Origin of hematite carrying a Late Paleozoic remagnetization in a quartz sandstone bed from the Silurian Rose Hill Formation, Virginia, USA

Abstract

Paleomagnetic and petrographic studies of a quartz sandstone bed from the Silurian Rose Hill Formation of the Central Appalachians show that hematite carrying a Late Paleozoic remagnetization is authigenic. Comparison of paleopole positions from the Rose Hill Formation with Late Paleozoic poles for North America suggests a synfolding remagnetization. The sandstone cement is characterized by pore-lining hematite, pore-filling berthierine and intergrowths of hematite, berthierine and quartz. These cements postdate pressure solution of detrital quartz grains. Late Paleozoic cementation is a consequence of diagenesis associated with Alleghanian deformation. Detrital FeMg silicate grains are believed to have been a local source of Fe for some authigenic hematite and berthierine, although mass balance calculations suggest that an external source is also required. Some berthierine aggregates are pseudomorphic after detrital Fe-bearing silicate grains. Trace amounts of detrital tourmaline are the only remnants of the detrital FeMg silicates.