Radiocarbon ages of peat, Guayana Highlands (Venezuela)

Schubert, Carlos; Fritz, P.

doi:10.1007/bf00404884

Cited by 30 publications

(9 citation statements)

References 11 publications

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“…The ecotone is characterised mainly by higher Bonnetia lanceifolia proportions. This is in agreement Table 1 Radiocarbon dating of samples, according to Schubert and Fritz (1985) and Rull (1991…”

Section: Upper-level Vegetationsupporting

confidence: 80%

“…The package MVSP 3.1 was used. Radiocarbon dates, taken from earlier work on the same cores (Schubert and Fritz, 1985;Rull, 1991), were calibrated with CALIB 4.3 (Stuiver et al, 1998a(Stuiver et al, , 1998b ( Table 1). Interpretation of pollen diagrams was based on modern analogues, derived from surface samples, and the known ecological requirements of the taxa found (Berry et al, 1995;Marchant et al, 2002;Rull, 2003).…”

Section: Methodsmentioning

confidence: 99%

“…Its existence has been questioned, however, arguing that these tepui summits were also arid or semi-arid and devoid of vegetation, during the LGM. This hypothesis is based on the apparent absence of peat of Pleistocene age on the tepuis (Schubert and Fritz, 1985;Schubert et al, 1986). Nevertheless, these hypotheses are largely based on present-day phytogeographical observations and need appropriate palaeoecological data to be tested.…”

Section: Introductionmentioning

confidence: 99%

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Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Rull

2005

J Quaternary Science

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The summits of the table mountains (tepuis) from the Neotropical Guayana region are remote environments suitable for palaeoecological studies with evolutionary, biogeographical and palaeoclimatic implications. Here, using palynological analyses of two radiocarbon-dated peat bogs from a tepui summit, the Holocene palaeovegetational trends are reconstructed, and related to possible forcing factors. Because of the pristine character of the Guaiquinima summit, the recorded palaeoenvironmental changes are probably due to natural causes, which makes them valuable archives of the natural component of climatic change at a millennial time scale. The sequence begins with pioneer communities or meadows similar to present-day ones, between about 8.4 and 4.5 ky BP. After this date, and until about 2 kyr BP the expansion of gallery forests suggests an increase in precipitation, documented also at regional (Neotropical) level. Between ca. 2 kyr BP and the last century, gallery forests are replaced by forests characteristic of the upper Guaiquinima altitudes, coinciding with a regional phase of reduced moisture. The present-day meadows, established relatively quickly during the last century, substituted the former upland forests. In the locality studied, the main controlling factor of the vegetation during the Holocene seems to have been the moisture balance. In contrast to other tepui summits, there is no clear evidence for changes linked to temperature oscillations. This could be due to the elevation of the site, far from any characteristic ecological boundary, that makes it insensitive to this parameter.

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Section: Upper-level Vegetationsupporting

confidence: 80%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Rull

2005

J Quaternary Science

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“…Around 11.7 k cal a BP, the shrubland was replaced by a treeless savanna, which was the dominant vegetation during the early Holocene, at least until 10.6 k cal a BP. These results do not support previous hypotheses, which considered the GS as a relict of more extensive glacial savannas (Eden, 1974), or proposed an almost barren postglacial landscape due to an arid or semi-arid climate until about 8.0 k 14 C a BP (Schubert and Fritz, 1985;Schubert et al, 1986). The following sections discuss the palaeoecological sequence in detail, in a Neotropical context, and the contribution of these results to our understanding of the origin of the GS.…”

Section: Discussioncontrasting

confidence: 55%

Vegetation changes in the Neotropical Gran Sabana (Venezuela) around the Younger Dryas chron

Montoya

Rull

Stansell

et al. 2011

J Quaternary Science

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The occurrence of the Younger Dryas cold reversal in northern South America midlands and lowlands remains controversial. We present a palaeoecological analysis of a Late Glacial lacustrine section from a midland lake (Lake Chonita, 4.6501 8N, 61.0157 8W, 884 m elevation) located in the Venezuelan Gran Sabana, based on physical and biological proxies. The sediments were mostly barren from $15.3 to 12.7 k cal a BP, probably due to poor preservation. A ligneous community with no clear modern analogues was dominant from 12.7 to 11.7 k cal a BP (Younger Dryas chronozone). At present, similar shrublands are situated around 200 m elevation above the lake, suggesting a cooling-driven downward shift in vegetation during that period. The interval from 11.7 to 10.6 k cal a BP is marked by a dramatic replacement of the shrubland by savannas and a conspicuous increase in fire incidence. The intensification of local and regional fires at this interval could have played a role in the vegetation shift. A change to wetter, and probably warmer, conditions is deduced after 11.7 k cal a BP, coinciding with the early Holocene warming. These results support the hypothesis of a mixed origin (climate and fire) of the Gran Sabana savannas, and highlight the climatic instability of the Neotropics during the Late Glacial.

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“…The only published radiocarbon dates of deposits beneath terra firme forests in this region come from the upper Rio Negro district ( N = 37) (Sanford et al 1985, Saldarriaga & West 1986), at Nouragues in northern French Guiana (Tardy et al 2000), the Gran Sabana in southeast Venezuela (Fölster 1992), and a pair of preliminary dates obtained in north central Guyana (Hammond & ter Steege 1998). Highland peat formations commonly forming in the Pantepui region of the Venezuelan Guayana have also been dated, but do not complement existing lowland site information given the contrasting environmental conditions and nature of carbon‐dated material (Schubert & Fritz 1985).…”

mentioning

confidence: 99%

Upland Soil Charcoal in the Wet Tropical Forests of Central Guyana

Hammond¹,

Steege

Borg

2007

Biotropica

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A soil charcoal survey was undertaken across 60,000 ha of closed-canopy tropical forest in central Guyana to determine the occurrence, ubiquity, and age of past forest fires across a range of terra firme soil types. Samples were clustered around six centers consisting of spatially nested sample stations. Most charcoal was found between 40 and 60 cm depth with fewest samples yielding material at 0-20 cm depth. The first core yielded charcoal at most stations. Charcoal ages of a random subsample ranged from less than 200 YBP to 9500 YBP with a noticeable peak between 1000 and 1250 YBP. Results reinforce a view that most closed-canopy tropical forests in eastern Amazonia have been subject to palaeo-fire events of unknown severity with a peak in charcoal age consistently appearing between 1000 and 2000 YBP. The two samples dated to the early Holocene represent some of the oldest indicators of paleo-fire known from upland Neotropical forest soils. Ubiquitous soil charcoal in central Guyana further indicate both forest resilience to fire and the widespread propensity for regional forests to burn, particularly during anomalous periods of drought.

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Radiocarbon ages of peat, Guayana Highlands (Venezuela)

Cited by 30 publications

References 11 publications

Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Vegetation changes in the Neotropical Gran Sabana (Venezuela) around the Younger Dryas chron

Upland Soil Charcoal in the Wet Tropical Forests of Central Guyana

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