Leaf Margin Analysis Research Articles

Should the relationship between leaf margin and temperature be re‐defined for areas with colder climates?

AbstractAimThe well‐proven positive correlation between the increased proportion of entire‐leaved woody dicotyledonous species and increased mean annual temperature has been commonly used to estimate temperature in the past. However, in regions of colder climates, this relationship is not straightforward, questioning the accuracy of temperature estimation.LocationFinland, Poland, Germany.TaxonDicotyledons.MethodsThe floristic composition of 10 × 10 km squares in 20 km wide transects through Finland, Poland and Germany was analysed.ResultsAt higher temperatures, deciduous woody plants appeared to show the expected positive relationship between mean annual temperature and the proportion of entire leaf margins. However, we found a negative correlation within woody deciduous plants at higher latitudes with mean annual temperature values from approximately −2.5°C to +2–4°C and at all temperatures when all woody plants were included. Herbaceous species showed a weak relationship between morphology and temperature.Main ConclusionsThe hypothesis that the phenomenon was caused by a large percentage of entire‐leaved evergreen species that winter under snow cover was rejected. These results indicate that using the leaf margin analysis method for past temperature estimation is increasingly inaccurate at colder temperatures. Consequently, we recommend avoiding this method at locations where the mean annual temperature falls below 5°C.

Latest Neogene Paleoclimate Variation in Yunnan, Southwest China, Revealed by Fossil Leaf Physiognomy

AbstractYunnan Province, located in the southeastern margin of the Tibetan Plateau, can provide important information on how climate change was influenced by global cooling. However, its variation patterns in temperature and precipitation during the latest Neogene are not well‐understood. Based on the 357 specimens assigned to 31 morphotypes of plant fossils from the upper Pliocene Ciying Formation in Yiliang County, Yunnan Province, Southwest China, paleoclimate was estimated by Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program. Compared to the present climate, the mean annual temperature and coldest month temperature have not changed significantly since the late Pliocene, whereas the warmest month temperature has decreased significantly. All precipitation‐related parameters have decreased, particularly winter precipitation. Combined with the climatic data of the same period in other areas of Yunnan, the western and eastern Yunnan has shown a similar pattern in temperature variation since the late Pliocene except for central Yunnan; whereas the variation in precipitation does not follow a common law except for a consistent decrease in winter precipitation. Our study reinforced the fact that under the background of global cooling and intensified monsoon systems, different areas of Yunnan exhibit different climatic responses to these changes because of their topographic heterogeneities.

Quantitative Reconstruction of Paleoclimatic Changes in the Late Miocene Eastern Zhejiang Based on Plant Fossils

With a series of Cenozoic climate fluctuations, the global paleoclimate shifted from a warm climate to a cold climate, causing Arctic ice caps to be formed. The Late Miocene is a critical time in this transition period, in which the climate was rapidly cooling. Plant fossils from this epoch could be used as ideal indicators for reconstructing climate change throughout this time interval. In this study, plant fossils were collected from the Shengxian Formation in Ninghai and Tiantai of eastern Zhejiang. We divided the fossiliferous strata of the Shengxian Formation into five layers according to different lithology and chronological order, which were named: JHU0, DLX, JHU1, JHUW, and JHU3 from old to new geological times, respectively. We used Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program to reconstruct paleoclimatic changes in eastern Zhejiang during the Late Miocene. The paleoclimatic information of the five stages from old to new times was obtained based on the plant fossils of each layer. The mean annual temperature values in eastern Zhejiang were reconstructed using the Climate Leaf Analysis Multivariate Program and Leaf Margin Analysis at the same time. However, the former mean annual temperature values are lower than the latter values. After comparing the two sets of mean annual temperature data with previously reported values, it is found that the results obtained by Climate Leaf Analysis Multivariate Program are more reliable, whose values are 18.05 °C, 16.03 °C, 17.96 °C, 16.57 °C, and 15.52 °C from old to new times, respectively. Moreover, 11 climatic parameters were reconstructed using the Climate Leaf Analysis Multivariate Program PhysgAsia2 calibration, among which the growing season precipitation was found to be 195.54 cm, 181.25 cm, 207.99 cm, 180.7 cm, and 165.07 cm; while the difference between the coldest and warmest months was found to be 22.14 °C, 23.4 °C, 22.07 °C, 21.36 °C, and 23.37 °C. The relatively low difference between the coldest and warmest months values and the growing season precipitation values during the Late Miocene might be due to a weaker East Asian monsoon system in the Late Miocene than in modern times.

