Structure and composition of the Aleutian island arc and implications for continental crustal growth

Anoxia proxies include the lack of pre-GOE continental redbeds, detrital grains of siderite, uraninite, or pyrite that would oxidize at high pO2, and paleosols with iron washed out by anoxic rainwater.

“Anoxia proxies that have long been recognized include the lack of pre-GOE continental sediments stained by red ferric oxides (redbeds), detrital grains from well-aerated rivers of siderite (FeCO3), uraninite (UO2), or pyrite that would oxidize and dissolve or rust at high pO2 (65, 66), and paleosols with iron washed out by anoxic rainwater [e.g., (67)].”

Prior to this study, animal diversification and colonization of the infaunal ecospace have been considered roughly synchronous.

“Prior to this study, animal diversification and colonization of the infaunal ecospace have been considered roughly synchronous [16].”

Before ~2.45 billion years ago, Earth's atmosphere was essentially devoid of molecular oxygen.

“whereas geologic and geochemical constraints suggest that before ~2.45 billion years ago (Ga), the atmosphere was essentially devoid of this gas (1–4).”

In the Precambrian ocean, intensive macrofaunal bioturbation is believed to have been universally insignificant or absent, regardless of sedimentation rates or Corg supply.

“In the Precambrian ocean, however, intensive macrofaunal bioturbation is believed to have been universally insignificant or absent (e.g. Droser et al., 1999; McIlroy & Logan, 1999; Seilacher, 1999; Bottjer et al., 2000; Droser et al., 2002a; Jensen, 2003; Droser et al., 2004; Jensen et al., 2005), regardless of the rates of sedimentation or Corg supply.”