Deposition of distal tephra-fall deposits in lake systems with low watershed sediment fluxes can represent large geochemical anomalies in sediment elemental composition. We examine the persistence of compositional effects of fallout from the 7.63 kyr BP Mt. Mazama caldera-forming event and other tephra deposits in the micro-laminated abyssal sediments of Pettit Lake, central Idaho, which received ~50 kg m−2 of Mazama tephra-fall material. Persistent post-depositional dominance of the Mazama material is reflected in elemental composition and grain size distribution and is related to lake hypsometry and the presence of a large in-lake sediment reservoir subject to remobilization. Decoupling of recycled clastic mineral material with Mazama compositional affinity from both biogenic matter and from clastic material derived from within the watershed is shown by coherence between dated primary tephras and a radiocarbon chronology.
Bibliographical noteFunding Information:
Core retrieval was supported by the Gordon and Betty Moore Foundation. Data analyses were supported by NSF award numbers EPS-0814387 and EPS-1006968 from the NSF Idaho EPSCoR Program. Field support was provided by The University of Minnesota LRC/LacCore and by the efforts of citizen scientists Tim Wilkins and Janet Holmgren. Eric Johnson performed grain-size analyses. Bob Griswold generously shared lake physiochemical data as well as valuable thoughts on Stanley Basin lakes.
© 2015, Springer Science+Business Media Dordrecht.
- Elemental composition
- Lake sediments
- X-ray fluorescence