A multiproxy record from a fast‐growing stalagmite reveals variable hydroclimate on the California coast across the 8.2 kyr event and a precursor event likely caused by initial drainage of proglacial Lake Agassiz. Using speleothem δ44Ca, we develop the first semiquantitative estimates of paleorainfall variability for California through calibration with measurements of the modern climate and cave environment. We find that the magnitude of rainfall variability during the 8.2 kyr event approached the multiyear variability observable in the recent past (1950–2019) and the magnitude of variability during the precursor event likely exceeded this range. Additionally, we observe other instances of multidecadal variability comparable in magnitude to the precursor event during the record. Our work suggests that speleothem calcium isotope ratios are a powerful semiquantitative means to reconstruct paleorainfall, although numerous factors must be assessed in each cave system before applying this approach.

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Recent wildfire activity in semi-arid regions like western North America exceeds the range of historical records. High-resolution paleoclimate archives such as stalagmites could illuminate the link between hydroclimate, vegetation change, and fire activity in pre-anthropogenic climate states beyond the timescale of existing tree-ring records. Here we present an analysis of levoglucosan, a combustion-sensitive anhydrosugar, and lignin oxidation products (LOPs) in a stalagmite, reconstructing fire activity and vegetation composition in the California Coast Range across the 8.2 kyr event. Elevated levoglucosan concentrations suggest increased fire activity while altered LOP compositions indicate a shift toward more woody vegetation during the event. These changes are concurrent with increased hydroclimate volatility as shown by carbon and calcium isotope proxies. Together, these records suggest that climate whiplash (oscillations between extreme wetness and aridity) and fire activity in California, both projected to increase with anthropogenic climate change, were tightly coupled during the early Holocene.

Cathodoluminescence (CL) images of kyanite reveal several internal textures, including sector zoning, oscillatory zoning, and cross‐cutting relationships among different domains. Many textures observed in kyanite correspond to discrete events, thereby connecting kyanite textures to the pressure–temperature (P–T) history of the rock. To evaluate the record of metamorphism preserved by kyanite, metapelites were selected from three different orogens that reflect P–T conditions ranging from amphibolite to ultrahigh‐pressure (UHP) facies. Cross‐correlation of variations in CL intensity, chemistry, and crystal orientation within kyanite indicate the following findings. First, the preservation of original growth zones in kyanite from poly‐metamorphic rocks demonstrates that growth zoning in kyanite persists through metamorphic events and is not erased by diffusion or complete recrystallization. In some samples, kyanite retains evidence of its reaction history during growth. Second, measured changes in absolute crystallographic orientation do not correspond with changes in CL intensity in any of the measured samples, including kyanite twins. Third, both kink banding and undulatory extinction are present across all samples, consistent with rotation about <010> in the (100)[001] slip system. Kyanite from (U)HP samples exhibits higher amplitude undulations than kyanite from lower‐grade lithologies, suggesting that crystallographic orientation data may provide complementary insight about deformation along the P–T path. Fourth, specific CL and trace element signatures in kyanite can be correlated with discrete metamorphic histories; yet, CL intensity and colour are affected by multiple elements, not a single controlling element. In sum, multiple generations of kyanite can be identified by careful cross‐correlation of CL and geochemical data, and when combined with crystal orientation data, kyanite provides a robust record of a rock's P–T evolution.