scholarly journals Late Quaternary Environments of the Teton Mountains, Wyoming: A Pollen Record from Green Lake

2018 ◽  
Vol 7 (2) ◽  
pp. 99
Author(s):  
Behnaz Balmaki ◽  
Peter Wigand
Keyword(s):  
Complex Dynamics ◽  
Forest Succession ◽  
Late Quaternary ◽  
Early Holocene ◽  
Pollen Record ◽  
The West ◽  
Middle Holocene ◽  
Mountain Glaciers ◽  
Green Lake ◽  
Plant Assemblages

Late Quaternary forest succession in Wyoming’s Rocky Mountains, occurred in random patterns, because it reflects differences between the Glacial vegetation at lower elevations on the east vs. the west of the Rockies, as well as along the mountain crest to the south. Differential melting of mountain glaciers resulted in differences in the timing of recolonization. Significant variations in the composition of plant assemblages occurred due to delays in species’ arrival, and even in the exclusion of species. Holocene climate variability, especially ongoing global warming, added to the complex dynamics of plant assemblages with warm climate species replacing early Holocene, cooler climate species. The pollen record from Green Lake (located in a glacial cirque on the west side of the Teton Mountains in Teton County, Wyoming) addresses the local vegetation response from just before the fall of Mazama ash to the end of the middle Holocene warm period. Although the earlier portion of the pollen sequence records some of the last adjustments as some plant species were still arriving after de-glaciation, by the time Mazama ash fell it was climate variation that determined most of the dynamics observed in the Green Lake record. The results reveal a sequence of wetter and drier periods based upon the presence of diagnostic tree species.  A moist late early Holocene was followed by a dry middle Holocene, which ended about 6,400 cal. B.P., and was followed between 5,000 to 2,800 cal. B.P. by a sequence of drier and moister climate episodes.

Late Quaternary Lacustrine History and Paleoclimatic Significance of Pluvial Lake Cochise, Southeastern Arizona

1989 ◽  
Vol 32 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Michael R. Waters
Keyword(s):  
Late Quaternary ◽  
American Southwest ◽  
Early Holocene ◽  
Central Portion ◽  
Ancient Lake ◽  
The Holocene ◽  
Middle Holocene ◽  
Ephemeral Lakes ◽  
Independent Evaluation ◽  
Paleoclimatic Significance

AbstractDuring the latest Quaternary, freshwater pluvial lakes intermittently formed in the topographically closed Willcox basin, Arizona. A lacustrine sequence of six separate high stands of Lake Cochise is documented by stratigraphic studies, 19 radiocarbon ages, and supplementary evidence. Two stands of pluvial Lake Cochise, older than 14,000 yr B.P., reached elevations above 1290 m. The prominent 1274-m shoreline of Lake Cochise, which circumscribes the basin, was largely created during a high stand between 13,750 and 13,400 yr B.P. During the Holocene, water filled the Willcox basin three times to an elevation slightly below the crest of the 1274-m shoreline. This occurred once during the early Holocene around or before 8900 yr B.P. and twice during the later part of the middle Holocene. Since the middle Holocene, only shallow ephemeral lakes have occupied the deflated central portion of ancient Lake Cochise, a depression known as the Willcox Playa. The lacustrine sequence of Lake Cochise provides an independent evaluation of late Quaternary paleoclimatic reconstructions for southern Arizona and the American Southwest.

Late Quaternary Inland Dunes of Southern Louisiana and Arid Climate Phases in the Gulf Coast Region

2001 ◽  
Vol 55 (2) ◽  
pp. 150-158 ◽  
Author(s):  
Ervin G. Otvos ◽  
David M. Price
Keyword(s):  
Gulf Coast ◽  
Late Quaternary ◽  
Coastal Region ◽  
Early Holocene ◽  
Arid Climate ◽  
Subtropical Climate ◽  
Mississippi Valley ◽  
Climate Conditions ◽  
Lower Mississippi Valley ◽  
Middle Holocene

AbstractThirty-five sand hills that form six scattered groups rise abruptly from the flat late Pleistocene coastal plain in southeastern Louisiana. New studies confirm their eolian origin. For the first time, several late Wisconsin to early Holocene episodes of arid climate conditions have been recognized and dated in this currently humid warm-temperate subtropical region. Periods of dune formation and reactivation (28,800 to 7900 yr B.P.) were determined by the thermoluminescence method. The onset of the current climate in this Gulf coastal region postdates early Holocene time. The textural and structural homogeneity of the ridge lithosomes, good sorting of their sand fraction, and the dominantly orange hues of the dune sediments contrast with the underlying yellowish–brown to light-brown sandy silts and the well-stratified, occasionally gravelly sands of the underlying alluvial Prairie Formation. Sharply defined, unconformable ridge bases; symmetrical, oval, occasionally parabolic mound shapes; and steep slopes confirm the dune origins. The dominant orientations of ridges and ridge chains clearly reflect paleowind directions. Age comparison with dunes of the lower Mississippi Valley, the northeastern–eastern Gulf of Mexico coast, and south Atlantic coastal areas confirms the existence of at least seasonally dry climate conditions from early Wisconsin to middle Holocene times. The onset of the modern humid-subtropical climate phase in this region thus dates back only to the middle Holocene.