An Eocene leaf flora from the northern Peruvian Andes

The fossil forest known as El Bosque Petrificado Piedra Chamana lies in close proximity to the village of Sexi in the Department of Cajamarca in northern Peru. The forest was deposited in either a lahar or pyroclastic flow, and ashfall deposits, as mineralized wood and leaf impressions 39 million years ago (late Middle Eocene). More than 30 types of non-monocot angiosperms have been described from the fossil wood, which is densely embedded in rock outcrops, scattered across the ground, and occasionally found in situ. Anatomical characteristics and identifications of the woods suggest a seasonally flooded lowland tropical forest with a dry period. This site also preserves a small leaf flora which has not received a full treatment in earlier works and is the focus of the present study. The leaves are described in detail using standard leaf architecture terminology. The flora has 31 non-monocot leaf morphotypes. The presence of more than 30 morphotypes suggests high diversity based on having only ∼210 non-monocot leaf specimens. The leaf collection also includes ∼10 monocot specimens. One of the leaf morphotypes shows similarities to the extant mangrove genus Avicennia, possibly confirming one of the fossil wood identifications. Most of the leaves are incomplete, but when the margin is preserved, it is untoothed. The lack of teeth indicates a warm, tropical climate (estimated mean annual temperature of >25 °C based on leaf margin analysis). Leaves in the collection are small with 28 of 31 morphotypes inferred as microphyll or notophyll in laminar size, providing support for the seasonal dryness indicated by the fossil woods. Despite the small size of the collection, this leaf flora is important to document as there are few Eocene plant macrofossil localities in Peru; it provides some insight into the Cenozoic forests in this understudied region.

Plant Megafossils, Palynomorphs, and Paleoenvironment from the Late Middle to Late Eocene Burnaby Mountain Flora, Huntingdon Formation, British Columbia, Canada

Premise of research. The Eocene fossil flora of the area around Vancouver, British Columbia, is poorly known despite work beginning in the 1890s to 1920s. The floristic character of the previously unstudied Burnaby Mountain flora from the Huntingdon Formation in British Columbia is reconstructed using plant megafossils and palynology. This site offers insight into the terrestrial vegetation and paleoclimate during the late middle to late Eocene of the Pacific Northwest of North America in a coastal setting during a global cooling trend.Methodology. Megaflora and microflora were identified, and the combined flora was compared with that of coeval floras from northwestern Washington. Paleoclimate was reconstructed from leaf morphology using the Climate Leaf Analysis Multivariate Program, leaf margin analysis, and leaf area analysis. A probabilistic nearest-living-relative approach was used to reconstruct paleoclimate independently of leaf morphology, using taxonomic identifications from both mega- and microfossils. These data were combined in an ensemble approach.Pivotal results. The Burnaby Mountain fossil flora is late middle Eocene to late Eocene in age and shares key plant taxa with the coeval Upper Ravenian flora of the Puget Group and the upper Chumstick Formation of northwestern Washington. The fossil flora contained a mix of subtropical and temperate forest elements, including rare palm and possible cycad leaf fragments, rare conifer pollen, and a diversity of broad-leaved trees.Conclusions. The reconstructed paleoclimate suggests humid warm-temperate to marginally subtropical conditions in coastal British Columbia during the late middle Eocene to late Eocene. An ensemble paleoclimate approach provided a most parsimonious mean annual temperature estimate of 16.2°C±3.1°C for the Burnaby Mountain fossils and mean annual precipitation of 134±56 cm. A modern climatic analog is present on the East Coast of the United States in North Carolina, where palms are part of the native flora.

