Late Quaternary Vegetation and Climate Changes in Central Texas Based on the Isotopic Composition of Organic Carbon

1994 ◽  
Vol 41 (1) ◽  
pp. 109-120 ◽  
Author(s):  
Lee C. Nordt ◽  
Thomas W. Boutton ◽  
Charles T. Hallmark ◽  
Michael R. Waters
Keyword(s):  
Organic Carbon ◽  
Late Pleistocene ◽  
Plant Biomass ◽  
Late Quaternary ◽  
Stable Carbon Isotope ◽  
Climatic Conditions ◽  
Significant Shift ◽  
Alluvial Deposits ◽  
The Past ◽  
Central Texas

AbstractStable carbon isotope analysis of organic carbon in alluvial deposits and soils of three streams in central Texas reveals significant shifts in the ratio of C3 to C4 plant biomass production during the past 15,000 yr. These temporal changes in vegetation appear to be in response to changes in climate. During the late Pleistocene, C4 plants comprised only about 45 to 50% of the vegetative biomass in this area, suggesting that conditions were cooler and wetter than at any time during the past 15,000 yr. The time between 11,000 and 8000 yr B.P. is interpreted as transitional between late Pleistocene conditions and warmer and drier Holocene conditions based on a slight increase in the abundance of C4 plant biomass. During the middle Holocene, between approximately 6000 and 5000 yr B.P., mixed C3/C4 plant communities were replaced almost completely by C4-dominated communities, indicating prairie expansion and warmer and drier climatic conditions. By 4000 yr B.P., the abundance of C4 plant biomass decreased to levels similar to the early Holocene transitional period, suggesting a return to cooler and wetter climatic conditions. No significant shift in the ratio of C3 to C4 productivity has occurred during the last 4000 yr, except for a slight increase in the abundance of C4 plant biomass around 2000 yr B.P. The results of this investigation correlate well with other regional late Quaternary climatic interpretations for central and north Texas, the Southern Plains region, and with other portions of the Great Plains.

Paleoclimatic Reconstruction in Northern Oman Based on Carbonates from Hyperalkaline Groundwaters

1990 ◽  
Vol 33 (3) ◽  
pp. 320-336 ◽  
Author(s):  
Ian D. Clark ◽  
Jean-Charles Fontes
Keyword(s):  
Late Pleistocene ◽  
Radiocarbon Dating ◽  
Arabian Sea ◽  
Flow System ◽  
Climatic Conditions ◽  
Current Phase ◽  
Groundwater Flow System ◽  
Paleoclimatic Reconstruction ◽  
The Past ◽  
Lacustrine Deposits

AbstractA paleoclimatic reconstruction for the past 35,000 years for northern Oman is based on an unusual approach using travertines and fracture calcites associated with hyperalkaline springs. High-pH groundwaters (pH up to 11.9) discharge from the mantle sequence of the Oman Ophiolite as the product of modern, low-temperature serpentinization. Under arid climatic conditions, hyperalkaline discharge occurs at the surface. Uptake of atmospheric CO2precipitates characteristic laminated travertines, accompanied by strong kinetic depletion of13C and18O. Pluvial climates supporting a shallow bicarbonate-groundwater flow system and vegetation are recorded by fracture calcites with equilibrium stable isotope contents and calcite-replaced roots and stems. All such carbonates have modern initial14C contents, allowing radiocarbon dating and paleoclimatic reconstruction for the late Pleistocene and Holocene. Our reconstruction shows a dominantly wet late Pleistocene up to 19,000 yr B.P., when a phase of climatic deterioration began, leading to a period of hyperaridity which dominated from ca. 16,300 to 13,000 yr B.P. The early Holocene pluvial occurred from 12,500 to ca. 6500 yr B.P. and was followed by renewed climatic deterioration and the current phase of hyperaridity. Comparison of this paleoclimatic reconstruction with that for lacustrine deposits from the A'Rub al Khali of central Saudi Arabia and the summer insolation-driven monsoon record of east Africa and the Arabian Sea is remarkably good.

