[8] It was hypothesized that the iridium was spread into the atmosphere when the impactor was vaporized and settled across Earth's surface among other material thrown up by the impact, producing the layer of iridium-enriched clay.

[6][10] The Alvarezes, joined by Frank Asaro and Helen Michel from University of California, Berkeley, published their paper on the iridium anomaly in Science in June 1980.

[10]: 83–84 [12] In 1978, geophysicists Glen Penfield and Antonio Camargo were working for the Mexican state-owned oil company Petróleos Mexicanos (Pemex) as part of an airborne magnetic survey of the Gulf of Mexico north of the Yucatán Peninsula.

When the gravity maps and magnetic anomalies were compared, Penfield described a shallow "bullseye", 180 km (110 mi) in diameter, appearing on the otherwise non-magnetic and uniform surroundings—clear evidence to him of an impact feature.

This layer could have resulted from the intense heat and pressure of an Earth impact, but at the time of the borings it was dismissed as a lava dome—a feature uncharacteristic of the region's geology.

[5] Penfield was encouraged by William C. Phinney, curator of lunar rocks at the Johnson Space Center, to find these samples to support his hypothesis.

[10] Unaware of Penfield's discovery, University of Arizona graduate student Alan R. Hildebrand and faculty adviser William V. Boynton looked for a crater near the Brazos River in Texas.

[10] Their evidence included greenish-brown clay with surplus iridium, containing shocked quartz grains and small weathered glass beads that looked to be tektites.

When Haitian professor Florentine Morás discovered what he thought to be evidence of an ancient volcano on Haiti, Hildebrand suggested it could be a telltale feature of a nearby impact.

Penfield also recalled that part of the motivation for the name was "to give the academics and NASA naysayers a challenging time pronouncing it" after years of dismissing its existence.

[6][4] Dissenters, notably Gerta Keller of Princeton University, have proposed an alternate culprit: the eruption of the Deccan Traps in what is now the Indian subcontinent.

[23] The impact has been interpreted to have occurred in the Northern Hemisphere's spring season based on annual isotope curves in sturgeon and paddlefish bones found in an ejecta-bearing sedimentary unit at the Tanis site in southwestern North Dakota.

[36][37] Material shifted by subsequent earthquakes and the waves reached to what are now Texas and Florida, and may have disturbed sediments as far as 6,000 kilometers (3,700 mi) from the impact site.

[31] A cloud of hot dust, ash and steam would have spread from the crater, with as much as 25 trillion metric tons of excavated material being ejected into the atmosphere by the blast.

[5][10]: 10–13 [6] Fossil evidence for an instantaneous extinction of diverse animals was found in a soil layer only 10 centimeters (3.9 in) thick in New Jersey, 2,500 kilometers (1,600 mi) away from the impact site, indicating that death and burial under debris occurred suddenly and quickly over wide distances on nearby land.

[33] Field research from the Hell Creek Formation in North Dakota published in 2019 shows the simultaneous mass extinction of myriad species, combined with geological and atmospheric features that are consistent with the impact event.

[6] Due to the relatively shallow water at the impact site, the rock that was vaporized included sulfur-rich gypsum from the lower part of the Cretaceous sequence, and this was injected into the atmosphere.

[33] This global dispersal of dust and sulfates would have led to a sudden and catastrophic effect on the climate worldwide, instigating large temperature drops and devastating the food chain.

[42] The emission of dust and particles could have covered the entire surface of Earth for several years, possibly up to a decade, creating a harsh environment for biological life.

[43][44] A model of the event developed by Lomax et al (2001) suggests that net primary productivity rates may have increased to higher than pre-impact levels over the long term because of the high carbon dioxide concentrations.

[45] A long-term local effect of the impact was the creation of the Yucatán sedimentary basin which "ultimately produced favorable conditions for human settlement in a region where surface water is scarce".

This survey also used ocean bottom seismometers and land stations to allow 3D travel time inversion to improve the understanding of the velocity structure of the crater.

[50] In 2016, a joint United Kingdom–United States team obtained the first offshore core samples from the peak ring in the central zone of the crater with the drilling of the borehole known as M0077A, part of Expedition 364 of the International Ocean Discovery Program.

[26] The central part of the crater lies above a zone where the mantle was uplifted such that the Mohorovičić discontinuity is shallower by about 1–2 kilometers (0.62–1.24 mi) compared to regional values.

[27] Before the impact, the geology of the Yucatán area, sometimes referred to as the "target rocks", consisted of a sequence of mainly Cretaceous limestones, overlying red beds of uncertain age above an unconformity with the dominantly granitic basement.

Late Paleozoic granitoids (the distinctive "pink granite") were found in the peak ring borehole M0077A, with an estimated age of 326 ± 5 million years ago (Carboniferous).

These have an adakitic composition and are interpreted to represent the effects of slab detachment during the Marathon-Ouachita orogeny, part of the collision between Laurentia and Gondwana that created the Pangaea supercontinent.

[60] The peak ring drilling below the sea floor also discovered evidence of a massive hydrothermal system, which modified approximately 1.4 × 105 km3 of Earth's crust and lasted for hundreds of thousands of years.

[16]: 4 [64] From the cenote locations, the karstic aquifer is clearly related to the underlying crater rim,[65] possibly through higher levels of fracturing, caused by differential compaction.

[68] A 2021 paper suggested, based on geochemical evidence including the excess of chromium isotope 54Cr and the ratios of platinum group metals found in marine impact layers, that the impactor matched the characteristics of CM or CR carbonaceous chondrites.