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21 October 2022 LEAVES IN IRON OXIDE: REMARKABLE PRESERVATION OF A NEOGENE FLORA FROM NEW CALEDONIA
Emma R. Locatelli, Derek E.G. Briggs, Andrew Leslie, Jérôme Munzinger, Philippe Grandcolas, Porter P. Lowry II, David J. Cantrill, Pierre Maurizot, Dominique Cluzel, Nicolas Folcher, Romain Garrouste, André Nel
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Abstract

A Neogene hematite-goethite concretionary ‘ironstone’ horizon in laterized fluvial sediments in the Massif du Sud of New Caledonia yields abundant fossil dicotyledonous angiosperm leaves. The leaves are preserved in iron oxide, mainly goethite, which replicates the morphology and anatomy of the leaf tissues and comprises 73% of the matrix. Organic remains are minimal and associated with aluminosilicate clay. Leaf tissues are preserved three-dimensionally in multiple ways including casts/molds, permineralization/petrifaction, and replacement. Although the mesophyll is less well preserved, reflecting its greater susceptibility to decay, cellular details of vascular and epidermal tissues are commonly evident. Analyses of leaves from an analogous modern setting reveal the early encrustation and impregnation of tissues by amorphous iron-oxides and clays in association with a microbial biofilm. We propose a taphonomic model in which the fossil leaves, like their modern counterparts, were permeated by iron oxides due to the high availability of iron derived from weathering of ultramafic basement. In contrast to the iron-rich aluminosilicate coatings that form in relatively iron-poor settings, the unusually high concentration of dissolved iron oxides permitted rapid anatomical preservation.

Copyright © 2022, SEPM (Society for Sedimentary Geology)
Emma R. Locatelli, Derek E.G. Briggs, Andrew Leslie, Jérôme Munzinger, Philippe Grandcolas, Porter P. Lowry II, David J. Cantrill, Pierre Maurizot, Dominique Cluzel, Nicolas Folcher, Romain Garrouste, and André Nel "LEAVES IN IRON OXIDE: REMARKABLE PRESERVATION OF A NEOGENE FLORA FROM NEW CALEDONIA," PALAIOS 37(10), 622-632, (21 October 2022). https://doi.org/10.2110/palo.2022.019
Received: 17 March 2022; Accepted: 18 July 2022; Published: 21 October 2022
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