scholarly journals Late Pliocene to early Pleistocene climate dynamics in western North America based on a new pollen record from paleo-Lake Idaho

2021 ◽  
Author(s):  
Frederik J. Allstädt ◽  
Andreas Koutsodendris ◽  
Erwin Appel ◽  
Wolfgang Rösler ◽  
Tammo Reichgelt ◽  
...  
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Ocean Circulation ◽  
Early Pleistocene ◽  
Pollen Record ◽  
Late Pliocene ◽  
Pleistocene Climate ◽  
Late Neogene ◽  
Study Interval ◽  
Northwestern North America

AbstractMarked by the expansion of ice sheets in the high latitudes, the intensification of Northern Hemisphere glaciation across the Plio/Pleistocene transition at ~ 2.7 Ma represents a critical interval of late Neogene climate evolution. To date, the characteristics of climate change in North America during that time and its imprint on vegetation has remained poorly constrained because of the lack of continuous, highly resolved terrestrial records. We here assess the vegetation dynamics in northwestern North America during the late Pliocene and early Pleistocene (c. 2.8–2.4 Ma) based on a pollen record from a lacustrine sequence from paleo-Lake Idaho, western Snake River Plain (USA) that has been retrieved within the framework of an International Continental Drilling Program (ICDP) coring campaign. Our data indicate a sensitive response of forest ecosystems to glacial/interglacial variability paced by orbital obliquity across the study interval, and also highlight a distinct expansion of steppic elements that likely occurs during the first strong glacial of the Pleistocene, i.e. Marine Isotope Stage 100. The pollen data document a major forest biome change at ~ 2.6 Ma that is marked by the replacement of conifer-dominated forests by open mixed forests. Quantitative pollen-based climate estimates suggest that this forest reorganisation was associated with an increase in precipitation from the late Pliocene to the early Pleistocene. We attribute this shift to an enhanced moisture transport from the subarctic Pacific Ocean to North America, confirming the hypothesis that ocean-circulation changes were instrumental in the intensification of Northern Hemisphere glaciation.

Reconstruction of environmental and climatic change during the late Pliocene and early Pleistocene in northwestern North America based on a new drill core from paleo-Lake Idaho

2020 ◽  
Author(s):  
Frederik Allstädt ◽  
Andreas Koutsodendris ◽  
Erwin Appel ◽  
Wolfgang Rösler ◽  
Alexander Prokopenko ◽  
...  
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Moisture Transport ◽  
Snake River Plain ◽  
Early Pleistocene ◽  
Snake River ◽  
Depth Interval ◽  
Late Pliocene ◽  
River Plain ◽  
Northwestern North America

<p>The Pliocene to early Pleistocene yields a close analogy to near-future climate, with atmospheric <em>p</em>CO<sub>2</sub> between pre-industrial and anthropogenically perturbed levels as they may be reached in few decades. A sedimentary archive that is well suited to study Plio-Pleistocene climate dynamics in the terrestrial realm has recently become available through the ICDP-sponsored HOTSPOT project on the evolution of the Snake River Plain (Idaho, USA). At the Mountain Home site, HOTSPOT drilling has yielded the MHAFB11 core that comprises 635 m of fine-grained lacustrine sediments (Shervais et al. 2013). Based on the yet available paleomagnetic age control, these sediments span from the late Pliocene to the early Pleistocene, which makes them the first archive in continental North America that covers this time interval at one site. Based on their geographic position, the sediments from paleo-Lake Idaho can contribute to a better understanding of climate variability across the Plio-Pleistocene transition in western North America, notably with respect to the hypothesis that enhanced moisture transport into the higher latitudes of North America from ~2.7 Ma onwards allowed the initiation of Northern Hemisphere glaciation (Haug et al., 2005).</p><p>To gain insight into the paleoclimatic evolution of northwestern North America during the late Pliocene to early Pleistocene, we have palynologically analyzed 131 samples from the 732–439 m depth interval (corresponding to an age of ~2.8 to ~2 Ma) of the MHAFB11 core. The obtained palynological dataset, which has a mean temporal resolution of ~7 ka, documents that a <em>Pinus</em>-dominated coniferous forest biome prevailed in the catchment area of paleo-Lake Idaho throughout the study interval. However, percentages of pollen from conifer taxa decrease in the latest Pliocene before reaching consistently lower values in the early Pleistocene at ~2.4 Ma. In contrast, pollen taxa representing an open vegetation (e.g., <em>Artemisia</em>, Asteraceae) and deciduous trees (e.g., <em>Quercus</em>, <em>Betula</em> and <em>Alnus</em>) become increasingly abundant in the early Pleistocene (at ~2.4 Ma). We interpret this vegetation shift to an open mixed conifer/deciduous forest to be caused by wetter climate conditions. This interpretation is supported by quantitative climate estimates, which show a gradual increase in mean annual precipitation in the early Pleistocene. This trend towards wetter conditions supports the notion that enhanced moisture transport to northern North America from the subarctic Pacific Ocean contributed to the onset of Northern Hemisphere glaciation at ~2.7 Ma (Haug et al., 2005).</p><p> </p><p>References:</p><p>Haug, G.H., Ganopolski, A., Sigman, D.M., Rosell-Mele, A., Swann, G.E., Tiedemann, R., Jaccard, S.L., Bollmann, J., Maslin, M.A., Leng, M.J. and Eglinton, G., 2005. North Pacific seasonality and the glaciation of North America 2.7 million years ago. <em>Nature</em>, 433, 821-825.</p><p>Shervais, J.W., Schmitt, D.R., Nielson, D., Evans, J.P., Christiansen, E.H., Morgan, L.A., Shanks, P. W.C., Prokopenko, A.A., Lachmar, T., Liberty, L.M., Blackwell, D.D., Glen, J.M., Champion, D., Potter, K.E., Kessler, J., 2013. First Results from HOTSPOT: The Snake River Plain Scientific Drilling Project, Idaho, U.S.A. <em>Scientific</em> <em>Drilling,</em> 3, 36-45.</p><p> </p>