Interpretação paleoclimática com base na análise da fisionomia foliar de duas floras pleistocênicas, Formação Rio Claro, São Paulo, Brasil

Paleoclimatic interpretation based on the analysis of the leaf physiognomy of two Pleistocene floras, Rio Claro Formation, São Paulo, Brazil. The Jaguariúna and Jazigo Vargem Grande do Sul fossil floras are well-preserved records of an ancestor of one of the phytophysiognomies of the Atlantic Forest, the oldest belt of tropical forest in the world. These fossil floras are associated with the Rio Claro Formation, one of the most important sedimentary records of the Pleistocene from the São Paulo State Peripheral Depression, Brazil. The main physiognomic characteristics–type of margins and leaf area – of the angiosperm leaves from these floras allowed us to carry out the reconstruction of the mean annual temperature (MAT) and the mean annual precipitation (MAP) for the moment of their deposition. The different equations used to reconstruct the MAT and the MAP are based on univariate methods known as Leaf Margin Analysis and Leaf Area Analysis. These equations indicated that the warm and humid subtropical/tropical climate under which the Jaguariúna fossil flora developed was characterized by a MAT of 22.1–22.8°C and a MAP of 566–831 mm, and also that the warm and humid subtropical climate under which the Jazigo Vargem Grande do Sul fossil flora developed was characterized by a MAT of 24.6–25.1°C and a MAP of 747–961 mm. These values indicate that, at the moment of deposition of the fossil floras of Jaguariúna and Jazigo Vargem Grande do Sul, conditions were warmer and less humid than the current ones. Therefore, it is possible to infer that these floras developed in a smaller climatic cycle, the interglacial period, during which the Rio Claro Formation was deposited. Keywords: Atlantic Forest, Pleistocene, physiognomic characteristics, angiosperm leaves, climatic cycle, interglacial period.

Climatic reconstruction at the early Miocene La Rinconada mine (Ribesalbes-Alcora Basin, eastern Spain) based on Coexistence Approach, CLAMP and LMA analysis

The early Miocene La Rinconada mine from eastern Iberian Peninsula contains a rich megafloral assemblage with abundant leaf fossils from a single stratigraphic level of the sedimentary succession. This has provided a good opportunity to undertake detailed comparative quantitative palaeoclimate reconstruction using different approaches, namely the Coexistence Approach (CA), Climate Leaf Analysis Multivariate Programme (CLAMP) and Leaf Margin Analysis (LMA). Considering the results of all techniques used, the palaeoclimate estimates are the following: mean annual temperature (MAT) CA = 10–16.5 °C/CLAMP = 11.48 °C, warmest month mean temperature (WMMT) CA = 25–26.4 °C/CLAMP = 23.31 °C, coldest month mean temperature (CMMT) CA = 4.3–4.8 °C/CLAMP = 0.84 °C, mean annual precipitation (MAP) CA = 1217–1297 mm, mean precipitation of the wettest month (MPWet) CA = 116–164 mm and mean precipitation of the warmest month (MPWarm) CA = 118–131 mm. Temperature and precipitation values obtained through CLAMP, LMA and CA indicate the occurrence of a wet and warm climate the whole year around with marked seasonality for rainfall and temperature but without a summer-dry regime. The climatic values obtained in the La Rinconada mine are in well accordance with other Burdigalian and late Burdigalian–early Langhian sites from the Iberian Peninsula (e.g. S 141 Borehole) and Central-Southern Europe (e.g. Holedeč, Čermníky, Přívlaky, Bílina Delta, Manisa-Soma, Spanokhorion and the Evia Island), suggesting the absence of a clear latitudinal gradient in temperature and precipitation for this period in Europe. This climate is consistent with the plant communities described in the area from taxonomic studies and IPR analysis.

Evaluating the sensitivity of paleoclimate results using different approaches of leaf morphotype resolution: A case study using the Eocene Florissant paleoflora, central Colorado

