scholarly journals High-quality fossil dates support a synchronous, Late Holocene extinction of devils and thylacines in mainland Australia

2018 ◽  
Vol 14 (1) ◽  
pp. 20170642 ◽  
Author(s):  
Lauren C. White ◽  
Frédérik Saltré ◽  
Corey J. A. Bradshaw ◽  
Jeremy J. Austin
Keyword(s):  
Late Holocene ◽  
Extinction Time ◽  
Tasmanian Devil ◽  
Before Present ◽  
High Quality ◽  
Radiocarbon Dates ◽  
Common Cause ◽  
Quality Filtering

The last large marsupial carnivores—the Tasmanian devil ( Sarcophilis harrisii ) and thylacine ( Thylacinus cynocephalus )—went extinct on mainland Australia during the mid-Holocene. Based on the youngest fossil dates (approx. 3500 years before present, BP), these extinctions are often considered synchronous and driven by a common cause. However, many published devil dates have recently been rejected as unreliable, shifting the youngest mainland fossil age to 25 500 years BP and challenging the synchronous-extinction hypothesis. Here we provide 24 and 20 new ages for devils and thylacines, respectively, and collate existing, reliable radiocarbon dates by quality-filtering available records. We use this new dataset to estimate an extinction time for both species by applying the Gaussian-resampled, inverse-weighted McInerney (GRIWM) method. Our new data and analysis definitively support the synchronous-extinction hypothesis, estimating that the mainland devil and thylacine extinctions occurred between 3179 and 3227 years BP.

Environmental implications of middle to late Holocene plains pocket gophers in Southeast Missouri

2019 ◽  
Vol 40 (4) ◽  
pp. 175-191
Author(s):  
James J Krakker ◽  
Linda A Krakker
Keyword(s):  
Late Holocene ◽  
Before Present ◽  
Pocket Gopher ◽  
Environmental Implications ◽  
Pocket Gophers ◽  
Radiocarbon Dates ◽  
Middle Holocene ◽  
Southeast Missouri ◽  
Geomys Bursarius

Plains pocket gopher, Geomys bursarius, a grassland inhabitant, is common among the mammal taxa identified on the southeast Ozark margin at the Lepold site, 23RI59, Ripley County, Missouri. Its presence throughout the midden depth, whether an incidental inclusion or human prey, implies that a favorable habitat existed in the immediate vicinity. As radiocarbon dates indicate midden deposition began about 7500 radiocarbon years before present, grassland was a component of the local vegetation beginning in the middle Holocene, if not before.

scholarly journals Late holocene trends of phytoplankton productivity and anoxia as inferred from diatom and geochemical proxies in Lake Victoria, Eastern Africa

2013 ◽  
Vol 10 (11) ◽  
pp. 17663-17682
Author(s):  
M. Andama ◽  
J. B. Lejju ◽  
C. U. Tolo
Keyword(s):  
Late Holocene ◽  
Lake Victoria ◽  
Eastern Africa ◽  
Before Present ◽  
Diatom Analysis ◽  
Phytoplankton Productivity ◽  
Radiocarbon Dates ◽  
X Ray ◽  
Ecological Changes ◽  
Diatom Productivity

Abstract. Lake Victoria ecosystem has undergone major ecological changes in the recent decades. Sedimentary diatom analysis and Fe / Mn determined by Energy Dispersive X-ray Fluorescence (EDXRF) have provided phytoplankton (diatom) productivity and the resultant anoxia (Fe / Mn) in Lake Victoria at Napoleon Gulf during the late Holocene (1778 cal yr BP (calibrated years before present) to 2008 AD) with radiocarbon dates determined using Accelerator Mass Spectrometry standard method. The results showed that increased total diatom counts in Napoleon Gulf during the late Holocene correspond with increased Fe / Mn ratio (anoxia) in some of the profiles and not in others and in most cases those that correspond correlate very well with increased eutrophication from nitrate input (Total Nitrogen, TN). Therefore slightly increased anoxia not related to increased diatom productivity was recorded in Lake Victoria at Napoleon Gulf from the period 1778 to 1135 cal yr BP. There was slightly increased diatom productivity at Napoleon Gulf from the period 857 to 758 cal yr BP but it did not increase anoxia in the lake. The period 415 cal yr BP to 2008 AD recorded increased anoxia at Napoleon Gulf related to high diatom productivity especially from 415 to 390 cal yr BP and 191 cal yr BP to 2008 AD.