scholarly journals Late Pliocene Cordilleran Ice Sheet development with warm northeast Pacific sea surface temperatures

2020 ◽  
Vol 16 (1) ◽  
pp. 299-313 ◽  
Author(s):  
Maria Luisa Sánchez-Montes ◽  
Erin L. McClymont ◽  
Jeremy M. Lloyd ◽  
Juliane Müller ◽  
Ellen A. Cowan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Gulf Of Alaska ◽  
Sea Surface ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Subarctic Pacific ◽  
Cordilleran Ice Sheet ◽  
Forcing Mechanisms ◽  
Atmospheric Co2 Concentrations

Abstract. The initiation and evolution of the Cordilleran Ice Sheet are relatively poorly constrained. International Ocean Discovery Program (IODP) Expedition 341 recovered marine sediments at Site U1417 in the Gulf of Alaska (GOA). Here we present alkenone-derived sea surface temperature (SST) analyses alongside ice-rafted debris (IRD), terrigenous, and marine organic matter inputs to the GOA through the late Pliocene and early Pleistocene. The first IRD contribution from tidewater glaciers in southwest Alaska is recorded at 2.9 Ma, indicating that the Cordilleran Ice Sheet extent increased in the late Pliocene. A higher occurrence of IRD and higher sedimentation rates in the GOA during the early Pleistocene, at 2.5 Ma, occur in synchrony with SSTs warming on the order of 1 ∘C relative to the Pliocene. All records show a high degree of variability in the early Pleistocene, indicating highly efficient ocean–climate–ice interactions through warm SST–ocean evaporation–orographic precipitation–ice growth mechanisms. A climatic shift towards ocean circulation in the subarctic Pacific similar to the pattern observed during negative Pacific Decadal Oscillation (PDO) conditions today occurs with the development of more extensive Cordilleran glaciation and may have played a role through increased moisture supply to the subarctic Pacific. The drop in atmospheric CO2 concentrations since 2.8 Ma is suggested as one of the main forcing mechanisms driving the Cordilleran glaciation.

scholarly journals Late Neogene Radiolaria from the East Coast Deformed Belt, New Zealand

2021 ◽  
Author(s):  
◽  
Jeffrey Noel Ashby
Keyword(s):  
New Zealand ◽  
Southern Ocean ◽  
Ocean Circulation ◽  
Deep Water ◽  
East Coast ◽  
Sedimentary Basins ◽  
Early Pleistocene ◽  
Time Segment ◽  
Shelf Slope ◽  
Late Neogene