We tested the sensitivity of paleoclimate estimates to different resolutions of leaf morphotype distinction by grouping one paleofloral collection three ways and comparing the results. We examined the different morphotype resolutions using a recently collected Eocene (34 Ma) fossil leaf assemblage from Florissant Fossil Beds National Monument Collection Site 9 (CS-9, Florissant, Colorado), an exposure that yields one of the most diverse sets of dicotyledonous angiosperm (‘dicot’) morphotypes yet analyzed from a single site within this well-studied formation. We grouped this collection using what are herein referred to as ‘Splitter’ (number of morphotypes n = 129), ‘Intermediate’ (n = 96), and ‘Lumper’ (n = 53) morphotyping approaches, which differed in their degree of delineating foliar morphotypes. Leaf Margin Analysis (LMA) and Leaf Area Analysis (LAA) were used to obtain paleotemperature and paleoprecipitation estimates from the morphotype datasets and Climate Leaf Analysis Multivariate Program (CLAMP) was employed to examine further parameters. We perform an additional paleoclimatic analysis of CS-9 in which we divide the site into three stratigraphic sections, and finally we perform an analysis on sample collections above and below a volcanic event horizon within CS-9. Whole collection results across the three morphotype resolutions indicate a mean annual temperature between 10.8 and 12.5 °C, and annual precipitation between 61.8 and 130.7 cm at the time of deposition. The ‘Splitter,’ ‘Intermediate,’ and ‘Lumper’ approaches provide very similar estimates by all methods of analysis and suggest that morphotype resolution specificity has very little effect on climatic results using these leaf physiognomic techniques.

Paleoclimate estimates for the Paleogene-Neogene in southern South America using fossil leaves as proxies

It is widely recognized that fossil leaves are good proxies for paleoclimate estimates, and leaf physiognomy analysis is a traditional technique used to make climate estimates. There are only a few paleoclimate reconstructions for the southern part of South America based on this technique. Here we report climate parameters using fossil leaves from the Río Turbio (Eocene-Oligocene) and Río Guillermo (Oligocene-early Miocene?) formations in southern South America, Cuenca Austral, Argentina. We used univariate (leaf margin and leaf foliar area analysis) and multivariate methods (CLAMP, DiLP) on two datasets from South America, in the Southern Hemisphere. Lower and upper members of the Río Turbio Formation show a mixed paleoflora represented by paratropical as well as cool-temperate taxa such as Nothofagus, with a similar percentage of untoothed fossil leaves. Climate estimates indicate warm and humid conditions for both Río Turbio Formation members. The Río Guillermo Formation is represented by mostly cool-temperate elements, mainly Nothofagus, and most with toothed margins. The paleoclimate analysis indicates a decrease in temperature and precipitation when comparing the two studied formations. Today, temperate forests in southern Argentina have a plant composition and climate more similar to the estimates made for the Río Guillermo Formation.

An Upper Pleistocene macroflora indicates warm and dry climate during an interglacial in central Brazil

This study is the first report of the fossil macroflora of the Paleolagoa Seca, an Upper Quaternary fossil locality of lacustrine origin in central Brazil. Here we present an analysis of well-preserved fossil leaves collected from an argillite level dated at ca. 43,000 cal yr BP and discuss the paleoclimatic implications of this record. We reconstructed paleotemperature and paleoprecipitation using Leaf Margin Analysis (LMA) and Leaf Area Analysis (LAA), respectively, and used mineralogical (XRD and IR) and palynological analyses of the fossiliferous level to assess a complete picture of the past landscape. To test the ability of LMA and LAA models available for Southern Hemisphere to correctly predict Mean Annual Temperature (MAT) and Mean Annual Precipitation (MAP) for the Paleolagoa Seca, we applied several calibration models to the leaf dataset of a modern Cerrado forest and then compared predictions with modern climate data. Six LMA calibration models presented consistent MAT results and all four LAA calibration models provided satisfactory estimations of the modern MAP. The botanical identification of the fossil leaves and the pollen record indicated a mosaic of open savanna, dry forests and gallery forest around the Paleolagoa Seca. The reconstructed MAP for the Paleolagoa Seca ranged between 647 and 948 mm depending on the LAA equation, which is at least 500 mm lower than the current MAP. The reconstructed Mean Annual Temperature (MAT) ranged between 22.6 and 26.3 °C, indicating a higher-than-present MAT, which we relate to a combination of high summer insolation and low humidity. Comparison with other local fossil macrofloras, including from nearby localities, and with other paleoclimatic records suggests that the observed dry conditions at Paleolagoa Seca were related to interhemispheric climate forcing and to a weakening of the South American Summer Monsoon (SASM).

