TRACKING PHOSPHORUS ACROSS THE KELLWASSER EVENT: A NUTRIENT PROFILE FROM EURAMERICA

The Late Devonian was a particularly dynamic time in Earth’s history and home to two significant extinction events, the Kellwasser and Hangenberg Events. The Devonian was also the Period in which land plants truly evolved and proliferated, developed extensive root systems and initiated modern soil formation processes. While the causal factors of the Kellwasser Event in particular are still debated, current theories point toward extensive volcanism as a likely cause. Whatever the ultimate attribution, widespread volcanism would have had a marked effect on plant life, with a high CO2 environment driving a warm and wet climate. This relatively abrupt, but sustained change in climate would have likely had a significant impact on nutrient flux from terrestrial landscapes. By analyzing local sinks such as fluvial and lacustrine sequences, it is possible to track these nutrient changes across the Kellwasser Event. Here we present phosphorus records from a Late Frasnian fluvial sequence in east Greenland, showing a punctuated phosphorus weathering event concurrent with the onset of the Upper Kellwasser Event (UKW). Phosphorus accumulation rates calculated compare strikingly well (both in magnitude and behavior) to studies of Holocene lakes during glacial retreat, followed by exposure of fresh surface and colonization by plants, an interval between glacial and interglacial soil states that is marked by a transient but significant loss of P from the landscape. This post-glacial Holocene environment may be analogous to conditions in the Devonian as plants began to dominate continental interiors during the Late Devonian, with growth in the late Frasnian likely accelerated by extremely favorable climatic conditions. This evidence of a substantial terrestrial weathering event concurrent with the UKW extinction event suggests that although not a causal factor in initiating the UKW, if this occurred over a large enough area, the resultant flux into Devonian seas could have exacerbated an already substantial marine extinction.