Expansion of Magellanic Moorland during the Late Pleistocene: Palynological Evidence from Northern Isla de Chiloé, Chile

1988 ◽  
Vol 30 (3) ◽  
pp. 304-314 ◽  
Author(s):  
Carolina Villagrán
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Marked Change ◽  
Climatic Conditions ◽  
Annual Precipitation ◽  
Palynological Analysis ◽  
Wetland Development ◽  
Average Temperature ◽  
Rio Negro

The late Quaternary vegetation of northern Isla de Chiloé is inferred from palynological analysis of a section in the Río Negro drainage (42°03′S, 73°50′W). At ca. 30,500 yr B.P., maxima of Astelia and Donatia occurred, suggesting wetland development. From that time until ca. 27,000 yr B.P., steppe indicators such as Compositae/Gramineae dominated, suggesting drier conditions. After 27,000 yr B.P., the moorland shrub Dacrydium gradually increased, reaching a maximum by 18,000 yr B.P. At this time Astelia increased again, suggesting development of cushion bog during cold and wet conditions. The glacial-postglacial transition is characterized by a marked change from peaty sediments to clays, a decrease in the cushion bog flora, and the prevalence of Gramineae/ Compositae and swamp taxa. This vegetation prevailed until ca.7000 yr B.P. when forest taxa became dominant. The floristic pattern inferred from the pollen spectra of the Rio Negro section suggests that the late Pleistocene vegetation of Chiloé resembled modern Magellanic Moorland vegetation (52°–56°lat S). Based on climatic conditions presently associated with Magellanic Moorland, its occurrence in Chiloé at low elevations during the late Pleistocene implies a decrease in average temperature of at least 4°C and an increase in annual precipitation of at least 1500 mm.

Late Quaternary Climate and Vegetation of the Sudanian Zone of Northeast Nigeria

2002 ◽  
Vol 58 (1) ◽  
pp. 73-83 ◽  
Author(s):  
Ulrich Salzmann ◽  
Philipp Hoelzmann ◽  
Irena Morczinek
Keyword(s):  
Environmental History ◽  
Late Pleistocene ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Lake Levels ◽  
The Holocene ◽  
Quaternary Climate ◽  
History Of ◽  
Sudanian Zone ◽  
Humid Period

AbstractThe Lake Tilla crater lake in northeastern Nigeria (10°23′N, 12°08′E) provides a ca. 17,000 14C yr multiproxy record of the environmental history of a Sudanian savanna in West Africa. Evaluation of pollen, diatoms, and sedimentary geochemistry from cores suggests that dry climatic conditions prevailed throughout the late Pleistocene. Before the onset of the Holocene, the slow rise in lake levels was interrupted by a distinct dry event between ca. 10,900 and 10,500 14C yr B.P., which may coincide with the Younger Dryas episode. The onset of the Holocene is marked by an abrupt increase in lake levels and a subsequent spread of Guinean and Sudanian tree taxa into the open grass savanna that predominated throughout the Late Pleistocene. The dominance of the mountain olive Olea hochstetteri suggests cool climatic conditions prior to ca. 8600 14C yr B.P. The early to mid-Holocene humid period culminated between ca. 8500 and 7000 14C yr B.P. with the establishment of a dense Guinean savanna during high lake levels. Frequent fires were important in promoting the open character of the vegetation. The palynological and palaeolimnological data demonstrate that the humid period terminated after ca. 7000 14C yr B.P. in a gradual decline of the precipitation/evaporation ratio and was not interrupted by abrupt climatic events. The aridification trend intensified after ca. 3800 14C yr B.P. and continued until the present.

