Iron Age Vegetation Dynamics and Human Impacts on the Vegetation of Upper Mun River Floodplain,N.E. Thailand1

Here we present a revised interpretation of pollen analyses at Iron Age archaeological sites on the floodplain of the Mun River, northeast Thailand. Following publication of a full chronometric data set for these sites, it has become apparent that the original and admittedly tentative conclusions from the pollen analyses require reassessment. The original account was flawed in two ways: the presumed time span of the record was considerably longer than we believe it to be now; and our correlation between neighbouring sequences was in error. Our new understanding of the evidence allows us to present a vegetation history of the study area that is confined to the details of land use and human impact during the latter half of the Thai Iron Age. Here we also are able to identify ecological groups and landscape partitioning patterns during that period. In particular, we record phases of human impact, with periods of forest clearance and its replacement by grasslands with likely rice cultivation and arboriculture.     

Syn-tectonic pluton intrusion during contractional deformation: microstructural and metamorphic evidence from the aureole of the Acadian Victory Pluton, north-eastern Vermont, USA

Structures within the aureole of the Acadian (Devonian) Victory Pluton suggest that movement along the Monroe Fault occurred during pluton intrusion. Pre- or syn-tectonic garnet textures, including discordant internal and external foliations, sigmoidal inclusion trails and deflection of the matrix foliation around garnet, are found along the Monroe Fault. In sillimanite+K-feldspar grade rocks, the matrix foliation, defined by biotite and fibrolitic sillimanite, wraps around garnet and sillimanite porphyroblasts. Granite dykes and sills near the pluton contact are folded and boundinaged, and leucosome fills garnet pressure shadows and shear bands. Away from the fault and pluton contact, microstructures indicate much less deformation during metamorphism, suggesting that deformation was partitioned into the fault or the pluton. Deformation ceased before crystallization of the main body of the Victory Pluton was complete. It is possible that magmatism facilitated deformation along the Monroe Fault, and/or that the magma was transported to the mid- to upper crust along the Monroe Fault. This study suggests that Acadian deformation in north-eastern Vermont occurred as late as 390–370  Ma.