Erratum to: The Piedra Chamana fossil woods and leaves: a record of the vegetation and palaeoenvironment of the Neotropics during the late Middle Eocene.

Background and aims The Piedra Chamana fossil forest in northern Peru is an assemblage of angiosperm woods and leaves preserved in volcaniclastic rocks dated to 39 Mya (late Middle Eocene). We analysed the anatomical and morphological features of the fossils to reconstruct the palaeoenvironment during this time of global warmth, taking advantage of the co-occurrence of woods and leaves to compare different proxies and analytical approaches. Methods Wood characters analysed include vessel-related functional traits, traits linked to Baileyan trends, and quantitative features such as vessel diameter and density. Diameter-distribution and diameter and position plots are used to represent vessel diameter and arrangement. Leaf margin and area analysis provides additional climate estimates. Key results The fossil woods show many similarities with modern tropical-forest woods and tropical fossil-wood assemblages; closest correspondence within the Neotropics is to semi-deciduous lowland tropical forest with moderate precipitation (~1000-1200 mm). Features unusual for the modern South American tropics are mainly vessel-related characters (semi-ring porosity, grouped vessels, helical vessel thickenings, short vessel elements) linked to water stress or seasonal water availability. Leaf analysis indicates mean annual temperature of 31 °C (n = 19, 100 % entire-margined) and mean annual precipitation of 1290 mm (n = 22, predominantly microphylls and notophylls). Conclusions The palaeovegetation was clearly lowland tropical forest with a dry aspect, but anomalous aspects of the wood anatomy are consistent with the high temperatures indicated by the leaves and are probably explained by differences in seasonality and water stress compared to the present-day Neotropics. A close modern analogue may be in very seasonal regions of Asia. Pronounced monsoonal (summer-rain) conditions may relate to a location (palaeolatitude of 13°S) outside the near-equatorial tropics.

The Piedra Chamana fossil woods and leaves: a record of the vegetation and palaeoenvironment of the Neotropics during the late middle Eocene.

The Piedra Chamana fossil forest in northern Peru is an assemblage of angiosperm woods and leaves preserved in volcaniclastic rocks dated to 39 Mya (late Middle Eocene). We analysed the anatomical and morphological features of the fossils to reconstruct the palaeoenvironment during this time of global warmth, taking advantage of the co-occurrence of woods and leaves to compare different proxies and analytical approaches. Wood characters analysed include vessel-related functional traits, traits linked to Baileyan trends, and quantitative features such as vessel diameter and density. Diameter-distribution and diameter and position plots are used to represent vessel diameter and arrangement. Leaf margin and area analysis provides additional climate estimates. The fossil woods show many similarities with modern tropical-forest woods and tropical fossil-wood assemblages; closest correspondence within the Neotropics is to semi-deciduous lowland tropical forest with moderate precipitation (~1000-1200 mm). Features unusual for the modern South American tropics are mainly vessel-related characters (semi-ring porosity, grouped vessels, helical vessel thickenings, short vessel elements) linked to water stress or seasonal water availability. Leaf analysis indicates mean annual temperature of 31 °C (n = 19, 100 % entire-margined) and mean annual precipitation of 1290 mm (n = 22, predominantly microphylls and notophylls). The palaeovegetation was clearly lowland tropical forest with a dry aspect, but anomalous aspects of the wood anatomy are consistent with the high temperatures indicated by the leaves and are probably explained by differences in seasonality and water stress compared to the present-day Neotropics. A close modern analogue may be in very seasonal regions of Asia. Pronounced monsoonal (summer-rain) conditions may relate to a location (palaeolatitude of 13°S) outside the near-equatorial tropics.

Paleoclimate and paleoecology of the latest Eocene Florissant flora of central Colorado, U.S.A.

