From source to sink: Glacially eroded, Late Devonian algal “cysts” (Tasmanites) delivered to the Gulf of Mexico during the Last Glacial Maximum

2020 ◽  
Author(s):  
Barry Kohl ◽  
B. Brandon Curry ◽  
Merrell Miller
Keyword(s):  
Gulf Of Mexico ◽  
Last Glacial Maximum ◽  
Lake Michigan ◽  
Clay Fraction ◽  
Black Shales ◽  
Glacial Maximum ◽  
Long Distance ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
Source To Sink

The source of reworked Devonian algal “cysts” in last glacial maximum (LGM) sediment in the Gulf of Mexico is traced to their host black shales, which ring the southwestern Great Lakes. The source-to-sink pathway includes intermediate storage in fine-grained LGM glacial lacustrine sediment and till. The “cysts” are pelagic chlorophyllous algae (Tasmanites and Leiosphaeridia), collectively referred to herein as tasmanitids. Radiocarbon dates of syndepositional Gulf of Mexico foraminifera, derived from accelerator mass spectrometry, bracket the Gulf of Mexico sediment age with common tasmanitids from 28.5 ± 0.6−17.8 ± 0.2 cal kyr B.P. Approximately 1400 km north of the Gulf of Mexico, tasmanitids are abundant in Upper Devonian black shales (New Albany, Antrim, and Ohio Shales) that ring the Michigan, Illinois, and Appalachian intracratonic basins. Tasmanitids were eroded from bedrock and incorporated in glacial sediment dating from ca. 28.0−17.6 cal kyr B.P. by the Lake Michigan, and Huron-Erie lobes of the Laurentide Ice Sheet. The physical characteristics of tasmanitids are ideal for long-distance transport as suspended sediment (density: 1.1−1.3 g/cc, size ranging from 63 µm to 300 µm), and these sand-sized tasmanitids traveled with the silt-clay fraction. Thus, the source-to-sink journey of tasmanitids was initiated by subglacial erosion by water or friction, sequestering in till or glaciolacustrine sediment, re-entrainment and suspension in meltwater, and final delivery in meltwater plumes to the Gulf of Mexico. River routes included the Mississippi, Illinois, Ohio, Wabash, Kaskaskia, and many of their tributaries. Reworked Devonian tasmanitids are a previously unrecognized link between their occurrence in deep-water deposits of the Gulf of Mexico and the late Wisconsin glacial history of the Upper Mississippi Valley. We propose that tracking occurrences of tasmanitid concentrations from the source area to sink, along with adjunct proxies such as clay minerals, will facilitate a more refined analysis of the timing and duration of megafloods. This study also demonstrates that isotopically dead carbon, from reworked Devonian tasmanitid “cysts,” can contaminate radiocarbon dating of LGM bulk sediment samples toward older ages.

Absence of Last Glacial Maximum Records in Lowland Tropical Forests

1998 ◽  
Vol 49 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Marie-Pierre Ledru ◽  
Jacques Bertaux ◽  
Abdelfettah Sifeddine ◽  
Kenitiro Suguio
Keyword(s):  
South America ◽  
Tropical Forests ◽  
Last Glacial Maximum ◽  
Sedimentation Rate ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

Environmental conditions of the lowland tropical forests during the last glacial maximum (LGM) between ca 20,000 and 18,000 14C yr B.P., are reevaluated in terms of dating control and lithology analyzed in seven pollen records from South America. The reevaluation shows that probably in none of the published records are LGM sediments present or abundant. This conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates. These findings suggest that the LGM was represented probably by a hiatus of several thousand years, indicative of drier climates than before or after.

scholarly journals Territoriality and the organization of technology during the Last Glacial Maximum in southwestern Europe

2019 ◽  
Author(s):  
João Cascalheira
Keyword(s):  
Last Glacial Maximum ◽  
Cultural Transmission ◽  
Adaptive Systems ◽  
Glacial Maximum ◽  
Morphological Data ◽  
Long Distance ◽  
Last Glacial ◽  
Southern Iberia ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Climate changes that occurred during the Last Glacial Maximum (LGM) had significant consequences in human eco-dynamics across Europe. Among the most striking impacts are the demographic contraction of modern humans into southern refugia and the potential formation of a population bottleneck. In Iberia and southern France transformations also included the occurrence of significant technological changes, mostly marked by the emergence of a diverse set of bifacially-shaped stone projectiles. The rapid dissemination of bifacial technologies and the geographical circumscription of specific projectile morphologies within these regions have been regarded as evidence for: (1) the existence of a system of long-distance exchange and social alliance networks; (2) the organization of human groups into cultural facies with well-defined stylistic territorial boundaries. However, the degree and modes in which cultural transmission have occurred within these territories, and how it may have influenced other domains of the adaptive systems, remains largely unknown. Using southern Iberia as a case-study, this paper presents the first quantitative approach to the organization of lithic technology and its relationship to hunter-gatherers' territorial organization during the LGM. Similarities and dissimilarities in the presence of metric and morphological data describing lithic technologies are used as a proxy to explore modes and degrees of cultural transmission. Statistical results show that similarities in technological options are dependent on the chronology and geographical distance between sites and corroborate previous arguments for the organization of LGM settlement in Southern Iberia into discrete eco-cultural facies.