<p>Within the East Coast Deformed Belt there are a number of Late Neogene sedimentary basins with relatively deep-water sediments which, at places, contain abundant radiolarian skeletons. The region was subject to relatively open ocean circulation patterns during the Neogene which, combined with the input of rhyolitic glass shards, has enhanced the siliceous microfossil preservation. A short review of the silica budget is presented and discussed in relation to the preservation of siliceous microfossils in the New Zealand sequences. Techniques were developed to extract and quantitatively study fossil Radiolaria from some of the relatively barren shelf/slope sediments. One hundred and thirty-eight radiolarian taxa are described, most of which can be assigned at the generic level, but thirty-one of which can not be assigned specific names and may eventually prove to be new species. The radiolarian zonation presented is based on detailed analysis of 155 samples from 26 sections and sites ranging in age from basal Tongaporutuan (early Late Miocene) to middle Nukumaruan (early Pleistocene). Sediments of the Kapitean (uppermost Miocene) were generally deposited in shallow water environments or are missing in unconformities in the East Coast Deformed Belt, consequently the radiolarian zonation is based on very poor data in this time segment. Also upper Opoitian and Waipipian (middle Pliocene) sediments, although at places deposited in relatively deep water, generally lack siliceous tuffs, and radiolarian preservation is poor. Five major radiolarian zones can be recognised: Diartus hughesi Zone, Didymocyrtis sp. A Zone, Didymocyrtis sp. A Zone, Didymocyrtis tetrathalmus tetrathalmus Zone, Lamprocyrtis heteroporos Zone, and Lamprocyclas gamphonycha Zone. In samples with good radiolarian preservation six subzones can be identified. The Diartus hughesi Zone can be divided into the Heliodiscus umbonatum Subzone, Didymocyrtis laticonus Subzone, Heliodiscus asteriscus forma large pores Subzone, and Anthocyrtidium ehrenbergi pliocenica Subzone. Additionally the Didymocyrtis tetrathalmus tetrathalmus Zone can be divided into the Lychnocanium sp. aff. grande Subzone and Lamprocyrtis hannai Subzone. The bioevents that define the zonal boundaries are discussed along with other biostratigraphically useful radiolarian datums. These zones and zubzones are correlated to the foraminiferal zonation which in turn has been related, in part, to the paleomagnetic time scale. Correlation are then made with other radiolarian zonations in the north Pacific, tropics, and southern ocean. Points to emerge from these correlations include the apparent provincialism in the transition from Stichocorys delmontense to Stichocorys peregrine in the tropical Pacific. This transition has been reported to occur during approximately 1.5Ma but in New Zealand occurs over a time segment of at least 5.5Ma. The first appearance of Lamprocyclas gamphonycha appears to be an isochronous datum level in temperate radiolarian faunas of the northern and southern Pacific. The last appearance datum of Diartus hughesi at about 7.5Ma is in good agreement with its level in the tropics. The presence of this taxon in lower Gilbert Antarctic cores suggests either a grossly diachronous event between tropical/temperate areas and the southern ocean or, more probably, a misinterpretation of the paleomagnetic signature from key southern ocean piston cores. If the latter situation is the case then the real age estimates on the "Pre middle Gilbert" southern ocean diatom and silicoflagellate stratigraphies are questionable because they are based on the same key cores. Statistical faunal analysis shows that during the Miocene there was not much change in the radiolarian faunas with time and a major change, probably climatically controlled, took place across the Miocene/Pliocene boundary. Variability in preservation has probably affected the faunas to obscure more precise time variation although post-Miocene faunas indicate that some is present. In conclusion, the Radiolaria, although not as common in the fossil record as the foraminifera, definitely contribute to New Zealand Late Neogene integrated stratigraphy and suggest that our knowledge could be greatly enhanced by the study of other siliceous microfossil groups.</p>

Long Plio-Pleistocene Terrestrial Record of Climate Change and Mammal Turnover in Southern Spain

2001 ◽  
Vol 56 (3) ◽  
pp. 411-418 ◽  
Author(s):  
Jordi Agustı́ ◽  
Oriol Oms ◽  
Eduard Remacha
Keyword(s):  
Climate Change ◽  
Northern Hemisphere ◽  
Western Europe ◽  
Southern Spain ◽  
Early Pleistocene ◽  
Dry Period ◽  
Late Pliocene ◽  
Southeastern Spain ◽  
The Mediterranean

AbstractCyclostratigraphic analysis of the Pliocene Zújar section (Guadix-Baza Basin, southeastern Spain) has enabled the recognition of a number of climatically forced cycles reflecting alternating dry and wet periods. Peaks of aridity are recorded at ca. 3.95, 3.55, 3.2, 2.8, and 1.8 myr B.P. The first dry period at about 4.0 myr B.P. corresponds to the early Ruscinian Mammal age, while the second arid interval at about 3.6 myr B.P. corresponds to the establishment of the Mediterranean double seasonality. The significant mammal turnover between the late Ruscinian and early Villanyian stages is placed between chron 2An.2n and the very base of chron 2An.1n, coincident with the dry phase recognized at about 3.2 myr B.P. The fourth aridity maximum at 2.8 myr B.P. roughly coincides with the Equus event in western Europe and is probably related to the beginning of the glacial–interglacial dynamics in the Northern Hemisphere. Finally, the last dry peak at about 1.8 myr B.P. is probably related to the set of mammalian events characterizing the transition from the late Pliocene faunas to those of the early Pleistocene.

