Accretion of ferromanganese nodules that form pavement in Second Connecticut Lake, New Hampshire

Abstract

We discovered ferromanganese nodules that measure up to 46 cm in diameter with stromatolitic growth patterns in the western central near-shore portion of Second Connecticut Lake, Pittsburg, New Hampshire. They occur as four distinct morphotypes: irregular laminated convex plates that form concentric rings around a nucleating center (''domed-plate''), continuous pustular pavements that extend >10 m 2 (''pustular''), nonlaminated and nonnucleated masses with pebbles scattered throughout the matrix (''lattice''), and small nonnucleated laminated structures >2 cm (''cup'') in water depths between 5 and 12 m. An estimated growth rate of 26 mm/100 years was determined from oxide deposits on datable debris. X-ray fluorescence showed an elemental composition comparable with that of nodule structures in other lakes. These sedimentary structures, the first seen in any of the six New England states, are the most morphologically distinct and varied lacustrine ferromanganese nodules known so far.concretions ͉ stromatolites ͉ microbialites ͉ precipitates ͉ oncoid

Emerging investigator series: geochemistry of trace elements associated with Fe and Mn nodules in the sediment of limed boreal lakes

“…Nodule sizes are consistent with the hypothesis that liming triggered their formation. Using 10 to 20 years as the typical period of elevated pH during and after liming, and an average nodule radius of 10 mm, we estimate a growth rate of 0.5 to 1 mm/yr at our sites, also consistent with previous growth rate estimates for lakes in the northeast United-States 28 or at the sediment-seawater interface , 29 . Although metal nodules are frequently reported in lakes 27, 28, 30-33 , we are not aware of such reports for acidic or formerly acidic humic lakes.…”

Manganese stromatolites in caves: El Soplao (Cantabria, Spain)

“…Paradoxically, microbial fossils are seldom reported in stromatolites (Grotzinger and Knoll, 1999). Manganese oxide stromatolites have been described in both marine (e.g., Planavsky et al, 2009) and lacustrine environments (e.g., Asikainen and Werle, 2007). They result from the activity of bacteria that catalyze the oxidation of aqueous Mn(II), resulting in the precipitation of Mn oxides (Nealson, 2006).…”

Reply to Boudreau: Morphologic expression of ferromanganese nodules

“…The statement that nodule formation, especially morphology, can be predicted by the Boudreau diagenetic model led us to state that ''diagenetic models that claim to predict nodule growth rate and morphologies from elemental concentrations (1) are not verified by our data'' for Second Connecticut Lake (SCL), New Hampshire (2). Comments on metal gradients and elemental concentration of manganese (Mn) and iron (Fe) required for accretion and morphologic expression of ferromanganese nodules are in Boudreau's original paper (3).…”

“…Some, inhabited or not inhabited, appeared yellowish-brown in color and are most likely associated with metal oxides. Because our purpose was to describe a new site of large, young lacustrine nodules, these observations were beyond the scope of the announcement paper (2).…”