|
Showing 1 - 2 of
2 matches in All Departments
Ancient iron formations - iron and silica-rich chemical sedimentary
rocks that formed throughout the Precambrian eons - provide a
significant part of the evidence for the modern scientific
understanding of palaeoenvironmental conditions in Archaean
(4.0-2.5 billion years ago) and Proterozoic (2.5-0.539 billion
years ago) times. Despite controversies regarding their formation
mechanisms, iron formations are a testament to the influence of the
Precambrian biosphere on early ocean chemistry. As many iron
formations are pure chemical sediments that reflect the composition
of the waters from which they precipitated, they can also serve as
nuanced geochemical archives for the study of ancient marine
temperatures, redox states, and elemental cycling, if proper care
is taken to understand their sedimentological context.
The stable chromium (Cr) isotope system has emerged over the past
decade as a new tool to track changes in the amount of oxygen in
earth's ocean-atmosphere system. Much of the initial foundation for
using Cr isotopes ( 53Cr) as a paleoredox proxy has required recent
revision. However, the basic idea behind using Cr isotopes as redox
tracers is straightforward-the largest isotope fractionations are
redox-dependent and occur during partial reduction of Cr(VI). As
such, Cr isotopic signatures can provide novel insights into Cr
redox cycling in both marine and terrestrial settings. Critically,
the Cr isotope system-unlike many other trace metal proxies-can
respond to short-term redox perturbations (e.g., on timescales
characteristic of Pleistocene glacial-interglacial cycles). The Cr
isotope system can also be used to probe the earth's long-term
atmospheric oxygenation, pointing towards low but likely dynamic
oxygen levels for the majority of Earth's history.
|
You may like...
Loot
Nadine Gordimer
Paperback
(2)
R398
R330
Discovery Miles 3 300
Tenet
John David Washington, Robert Pattinson, …
DVD
R53
Discovery Miles 530
Not available
Loot
Nadine Gordimer
Paperback
(2)
R398
R330
Discovery Miles 3 300
|
Email address subscribed successfully.
A activation email has been sent to you.
Please click the link in that email to activate your subscription.