scholarly journals Late Holocene landscape change history related to the Alpine Fault determined from drowned forests in Lake Poerua, Westland, New Zealand

2012 ◽  
Vol 12 (6) ◽  
pp. 2051-2064 ◽  
Author(s):  
R. M. Langridge ◽  
R. Basili ◽  
L. Basher ◽  
A. P. Wells
Keyword(s):  
Lake Level ◽  
Late Holocene ◽  
Alluvial Fan ◽  
Time Of Death ◽  
Fault Rupture ◽  
Radiocarbon Dates ◽  
Living Tree ◽  
Alpine Fault ◽  
History Of ◽  
Lowland Forests

Abstract. Lake Poerua is a small, shallow lake that abuts the scarp of the Alpine Fault on the West Coast of New Zealand's South Island. Radiocarbon dates from drowned podocarp trees on the lake floor, a sediment core from a rangefront alluvial fan, and living tree ring ages have been used to deduce the late Holocene history of the lake. Remnant drowned stumps of kahikatea (Dacrycarpus dacrydioides) at 1.7–1.9 m water depth yield a preferred time-of-death age at 1766–1807 AD, while a dryland podocarp and kahikatea stumps at 2.4–2.6 m yield preferred time-of-death ages of ca. 1459–1626 AD. These age ranges are matched to, but offset from, the timings of Alpine Fault rupture events at ca. 1717 AD, and either ca. 1615 or 1430 AD. Alluvial fan detritus dated from a core into the toe of a rangefront alluvial fan, at an equivalent depth to the maximum depth of the modern lake (6.7 m), yields a calibrated age of AD 1223–1413. This age is similar to the timing of an earlier Alpine Fault rupture event at ca. 1230 AD ± 50 yr. Kahikatea trees growing on rangefront fans give ages of up to 270 yr, which is consistent with alluvial fan aggradation following the 1717 AD earthquake. The elevation levels of the lake and fan imply a causal and chronological link between lake-level rise and Alpine Fault rupture. The results of this study suggest that the growth of large, coalescing alluvial fans (Dry and Evans Creek fans) originating from landslides within the rangefront of the Alpine Fault and the rise in the level of Lake Poerua may occur within a decade or so of large Alpine Fault earthquakes that rupture adjacent to this area. These rises have in turn drowned lowland forests that fringed the lake. Radiocarbon chronologies built using OxCal show that a series of massive landscape changes beginning with fault rupture, followed by landsliding, fan sedimentation and lake expansion. However, drowned Kahikatea trees may be poor candidates for intimately dating these events, as they may be able to tolerate water for several decades after metre-scale lake level rises have occurred.

scholarly journals Pollen-inferred regional vegetation patterns and demographic change in Southern Anatolia through the Holocene

The Holocene ◽  
2019 ◽  
Vol 29 (5) ◽  
pp. 728-741 ◽  
Author(s):  
Jessie Woodbridge ◽  
C Neil Roberts ◽  
Alessio Palmisano ◽  
Andrew Bevan ◽  
Stephen Shennan ◽  
...  
Keyword(s):  
Demographic Change ◽  
Late Holocene ◽  
Vegetation Change ◽  
Anthropogenic Activities ◽  
Population Expansion ◽  
Ecological Systems ◽  
Archaeological Sites ◽  
Radiocarbon Dates ◽  
Significant Area ◽  
The Mediterranean

