Paleoenvironmental Evidence Research Articles

Subaerially exposed Late-Quaternary basinal shelf of the inner Mersin Bay, Eastern Mediterranean: Paleoenvironmental evidence

High-resolution seismic profiles and petrographic data from surface and subsurface sediment samples from Mersin Bay, together with lithologic data from boreholes, were used to determine the origin and distribution of the pre- or early-Holocene unconformities in Mersin Bay (eastern Mediterranean). Reflectors corresponding to unconformities separate the younger, unconsolidated, marine transgressive sediments (Holocene) from the underlying, relatively coarser, consolidated sediments (Plio-Pleistocene). These unconformities correspond mainly to the erosional and subaerially deposited or later subaerially weathered land surfaces. These unconformities are probably related to the latest Pleistocene or earliest Holocene sea-level low stands.

Paleoenvironmental and Taphonomic Evidence of Diverse Bioclast Sources for Southwestern Louisiana Cheniers: ABSTRACT

Paleoenvironmental and Taphonomic Evidence of Diverse Bioclast Sources for Southwestern Louisiana Cheniers: ABSTRACT

Vermilion Lakes Site: Adaptations and Environments in the Canadian Rockies during the Latest Pleistocene and Early Holocene

The Vermilion Lakes site in Banff National Park, Alberta, has yielded cultural remains suggesting a possible sheep-hunting focus during the Paleoindian period and providing evidence for windbreaks or shelters dating as early as 10,300 B.P. Debris flows at this site have separated and preserved six or more cultural components dating between the mid-eleventh and mid-tenth millennia before present. Paleoenvironmental evidence suggests that most of these components date to a period of severe climate. Accelerator and conventional carbon dating of these strata suggest that, for at least part of this time, the detail of the temporal sequence is beyond the resolution of these techniques. Apparent14C inversions can best be explained by14C plateaus during key periods of the site's occupation.

Paleohydrology of the Laguna Lejía (north Chilean Altiplano) and climatic implications for late-glacial times

Paleoenvironmental and sedimentological data from Laguna Lejía (23°30′S, 67°42′W, 4325 m) in the high Altiplano of the Chilean Atacama desert indicate that climatic conditions during late-glacial times were significantly wetter than today. A water and energy budget model was used to simulate climatic scenarios that would have resulted in the observed changes in the water levels, water surfaces, water volumes and salinity during the time interval. Different climatic scenarios for the Laguna Lejía catchment include precipitation increases of over 100% up to 400−>500 mm/yr (today 200 mm/yr) to account for the late-glacial lake levels with shorelines 15–25 m higher than at present, and a lake surface of 9–11 km 2 compared to the present 2 km 2. During the lake maximum about 13,500–11,300 yr B.P. finely laminated sediments consisting of Mg-calcite, diatoms and sometimes gypsum were deposited. The paleoenvironmental evidence indicates that (north)easterly wind direction prevailed, and the summer rainfall resulted from a seasonal poleward shift of the tropical circulation. The lake history of Laguna Lejía is representative for the Altiplano area between 21° and 24°S.

The Contours of Vegetation Change and Human Agency in Eastern Africa's Great Lakes Region:ca. 2000 BC toca. AD 1000

Elsewhere I have set forth a basic outline for charting histories of vegetation change through the use of paleoenvironmental data (Schoenbrun 1991). This essay builds on the previous one by laying out the contours of vegetation change and human agency in the Great Lakes region (Map 1) over the roughly three millennia afterca. 2000 BC.The history of the vegetation in eastern Africa's Great Lakes region brings into focus several important features of long-term environmental change—human action, climatic shift, and internal successional patterns. The primary sources for this history come from a variety of published palynological and limnological studies from Burundi, Rwanda, Uganda, and Zaire. Perhaps the most rewarding data for reconstructing climatic and vegetational change come from palynological studies. Pollen studies often reflect detailed changes in the constitution of plant communities, and their value for reconstructing the vegetational and climatic contexts for Holocene human history has provoked the development of a rigorous method for their analysis. Contemporary studies of plant community succession and human-vegetation relationships are a secondary source for the history of land clearance in the Great Lakes region. These works provide a means to determine the different imprints of human and climatic action on the paleoenvironmental record.In this study I combine the full range of paleoenvironmental evidence to reconstruct the form and pace of vegetation change. I focus on a part of eastern Africa famous for its great ecological diversity. One of the rewards of this endeavor is to demonstrate to paleoecologists, archaeologists, and historians alike the value of a truly interdisciplinary approach to environmental change.

