What types of geologic evidence are used to study the rise of atmospheric O2?
What will be an ideal response?
There are a number of pieces of evidence used to study the rise of atmospheric O2. The presence of banded iron formations, the existence of detrital uraninite and pyrite, the prevalence of mass-independent sulfur isotope fractionation, the absence of redbeds, and the loss of Fe during weathering of paleosols all indicate low atmospheric O2 prior to 2.3Ga. The most convincing evidence is the preservation of mass-independent sulfur isotope fractionation, for which no other adequate explanation has been put forth.
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How many valence electrons does boron (B, atomic no. = 5) have?
A. 1 B. 2 C. 3 D. 4 E. 5
Each of the major continents at the beginning of the Paleozoic can be divided into two major components, a(n) ____
a. trough and a range b. craton and a mobile belt c. immobile belt and a rift margin d. craton and an ocean basin e. immobile belt and a mobile belt
Deep-ocean trenches and volcanic arcs result from the collision of two plates at convergent plate boundaries and mostly occur along the margins of which of the following oceans?
A) Pacific Ocean B) Atlantic Ocean C) Indian Ocean D) Arctic Ocean E) Southern Ocean
Seasons on Earth are regulated by ___
A) only the length of daylight hours B) both the length of daylight hours and the angle sunlight strikes Earth's surface C) only the angle sunlight strikes Earth's surface D) only Earth's nearness to the sun