Confirmation of the K1 Cosmic Dust Event: A 3 Myr Extraterrestrial 3He Pulse Coincident with the C33R-C33N Boundary at 80 Ma

Variations in ET 3He concentrations in deep-sea sediments identify two 3 Myr long episodes of enhanced cosmic dust flux, at 35 Ma and at 8 Ma [1,2]. Respectively, these have been attributed to a comet (or asteroid [3]) shower and the collisional destruction of the parent body of the Veritas asteroid family. Additional 3He events were tentatively identified in the Cretaceous [4], including the Campanian-age ( 80 Ma) "K1" event. At Gubbio (Italy), K1 is identified by an abrupt increase in 3He associated with a lithologic change, the C33R-C33N boundary, and the first appearance of syndepositional slumping and faulting. These characteristics suggest sediment disturbance and missing section, making it difficult to interpret the 3He data. A new high temporal resolution record from an apparently complete and undisturbed section (Apiro, 40 km east of Gubbio) reveals a well-developed >3 Myr-duration 3He peak, with a maximum amplitude 10x above pre-event levels. To within a few cm the 3He maximum coincides with the C33R-C33N transition. The temporal evolution of this event is remarkably similar to the late Eocene comet (or asteroid) shower. The synchroniety of K1, the magnetochron boundary, and the onset of sedimentary disturbances (turbidities) attributed to eustasy-induced seismicity [3] encourages speculation of a causal link, perhaps through comet-shower related bolide impact(s). The possibility of impact-induced magnetic field changes has been noted previously [6]. A few minor impact craters (Lappajarvi, Wetumpka [7]) are plausibly coincident with K1, but apparently other impact indicators are unknown. These data invite closer scrutiny of impact indicators in the early to middle Campanian and reinforce the possible linkage between impacts and magnetic field reversals.. 1. Farley et al. 1996; 2. Farley et al. 2006; 3. Tagle and Claeys 2004; 4. Farley et al. 2012; 5. Bice et al. 2007; 6. Schneider et al. 1992; 7. Earth Impact Database, 2017.