Marine faunas in the Holocene of the Oslofjord area – climate, sea level, faunal invasion
Marine sediments of the Holocene (last 10,000 years) in the Oslofjord area are now widely exposed on land because of relative drop in sea level. These clays and sands are rich in well-preserved fossils of bivalves, gastropods and other invertebrates, recording dramatic changes in climate, sea level and ecology through time.
These faunas have not been extensively studied for more than a hundred years (Brøgger 1901). Since then, our understanding of Holocene climate and ecology has increased enormously, and methods have vastly improved regarding e.g. radiocarbon dating, geochemistry for climate reconstruction, and ecological and stratigraphic data analysis.
We believe that the Holocene marine faunas in the Oslofjord area can provide a fruitful field of research into the ecology of environmental change. Since the taxa are the same as in our time, the Holocene data can be used as good analogues for modern processes, and possibly inform predictions about marine faunal responses to anthropogenic warming, sea level rise and faunal invasion such as that of the Pacific oyster.
We need several MSc students (biology or geology) to carry out a pilot study, giving you a unique opportunity to open up a new area of research. Old localities must be rediscovered, so some treasure hunting will be required!
1. The Preboreal invertebrate faunas of the Oslofjord area
This project will focus on the first invertebrates to colonize the area after the ice cap receded, especially the bivalves, crustaceans and foraminifera near the so-called “marine limit”, i.e. the locally highest sea-level during deglaciation. What can the taxonomic composition of the faunas (often with Mytilus and barnacles), size distributions, sediment properties and geochemistry tell us about the early Holocene succession during rapid climatic warming and sea-level drop?
The material will come from field work at localities around Oslo as well as from museum collections. The data will be used for ecological data analysis, especially ordinations and diversity analysis, and some biogeographical analysis and plotting (GIS).
2. The late Atlantic shallow-water oyster banks of the Oslofjord area
Throughout the Oslofjord area, mollusc faunas rich in oysters (“oyster banks”) are found ca. 10-40 meters above present sea level. Preliminary radiocarbon dating indicates that at least some of these are from late Atlantic time (ca. 4,000 BC), i.e. during the warm “climatic optimum” of the Holocene.
The project will focus on the ecology of these oyster banks, with field and laboratory work. Possible localities include low-lying areas around Oslo (e.g. Slemmestad and Malmøya), and Hvaler ca. 100 km south of Oslo. Associated fossils will also be collected and identified for ecological data analysis. Are these oyster banks all of similar age, recording an event of regional significance? Do they represent a faunal invasion? We would also like to look at age distributions, shape variation etc. Encrusting and infestation (polychaete tubes and burrows, sponge borings, etc.) will be studied with microfocus CT.
3. Seawater paleotemperatures of the Holocene in the Oslofjord area
The student will attempt to estimate seawater temperatures using classical geochemical and paleoecological techniques applied to the fossil faunas. This will include oxygen isotope analysis (clumped isotopes may be attempted, depending on funding), Mg/Ca and Sr/Ca ratios, and comparing fossil assemblages with present-day faunas. We may also attempt reconstruction of paleosalinity using e.g. Ba/Ca ratios.