The uppermost Eocene Florissant Formation of central Colorado, U.S.A. contains a diverse flora and fauna preserved in lacustrine facies and represents a key episode in Earth history immediately preceding the Eocene-Oligocene boundary. Laminated shales contain impressions of non-monocot angiosperm leaves that were used to estimate paleoecological and paleoclimatic parameters using leaf physiognomic methods including: leaf mass per area (MA), digital leaf physiognomy (DiLP), leaf margin analysis (LMA), and leaf area analysis (LAA). The majority (58%) of the morphotypes analyzed for MA suggested a semi-evergreen leaf lifespan, whereas another 27% indicated a deciduous habit and 15% an evergreen habit. There was no significant relationship between MA and insect damage based on a small subset of Florissant's leaves. Higher MA values (~73% of leaves ≥ one-year lifespan), coupled with a tendency toward long and narrow leaf shapes and small leaf areas, indicate the existence of sclerophyllous vegetation. Using the global regression for mean annual temperature (MAT), the DiLP estimate of MAT was anomalously cold: 5.5 ± 4 °C. However, using a Northern Hemisphere regression the DiLP MAT estimate of 11.6 ± 3.3 °C was more plausible. Using DiLP, mean annual precipitation (MAP) was estimated at 740 + 608/−334 mm∙yr−1, which supports dry conditions. Estimates for MAT and MAP using the univariate LMA and LAA methods overlapped within uncertainty of the DiLP results. In addition, those taxa classified as growing in wet areas (riparian) had significantly more teeth than non-riparian taxa. These paleoclimatic and paleoecological results suggest that outside the riparian forest, the Florissant flora sampled a seasonally dry temperate sclerophyllous shrubland to woodland, perhaps similar to modern chaparral forests, in the western interior of the U.S.A. just before the transition into the cooler Oligocene.

The Kanaka Creek fossil flora (Huntingdon Formation), British Columbia, Canada — paleoenvironment and evidence for Paleocene age using palynology and macroflora

Paleogene sediments of the Huntingdon Formation, a correlative to the Chuckanut Formation of neighbouring Washington State, USA, are exposed in the Greater Vancouver area, British Columbia, Canada. Palynology and plant macrofossils suggest the Kanaka Creek section is Paleocene rather than Eocene in age. Detrital zircon dating is less decisive, yet indicates the Kanaka rocks are no older than Maastrichtian. Analyses of plant macro- and micro-fossils suggest an early to middle Paleocene age for the Kanaka fossil flora. Paleocene indicators include macrofossils such as Platanus bella, Archeampelos, Hamamelites inequalis, and Ditaxocladus, and pollen taxa such as Paraalnipollenites, Triporopollenites mullensis, and Duplopollis. Paleogene taxa such as Woodwardia maxonii, Macclintockia, and Glyptostrobus dominate the flora. Fungal spores including the Late Cretaceous Pesavis parva and the Paleogene Pesavis tagluensis are notable age indicators. Physiognomy of 41 angiosperm leaf morphotypes from Kanaka Creek yields mean annual temperatures in the microthermal to lower mesothermal range (11.2 ± 4.3 to 14.6 ± 2.7 °C from leaf margin analysis; 14.8 ± 2.1 °C from Climate Leaf Analysis Multivariate Program), with mild winters (cold month mean temperature 3.9 ± 3.4 °C). Paleoclimate was cooler than the upper Paleocene and Eocene members of the Chuckanut Formation. Mean annual precipitation is estimated at ∼140 cm with large uncertainties. The Kanaka paleoflora is reconstructed as a mixed conifer–broadleaf forest, sharing common taxa with other western North American Paleocene floras and growing in a temperate moist climate. Kanaka Creek is a rare coastal Paleocene plant locality that provides new insights into coastal vegetation and climate prior to the Paleocene–Eocene Thermal Maximum.

The Cenozoic leaf morphotypes and palaeoclimate interpretation from the Doi Ton Formation, Mae Sot District, Tak Province, western Thailand

