Boltysh crater

Boltysh crater is located in central Ukraine, in the basin of the Tiasmyn River, a tributary of the Dnieper River. It is {{convert|24|km|mi}} in diameter, and is surrounded by an ejecta blanket of breccia preserved over an area of {{convert|6500|km2|sqmi}}. It is estimated that immediately after the impact, ejecta covered an area of {{convert|25,000|km2|sqmi}} to a depth of {{convert|1|m|ft}} or greater, and was some {{convert|600|m|ft}} deep at the crater rim.

The crater contains a central uplift about {{convert|6|km|mi}} in diameter, rising about {{convert|550|m|ft}} above the base level of the crater. This uplift currently lies beneath about {{convert|500|m|ft}} of sediment deposited since the impact, and was discovered in the 1960s during oil shale deposits exploration.

The Boltysh depression was identified as a fossil meteorite crater by 1975.{{cite journal |vauthors=((Yurk YuYu)), Yeremko GK, ((Polkanov YuA)) |title=The Boltysh depression-a fossil meteorite crater |journal=Sov Geol |date=1975 |volume=2 |page=138-144}} By 1987, it was dated to 100 ± 12 million years old.{{cite journal |last1=Grieve |first1=R.A.F. |last2=Reny |first2=G. |last3=Gurov |first3=E.P. |last4=Ryabenko |first4=Z. |title=The melt rocks of the Boltysh impact crater, Ukraine, USSR |journal=Contributions to Mineralogy and Petrology |date=1987 |volume=96 |page=56 |doi=10.1007/BF00375525|s2cid=140563900 }} Early age estimates could only be roughly constrained between the age of the impacted rocks (the target) and the age of overlying sediments. The target rocks date from the Cenomanian (98.9 to 93.5 million years ago) and Turonian (93.5 to 89 million years ago) epochs. Bore samples of sediments overlying the crater contain fossils dating from the Paleocene epoch, 66 to 54.8 million years ago. The age of the crater was thus constrained to between 54 and 98 million years.

Subsequent radiometric dating reduced the uncertainty. The concentration of {{chem|U|238|link=uranium-238}} decay products in impact glasses from the crater were used to derive an age of 65.04 ± 1.10 million years. A 2002 analysis of argon radioactive decay products yielded an age of 65.17 ± 0.64 million years.{{Cite journal |last1=Kelley|first1=Simon P.|last2=Gurov|first2=Eugene|date=August 2002 |title=Boltysh, another end-Cretaceous impact|journal=Meteoritics & Planetary Science|volume=37|issue=8|pages=1031–1043|doi=10.1111/j.1945-5100.2002.tb00875.x|bibcode=2002M&PS...37.1031K|issn=1086-9379|doi-access=free}} While these radiometric dating measurements place the Boltysh crater hundreds of thousands of years after the Chicxulub crater, a 2010 radiometric and palynological study of fern spore (fern spikes) abundance suggested the Boltysh impact may have occurred several thousand years before Chicxulub.{{Cite journal|last1=Jolley|first1=David|last2=Gilmour|first2=Iain|last3=Gurov|first3=Eugene|last4=Kelley|first4=Simon|last5=Watson|first5=Jonathan|date=September 2010|title=Two large meteorite impacts at the Cretaceous-Paleogene boundary|url=http://pubs.geoscienceworld.org/geology/article/38/9/835/130359/Two-large-meteorite-impacts-at-the|journal=Geology|language=en|volume=38|issue=9|pages=835–838|doi=10.1130/G31034.1|bibcode=2010Geo....38..835J|s2cid=120172960 |issn=1943-2682}} However, in response, a follow-up study in 2021 estimated using argon–argon dating that Boltysh formed about 65.39 ± 0.14/0.16 million years ago, 650,000 years after the Chicxulub catastrophe, and suggested that the fern spike was plausibly a result of the impact itself. The authors of the paper suggested that the impact may have disrupted recovery after the K/Pg extinction.{{Cite journal |last1=Pickersgill|first1=Annemarie E. |last2=Mark|first2=Darren F. |last3=Lee|first3=Martin R. |last4=Kelley|first4=Simon P. |last5=Jolley|first5=David W. |date=2021-06-01 |title=The Boltysh impact structure: An early Danian impact event during recovery from the K-Pg mass extinction|journal=Science Advances|language=en|volume=7|issue=25|pages=eabe6530|doi=10.1126/sciadv.abe6530|issn=2375-2548|pmid=34144979|pmc=8213223|bibcode=2021SciA....7.6530P|doi-access=free}}

{{Reflist}}

• Grieve, R. A. F., Reny, G., Gurov, E. P., & Ryabenko, V. A. (1987). The melt rocks of the Boltysh impact crater, Ukraine, USSR. Contributions to Mineralogy and Petrology, 96(1), 56–62.
• Grieve R.A.F., Reny G., Gurov, E.P., Ryabenko V. A. (1985), Impact Melt Rocks of the Boltysh Crater, Meteoritics, v. 20, p. 655
• Gurov, E. P., Kelley, S. P., Koeberl, C., & Dykan, N. I. (2006). Sediments and impact rocks filling the Boltysh impact crater. In Biological processes associated with impact events (pp. 335–358). Springer Berlin Heidelberg.
• Gurov E.P., Gurova H.P. (1985), Boltysh Astrobleme: Impact Crater Pattern with a Central Uplift, Lunar & Planetary Science XVI, pp. 310–311
• Jolley D., Gilmour I., Gurov E., Kelley S., Watson J. (2010) Two large meteorite impacts at the Cretaceous-Paleogene boundary Geology September 2010, v. 38, pp. 835–838, {{doi|10.1130/G31034.1}}
• Kashkarov L.L., Nazarov M.A., Lorents K.A., Kalinina G.V., Kononkova N.N. (1999), The Track Age of the Boltysh Impact Structure, Astronomicheskii Vestnik, v. 33, p. 253
• Kelley S.P., Gurov E. (2002), The Boltysh, another end-Cretaceous impact, Meteoritics & Planetary Science, v. 37, pp. 1031–1043

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Category:Impact craters of Ukraine

Category:Geography of Kirovohrad Oblast

Category:Paleocene impact craters

Category:Cretaceous–Paleogene boundary