Angela A Bruch

Testing the climatic estimates from different palaeobotanical methods: an example from the Middle Miocene Shanwang flora of China

The Miocene Shanwang biota from eastern China contains exceptionally well-preserved plant fossils with abundant leaf fossils and palynomorphs co-occurring at several levels in the sedimentary succession. This has provided an ideal opportunity to undertake detailed comparative quantitative palaeoclimate reconstruction, based on both mega- and microfloral assemblages, using various approaches, namely the coexistence approach (CoA), leaf margin analysis (LMA) and Climate Leaf Analysis Multivariate Programme (CLAMP). By applying these approaches to the same dataset and using multiple fossil assemblages from different levels we are able to compare results from the different methods of climate prediction. CLAMP and LMA give consistently lower temperature (mean annual temperature, MAT) predictions than the CoA. Taking errors into account all methods indicate no overall climate change through the sequence studied. Results from CoA show overall agreement in the palaeoclimate parameters obtained using both pollen and leaf datasets indicating a high degree of internal consistency with this method.

Reconstructing palaeotemperatures using leaf floras – case studies for a comparison of leaf margin analysis and the coexistence approach

Abstract In the past the problems and advantages of the nearest-living-relative (NLR) and leaf physiognomy approaches have been repeatedly discussed and it has been demonstrated that both approaches frequently show broad agreement with each other. However, detailed comparisons of the various methods for accuracy in estimation of palaeoclimate at individual localities are still lacking. Such studies are needed before data obtained from different approaches can be integrated in palaeoclimate maps and models. Moreover, there are some indications that leaf physiognomy and NLR approaches may lead to different results. In this study we applied a physiognomic method based on leaf margin analysis and the coexistence approach, a recent variation of the NLR approach, to two Tertiary palaeofloras (Schrotzburg, Middle Miocene, south Germany; Kleinsaubernitz, Upper Oligocene, east Germany). We demonstrated that both approaches can produce reasonable and consistent results if the standard error of the leaf physiognomy palaeoclimate data is taken into account. However, our results and interpretations indicate that reconstructions based on leaf physiognomy are influenced by factors not related to climate, such as sample size and differential preservation or transport. In contrast, reconstructions for the same fossil assemblages based on the coexistence approach seem to be less affected by taphonomic variables, but may be less sensitive to minor climate changes.

Palaeoclimate versus vegetation reconstruction – palynological investigations on the Oligocene sequence of the Sava Basin, Slovenia

Abstract An Oligocene succession from the Slovenian Sava Basin (Zasavje) was analysed to reconstruct climate and vegetation of the interval. Independent quantitative approaches were applied on a detailed palynological data set to reconstruct both parameters separately allowing for a synthesis and interpretation. The reconstruction of palaeoclimate is based on the coexistence approach and documents an equal, warm-temperate, humid climate with low annual variation. Quantitative results indicate values of mean annual temperature of 16–19°C, with winter temperatures of 6–9°C and summer temperatures of 25–28°C, and a mean annual precipitation ranging between 1100 and 1300 mm. In contrast to the very homogeneous climatic signal, the vegetational reconstruction based on multivariate statistical analyses shows distinct changes through time. During intervals of peat accumulation, the environment was a typical swamp vegetation dominated by Taxodiaceae and ferns, in which ephemeral small ponds developed due to changing groundwater levels. With the development of an expanded limnic environment, the Taxodiaceae retreated and a riparian swamp flora dominated. This vegetation, in turn, was displaced by elements of drier mesophytic habitats that increased in abundance during a tectonically forced lowering of the groundwater table. Subsequently, the entire study area was flooded by transgression and overlain by marine sediments. All changes in vegetation can be explained by influences of the basin development on the habitats of the plant communities. The results demonstrate a vegetational change in the Oligocene of the Sava Basin that is independent from climate. Vegetation change dynamics were controlled probably by the regional tectonic–palaeogeographic development within a very equable, warm-temperate, and humid climate.

Monsoon versus Uplift in Southwestern China–Late Pliocene Climate in Yuanmou Basin, Yunnan

Yuanmou Basin of Yunnan, SW China, is a famous locality with hominids, hominoids, mammals and plant fossils. Based on the published megaflora and palynoflora data from Yuanmou Basin, the climate of Late Pliocene is reconstructed using the Coexistence Approach. The results indicate a warm and humid subtropical climate with a mean annual temperature of ca. 16–17°C and a mean annual precipitation of ca. 1500–1600 mm in the Late Pliocene rather than a dry, hot climate today, which may be due to the local tectonic change and gradual intensification of India monsoon. The comparison of Late Pliocene climate in Eryuan, Yangyi, Longling, and Yuanmou Basin of Yunnan Province suggests that the mean annual temperatures generally show a latitudinal gradient and fit well with their geographic position, while the mean annual precipitations seem to be related to the different geometries of the valleys under the same monsoon system.