MORPHOLOGY AND TAPHONOMY OF ROOT AND STUMP CASTS OF THE EARLIEST TREES (MIDDLE TO LATE DEVONIAN), PENNSYLVANIA AND NEW-YORK, USA

Two types of root casts attached to in situ stump casts of early trees from the Catskill Delta Complex are described and contrasted. The fir st type is attached to bulbous sandstone tree-stump casts (Eospermatop eris sp.?) occurring in a low-chroma (gray-green), pyritic, gley silts tone paleosol of Middle Devonian (Givetian) age that is interpreted as waterlogged; this paleosol formed in a coastal-margin setting charact erized by a shallow water-table. Root casts in the Middle Devonian. pa leosol are horizontal to subhorizontal, strap-like (measuring 0.5-2 cm in width and up to meters long), and radiate outward fi om stump cast s with distinctly flared bases. Root casts with a similar morphology a lso occur attached to the upper portions of stump casts, and comprised an aerial root mantle. The second type of root cast is attached to we akly flared to corm-like sandstone tree-stump casts of probable progym nosperms (Archaeopteris sp.?) occurring in a moderate-chroma (red), ox idized sandy paleosol of Late Devonian (Famennian) age that is interpr eted as well-drained; this paleosol formed proximal to active alluvial channels. Root casts are dominantly vertical, taproot-lib (measuring up to 10-15 cm in diameter and up to 1.5 m long), and descend downward from the bases of stump casts with approximately a 60 degrees angle o f attachment. The two types of tree-root casts differ due to developme nt under different soil-drainage conditions. Preservation of in situ D evonian tree-stump casts and attached root casts involved degradation of interior tissues, followed by sediment infilling; outer tissue (per iderm) persisted longer before decay and infilling. Preservation is fa vored by conditions of rapid sediment accumulation, generally associat ed with sandstone deposition, as is the case for Carboniferous lycopod tree stumps documented by other workers. Lack of preservation in fine -grained claystone paleosols associated with either coastal-margin mud flat or alluvial floodplain deposition reflects either (I) no coloniza tion of these soil environments by mature trees, (2) selective destruc tion of the root traces by intensive physical mixing associated with v ertic (shrink-swell) soil processes in clay paleosols, or (3) average sediment accumulation rates that were too low to bury and preserve in situ stump casts.