Dating Amber: Review and Perspective

Abstract

Amber is a fossilized tree resin that ranges in age from the Carboniferous to the Cenozoic. It occurs globally from the Arctic to Antarctica. As the resin petrifies and turns into amber, it can enclose and preserve other materials. Amber with inclusions can help reconstruct past biodiversity and ecosystems. Some amber contains fossils representing the oldest and most detailed records of critical evolutionary traits or markers. Inclusions can even capture behavioral indicators previously only observed in extant organisms. Evidence of insect pollination of flowering plants and dragonfly mating behavior appears in amber, as does the morphological specialization of insects, indicating sociality and social parasitism. Dating amber deposits can help calibrate evolutionary events and inform reconstructions of past ecosystems. While the direct dating of amber remains impossible, age constraints on most amber deposits are based on correlations or relative dating, methods that come with significant uncertainties. This study discusses two cases using 40Ar/39Ar and U–Pb geochronologic methods to constrain the ages of amber deposits in China and the paleo-ecosystems they record. This paper also summarizes how radio-isotopic dating and other techniques combined with the analysis of inclusions in amber can help elucidate biogeography and the dynamic relationship between life and the physical environment.

Eocene amber provides the first fossil record and bridges distributional gap in the rare genus Robsonomyia (Diptera: Keroplatidae)

“…However, the precise age of the amber remains unknown. The main reason is secondary redeposition; the amber has been transported and dispersed across the Northern European Plain, due to inter alia marine transgression and glaciers during the Pleistocene 26 , 27 . Consequently, the amber is not found in its original sedimentary context, and its stratigraphic history remains elusive 28 .…”

“…Consequently, the amber is not found in its original sedimentary context, and its stratigraphic history remains elusive 28 . Additionally, Baltic amber lacks radiogenic isotopes with long-term half-lives, preventing the direct application of radioisotopic dating methods for precise age determination 26 . The age of Baltic amber has been a subject of extensive debate, leading to the implementation of various methods that have yielded different results.…”

New fossil data reveal evolutionary pathways within the genus Trichoneura Loew, 1850 (Diptera, Limoniidae)

“…There are other rich Cretaceous deposits, e.g. in China, like Late Cretaceous Xixia of Henan in Henan Province, Upper Cretaceous Jiayin amber in Heilongjiang Province 28 or Hailar amber, the oldest known amber in China 29 , located within the Central Asian Orogenic Belt between the Siberian and North China–Mongolian cratons 30 . It was proposed that amber discovered from Lower Cretaceous deposits would bridge gaps among several well-known amber deposits, including Lebanese amber and Spain amber, amber from France or from Myanmar 29 .…”