Overview of amino acid geochronology

Amino acid geochronology is an increasingly important chronostratigraphic tool than can be used in a wide range of Quaternary geologic settings. The technique has been applied to deep-sea and coastal marine deposits, terrestrial deposits and archeological sites. Although a wide variety of preserved organic remains have been used, most recent studies have focused on marine molluscs and foraminifera. Studies utilizing bone remain controversial. The most successful applications rely on d l ratios as relative-age indices that are independent of assumptions regarding post-depositional temperatures. As a relative-age tool, d l ratios provide a basis for identifying unconformities in stratigraphic sequences, resolving mixed populations of reworked material and evaluating stratigraphic correlations between disjunct exposures. d l ratios, combined with independent paleoenvironmental evidence, can be used to constrain the reasonable time/temperature range of a stratigraphic unit. Where the ages of units are known from independent determinations, d l ratios can be used to evaluate the overall temperature history of a deposit. A newly emerging and particularly promising application of the amino acid geochronology is in dating eggshell from archeological sites. The outstanding potential of this application is derived from the integrity of the eggshell carbonate matrix which, better than any other carbonate system, approximates a closed system for the retention of amino acids.

Functional comparisons among modern and Paleogene mammals based on quantitative analyses of skeletal element outlines

The inference of locomotor mode in Paleogene mammalian faunas has traditionally been based on qualitative comparisons between fossil postcranial skeletal elements and those of modern forms whose range of locomotor behavior is known. Recently, Van Valkenburgh (1987) has shown that detailed functional interpretations can also be obtained by using a series of geometric indices to quantitatively assess correspondences between Oligocene carnivores and a predominately carnivorous assemblage of modern mammalian species. We generalize and extend Van Valkenburgh's morphometric approach by focusing on the analysis of ungual phalanx and proximal radial head outlines using a variant of the eigenshape procedure.Results of the phalanx analyses show that the geometric consideration of the lateral outline is, for the most part, sufficient to discriminate among modern arboreal / scansorial, fossorial, and cursorial species. In modern mammals, this skeletal element displays a wide range of variational modes (e.g., relative thickness of the proximal phalanx shaft, curvature of the ventral margin, degree of both lateral and dorso-ventral compression, relative differentiation of the extensor tubercle) that appear to reflect differences among the various locomotor guilds involving relative degrees of phalanx robustness along with both the precision and strength of phalanx movement. While a separate analysis of modern mammal phalanx shape in dorsal view failed to reveal a similar degree of variation among the various locomotor guilds, our study did uncover an intriguing geometric conservatism in this aspect of phalanx morphology that appears to cut across both taxonomic and adaptive classifications. Two-dimensional outline analyses of modern mammal proximal radial heads indicate that this skeletal element can ordinate taxa on the basis of relative ability to supinate the forearm that, in turn recognizes functional distinctions between arboreal / scansorial and fossorial / cursorial taxa. Finally, our results reveal that when modern mammalian taxa are grouped by geometric correspondences among these two skeletal character complexes, the consequent associations of taxa are almost invariably polyphyletic, indicating widespread evolutionary convergence on a relatively small number of alternative morphotypes.In order to test the feasibility of using an outline-based morphometric approach for the inference of locomotor behavior in fossil mammals, ungual phalanx and proximal radial head outlines from a suite of Paleogene species were projected into their respective modern mammal shape spaces, thereby allowing these morphologies to be directly compared with those of modern morphological analogues at highly detailed levels of shape resolution. These results indicate that Cantius, Chriacus, Kopidodon, Nannodectes, Plesiadapis, Thyptacodon, and Vulpavus ungual phalanx and/or radial head outlines are similar to those of modern arboreal / scansorial mammals; Bunophorus, Diacodexis, Pachyaena, Prolimnocyon, and Oxyaena appear to be morphologically similar to modern ambulatory or cursorial forms; and Palaeanodon exhibits a strong shape correspondence with modern fossorial taxa. In each case, our outline-based functional diagnoses are consistent with independent interpretations based on qualitative studies of other skeletal character complexes and associated paleoenvironmental evidence.

