Spheroidal carbonaceous particles and other black carbon from Crawford Lake, Ontario, Canada

Spheroidal carbonaceous particles (SCPs) are formed from the incomplete, high-temperature combustion of fossil fuels. They are transported to a variety of depositional environments downwind of their sources and thus have the potential to be used to measure human activity on a regional scale. Composed mainly of elemental carbon, these fly ash particles are chemically inert and survive acid treatment, including HF. However, unlike microcharcoal, SCPs are typically overlooked during palynological analysis. Both types of black carbon are common in palynological preparations of varved sediments from Crawford Lake, Ontario, Canada where they can be correlated with the historic record of land use over the past two centuries. Increases in microcharcoal concentration correlate with historic records of land clearing in the early-mid nineteenth century and logging and lumber milling between 1885 and 1957 CE. The rapid increase in SCP concentration during the mid-twentieth century is attributed to the global increase in fossil fuel combustion and industrial activity (the Great Acceleration) and the decline during the early 1980s records increasingly stringent air quality standards as well as decreased demand for steel (and coking coal) in nearby Hamilton. Palynologists are urged to pay attention to these useful proxies of fossil fuel combustion in their slides.