Amber taphonomy and the Grassy Lake, Alberta, amber fauna

Abstract

A taphonomic model of processes affecting samples of amber inclusions is outlined. Comparison of collecting methods indicates that significant amounts of amber are overlooked by traditional methods. Screened samples produce more inclusions with lower between-sample variation and more Homoptera per kilogram of amber. Collecting method affects the paleoecological and paleoenvironmental interpretation of samples. Community structure and organization can be more accurately described and compared using screened samples. Also, changes in terrestrial arthropod diversity can be more accurately measured. Comparison is difficult if samples have been collected by different methods and will produce poorer results. Data from resin in a modern forest correspond well with fossil resin data. Mesozoic resins (120 to 75 million years old) trapped arthropod taxa very consistently. Cenozoic resins trapped arthropods in almost the same manner as measured by taxon rank, but presented very different taxon percentages. Differences between Cenozoic and Cretaceous taxon ranks are due to changes in arthropod faunas. Acari, Collembola, and Lepidoptera are the best candidates for study of changes in diversity and abundance. There are about 130 hexapod species recognized in this deposit, the most diverse Cretaceous insect assemblage known. Of 65 identified families, 15 are extinct. Only one of about 77 genera identified is extant. All recognized species are extinct. Morphology and feeding structures are within the variation seen in modern insects. The taxonomic structure of modern insect communities was well established before the end of the Cretaceous, with few exceptions.