Micromammals and paleoenvironmental interpretation in southern Africa

AbstractMicromammalian remains from archaeological sites in southern Africa provide paleoenvironmental evidence at a number of levels of precision. At the lowest level, broad vegetation categories can be identified. At the second level, proportional representation of vegetation categories and general climatic conditions are indicated. the possible overlying effects of agriculture and sea‐level changes can also be identified. At the third level, there is clear but as yet largely unrealized potential for quantifying climatic variation and specifying environmental factors. In order to improve potential for interpretation, greater rigor is necessary in sample collection and in the establishment of the widest possible comparative data base, with the latter being in particular need of attention. Detailed paleoenvironmental information can also provide an independent data base for assessment of ecological approaches to archaeology.

New pollen and beetle analyses at the Mary Jane site, Colorado: Evidence for late glacial tundra conditions

Research Article| May 01, 1987 New pollen and beetle analyses at the Mary Jane site, Colorado: Evidence for late glacial tundra conditions SUSAN K. SHORT; SUSAN K. SHORT 1Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, Colorado 80309 Search for other works by this author on: GSW Google Scholar SCOTT A. ELIAS SCOTT A. ELIAS 1Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, Colorado 80309 Search for other works by this author on: GSW Google Scholar Author and Article Information SUSAN K. SHORT 1Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, Colorado 80309 SCOTT A. ELIAS 1Institute of Arctic and Alpine Research, University of Colorado, Campus Box 450, Boulder, Colorado 80309 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1987) 98 (5): 540–548. https://doi.org/10.1130/0016-7606(1987)98<540:NPABAA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation SUSAN K. SHORT, SCOTT A. ELIAS; New pollen and beetle analyses at the Mary Jane site, Colorado: Evidence for late glacial tundra conditions. GSA Bulletin 1987;; 98 (5): 540–548. doi: https://doi.org/10.1130/0016-7606(1987)98<540:NPABAA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Analyses of fossil pollen and beetles from a late Pinedale peat deposit from the upper Fraser River, Colorado, allow a reassessment of previously published paleoenvironmental evidence from the site. Between 13,800 and at least 12,600 yr B.P., the environment was an open tundra indicative of a cold, dry climate. Scattered spruce trees were probably present at the site by the end of the record, ca. 12,300 yr B.P. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The development of antarctic glaciation and the Neogene paleoenvironment of the Maurice Ewing Bank

A micropaleontologic, magnetostratigraphic, and sedimentologic analysis of 56 piston cores provides the basis of a geologic study of the late Miocene to Holocene depositional and erosional history of the intermediate-depth Maurice Ewing Bank (MEB) located at the eastern extremity of the Falkland (Malvinas) Plateau, southwest Atlantic Ocean. Sedimentation on the MEB is controlled presently by the position of the Polar Front and strong bottom currents beneath the axis of the Antarctic Circumpolar Current (ACC). Fluctuations in the position of the Polar Front and in the intensity of the ACC are inferred to have largely controlled deposition on the MEB since the initiation of ACC flow over the bank in the Miocene. The sedimentary record of the MEB is used to infer the late Miocene to Holocene oceanographic and climatic conditions in the South Atlantic sector of the Southern Ocean. The MEB suffered major erosion by intense ACC flow during late Miocene time which exposed Cretaceous—Miocene sediment near the surface and shaped the present configuration of the bank. This erosional event is inferred to have occurred during late Miocene to early Pliocene time (∼7.2–4.7 m.y.B.P.) with the major phase of erosion occurring between middle magnetostratigraphic Chron 7 and late Chron 6 (∼7.2–6.2 m.y.B.P.). We suggest that the Miocene sedimentary record of the MEB and other paleoenvironmental evidence from the circum-Antarctic region precludes the existence of a West Antarctic ice sheet or extensive ice shelves along the Antarctic margin prior to the late Miocene. During the late Miocene a West Antarctic ice shelf formed in the former West Antarctic Sea and rapidly thickened until it grounded below sea level to form the West Antarctic ice sheet. Formation of this ice sheet, with floating and partially grounded extensions (ice shelves) in the Ross and Weddell embayments, led to the first major production of true Antarctic Bottom Water (formed in a manner similar to today) which permanently altered global abyssal circulation. Late Miocene changes in oceanic CCD levels and a permanent shift in the oceanic 13 C 12 C composition may be attributed to this major change in abyssal circulation. A decrease in ACC velocity during an early Pliocene amelioration of climate led to resumption of deposition on the bank from ∼4.7 to 3.9 m.y.B.P. Intensification of the ACC during the late Gilbert and early Gauss Chrons again resulted in limited deposition and widespread erosion and/or non-deposition over most of the MEB from ∼4.0 to 3.2 m.y.B.P. ACC velocity apparently began to wane during the middle of the Gauss Chron and allowed widespread deposition on the bank during late Gauss time (2.9–2.48 m.y.B.P.) and over more limited areas during earliest Matuyama time (2.48 to about 2.2 m.y.B.P.). During middle to late Matuyama time bottom current intensity reached its greatest post-Miocene level forming a regional disconformity between sediments of about 2.0 and 1.0 m.y. in age. This increased circumpolar circulation and associated erosion is inferred to have peaked during the late Matuyama Chron (1.2–1.0 m.y.B.P.) and is approximately the same age as the tentatively dated greatest Patagonian Glaciation in nearby southern Argentina. Between ∼1.0 and 0.7 m.y.B.P., the bank was blanketed with a coarse, erosion-resistant layer of ice-rafted detritus which armored the older sediment thereby protecting it from major subsequent erosion. Sedimentation on the MEB during the Bruhnes Chron (720,000 yr B.P.–Present) was intermittent and finally culminated with the deposition of a veneer of carbonate ooze during or since latest Pleistocene time.

