178-5 New Evidence of Deciduous and Evergreen Conifers in Late Cretaceous Antarctic Forests

Session: Paleontology, Diversity, Extinction, Origination

Presenting Author:

Authors:

Abstract:

The temperate forests of the Late Cretaceous of Antarctica comprised an enigmatic ecosystem with no direct modern analogue due to the combination of consistently above-freezing temperatures and the presence of a polar light regime. These dynamics lead to the hypothesis that seasonality in this environment was controlled at least in part by light dynamics in addition to climate. The impact of light-availability-based seasonality and other stresses associated with prolonged exposure and absence of sunlight on the paleoenvironment of southern temperate polar forests is still unclear. However, anatomical signals from permineralized fossil wood, ubiquitous in the Late Cretaceous strata of James Ross Island, provide valuable insights into leaf abscission and retention in conifers, a cycle that can be strongly influenced by seasonality. Quantitative measurements of tracheids in gymnosperm wood allow a technique called the Cumulative Sum of Deviation from the Mean (CSDM) curve to be used, which estimates the seasonal timing of leaf retention and abscission in conifers. Using this method, the first unambiguously deciduous conifer in the Late Cretaceous of Antarctica is reported. New evergreen conifer specimens are also present, with estimated leaf retention times ranging from 1–5 years. These new data on temperate polar forest dynamics add to scientific understanding of the impacts of past greenhouse climates and can inform future polar climate predictions.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9876

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