landscape systems vary considerably in space. This implies that the spatiotemporal uniformity in which soil is typically described in Earth system modeling and analysis (e.g. carbon cycle) grossly underestimates their actual complexity.

Of numerous theories of drumlin genesis, none has been widely accepted. It seems evident, however, that some form of positive feedback process is involved. Under certain circumstances perturbations are amplified. Herein we suggest that patchy areas of frozen bed provide the initial perturbation. Such frozen patches may occur in local areas underlain by material of lower thermal conductivity or on slight topographic highs. Drag exerted by the frozen patch deflects ice flow into its lee, dragging with it mobile till eroded from the thawed area. The energy balance is such that this till likely refreezes, either producing a topographic perturbation or amplifying an existing one. The resulting topography then deflects more of the geothermal heat away from the developing hill and into the adjacent trough, resulting in a positive feedback. Once the thermal perturbation exceeds a critical (though as yet undefined) level, melting may decouple the ice from the bed, preventing further entrainment of till from thawed areas, and thus limiting the height and length of the drumlin.

Magnetic grain-size variations have been used as sensitive paleoclimate proxies to investigate the evolution of the East Asian summer monsoon, but their relationship with temperature and precipitation is not entirely clear. Here we find that two magnetic grain-size proxy records (χARM/χLF and χARM/SIRM, where χARM, χLF and SIRM are anhysteretic remanent magnetization susceptibility, magnetic susceptibility measured at 470 Hz and saturation isothermal remanent magnetization, respectively) of Chinese loess and red-clay sediments co-vary during the last 6 Ma, except between ~ 4.5 and 2.6 Ma, when these two records had opposite trends. We attribute this disparate behavior to the different responses of χARM/χLF and χARM/SIRM to temperature and precipitation during ~ 4.5–2.6 Ma, when temperature and precipitation on the Chinese Loess Plateau were decoupled. A comparison of the loess and red-clay χARM/χLF and χARM/SIRM records with the global ice-volume proxy records reveals that χARM/χLF is more sensitive to temperature variations than χARM/SIRM. The results suggest that temperature on the Chinese Loess Plateau had a cooling trend from ~ 4.5 to ~ 2.6 Ma, whereas rainfall tended to increase. Our studies demonstrate that joint analysis of loess χARM/χLF and χARM/SIRM records can reveal paleoclimatic information that cannot be revealed by a single parameter.