Late Quaternary ice age climates of tropical Australasia: Interpretations and reconstructions

Paleoecological and paleogeographical evidence is used to mold a framework from which the basic parameters of the late Quaternary glacial-age climate of tropical Australasia can be inferred. The theory of physical circulations, a knowledge of present tropical circulation patterns, and a study of anomalous and extreme events in the present era are used to reemphasize the view of a less pluvial tropical and subtropical zone at that time. Cooler sea-surface temperature, cooler trades, and the effect of the then exposed land areas are indicated as instrumental in producing drier conditions. Tropical areas west of Cape York Peninsula and Torres Strait were subject to fewer tropical disturbances and were similar to the present tropical savannah of the northern interior of Australia. Such effects would exist even without shifts in major climatic zones, although they are shown to be consistent with an equatorward shift of the westerlies brought about by the increased pole to equator temperature gradient. Paleoenvironmental evidence from the New Guinea Highlands and southeastern Australia suggests that their climates were anomalous. Substantial data of the glacial period in New Guinea show snow lines to be 1000 to 1500 m lower than at present which matches a 6 to 8°C lowering of temperature in highland New Guinea. The deep-sea cores of the CLIMAP Project suggest a mere 2°C cooling of the surrounding tropical oceans. It is shown that it is highly unlikely that an upper-level decrease in temperature of 6 to 8°C could be maintained while the surface cools by only 2°C. It is suggested that either the temperature of the tropical oceans of the western Pacific were overestimated by CLIMAP or that cold air incursions from higher latitudes (for which some analogs exist today) were sufficiently frequent to allow the maintenance of a snow line well below the freezing level of the ancient ambient tropical atmosphere. It is shown that in southeastern Australia considerable evidence of aridity cannot be explained by merely displacing the westerlies more equatorward. To account for the aridity, a new circulation pattern is proposed. Noting that there is CLIMAP evidence of preferred equatorward extension of sea ice, a pattern is postulated that displays only small seasonal change and is characterized by an enhanced Indian Ocean trough, marked ridging at eastern Australian longitudes, and a further trough in the western Tasman. Such a basic flow is consistent with (i) a low rainfall over southeastern Australia, (ii) frequent cold outbreak conditions favorable for the maintenance of the New Guinea glaciers, and (iii) considerable precipitation to nourish the ice caps of Tasmania and the Australian and New Zeland Alps.

Quaternary Environmental History of Interior Alaska: Pollen Samples from Organic Colluvium and Peats

Thick sequences of late Pleistocene frozen silts and peats are exposed in many areas of forested interior Alaska. Pollen samples from such sediments show, like other types of paleoenvironmental evidence (fossil mammals, fossil insects, etc.), that an arctic environment once prevailed in large areas of lowland interior Alaska. Furthermore, a few of these pollen samples are referred to Livingstone's Herb Zone, suggesting that the Late Wisconsin environment of lowland interior Alaska was similar in some respects to that of present day Barrow, Alaska. During that time, spruce woodlands would have been nearly eliminated from interior Alaska. Two of the pollen samples represent forested conditions. One of these, of probable interglacial age, provides the first evidence from interior Alaska of a westward advance of pines during the Pleistocene. Surface samples from interior Alaska are presented for comparison with the fossil pollen samples.