The Last Glacial Maximum in northern Baffin Bay

2021 ◽  
Author(s):  
Karen Søby Özdemir ◽  
Henrieka Detlef ◽  
Linda Lambertucci ◽  
Christof Pearce
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Ice Shelf ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Baffin Bay ◽  
Last Glacial ◽  
The Core ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Little is known about climate and ocean conditions during the Last Glacial Maximum in Baffin Bay, Greenland. This is partly due to the dissolution of biogenic carbonates in the central Baffin Bay, preventing reliable <sup>14</sup>C-chronologies. We present the results from a transect of gravity cores retrieved during the 2019 BIOS cruise on the HDMS Lauge Koch in the northern Baffin Bay. Core LK19-ST8-14G has been analyzed for grain size variations, sea-ice biomarkers, XRF, and color spectrophotometry. A preliminary chronology based on radiocarbon dates from foraminifera show that the bottom of the core is approximately 35.000 cal. years BP while the top sediments are of Late Holocene age. The sediment archive thus covers the full extent of the LGM and the last deglaciation. High-resolution photography and CT scans allowed the identification of distinctly different lithofacies in the sediment archive. The lower sections of the core are characterized by laminated mud with no IRD and absence of microfossils indicating a sub ice-shelf environment during the glacial period. The laminated sequence is interrupted by several coarser, detrital-carbonate (DC) rich layers which are interpreted as episodes of glacial retreat or ice-shelf collapse. The youngest of these DC layers immediately precedes the Holocene, which is represented by approximately 40 cm of bioturbated sediments with some IRD. This interpretation is supported by the concentrations of HBIs and sterols throughout the core, which indicate near perennial ice cover in the glacial northern Baffin Bay and more open water conditions during the Holocene.</p>

Sediment record of precipitation and changes in circulation in Bohol Sea area since the Last Glacial Maximum

2020 ◽  
Author(s):  
Sarahmae Buen ◽  
Fernando Siringan ◽  
Ronald Lloren
Keyword(s):  
Sea Level ◽  
Last Glacial Maximum ◽  
Accumulation Rate ◽  
The Philippines ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
Sediment Input ◽  
The Last Glacial Maximum ◽  
The Last Glacial

<p>Deep marine sediments may provide insights of past climate and oceanographic events. Knowledge of the past events can aid in scenario setting of future climate and their oceanographic consequences. A deep sea sediment core from the western side of Bohol Sea, a marginal sea located south of the Philippines, was used to reconstruct precipitation and identify the impacts of sea level rise on the circulation of Bohol Sea.  Five radiocarbon dates from bulk organic matter provide age control spanning back to the Last Glacial Maximum. Sedimentological (lithics and carbonate fractions; bulk density; sedimentation rate and mass accumulation rate) and geochemical (Ti, Al, Zr, Ti/Al and Y/Ni) data were used to reconstruct the sediment input for the area. Sediment input was decreasing from 20-15ka, followed by a relatively stable trend until ~9ka. After ~9ka sediment input increased up until the most recent years. Sedimentation trend follows the average winter (DJF) insolation curve at 10<sup>o</sup>N. This signifies that the sediment input reflects the general changes in precipitation in the area. Lithics and carbonate contents reflect a shift in sediment source that could be attributed to the change in circulation in the basin as the sea level rose to overtop the Surigao Strait located at the northeastern side of the basin. Greater westward transport of suspended material from large rivers to the east would contribute to the sedimentation in the western part of Bohol Sea.</p>

Decadal to millennial-scale solar forcing of Last Glacial Maximum climate in the Estancia Basin of Central New Mexico

2015 ◽  
Vol 83 (3) ◽  
pp. 545-554 ◽  
Author(s):  
Kirsten M. Menking
Keyword(s):  
New Mexico ◽  
Last Glacial Maximum ◽  
Drainage Basin ◽  
Lacustrine Sediments ◽  
Rietveld Analysis ◽  
Glacial Maximum ◽  
X Ray Diffraction ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
Sediment Mineralogy

