Magnetic spherules in coastal plain sediments, Sullivan's Island, South Carolina, USA

Abstract

Abstract— We extracted black, magnetic spherules from well cuttings of Oligocene sediments in the coastal plain of South Carolina, USA. Three possible origins were considered: industrial, volcanic, and extraterrestrial. An extraterrestrial origin by ablation of parent meteoroid material is proposed, based on the spherule morphologies, the presence of metallic Fe cores in many of the spherules, and the detection of wüstite in some of the oxide rims. Low Ni contents are problematic but may be attributed to the ablation of a low‐Ni parental body, such as hexahedrite. The presence of spherules in somewhat clay‐like, sandy sediments is unusual, as most magnetic spherules are found in abyssal muds. Based on benthic foraminiferal assemblages and sediment distribution above, within, and below the beds containing spherules, it is unlikely that the spherules were transported from a deep‐sea environment.

Cosmic spherules from the Ordovician of Argentina

“…Depending on the deceleration experienced, metallic cores of the spherules migrate to the front of the particle and separate, leaving a remnant that comprises a Fe‐oxide spherule free of Ni (Bi et al ., ; Yada et al ., ). Similar I‐type spherules depleted in Ni occur in Ordovician rocks of the Durness Group in NW Scotland (Dredge et al ., ), in Oligocene sediments in the coastal plain of South Carolina, USA (Taylor et al ., ), and in modern collections from the Transantarctic Mountains (Rochette et al ., ) and the Central Indian Ocean (Parashar et al ., ). Conversely, droplets produced during meteorite ablation form at lower altitudes and contain higher Ni concentrations, in response to the higher oxygen fugacity (Genge and Grady, ).…”

The peatland/ice age hypothesis revised, adding a possible glacial pulse trigger

“…Various methods have been tried in the struggle to distinguish cosmic from industrial iron spher- Taylor et al 1996), a form of magnetite which is believed to form in the upper atmosphere under low oxygen pressures. The natural terrestrial spherules are believed to originate either from volcanism, forest wildfires or lightning.…”