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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: From Greenhouse to Icehouse—The Azolla Trigger: Implications for Climate Change and Arctic Petroleum Source Rocks
Bujak Research Limited
The modern icehouse world is characterized by bipolar glaciation, resulting from relatively low levels of atmospheric CO2 and thermal isolation of the poles from lower latitude warm oceanic currents. In contrast, the Mesozoic greenhouse world had no permanent glaciation at either pole, with the greenhouse state continuing through the K/T boundary into the Paleocene.
At the end of the Paleocene, the Paleocene-Eocene Thermal Maximum was triggered by extreme levels of greenhouse gases due to extensive volcanism and the expulsion of submarine methane hydrates. This resulted in the highest temperatures known for the Cenozoic, characterizing a super-greenhouse state that persisted through the Early Eocene. It is therefore surprising that various independent parameters indicate that the supergreenhouse was truncated in the earliest Middle Eocene by the initial shift toward modern icehouse. Estimates of atmospheric CO2 values show a major decrease at this time, but this cannot be explained by “normal” sequestration processes. Instead, a unique geological event is proposed to explain this fall, centered on processes within the Arctic Ocean Basin.
“The Azolla Model
” is
based on Arctic Coring
Expedition (ACEX) cores
from Lomonosov Ridge
plus unpublished data
from 65 Arctic petroleum
exploration wells (Bujak
Research non-exclusive
well studies). The
model
combines oceanographic
reconstructions for the
basin with a major
decrease in greenhouse
gases during the middle
Eocene. The Early Eocene Arctic Ocean Basin was largely
enclosed following uplift of the Greenland Mantle Plume, with
elevated temperatures, evaporation and
precipitation leading to increased runoff
and the development of extensive surface
freshwater layers. These were colonised
in the earliest Middle Eocene by floating
mats of the opportunistic freshwater fern
Azolla, which persisted for up to 800,000
years as a series of repeated cyclical
events.
Modern Azolla is one of the fastest
growing plants on the planet and draws down large quantities
of carbon and nitrogen. Calculations of carbon drawdown
combined with the large potential areas of Azolla development in
the Arctic, plus the 800,000-year time frame indicate levels of
CO2 sequestration that are easily sufficient to shift the world
from Mesozoic—Early Eocene greenhouse towards the modern
icehouse world. The model
also indicates the deposition of
potentially widespread petroleum source rocks across the Arctic
due to the massive carbon drawdown. It is currently being tested
by multidisciplinary teams at ACEX and various universities
worldwide, and it has already attracted considerable attention
including articles in National Geographic (May 2005), Nature
(June 1, 2006), and the New York Times (November 20, 2004).
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