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Ejecta surrounding the 26-km-diameter Ries Crater, Germany, may be helpful to the interpretation of the Cretaceous Tertiary (C T) Boundary Event. The Ries ejecta can be classified into three major facies: (1) moldavite tektites, (2) Bunte Breccia, and (3) suevite, each of which represents a temporally and spatially distinct ejection regime. The petrographic and geochemical characteristics of each facies are also distinct, reflecting an orderly stratigraphic succession of the Ries target. Moldavites represent early high-speed ejecta originating at or close to the projectile-target interface; Bunte Breccia reflects the major excavation and ejection phase and comprises >90% of all ejecta beyond the rim crest; suevite is deposited last and is derived from the most deep-seated target strata. Details of the tektite transportation mechanism(s) are still poorly understood, but it is virtually certain that drag forces in a rapidly ascending cloud of vaporized target and projectile materials must be invoked. In contrast, individual components of the Bunte Breccia are ejected in direct ballistic trajectories and at sufficient velocities to generate a secondary cratering action upon landing, which in turn leads to a highly turbulent, ground-hugging debris surge. Finally, transportation and deposition of suevite seems to require a turbulent, radially expanding gas phase composed of volatiles (H2O; CO2) liberated from the target rocks. It is estimated that this vapor cloud persisted for a minimum of 5 min and that the ambient atmosphere was severely perturbed for at least this long.

Using various scaling laws that relate the bolide’s kinetic energy to crater geometry or volume and assuming 25 km/s as impact velocity, a projectile diameter of 1 to 2 km results for a stony object; corresponding ratios of ejecta mass (Me) and projectile mass (Mp) range from 6 × 101 (min) to 4 × 104 (max); Me/Mp of ≃ 102 seems to be a reasonable estimate. These calculations contrast with the bolide mass as estimated by geochemical means.

Geochemical studies reveal that projectile dissemination is heterogeneous and that maximum extraterrestrial contamination modeled as a C1 chondrite is 4 × 10−3 wt %; moldavites—at most—contain 4 × 10−5 wt % C1 chondrite. Thus, projectile masses based on cratering theory conflict by orders of magnitude with measured concentrations of meteoritic indicator elements. This discrepancy seems to imply that most of the bolide mass is lost to the atmosphere.

Observations from the Ries and other terrestrial craters indicate that tektites and microtektites provide the sole, albeit crucial, evidence for widespread impact deposits.

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