Abstract
We constructed a numerical model of the Chicxulub impact event using
the Chart-D Squared (CSQ) code coupled with the ANalytic Equation
Of State (ANEOS) package. In the simulations we utilized a target
stratigraphy based on borehole data and employed newly developed
equations of state for the materials that are believed to play a
crucial role in the impact-related extinction hypothesis: carbonates
(calcite) and evaporites (anhydrite). Simulations explored the effects
of different projectile sizes (10 to 30 km in diameter) and porosity
(0 to 50%). The effect of impact speed is addressed by doing simulations
of asteroid impacts (upsilon(i)=20 km/s) ana comet impacts (upsilon(i)
=50 km/s). The masses of climatically important species injected
into the upper atmosphere by the impact increase with the energy
of the impact event, ranging from 350 to 3500 Gt for CO2, from 40
to 560 Gt for S, and from 200 to 1400 Gt for water vapor. While our
results are in good agreement with those of Ivanov et al. 1996,
our estimated CO2 production is 1 to 2 orders of magnitude lower
than the results of Takata and Ahrens 1994, indicating that the
impact event enhanced the end-Cretaceous atmospheric CO2 inventory
by, at most, 40%. Consequently, sulfur may have been the most important
climatically active gas injected into the stratosphere. The amount
of S released by the impact is several orders of magnitude higher
than any known volcanic eruption and, with H2O, is high enough to
produce a sudden and significant perturbation of Earth's climate.
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