scholarly journals Late Pliocene and early Pleistocene environments of the north-eastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

2013 ◽  
Vol 9 (4) ◽  
pp. 4599-4653 ◽  
Author(s):  
A. A. Andreev ◽  
P. E. Tarasov ◽  
V. Wennrich ◽  
E. Raschke ◽  
U. Herzschuh ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Lacustrine Sediments ◽  
Early Pleistocene ◽  
Pollen Record ◽  
Russian Arctic ◽  
Coprophilous Fungi ◽  
Climate Conditions ◽  
Late Pliocene ◽  
The North ◽  
Lake El’Gygytgyn

Abstract. The 318 m thick lacustrine sediment record in Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities allowing the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments show their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.50–3.35 Myr BP the vegetation at Lake El'gygytgyn, in nowadays tundra area, was dominated by spruce-larch-fir-hemlock forests. After ca. 3.4 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental changes took place at ca. 3.305–3.275 Myr BP, corresponding with the Marine Isotope Stage (MIS) M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated in the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.04–3.02, 2.93–2.91, and 2.725–2.695 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Revealed peaks in green algae colonies (Botryococcus) around 2.53, 2.45, 2.320–2.305 and 2.175–2.150 Myr BP suggest a spread of shallow water environments. Few intervals (i.e. 2.55–2.53, ca. 2.37, and 2.35–2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively short-term climate ameliorations.

scholarly journals Dating North Pacific Abyssal Sediments by Geomagnetic Paleointensity: Implications of Magnetization Carriers, Plio-Pleistocene Climate Change, and Benthic Redox Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Wanzhang Wang ◽  
Tilo von Dobeneck ◽  
Thomas Frederichs ◽  
Yang Zhang ◽  
Lester Lembke-Jene ◽  
...  
Keyword(s):  
North Pacific ◽  
Sediment Cores ◽  
Coarse Grained ◽  
Early Pleistocene ◽  
Stratigraphic Correlation ◽  
Major Step ◽  
Late Pliocene ◽  
The North ◽  
Magnetic Carriers ◽  
Pleistocene Climate

Non-carbonaceous abyssal fine-grained sediments cover vast parts of the North Pacific’s deep oceanic basins and gain increasing interests as glacial carbon traps. They are, however, difficult to date at an orbital-scale temporal resolution and still rarely used for paleoceanographic reconstructions. Here, we show that sedimentary records of past geomagnetic field intensity have high potential to improve reversal-based magnetostratigraphic age models. Five sediment cores from Central North Pacific mid-latitudes (39–47°N) and abyssal water depths ranging from 3,900 to 6,100 m were cube-sampled at 23 mm resolution and analyzed by automated standard paleo- and rock magnetic methods, XRF scanning, and electron microscopy. Relative Paleointensity (RPI) records were determined by comparing natural vs. anhysteretic remanent magnetization losses during alternating field demagnetization using a slope method within optimized coercivity windows. The paleomagnetic record delivered well interpretable geomagnetic reversal sequences back to 3 Ma. This age span covers the climate-induced transition from a biogenic magnetite prevalence in the Late Pliocene and Early Pleistocene to a dust-dominated detrital magnetic mineral assemblage since the Mid-Pleistocene. Volcaniclastic materials from concurrent eruptions and gravitational or contouritic sediment re-deposition along extinct seamount flanks provide a further important source of fine- to coarse-grained magnetic carriers. Surprisingly, higher proportions of biogenic vs. detrital magnetite in the late Pliocene correlate with systematically lowered RPI values, which seems to be a consequence of magnetofossil oxidation rather than reductive depletion. Our abyssal RPI records match the astronomically tuned stack of the mostly bathyal Pacific RPI records. While a stratigraphic correlation of rock magnetic and element ratio logs with standard oxygen isotope records was sporadically possible, the RPI minima allowed to establish further stratigraphic tie points at ∼50 kyr intervals. Thus, this RPI-enhanced magnetostratigraphy appears to be a major step forward to reliably date unaltered abyssal North Pacific sediments close to orbital-scale resolution.