Measuring Late Quaternary Ursid Diminution in the Midwest

1998 ◽  
Vol 49 (3) ◽  
pp. 322-329 ◽  
Author(s):  
Steve Wolverton ◽  
R.Lee Lyman
Keyword(s):  
Late Pleistocene ◽  
North American ◽  
Ursus Americanus ◽  
Late Quaternary ◽  
Black Bears ◽  
American Midwest ◽  
The Past ◽  
American Black ◽  
American Black Bears ◽  
Average Size

Paleobiologists generally agree that within the past 10,000 yr North American black bears (Ursus americanus) have decreased in body and tooth size. Some researchers infer that diminution was gradual and continuous; thus, one might infer that a specimen is old if it is larger than an average-size modern bear. Ursid remains recovered in the 1950s from Lawson Cave, Missouri, that are larger than some modern bears have been reported to date to the late Pleistocene, but association with modern taxa, taphonomic considerations, and a radiocarbon date of 200 yr B.P. indicate that they are modern. Modern specimens from Lawson Cave and other parts of the American Midwest are relatively large compared to modern North American black bears from other areas, suggesting that many supposed late Pleistocene bears from the area might be modern also.

scholarly journals Climatic variations during the Holocene inferred from radiocarbon and stable carbon isotopes in a high-alpine cave

2021 ◽  
Author(s):  
Caroline Welte ◽  
Jens Fohlmeister ◽  
Melina Wertnik ◽  
Lukas Wacker ◽  
Bodo Hattendorf ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotopes ◽  
Stable Carbon Isotope ◽  
Climatic Conditions ◽  
Stable Carbon ◽  
Novel Technique ◽  
Climatic Variations ◽  
Spatially Resolved ◽  
Exchange Processes ◽  
Carbon Reservoir

<div> <p>Laser ablation coupled online to accelerator mass spectrometry [1] allows analyzing the radiocarbon (<sup>14</sup>C) concentration in carbonate samples in a fast and spatially resolved manner. This novel technique can provide <sup>14</sup>C data at a spatial resolution comparable to that of stable carbon isotope measurements and, thus, can help to interpret δ<sup>13</sup>C signatures. In this work, we analyzed δ<sup>13</sup>C and <sup>14</sup>C of a Holocene stalagmite from the high-alpine Spannagel Cave (Austria). Combined δ<sup>13</sup>C and <sup>14</sup>C profiles allow identifying three growth periods : (i) the period > 8 ka BP exhibits relatively low δ<sup>13</sup>C values with small variability combined with a comparably high dead carbon fraction (dcf) of around 60%. This points towards C contributions of an old organic carbon reservoir in the karst potentially mobilized due to the warm climatic conditions of the early Holocene. (ii) Between 3.8 and 8 ka BP, a strong variability in δ<sup>13</sup>C with values from -8 to +1‰ and a generally lower dcf was observed. The δ<sup>13</sup>C variability was most likely caused by changes in gas exchange processes in the cave, which are induced by reduced drip rates as derived from lower stalagmite growth rates. Additionally, the lower dcf indicates that the OM reservoir contributed less to stalagmite growth in this period possibly as a result of reduced precipitation or because the OM reservoir became exhausted. (iii) In the youngest section between 2.4 and 3.8 ka BP, comparably stable and low δ<sup>13</sup>C values combined with an increasing dcf reaching up to 50% are again hinting towards a contribution of an aged organic carbon reservoir in the karst.</p> </div><p>[1] C. Welte, et al., (2016). Anal. Chem., 88, 8570– 8576.</p>

scholarly journals Biogenic Silica and Organic Carbon Records in Zhoushan Coastal Sea over the Past One Hundred Years and Their Environmental Indications

2020 ◽  
Vol 17 (11) ◽  
pp. 3890
Author(s):  
Hao Xu ◽  
Shangwei Jiang ◽  
Jialin Li ◽  
Ruiliang Pu ◽  
Jia Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Primary Productivity ◽  
Biogenic Silica ◽  
Sediment Cores ◽  
Stable Carbon Isotope ◽  
Offshore Area ◽  
Northern Area ◽  
The Past ◽  
Southern Area ◽  
Coastal Sea

