Dr. Mohamed K Zobaa :: Publications:

The state of Louisiana alone has been hit by hurricanes 28 times in the past two decades, and eight of them were classified as category 3 and 4. It is possible that this hurricane pattern existed in the geologic past and dramatically affected the fossil record in the region. Samples from two closely spaced borings drilled in New Orleans in 2006, in the aftermath of Hurricane Katrina, were analyzed for palynomorphs to detect paleoenvironmental and paleofloristic changes. Limited ¹4C analysis indicates an age range of 1341–4388 years before present (ybp) for the studied interval. Palynology confirmed the Holocene age and also revealed a major distortion in palynomorph fossil record between 5.0 and 8.5 meters below sea level based on two distinguishing factors: 1) Holocene marine palynomorphs in continentally deposited sediments, and 2) the co-occurrence of Holocene and reworked Cretaceous and Paleogene palynomorphs in the same interval. The inferred distortion may be the result of major devastation, when 4.6 to 6 meters of sediments were rapidly deposited, around 1350 ybp, due to a major marine surge resulting from hurricane activity. Gravity faulting in this area is a possible alternative for triggering this sequence of rapid deposition. Either of these mechanisms might explain the anomalous mixture of fossils. The gradual replacement of pine forest by Taxodium forest suggests a change from subtropical-temperate to tropical conditions.