Southern Anatolia is a highly significant area within the Mediterranean, particularly in terms of understanding how agriculture moved into Europe from neighbouring regions. This study uses pollen, palaeoclimate and archaeological evidence to investigate the relationships between demography and vegetation change, and to explore how the development of agriculture varied spatially. Data from 21 fossil pollen records have been transformed into forested, parkland and open vegetation types using cluster analysis. Patterns of change have been explored using non-metric multidimensional scaling (nMDS) and through analysis of indicator groups, such as an Anthropogenic Pollen Index, and Simpson’s Diversity. Settlement data, which indicate population densities, and summed radiocarbon dates for archaeological sites have been used as a proxy for demographic change. The pollen and archaeological records confirm that farming can be detected earlier in Anatolia in comparison with many other parts of the Mediterranean. Dynamics of change in grazing indicators and the OJCV ( Olea, Juglans, Castanea and Vitis) index for cultivated trees appear to match cycles of population expansion and decline. Vegetation and land use change is also influenced by other factors, such as climate change. Investigating the early impacts of anthropogenic activities (e.g. woodcutting, animal herding, the use of fire and agriculture) is key to understanding how societies have modified the environment since the mid–late Holocene, despite the capacity of ecological systems to absorb recurrent disturbances. The results of this study suggest that shifting human population dynamics played an important role in shaping land cover in central and southern Anatolia.

Climate change and human disturbance of fynbos vegetation during the late Holocene at Princess Vlei, Western Cape, South Africa

The Holocene ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1137-1149 ◽  
Author(s):  
F.H. Neumann ◽  
L. Scott ◽  
M.K. Bamford
Keyword(s):  
Anthropogenic Disturbance ◽  
Late Holocene ◽  
Climate Changes ◽  
Western Cape ◽  
Radiocarbon Dates ◽  
The Core ◽  
Pollen Types ◽  
Hydrological System ◽  
Vegetation And Climate ◽  
Floating Mat

Pollen analysis of a core in Princess Vlei in the Fynbos Biome near Cape Town gives a 4150 year record of vegetation and climate changes followed by disturbance by colonial settlers since c. 300 years ago. Their impact replaced climate as a major factor in changing the vegetation. The chronology is based on eight radiocarbon dates. Pollen types such as Restionaceae, Ericaceae, and Proteaceae reflect changes in fynbos. Pollen indicators at the bottom of the core suggest drier conditions followed by an increase in Morella, Cyperaceae and Carpacoce pollen, which might indicate moist conditions c. 3400–2600 cal. yr BP. Drier conditions prevail c. 2600–1900 cal. yr BP. Apparent light disturbance after c. 2000 cal. yr BP might be attributed to Khoi herders. Deeper water and damp surroundings are indicated c. 1900–1000 cal. yr BP. The top of the core shows an increase of Poaceae while Restionaceae decrease with anthropogenic disturbance, including the introduction of neophytes such as Pinus ( c. 300 years ago) and Zea mays. Charcoal percentages point to intense fires after the arrival of the Europeans. Water between 105 and 75 cm indicates the development of a floating mat resulting from changes in the hydrological system possibly connected to disturbances by settlers.

Influence of regional anthropogenic changes over Nile region on the climate system during the late Holocene (~2500 years before present)

2020 ◽  
Author(s):  
Ram Singh ◽  
Allegra N. LeGrande ◽  
Kostas Tsigaridis
Keyword(s):  
Late Holocene ◽  
Volcanic Eruptions ◽  
Climate System ◽  
Anthropogenic Factors ◽  
Nile River ◽  
Before Present ◽  
Anthropogenic Changes ◽  
River Floodplains ◽  
Spatial Coverage ◽  
The Impact