The influence of terrestrial and marine input has dramatically changed eutrophication in coastal seas over the past 100 years. In this study, Zhoushan coastal sea (ZCS) is taken as a study area. We studied ZCS as it is a sink of the temporal and spatial variation of primary productivity, dominant species of algae, and the variation of provenance in this area over the past 100 years. We performed analysis using three sediment cores and the carbon and silicon deposition records. The analysis results demonstrate that: (1) The primary productivity in the northern area of the ZCS close to the Yangtze Estuary was the highest comparatively, but it declined slightly before 2010. The primary productivity in the southern area had an increasing trend over the past 100 years. The value of total organic carbon (TOC) in the northern area was relatively high, with an average value of 0.532% over the past 100 years, with a decreasing trend in recent years. On the contrary, TOC in the southern area was relatively low, but it was increased dramatically after 1995. (2) Diatom might play an important role in the variations. The biogenic silica (BSi) and TOC in the northern area showed a synchronous declining trend, while the BSi/TOC ratio did not change significantly. This indicates the algae population structure in this area was relatively stable over the past 100 years. The BSi/TOC ratio decreased continuously in the southern area, indicating that the dominance of diatoms was decreasing continuously. (3) The variation of diatom dominance in this area might have a great relationship with the change of nutrients’ provenance. A mean value of stable carbon isotope (δ13C) in the north of Zhoushan was −23.46‰, indicating that the terrestrial-source input was the highest. (4) The change of provenance in the study area was quite different. This illustrates that the terrestrial input impacted the largest area of ZCS while marine input became dominant in the offshore area.

scholarly journals Late Glacial–Holocene climatic transition record at the Argentinian Andean piedmont between 33 and 34° S

2014 ◽  
Vol 10 (2) ◽  
pp. 863-875 ◽  
Author(s):  
A. E. Mehl ◽  
M. A. Zárate
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Early Holocene ◽  
South American ◽  
Aeolian Deposits ◽  
The Andes ◽  
Climatic Transition ◽  
Flooding Events

Abstract. The Arroyo La Estacada (~ 33°28' S, 69°02' W), eastern Andean piedmont of Argentina, cuts through an extensive piedmont aggradational unit composed of a dominant Late Pleistocene–early Holocene (LP–EH) alluvial sequence that includes several paleosols. One of these paleosols developed affecting the topmost part of likely Late Glacial aeolian deposits aggraded into a floodplain environment by the end of the Late Pleistocene. The paleosol shows variable grade of development along the arroyo outcrops. Organic matter humification, carbonate accumulation and redox processes were the dominant processes associated with paleosol formation. By the early Holocene, when the formation of the paleosol ended, renewed alluvial aggradation and high magnitude flooding events affected the arroyo's floodplain environment. Accordignly, a period of relative landscape stability in the Arroyo La Estacada basin is inferred from the paleosol developed by the LP–EH transition in response to the climatic conditions in the Andes cordillera piedmont after the Late Glacial arid conditions. The analyzed Late Glacial–Holocene alluvial record of the Andean piedmont constitutes a suitable record of the LP–EH climatic transition in the extra-Andean region of Argentina. It is in agreement with regional paleoclimatic evidence along the southern tip of the South American continent, where other pedosedimentary sequences record similar late Quaternary paleoenvironmental changes over both fluvial and interfluvial areas.

STRATIGRAPHICAL SIGNIFICANCE OF THE GORNY ALTAI ALLUVIAL DEPOSITS IN THE LATE PLEISTOCENE AND HOLOCENE

2021 ◽  
pp. 28-35
Author(s):  
I. D. Zolnikov ◽  
◽  
E. V. Deev ◽  
◽  
◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Radiocarbon Dating ◽  
Late Quaternary ◽  
Optically Stimulated Luminescence ◽  
Alluvial Deposits ◽  
Reference Sections ◽  
Gorny Altai ◽  
Quaternary Glaciations

It is shown that representative sections of the Late Pleistocene alluvial deposits are found mainly in planations of main valleys and intermountain basins of the Gorny Altai. The data of optically stimulated luminescence and radiocarbon dating characterizing the Malyi Yaloman alluvium in the stratotypic Malyi Yaloman section and in same-age reference sections in the upper, middle and lower reaches of the Katun River are presented. That implied the regional stratigraphical significance of the Malyi Yaloman alluvium and it attribution to the epoch separating two Late Quaternary glaciations of the Gorny Altai. The question is raised of the need to identify the stratigraphical significance of regional and local events that caused not only glacial, but also seismic damming of the Gorny Altai valleys in the Late Pleistocene.

