It Hit The Glacier.

[E.P. Grondine]

The best piece I read on the Shiva impact (in the Economist) indicated the nearly simultaneous (300,000 years at most) impact of two very large COMET fragments.

To call 300,000 years apart 'nearly simultaneous' is a stretch, imo.

In rewriting I left out the clause ('in geological terms"). My apologies.

uniface's point about refinements in dating is well taken. Dates for the KT impacts have varried by 2-3 milliong years. I suspect that the separation may be well less than 300,000 years, but we'll see. The fundamental point is that no one suspected two large impacts near to each other - except for the comet impact folks: one comet fragment hits, and then later on another one. Or two comets are perturbed by our solar system passing through the plane of our galaxy, and many comets are sent inward, with some of them hitting the Earth, while others hit Mars and other planets.

E.P. Grondine
Man and Impact in the Americas

[Rokcet Scientist]

[...]I suspect that the separation may be well less than 300,000 years, but we'll see. The fundamental point is that no one suspected two large impacts near to each other - except for the comet impact folks: one comet fragment hits, and then later on another one. [...]

Later on. Sure. Hours apart. Maybe even days, weeks, or even months apart. That could still be considered near-simultaneous, in planetary geological terms. But a couple hundred thousand years apart cannot.