Stratigraphical and Palynological Appraisal of the Late Quaternary Mangrove Deposits of the West Coast of India

2005 ◽  
Vol 64 (3) ◽  
pp. 418-431 ◽  
Author(s):  
K.P.N. Kumaran ◽  
K.M. Nair ◽  
Mahesh Shindikar ◽  
Ruta B. Limaye ◽  
D. Padmalal
Keyword(s):  
Late Holocene ◽  
Asian Summer Monsoon ◽  
Late Quaternary ◽  
The West ◽  
Middle Holocene ◽  
Mangrove Ecosystems ◽  
Drying Up ◽  
Asian Summer ◽  
Organic Deposits

AbstractThe organic deposits derived from the mangrove swamps form reliable stratigraphic markers within the Late Quaternary sequence of Kerala–Konkan Basin. Three generations of such deposits have been identified. The older one is dated to around 43,000–40,000 14C yr B.P., with a few dates beyond the range of radiocarbon. The younger ones date from the Middle Holocene to latest Pleistocene (10,760–4540 14C yr B.P.) and the Late Holocene (<4000 14C yr B.P.). Pollen analyses confirm that the deposits are mostly derived from the mangrove vegetation. Peat accumulation during the period 40,000–28,000 14C yr B.P. can be correlated with the excess rainfall, 40–100% greater than modern values, of the Asian summer monsoon. The low occurrence of mangrove between 22,000 and 18,000 14C yr B.P. can be attributed to the prevailing aridity and/or reduced precipitation associated worldwide with Last Glacial Maximum, because exposure surfaces and ferruginous layers are commonly found in intervals representing this period. The high rainfall of 11,000–4000 14C yr B.P. is found to be the most significant as the mangrove reached an optimum growth around 11,000 14C yr B.P. but with periods of punctuated weaker monsoons. From the present and previous studies, it has been observed that after about 5000 or 4000 14C yr B.P., the monsoons became gradually reduced leading to drying up of many of the marginal marine mangrove ecosystems. A case study of Hadi profile provided an insight to the relevance of magnetic susceptibility (χ) to record the ecological shift in Late Holocene.

scholarly journals New insights from multi-proxy data from the West Antarctic continental rise: Implications for dating and interpreting Late Quaternary palaeoenvironmental records

2021 ◽  
Vol 257 ◽  
pp. 106842
Author(s):  
C.-D. Hillenbrand ◽  
S.J. Crowhurst ◽  
M. Williams ◽  
D.A. Hodell ◽  
I.N. McCave ◽  
...  
Keyword(s):  
Late Quaternary ◽  
The West ◽  
Proxy Data ◽  
Continental Rise ◽  
West Antarctic

Late Pleistocene and Holocene Paleoenvironments of Chalco Lake, Central Mexico

1993 ◽  
Vol 40 (3) ◽  
pp. 332-342 ◽  
Author(s):  
Maria Socorro Lozano-Garcı́a ◽  
Beatriz Ortega-Guerrero ◽  
Margarita Caballero-Miranda ◽  
Jaime Urrutia-Fucugauchi
Keyword(s):  
Volcanic Activity ◽  
Lake Level ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Cold Climate ◽  
Central Mexico ◽  
Pollen Record ◽  
Loss On Ignition ◽  
Southeastern Part ◽  
Saline Marsh

AbstractIn order to establish paleoenvironmental conditions during the late Quaternary, four cores from the Basin of Mexico (central Mexico) were drilled in Chalco Lake, located in the southeastern part of the basin. The upper 8 m of two parallel cores were studied, using paleomagnetic, loss-on-ignition, pollen, and diatom analyses. Based on 11 14C ages, the analyzed record spans the last 19,000 14C yr B.P. Volcanic activity has affected microfossil abundances, both directly and indirectly, resulting in absence or reduction of pollen and diatom assemblages. Important volcanic activity took place between 19,000 and 15,000 yr B.P. when the lake was a shallow alkaline marsh and an increase of grassland pollen suggests a dry, cold climate. During this interval, abrupt environmental changes with increasing moisture occurred. From 15,000 until 12,500 yr B.P. the lake level increased and the pollen indicates wetter conditions. The highest lake level is registered from 12,500 to ca. 9000 yr B.P. The end of the Pleistocene is characterized by an increase in humidity. From 9000 until ca. 3000 yr B.P. Chalco Lake was a saline marsh and the pollen record indicates warmer conditions. After 3000 yr B.P. the lake level increased and human disturbance dominates the lacustrine record.

scholarly journals Modeling oscillations in connected glacial lakes

2019 ◽  
Vol 65 (253) ◽  
pp. 745-758 ◽  
Author(s):  
Aaron G. Stubblefield ◽  
Timothy T. Creyts ◽  
Jonathan Kingslake ◽  
Marc Spiegelman
Keyword(s):  
Complex Dynamics ◽  
Equation Model ◽  
Qualitative Behavior ◽  
Glacial Lakes ◽  
West Antarctica ◽  
Ice Streams ◽  
Mountain Glaciers ◽  
Lake Model ◽  
Dependent Model ◽  
Subglacial Lakes

AbstractMountain glaciers and ice sheets often host marginal and subglacial lakes that are hydraulically connected through subglacial drainage systems. These lakes exhibit complex dynamics that have been the subject of models for decades. Here we introduce and analyze a model for the evolution of glacial lakes connected by subglacial channels. Subglacial channel equations are supplied with effective pressure boundary conditions that are determined by a simple lake model. While the model can describe an arbitrary number of lakes, we solve it numerically with a finite element method for the case of two connected lakes. We examine the effect of relative lake size and spacing on the oscillations. Complex oscillations in the downstream lake are driven by discharge out of the upstream lake. These include multi-peaked and anti-phase filling–draining events. Similar filling–draining cycles have been observed on the Kennicott Glacier in Alaska and at the confluence of the Whillans and Mercer ice streams in West Antarctica. We further construct a simplified ordinary differential equation model that displays the same qualitative behavior as the full, spatially-dependent model. We analyze this model using dynamical systems theory to explain the appearance of filling–draining cycles as the meltwater supply varies.

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