Geoscience Reference
In-Depth Information
FIGURE
20 The Signor-Lipps effect in operation at a modern tidal flat.
Depending on their rarity, species appear to become extinct at different
depths in the core, equivalent to different times in the past. Yet each species
is alive today. [After Meldahl.
18
]
tion do not necessarily eliminate catastrophic extinction hypotheses,"
Signor and Lipps concluded at Snowbird I. "The recorded ranges of
fossils . . . may be inadequate to test either gradual or catastrophic
hypotheses."
INTERPRETING THE FOSSIL RECORD
Remember that to test the Alvarez theory, we want to know
whether fossil species were already on the way out in advance of the
Chicxulub impact, and whether those that became extinct did so