<p>The societal impacts of climate change during the late Holocene leads to regional anthropogenic changes over the Nile region floodplain and could have acted in tandem with natural factors like major volcanic eruptions on the regional climate system to magnify the local climatic impacts. This study aims to explore and investigate the sensitivity of climatic changes to the regional anthropogenic changes due to various factors over the Nile river floodplains during the late-Holocene (2.5K years before present). The GISS ModelE Earth system model will be used to simulate the various scenarios of regional increasing/decreasing river fraction, changes in vegetation type and cover, along with changes in land surface type against the no-changes scenario in absence of volcanic eruptions. The spatial coverage of the Nile river basin is estimated using the GIS shapefile based on elevation data from Shuttle Radar Topography Mission (SRTM) at 3 Arc-seconds (approx. 90-meter) horizontal resolution. The extent of flooding in the model grid (2.0°x2.5° in latitude and longitude) is estimated using the existing high-resolution (0.125°x0.125°) gridded topographic elevation information and mapped over the Nile river floodplains. This study also focuses on evaluating the NASA GISS ModelE for resolving the climate feedbacks and response on climate system due to anthropogenic changes and volcanic eruptions. It is also aimed to analyze and quantify the impact of various anthropogenic factors over the African monsoon system and rainfall over the region, which feeds the Nile River.</p>

Late Pleistocene and Late Holocene Lake Highstands in the Pyramid Lake Subbasin of Lake Lahontan, Nevada, USA

2005 ◽  
Vol 64 (2) ◽  
pp. 257-263 ◽  
Author(s):  
Richard W. Briggs ◽  
Steven G. Wesnousky ◽  
Kenneth D. Adams
Keyword(s):  
Sierra Nevada ◽  
Late Pleistocene ◽  
Late Holocene ◽  
Large Lakes ◽  
Western Basin ◽  
Radiocarbon Dates ◽  
Beach Ridges ◽  
Climate Proxy ◽  
Pyramid Lake ◽  
Proxy Records

AbstractShoreline geomorphology, shoreline stratigraphy, and radiocarbon dates of organic material incorporated in constructional beach ridges record large lakes during the late Pleistocene and late Holocene in the Pyramid Lake subbasin of Lake Lahontan, Nevada, USA. During the late Holocene, a transgression began at or after 3595 ± 35 14C yr B.P. and continued, perhaps in pulses, through 2635 ± 40 14C yr B.P., resulting in a lake as high as 1199 m. During the latest Pleistocene and overlapping with the earliest part of the Younger Dryas interval, a lake stood at approximately 1212 m at 10,820 ± 35 14C yr B.P. and a geomorphically and stratigraphically distinct suite of constructional shorelines associated with this lake can be traced to 1230 m. These two lake highstands correspond to periods of elevated regional wetness in the western Basin and Range that are not clearly represented in existing northern Sierra Nevada climate proxy records.

Postglacial relative sea-level change, Port au Port area, west Newfoundland

1985 ◽  
Vol 22 (7) ◽  
pp. 1039-1047 ◽  
Author(s):  
I. A. Brookes ◽  
D. B. Scott ◽  
J. H. McAndrews
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
High Water ◽  
Relative Sea Level ◽  
Radiocarbon Dates ◽  
Ice Load ◽  
Bay Area ◽  
Port Area ◽  
Minimum Age ◽  
Late Wisconsinan

We first report pollen and foraminifera analyses and radiocarbon dates from two cores taken from salt-marsh deposits bordering Port au Port Bay, southwestern Newfoundland. Results show that relative sea level (RSL) stood at 2.8 m below present higher high-water level (HHWL) at 2770 ± 300 years BP and at −1.8 m at 2365 ± 175 years BP at the core sites. They permit calculation of a rate of late Holocene RSL change from western Newfoundland. We then report other available dates bearing on the earlier RSL record of this area.A date of 5800 ± 200 years BP fixes the age of minimum RSL in Port au Port Bay at 11–14 m below present. A date of 9350 ± 120 years BP from St. George's provides a minimum age for the passage of sea level below present there. A date of 12 600 ± 140 years BP from Stephenville fixes a sea level at 29 m above present, whereas one of 13 600 ± 110 years BP from Abrahams Cove dates the marine limit at 44 m. These geographically restricted data closely constrain a curve of postglacial RSL change in the Port au Port Bay – northern St. George's Bay area. The form of the curve supports a recent model predicting sea-level response to wastage of a limited late Wisconsinan ice load in the wider region.

