Final answer:
The presence of stishovite, coesite, and tektites in a rock is indicative of shock metamorphism caused by a meteorite impact. These high-pressure minerals, especially when found with an enriched iridium layer and a related crater, point to a significant historical collision with an extraterrestrial object, such as the one that created the Chicxulub crater and may have caused the Cretaceous-Paleogene mass extinction.
Step-by-step explanation:
The presence of stishovite, coesite, and tektites in a rock would be evidence for the past existence of shock metamorphism, as from a meteorite impact. These minerals are high-pressure polymorphs of silica that form under extreme pressures and temperatures, typically associated with the impact of a meteorite or asteroid hitting the Earth's surface. Tektites are natural glass materials that can also be formed by the intense heat and pressures generated during such extraterrestrial collisions.
In particular, the shock metamorphism that results from a meteorite impact can produce these unique minerals, which are not typically found in other geological settings. For example, a meteorite impact is capable of creating pressures so extreme that they transform the common mineral quartz into the much rarer polymorph stishovite. Similarly, coesite is another high-pressure form of silica that forms under slightly less extreme conditions but still indicative of an impact.
The geological record has several examples where these minerals, alongside other signs such as a layer enriched with the element iridium, suggest past meteorite impacts. One of the most famous is the Cretaceous-Paleogene boundary, where a significant concentration of iridium and shock-metamorphic features provide evidence of an asteroid impact that is thought to have contributed to the mass extinction of the dinosaurs. Additionally, the discovery of the Chicxulub crater in the Yucatan Peninsula has been linked to this event, aligning with the presence of impact-related minerals and supporting the hypothesis of a significant meteorite impact at the end of the Cretaceous period.