The Cenozoic palaeovegetation and palaeoclimate of Doi Ton, western Thailand, megaflora are reconstructed based on physiognomic climate analysis, including Leaf Margin Analysis (LMA), Leaf Area Analysis (LAA), Leaf Size Index (LSI), Climate Leaf Analysis Multivariate Program (CLAMP), and systematic descriptions of each leaf morphotype. The leaf fossils were divided into 23 dicotyledonous leaf morphotypes and two unknown leaf morphotypes. The mean annual temperature results from LMA indicate 32.3 ± 1.17 °C and CLAMP shows 21.2°C. CLAMP also provides temperature data of a warm month mean temperature (WMMT) of 27.4 °C and a CMMT of 14.2 °C, which is similar to the present climate. The mean annual precipitation is estimated by LAA to be ~ 125 cm. CLAMP suggests precipitation in the 11 months of growing period was 154.9 cm with the three wettest months having precipitation of 73 cm, widely contrasting with 15.5 cm for the three driest months. The precipitation shows the signal of the monsoon effect. The temperature, precipitation, and LSI mirrored the vegetation of the contemporary Doi Ton area which is a semi-evergreen forest in the tropical zone. The palaeoclimatic parameters of Doi Ton are in good agreement with those of south China and northwestIndia from the Eocene period and the present-day Mae Sot area. Moreover, the Doi Ton flora also closely matches the humid subtropical modern vegetation of south China. Palaeoclimate and vegetation analysis support an Eocene age estimate for the Doi Ton Formation however further independent age estimates are required to test this working hypothesis.

THE PALEOBOTANY AND PALEOECOLOGY OF THE EOCENE HERREN BEDS OF NORTH-CENTRAL OREGON, USA

ABSTRACTNew collections of plant macrofossils and radiometric dates from the Herren beds of north-central Oregon provide the opportunity to document floral communities and calculate foliar-derived climate estimates from the warm early Eocene and the cooler middle Eocene. Plant macrofossils were collected from one fluvial site at East Birch Creek approximately 2 m below a 51.9 ± 0.9 Ma tuff. Collections were also made at two co-occurring fluvial sites at Arbuckle Mountain, whose ages are constrained to ca. 44.5–43.8 Ma based on a dated tuff from Willow Creek (44.5 ± 0.8 Ma) and reported ages for the overlying Clarno Formation. Floral findings show an almost complete vegetation overturn, with only two genera (Glyptostrobus and Allantodiopsis) appearing in both floras. Both floras are species poor, but the older East Birch Creek flora has higher richness and evenness than the younger Arbuckle Mountain flora. The four named genera at East Birch Creek are taxa found throughout Eocene North America; named genera at Arbuckle Mountain also include taxa restricted to the Pacific Northwest. Leaf margin analysis and leaf area analysis of the East Birch Creek community suggest a warmer and possibly wetter (mean annual temperature 23.4 ± 4.3 °C; mean annual precipitation 206 +89, -63 cm) climate than the Arbuckle Mountain flora (16.4 ± 4.2 °C; 165 +50, -71.4 cm). This research provides a framework for future research on Eocene floristic, environmental, and climatic trends of the Pacific Northwest.

Fossil mega- and micro-flora from Bernasso (Early Pleistocene, southern France): A multimethod comparative approach for paleoclimatic reconstruction

Bernasso is an Early Pleistocene locality that has a well-dated floral fossil content including both pollen grains and megaremains. Pollen record shows vegetation changes corresponding to two glacial and one interglacial periods. The megafloral fossil assemblage was interpreted as an association of present-day Mediterranean and Caucasian taxa that developed during a late interglacial stage of the beginning of the Pleistocene. In the present study, climatic reconstruction using the Climate Leaf Analysis Multivariate Program (CLAMP) and the Leaf Margin Analysis (LMA) methods based on the megaflora on one hand and using the Climatic Amplitude Method (CAM) based on the pollen flora on the other hand have been used to check the qualitative climatic estimates based on the comparison between paleovegetation data and similar modern ecosystems. CLAMP and LMA analyses show that the Bernasso climate was colder than the present-day climate of Southern France and of the Hyrcanian and Euxinian regions. On contrary, CAM shows mean annual temperatures higher than the modern Bernasso temperature and equivalent to the temperature of the Hyrcanian and Euxinian regions. Mean annual precipitation and relative humidity reconstructed by CLAMP and CAM are in agreement and indicate that the climate was wetter than today at Bernasso. The differences between the three methods highlight important methodological biases that could be solved by including additional calibration sites in Europe and in the Mediterranean region.