Spatial and Temporal Variability in Chert Exploitation on Santa Cruz Island, California

2010 ◽  
Vol 75 (1) ◽  
pp. 177-198 ◽  
Author(s):  
Jennifer E. Perry ◽  
Christopher S. Jazwa
Keyword(s):  
Late Holocene ◽  
Channel Islands ◽  
Spatial And Temporal Variability ◽  
Santa Cruz Island ◽  
Santa Cruz ◽  
Shell Middens ◽  
Tool Manufacture ◽  
Radiocarbon Dates ◽  
California Channel Islands ◽  
Northern Channel Islands

Chert outcrops on eastern Santa Cruz Island were of vital importance to the inhabitants of the Santa Barbara Channel region because of their comparatively limited availablity elsewhere on the California Channel Islands. Temporally diagnostic artifacts and radiocarbon dates from associated shell middens suggest that chert quarries were exploited throughout the Holocene. The importance of these quarries has been well documented in regard to microlith production as part of the shell bead industry during the late Holocene. However, relatively little is known about local chert tool manufacture and exchange in earlier times. Systematic documentation of 26 known chert quarries, and sampling at associated shell middens on eastern Santa Cruz Island has resulted in the identification of significant spatial variability in chert exploitation through time. Whereas chert quarrying during the middle Holocene appears to have been opportunistic and dispersed throughout the landscape, comparable activities during the late Holocene became increasingly circumscribed as microlith production was intensified. These trends in chert procurement are interpreted in the context of temporal changes in subsistence, tool manufacture, and residential mobility on the northern Channel Islands, and have broad implications for spatial and temporal patterning in prehistoric lithic exploitation.

Siliceous microfossils and mineral magnetic characteristics in a sediment core from Lake Manitoba, Canada: a remnant of glacial Lake Agassiz

1999 ◽  
Vol 36 (8) ◽  
pp. 1299-1314 ◽  
Author(s):  
Jan Risberg ◽  
Per Sandgren ◽  
James T Teller ◽  
William M Last
Keyword(s):  
Great Plains ◽  
Late Holocene ◽  
Climatic Conditions ◽  
Glacial Lake ◽  
Magnetic Characteristics ◽  
Northern Great Plains ◽  
Silty Clay ◽  
Lake Agassiz ◽  
Radiocarbon Dates ◽  
Glacial Lake Agassiz

A 14.2 m long core was recovered from the southern Lake Manitoba basin. The sediment, consisting mainly of silty clay, was studied for siliceous microfossil content and mineral magnetics; 14 new accelerator mass spectrometry (AMS) radiocarbon dates provide chronological control of the paleoenvironmental history of the basin. The basal 5 m contains ice-rafted clasts and is largely barren of siliceous microfossils; these sediments were deposited when the lake was part of glacial Lake Agassiz. Sediments immediately overlying the barren part of the sequence contain AMS dates of 7700-7400 BP and reflect a dramatic change in conditions in the basin. Diatom abundances rise abruptly. Magnetic characteristics change substantially. The presence of freshwater taxa such as Stephanodiscus niagarae, together with brackish water diatoms, indicate that shallow, turbid, high-nutrient conditions with variable salinity occurred during the early part of the middle Holocene. Although climatic conditions throughout the northern Great Plains are known to have become drier and warmer during the mid-Holocene, there is a distinct change in diatom taxa in the Lake Manitoba sequence toward less saline conditions at this time. The presence of the riverine diatom Aulacoseira granulata in this interval supports previous conclusions that these freshwater conditions resulted from the northward diversion of the Assiniboine River into the basin. Following this, diatoms indicate an abrupt increase in salinity to >1500 mg·L-1 total dissolved solids between 4000 and 2600 BP, reflecting the diversion of the fresh waters of the Assiniboine River away from Lake Manitoba. Increasingly cooler and wetter conditions during the late Holocene, combined with differential isostatic rebound, caused a freshening of the lake during the late Holocene.

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