![[Visit Client Website]](/img/gsa/banner.jpg)
BIOTIC RECOVERY FOLLOWING THE END-CRETACEOUS ASTEROID IMPACT RECORDED FROM GORGONILLA ISLAND, COLOMBIA (Invited Presentation)
Except for very scarce specimens in some levels, planktic foraminifers are absent within and below the spherule bed, suggesting that Maastrichtian succesions were deposited below CCD. The absence also of terrestrially derived pollen and spores indicates off-shore conditions for the Maastrichtian. However, the post-impact deposit, occurring above the spherule layer at Gorgonilla, shows an interesting recovery succession representing both marine and terrestrial assemblages. Planktic foraminifers are also absent in the first 5 cm above the spherule bed, suggesting these sediments were still deposited below the CCD. However, in the following 110 cm planktic foraminifers belonging to the lowermost Danian Zone Pα are preserved, indicating a pronounced deepening of the local CCD.
The vegetation recovery is represented by fern spores, more specifically by ground fern taxa such as Gleicheniaceae and Dictyophyllum, together with abundant occurrence of the aquatic fern Azolla. These interestingly co-occur with fungal spores and hyphae. A so-called fern-spike has previously been described from New Zealand K/Pg boundary clay coincident with the iridium-enriched layer and interpreted as a response to short term darkness. The genus Azolla consistently characterizes warm-climate lacustrine environments and ranges of many Azolla species span the K/Pg boundary at other sites. The identification in Colombia of Azolla microspores and massulae directly above the K/Pg boundary at the Gorgonilla locality shows their potential to endure altered environmental conditions.