scholarly journals Thermocline state change in the Eastern Equatorial Pacific during the late Pliocene/early Pleistocene intensification of Northern Hemisphere Glaciation

2017 ◽  
Author(s):  
Kim A. Jakob ◽  
Jörg Pross ◽  
Christian Scholz ◽  
Jens Fiebig ◽  
Oliver Friedrich
Keyword(s):  
Northern Hemisphere ◽  
Equatorial Pacific ◽  
Early Pleistocene ◽  
Trade Wind ◽  
Thermocline Depth ◽  
State Change ◽  
Final Phase ◽  
Late Pliocene ◽  
Eastern Equatorial Pacific ◽  
Earth’S Climate

Abstract. The late Pliocene/early Pleistocene intensification of Northern Hemisphere Glaciation (iNHG) ~ 2.5 million years ago (Marine Isotope Stages [MIS] 100–96) stands out as the most recent major tipping point in Earth's climate history. It strongly influenced oceanographic and climatic patterns including trade-wind and upwelling strength in the Eastern Equatorial Pacific (EEP). The thermocline depth in the EEP, in turn, plays a pivotal role in the evolution of short-term climate phenomena such the El Niño-Southern Oscillation, and thus bears important consequences for the Earth's climate system. However, thermocline dynamics in the EEP during to the iNHG have yet remained unclear. While numerous studies have suggested a link between a thermocline shoaling in the EEP and Northern Hemisphere ice growth, other studies have indicated a stable thermocline depth during iNHG, thereby excluding a causal relationship between thermocline dynamics and ice-sheet growth. In light of these contradictory views, we have generated geochemical (planktic foraminiferal δ18O, δ13C and Mg/Ca), sedimentological (sand-accumulation rates) and faunal (abundance data of thermocline-dwelling foraminifera) records for Ocean Drilling Program Site 849 located in the central part of the EEP. Our records span the interval from ~ 2.75 to 2.4 Ma (MIS G7–95), which is critical for understanding thermocline dynamics during the final phase of the iNHG. They document a thermocline shoaling from ~ 2.64 to 2.55 Ma (MIS G2–101) and a relatively shallow thermocline from ~ 2.55 Ma onwards (MIS 101–95). This indicates a state change in EEP thermocline depth shortly before the final phase of iNHG. Ultimately, our data support the hypothesis that (sub-)tropical thermocline shoaling may have contributed to the development of large Northern Hemisphere ice sheets.

scholarly journals Evidence for early glaciation of southeastern Beringia

2020 ◽  
Vol 57 (2) ◽  
pp. 199-226
Author(s):  
Rodney Arthur Savidge
Keyword(s):  
North America ◽  
Ice Sheet ◽  
Extended Period ◽  
Pleistocene Glaciations ◽  
Late Pliocene ◽  
Ice Caps ◽  
Northwestern North America ◽  
Working Hypotheses ◽  
Minimal Research ◽  
Red Bed

Between the Klondike Plateau and Yukon–Tanana highlands of Yukon and Alaska, respectively, current maps explain glaciated alpine locales and periglacial areas in terms of localized Pliocene–Pleistocene montane ice caps, alpine glaciers, and periglacial changes. However, this region’s plateau topography is populated with long undulating ridges having wide flattened tops; it contrasts with relief of other regions of northwestern North America also affected by ice caps, cryoplanation, and erosion over similar duration during the same epochs. This region has received minimal research and appears to present a new opportunity for resolving outstanding glaciological and stratigraphy issues. The glaciological history is reviewed, placing particular emphasis upon the low-elevation ridges within the “unglaciated” region, suggesting that those ridges are relict arête/cirque remnants. Sites of subalpine glacial grooving and mountaintop planing are also identified, and a conglomeratic red bed containing erratic clasts is described. All indications point to the “unglaciated” region having been glaciated before late Pliocene. Two working hypotheses are proposed: (1) The landscape once supported a range of young mountains that became glaciated then overridden and pared to a plateau by an ice sheet. (2) Following deglaciation, an extended period of paraglacial activity removed most of the former drift and excised new valleys to give the region an unglaciated appearance, which thereafter became modified into its present state by local montane/alpine glaciations, interglacial cryoplanation, periglacial gelifraction, and erosion. In addition to Pliocene–Pleistocene glaciations, a northeastward advancing Miocene ice sheet seems plausible and, on the basis of paleographic considerations and lithology, a Cretaceous glaciation evidently is also not out of the question.

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