Modulation of planetary tectonics by larger asteroids impacts: Evidence from Cretaceous-Paleogene impact
Abstract
Extreme seismic waves from large asteroid impacts interact with stress concentrations in the lithosphere to trigger earthquakes. This process might globally kick start plate tectonics or regionally commence a new plate boundary. We examine field evidence that the relatively modest Cretaceous-Paleogene (K-Pg) impact affected intraplate stresses for 10,000s of years. We studied well-known outcrops of the impact layer at Madrid and Trinidad Lake, Colorado; Goat Hill, Raton, New Mexico; and Hell Creek Marina Road, Montana. Multiple normal faults offset the impact horizon by a fraction of a meter vertical throw. These faults have remained inactive over the subsequent ca. 66 million years. At all our sites, the earthquake faults offset the spherule layer, which accumulated after the first extreme seismic waves arrived. The some triggered earthquakes, notably, occurred significantly after the impact. Numerous fault splays offset a ca. 30 cm thick mudstone above the impact layer at Goat Hill with an uncertain age interval. Faults at Hell Creek offset part or all of the ca. 1.5 m thick Z Coal above the impact layer, but not overlying strata. Bentonite Beds provide age control (Renne et al., Science, 2013). Earthquakes occurred ca. 40,000 years after the impact. In addition, normal faults of parallel strike and opposite dip direction slipped at Hell Creek. The near-sea-level region was thus in a full normal faulting environment after the impact. An hypothesis is that seismic waves from the impact triggered globally major intraplate earthquakes that transiently relaxed intraplate compressive and/or tensional stresses. In addition, the effective moment magnitude of the impact may be underestimated or a double asteroid may have caused an associated marine impact with a since subducted crater. In any case, modest impacts do affect tectonics and hypotheses involving impacts to kick start and modulate tectonics are viable.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP51B..01S
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0473 Paleoclimatology and paleoceanography;
- BIOGEOSCIENCESDE: 1030 Geochemical cycles;
- GEOCHEMISTRYDE: 5225 Early environment of Earth;
- PLANETARY SCIENCES: ASTROBIOLOGY