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Myanmar is located within an important geographic corridor of prehistoric demographic and technological exchange, yet relatively few archaeological sites have been securely dated. Here, the authors present a new radiocarbon chronology for Halin, a UNESCO-listed complex in the north-central Sagaing Division of Myanmar, which contributes to the generation of nuanced regional chronologies and to improving the temporal resolution of Southeast Asia more generally. Discussion of 94 radiocarbon determinates, together with site stratigraphy and pottery traditions, provides a chronological sequence from the early third millennium BC to the early second millennium AD. Corroboration of the beginning of this sequence would place Halin as the oldest currently dated Neolithic site in Mainland Southeast Asia and would provide support for the two-layer model of Neolithic migration. Keywords: Southeast Asia, Neolithic, Bronze Age, Iron Age, Pyu, radiocarbon, Introduction The national territory of the Union of the Republic of Myanmar (henceforth, Myanmar) constitutes the sub-Himalayan corridor for terrestrial human interactions from Initial Human Colonisation about 60 kya to [...]

Our study underpins the mechanism of organo-mineral interaction between black carbon (BC, biochar) and associated minerals in the historical BC-rich Amazonian Dark Earth (ADE) by using synchrotron-based microscopic (TXM), microspectroscopic (μFTIR) and spectroscopic (XAS and μ-diffraction) approaches. The BC-rich ADE contained over 100% more poorly crystalline minerals than the adjacent tropical soil. Linear combination fitting of k-spacing in the X-ray Absorption Spectra (XAS) revealed that ferrihydrite contributed to 81.1% of the Fe-minerals in BC. A small but distinct peak was observed at 5.7 Å-1 in the extended X-ray absorption fine structure k oscillation of BC, revealing the presence of FeC (including Fe-O-C) covalent bonds. No FeC path was yielded by the XAS fitting when an obvious peak downshift of the first (FeFe1) shell was observed, suggesting that the availability of inner-sphere FeC complexation was limited to the BC surface and interphase region. The main minerals for organo-mineral complexation were short-range-order (SRO) ferrihydrite on BC instead of corner-sharing FeO6 octahedra. Compared to ADE, the coordination number of the first (FeFe1) and second (FeFe2) shell was higher in BC, revealing a higher degree of order in coordination between the neighboring Fe mineral crystals. Black C limited the progressive aging of amorphous Fe phases and greatly enriched SRO ferrihydrite in the redox-fluctuating and high-leaching environment. The transformation of SRO ferrihydrite into the more crystalline Fe oxides was controlled by the local pH environment. A strong signal from the complexed phenolic group (aryl-OH, 1241 cm-1) and a distinct band of inner-sphere complexation (Fe-aryl C, 1380-1384 cm-1) were identified in the FTIR spectra. The enrichment of poorly crystalline minerals can have positive feedback on the long-term stabilization of BC. The scale-up application of biochar to agricultural and ecological systems may have a long-lasting impact on the enrichment and transformation of the SRO minerals in the soil.

Due to the incorrect speciation of iron during thermometry modelling, Coulthard et al. (2024) produced an incorrect olivine‐liquid equilibrium diagram, which failed to identify multiple potential equilibrium olivine‐melt pairs. With the new pairs identified here, the temperatures inferred from olivine‐groundmass pairs move closer in temperature space to those inferred from olivine‐glass pairs. Additionally, it is recognised that the most significant difference between these thermometry data is due to differences in inferred melt water mass fraction. If a mean value of water is used for all thermometry, the mean temperatures calculated for olivine‐glass and olivine‐groundmass pairs converge to within 10 °C of one another. This indicates that groundmass compositions inferred via the defocused beam analysis of a polyphase groundmass may reproduce enough information to confidently perform olivine‐melt thermometry despite the glass and groundmass data representing significantly different compositions in multivariate space. [ABSTRACT FROM AUTHOR]

Polyphase groundmasses (micro‐scale minerals with or without glass) are generated from silicate liquids during the cooling of natural lavas often alongside larger minerals formed long before eruption. Many researchers have posited that compositions gleaned from the analysis of groundmasses closely approximate the compositions of the melts they were derived from, and these have been used frequently to model pre‐eruptive magma conditions. However, it is difficult to confidently identify and sample these groundmasses once they are formed. Using a sample of lava that exhibits a wide degree of textural variation (ranging from holocrystalline to hypohyaline) we show that compositions of groundmasses sampled using defocused electron beams are significantly different from glass compositions in terms of mean composition and covariance. Despite this, several groundmass compositions qualify as 'in equilibrium' with matrix/rim olivine. When processed using available thermometers, however, modelled equilibrium temperatures are significantly higher than those produced using glass data, on average. Because of this, we prescribe caution in using polyphase groundmass data generated using defocused beam analysis even as a rudimentary approach. [ABSTRACT FROM AUTHOR]

The residence timescales of antecrystic minerals contribute a key piece of information regarding the petrologic evolution of transcrustal magmatic systems and may be inferred using a combination of observations derived from microanalytical chemistry and diffusion modelling. Here, we present state-of-the-art stacked CMOS-type active pixel sensor (SCAPS) isotopographic images of tephra-hosted plagioclase microantecrysts from Tongariro Volcanic Centre in the southern Taupo Volcanic Zone, New Zealand. These crystals exhibit high-frequency Sr and anorthite zonation at sub-micron spatial resolution. We also find that all crystals display high-frequency intracrystalline Sr chemical potential variations, indicating that they have not resided at magmatic temperature for diffusive relaxation to advance significantly. To quantify crystal residence times at the well-constrained magmatic temperatures of these tephras, we first forward-modeled intracrystalline Sr diffusion over time using numerical methods. Results were then analyzed using novel spatial Fourier-transform techniques developed to understand the systematics the diffusive decay of Sr disequilibria in the spatial frequency domain. This ultimately permitted the estimation of Sr concentration profiles at crystal formation, prior to uptake into the carrier melt at the onset of eruption. Our data imply residence times of hours to days for the studied microantecrysts. This is inconsistent with long antecryst residence times in magmatic mushes at elevated temperatures, pointing instead to a cool plutonic nature of the magmatic plumbing system beneath the southern Taupo Volcanic Zone. [ABSTRACT FROM AUTHOR]

Late prehistoric archaeological research in Myanmar is in a phase of rapid expansion. Recent work by the Mission Archeologique Francaise au Myanmar aims to establish a reliable Neolithic to Iron Age culture-historical sequence, which can then be compared to surrounding regions of Southeast Asia. Excavations at Nyaung'gan and Oakaie in central Myanmar have provided 52 new AMS dates, which allow the creation of Myanmars first reliable prehistoric radiometric chronology. They have also identified the Neolithic to Bronze Age transition in central Myanmar, which is of critical importance in understanding long-range interactions at the national, regional and inter-regional level. This research provides the first significant step towards placing late prehistoric Myanmar in its global context. Keywords: Southeast Asia, Myanmar, Late Neolithic, Bronze Age, Introduction Myanmars location makes it pivotal to tracing cultural, genetic, linguistic and technological links between South, East and Southeast Asia. Investigations of its prehistory, however, are in their infancy, with [...]