Monsoon-induced errors in paleotemperature estimation based on leaf morphology analysis in central Japan

Models based on the relationship between leaf morphology and climate parameters of different regions have been used for paleoclimate estimation. Information from Japanese floras has been included in some of these models; however, variation in the distribution pattern of leaf margin within Japan caused by the effect of topography and East Asian Monsoon has not been reflected in these previously published leaf margin analysis models. In this study, we investigate the relationship between leaf characters and climate parameters under different climate conditions within a small geographical scale and, in doing so, improve the accuracy of leaf physiognomy-based paleoclimate reconstruction. We use the local flora in central Japan as an example to determine the distribution pattern of leaf margin (toothed and untoothed) and habit (evergreen and deciduous) characteristics under monsoon climate conditions. In areas along the Pacific Ocean (P-zone), the leaf margin and habit types correlated with the temperature parameters and growing season precipitation. The P-zone includes more toothed species than in other regions of the world obtained with published models at a given mean annual temperature. In the areas along the Sea of Japan (J-zone) with deeper snow cover during the winter, the percent of sub-canopy evergreen shrubs increases, especially at higher altitudes. No significant relationship between leaf margin characters and climate parameters was observed in this area. As heavy snow was a feature of this region since late Early Pleistocene times, paleoclimate estimation based on leaf margin of fossil assemblages younger than Early Pleistocene from these areas might be less reliable. In addition, we found that the leaf margin of woody shrub species is less sensitive to the mean annual temperature than tree species.

An Oligocene microthermal forest dominated by Nothofagus in Sierra Baguales, Chilean Patagonia: Response to global cooling and tectonic events

A large fossil leaf assemblage (>3700 specimens) is reported from the Oligocene Río Leona Formation in the Sierra Baguales of Chilean Patagonia. The association comprises 29 species but is dominated by Nothofagus genera, which constitutes 65% of specimens. The collection can be classified as a Mixed Palaeoflora of the Austral-Antarctic association. Stratigraphic analysis of the assemblage indicates a decrease in species diversity and richness over time, which was accompanied by species turnover. Quantitative studies of foliar morphology (CLAMP, Leaf Margin Analysis) indicates cool-to-cold and dry climatic conditions, with a Mean Annual Temperature of 9.2 °C, a relatively high seasonality in temperature and precipitation, and a Mean Annual Precipitation of 931 mm. Nothofagus only became dominant in southeastern Patagonia during the Rupelian, coinciding with a marked global cooling period linked to the initiation of glaciation in Antarctica about 34 Ma. The decrease in precipitation following this event is attributed to the development of a rain shadow to the east of the rising Southern Patagonian Andes, which must have been of the order of 1000 m or more for topographic climate forcing to take effect. This contrasts with the rain shadow development east of the Andes at lower latitudes, which was mainly manifested after the middle Miocene.

Interpretações paleoclimáticas a partir da tafoflora de Caieira, Formação Pirabas, Oligoceno/Mioceno da Amazônia Oriental, Pará, Brasil

The Caieira taphoflora, which is associated with the Pirabas Formation, is the best documented one for the Oligocene/ Miocene of the eastern Amazonia. The taphoflora represents a predecessor of a phytophysiognomy of the Amazon Forest, specifically of a floodplain forest, which has developed under a warm and humid climate. The main physiognomic characteristics – type of margins and leaf area – of the angiosperm leaves of 19 species of this taphoflora, allowed us to carry out the reconstruction of the mean annual temperature (MAT) and the mean annual precipitation (MAP) for the moment of its deposition. The different equations used to reconstruct the MAT and the MAP are based on univariate methods known as Leaf Margin Analysis and Leaf Area Analysis. These equations indicated that the Caieira taphoflora developed under a MAT between 24.6 and 25.0 °C, and a MAP between 1849 and 2423 mm. The values are similar to the current values for the region where the taphoflora was collected, therefore, it is possible to infer that the current climatic configuration has been firmly established since the Oligocene/Miocene, as well as its vegetation. The values also indicate that the climate was colder, between 1.1 and 1.5 °C, and less humid, between 42 and 619 mm, for the moment of deposition of the Caieira taphoflora, possibly due to the global cooling event known as Mi-1 glaciation, which affected the whole Amazonia during the Oligocene/Miocene transition.