Lacustrine sediments from the Estancia Basin of central New Mexico reveal decadal to millennial oscillations in the volume of Lake Estancia during Last Glacial Maximum (LGM) time. LGM sediments consist of authigenic carbonates, detrital clastics delivered to the lake in stream flow pulses, and evaporites that precipitated in mudflats exposed during lake lowstands and were subsequently blown into the lake. Variations in sediment mineralogy thus reflect changes in hydrologic balance and were quantified using Rietveld analysis of X-ray diffraction traces. Radiocarbon dates on ostracode valve calcite allowed the construction of mineralogical time series for the interval ~ 23,600 to ~ 18,300 ka, which were subjected to spectral analysis using REDFIT (Schulz and Mudelsee, 2002). Dominant periods of ~ 900, ~ 375, and ~ 265 yr are similar to cycles in Holocene 14C production reported for a variety of tree ring records, suggesting that the Lake Estancia sediments record variations in solar activity during LGM time. A prominent spectral peak with a period of ~ 88 yr appears to reflect the solar Gleissberg cycle and may help, along with the ~ 265 yr cycle, to explain an ongoing mystery about how Lake Estancia was able to undergo abrupt expansions without overflowing its drainage basin.

Episodic deposition of Illinois Valley Peoria silt in association with Lake Michigan Lobe fluctuations during the last glacial maximum

2017 ◽  
Vol 89 (3) ◽  
pp. 739-755 ◽  
Author(s):  
Thomas A. Nash ◽  
Jessica L. Conroy ◽  
David A. Grimley ◽  
William R. Guenthner ◽  
Ben Brandon Curry
Keyword(s):  
Last Glacial Maximum ◽  
Lake Michigan ◽  
Climatic Factors ◽  
The United States ◽  
Glacial Maximum ◽  
Sediment Supply ◽  
Illinois River ◽  
Last Glacial ◽  
Age Model ◽  
Lake Michigan Lobe

AbstractThe chronology and cause of millennial depositional oscillations within last glacial loess of the Central Lowlands of the United States are uncertain. Here, we present a new age model that indicates the Peoria Silt along the Illinois River Valley accumulated episodically from ~28,500 to 16,000 cal yr BP, as the Lake Michigan Lobe margin fluctuated within northeastern Illinois. The age model indicates accelerated loess deposition coincident with regional glacial advances during the local last glacial maximum. A weakly developed paleosol, the Jules Geosol, represents a period of significantly slower deposition, from 23,700 to 22,000 cal yr BP. A gastropod assemblage-based reconstruction of mean July temperature shows temperatures 6–10°C cooler than modern during Peoria Silt deposition. Stable oxygen and carbon isotope values (δ18O and δ13C) of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the Jules Geosol, suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors. However, a decrease in δ18O values occurred between 26,000 and 24,000 cal yr BP, synchronous with the Lake Michigan Lobe’s southernmost advance. This δ18O decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period.

Extent and Timing of the Last Glacial Maximum in Southwestern Alaska

1994 ◽  
Vol 42 (2) ◽  
pp. 136-148 ◽  
Author(s):  
Daniel H. Mann ◽  
Dorothy M. Peteet
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Lower Latitude ◽  
Radiocarbon Dates ◽  
Alaska Peninsula ◽  
Last Glacial ◽  
Kodiak Island ◽  
The Last Glacial Maximum ◽  
The Last Glacial ◽  
Southwestern Alaska

AbstractA glacier complex composed of confluent alpine glaciers, island ice caps, and piedmont lobes covered much of the Alaska Peninsula and Kodiak Island during the last glacial maximum (LGM). Because this glacier complex formed the southeastern border of Beringia, its dynamics may have been important in the timing and feasibility of the northwest coast route for human migration into lower-latitude North America. Radiocarbon dates from stratigraphic sections on Kodiak Island and in the Bristol Bay lowlands bracket the LGM in southwestern Alaska between 23,000 and 14,700 yr B.P. Reconstruction of ice thickness based on glacier trimlines, moraines, and calculations of basal-shear stress depict the Alaska Peninsula Glacier Complex flowing to the outer edge of the continental shelf in the Gulf of Alaska. Equilibrium-line altitudes (ELAs) were 300 to 700 m lower than today and approached sea level on the southwestern Alaska Peninsula. In northeastern areas where ELAs were higher, bedrock topography largely controlled ice flow except where ice saddles bridged straits and inlets.

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