**Title: Anoxia and Climate Change: using constraints from ancient ore
deposits for modeling modern marine chemistry -** Central Region Mineral
Resources Team (Connie Nutt)

**Statement of Problem**:

*BATON ROUGE, LOUISIANA\--Negotiations have been raging for months over
how to shrink the \"dead zone\" in the Gulf of Mexico (Science, 23 June,
p. 2111). On 11 October, federal and state officials finally agreed on
an ambitious \$1-billion-per-year plan to revive as much as 30 percent
of the dead zone by 2015. The plan could also help head off a crash of
Gulf fisheries, officials say
(http://oceanservice.noaa.gov/products/pubs_hypox.html#fia).*

Marine eutrophication is devastating coastal marine ecosystems. Though
this phenomenon is not entirely understood, it is clear that it results
from ever-increasing fluxes of anthropogenic nutrients to the world's
oceans. Marine primary productivity generates extraordinary amounts of
organic carbon in response to minor increases in nutrients.
Decomposition of produced organic carbon depletes marine oxygen levels
to create large "dead zones" in coastal areas. It is also uncertain how
climate change will affect the nutrient balance of the ocean. At the
same time, many scientists are advocating fertilization of marine
primary productivity as a mechanism to sequester CO~2~ and mitigate
global warming. Opponents of this idea suggest that little is known
about biologic/chemical feedbacks and hidden tipping points that could
have long-term consequences for marine chemistry and ecosystems.

Recent MRP research has shown that enormous amounts of nutrients (NH~4~,
Fe and other trace elements, P, CH~4~, H~2~S, Si) were discharged into
ancient marine basins during the formation of Zn-Pb-Ag-Ba SEDEX deposits
on the seafloor. Similar to modern environments, these nutrients had
dramatic impacts on the chemistry and biology of ore-hosting marine
basins. More ominous is direct evidence that nutrient flux from giant
SEDEX systems were sufficient to propagate anoxia from local basins to
the global ocean causing severe disruptions to global nutrient, biologic
and carbon cycles, and global climate.

**Objectives:** Ancient SEDEX basins are an ideal natural laboratory for
interdisciplinary study of carbon sequestration, biologic productivity
and aquatic mortality, marine chemical/isotopic cycles, and climate
change resulting from increased nutrient fluxes. Holistic research of
ancient systems with understating from modern environments will provide
constraints to evaluate, model, and mitigate challenges of global
change.

**Work Strategy**: New methodologies for high-resolution sampling of
sediments and fossil biologic apatite (conodonts), combined with MRP's
state-of-the-art LA-ICP and multi-collector labs are being used in ore
deposit and environmental studies. In SEDEX work, they are proving to be
remarkable monitors of the trace/REE elements and radiogenic/stable
isotopic (S, O, C, Sr, Pb, B, Nd) evolution of marine chemistry. Ore
genesis studies provide firm constraints on nutrients fluxes, while
sedementologic/ paleontologic/ geochemical/ isotopic studies monitor
changes to marine chemistry. Expertise from biologists and marine
chemists/oceanographers would help unravel complex systematics and
export of discoveries to scientists studying modern systems.
Additionally, MRP low-temperature inorganic research might contribute
forensic constraints on nutrients flux and in modern environments.
Recent work shows that REE elements are a proxy for organic contaminants
down stream from waste-water plants. Bridging the gap between studies of
ancient and modern systems will supply knowledge necessary to develop
policies that support sustainability in the face of global change.

**Relevance and Impact**: Project results are directly relevant to
ecosystems and climate change mandates highlighted in the USGS Science
Strategy. In addition, they add to knowledge of ore deposit formation.

**Partnerships**: Within USGS, partnerships with Coastal Marine,
Minerals, and ESP; Biology; and Water are anticipated. Outside the
Survey, the larger climate change community could incorporate resulting
data in sophisticated climate modeling.