C4 Plant Productivity and Climate-CO2 Variations in South-Central Texas during the Late Quaternary

2002 ◽  
Vol 58 (2) ◽  
pp. 182-188 ◽  
Author(s):  
Lee C. Nordt ◽  
Thomas W. Boutton ◽  
John S. Jacob ◽  
Rolfe D. Mandel
Keyword(s):  
Late Pleistocene ◽  
Mississippi River ◽  
Late Quaternary ◽  
Plant Productivity ◽  
Glacial Meltwater ◽  
The Holocene ◽  
Global Circulation ◽  
South Central ◽  
Central Texas ◽  
Ecophysiological Responses

AbstractA continuous record of organic carbon δ13C from a buried soil sequence in south-central Texas demonstrates: 1) strong coupling between marine and adjacent continental ecosystems in the late Pleistocene as a result of glacial meltwater entering the Gulf of Mexico and 2) ecosystem decoupling in the Holocene associated with a reduction of meltwater and a shift in global circulation patterns. In the late Pleistocene, reduction in C4 plant productivity correlates with two well-documented glacial meltwater pulses (∼15,000 and 12,000 14C yr B.P.), indicating a cooler-than-present adjacent continental environment. Increased C4 production between 11,000 and 10,000 14C yr B.P. suggests that the Younger Dryas was a warm interval responding to the diversion of glacial meltwater away from the Mississippi River. With waning meltwater flow, C4 productivity generally increased throughout the Holocene, culminating in peak warm intervals at ∼5000 and 2000 14C yr B.P. Shifts in the abundances of C3–C4 plants through the late Quaternary show no correlation to ecophysiological responses to atmospheric CO2 concentration.

Tectonic and climatic controls on the late Pleistocene to Holocene evolution of Paleolake Ullum-Zonda in the Precordillera of the central Andes, Argentina

2017 ◽  
Vol 88 (2) ◽  
pp. 248-264 ◽  
Author(s):  
Pablo A. Blanc ◽  
Laura P. Perucca
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Hanging Wall ◽  
Central Andes ◽  
Alluvial Deposits ◽  
Growth Strata ◽  
Middle Holocene ◽  
San Juan River ◽  
Late Pleistocene To Holocene ◽  
Holocene Activity

AbstractThe Ullum-Zonda tectonic depression located in the central Andes Precordillera records several lacustrine episodes from frequent natural damming of the San Juan River during the late Quaternary. We analyzed stratigraphic, geomorphic, and geologic data and obtained new radiocarbon ages for Paleolake Ullum-Zonda. Results show the existence of a late Pleistocene age (16.7–15.2 ka BP) unit and an early to middle Holocene (9475–7685 yr BP) unit. Subsurface data show lacustrine episodes were common during the late Pleistocene, with probably nine episodes occurring during that period. Two transgressive events are evident in the Holocene unit, dated to ~8420±30 and shortly after 7460±30 14C yr BP. The maximum extent of the paleolake occurred at 6930±30 14C yr BP, shortly before the lake desiccated. Fault propagation folds and growth strata in Quaternary alluvial deposits relate to the Villicum-Zonda Fault and may indicate early to middle Holocene activity for this fault. The deformation observed in an ancient shoreline of the paleolake could be related to middle to late Holocene activity of the Cerro Zonda Norte Fault at a mean vertical uplift rate of ~0.8 mm/yr in the hanging wall block.

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