Devonian Early

Various shale sequences, both bioturbated and laminated, especially from the Camp Run Member of the New Albany Shale (Late Devonian-Early Mississippian age)... 

Kalvoda, J. and Walliser, O.H.E. (1990) Late Devonian-Early Carboniferous paleobiogeogra-phy of benthic Eoraminifera and climatic oscillations. Lecture Notes in Earth Sciences, 30 183-188. 

The Elura deposit (45 Mt (g 8.5% Zn, 5.3% Pb, 69 ppm Ag) is located 43 km north-northwest of Cobar in western New South Wales (Lorrigan 2005). The deposit is hosted by weakly metamorphosed and deformed turbiditic sedimentary rocks of the Early Devonian Cobar Basin. It consists of a series of vertical, pipe-like sulfide concentrations composed of varying proportions of pyrrhotite, pyrite, sphalerite, galena and accessory sulfide... 

Abstract Nash creek is the largest Zn-Pb deposit in the Tobique-Chaleurs Zone, and contains indicated and inferred resources of 7.8 Mt grading 2.72% Zn, 0.55% Pb and 18.26 g/t Ag and 1.2 Mt grading 2.66% Zn, 0.52% Pb and 18 g/t Ag, respectively. The deposit is hosted by Early Devonian bimodal volcanic and minor interlayered sedimentary rocks that were deposited in a trans-pressional rift. The host rocks sequence includes the Archibald Settlement Formation (rhyolite flows domes and related rocks), and the Sunnyside Formation (mafic lava flows and interlayered volcaniclastic and sedimentary rocks). 

The study area is situated in the Tobique-Chaleurs Zone, (TCZ) which contains early to middle Silurian sedimentary and volcanic rocks (Chaleurs group) that are disconformably overlain by Lower Devonian volcanic and sedimentary rocks of the Dalhousie and Tobique groups (Wilson 2004) and is bounded by the Rocky Brook-Millstream Fault to the northeast and the Mackenzie Gulch Fault to the north (Fig.1). The McCormack Brook Fault (a splay of the Rocky Brook-Millstream Fault) lies to the north of the... 

The Williams Brook area is underlain by the Wapske Formation (Tobique Group), that contains mafic and felsic volcanic rocks interlayered with fine-grained sedimentary rocks. Mineralization at Williams Brook is hosted within and/or is spatially related to red to pink rhyolites. The rhyolites were unknown in this area prior to the 2008 exploration program, but are tentatively assigned to the Wapske Formation. The Wapske Formation is conformably overlain by the Early Devonian Greys Gulch Formation that... 

Early Devonian felsic volcanic rocks and associated Zn-Pb mineralization, Tobique-Chaleurs Zone, New Brunswick, Canada... 

The Siluro-Devonian Tobique-Chaleurs Zone (TCZ) of New Brunswick is host to several relatively small Zn-Pb Cu-Ag sulfide deposits and occurrences that are all spatially associated with Early Devonian felsic volcanic and related sedimentary rocks (Fig. 1). The sulfide mineralization occurs as veins, veinlets and replacements of rock units that had high primary permeability (e.g., flow top breccias). Massive bedded sulfides that are typical of many modern and ancient VMS deposits are not present however, their absence is not surprising given the relatively shallow oxidizing marine conditions at that time therefore, the TCZ deposits belong to that part of the VMS family formed beneath the seafloor. This study was undertaken to assess the nature of the felsic volcanic host rocks and their control on mineralization. 

In the southern TCZ only Early Devonian rocks are exposed, and all of them are assigned to the Tobique Group. The Tobique and Dalhousie groups are in part coeval and are similar in terms of rock types. The depositional environment for the Tobique Group is, for the most part, thought to be outer shelf or slope based on sedimentary bed forms and ichnofauna and the presence of abundant pillow lava and hyaloclastite in mafic volcanic units. In... 

The submarine depositional setting inferred for most Early Devonian volcanic rocks in part explains the highly variable alkali contents. Specifically, many have generally low Na20 (< 3 wt.%) and high... 

Estimates like these indicate that hemoglobins arc very old and that 11 may he possible 10 tind relatives of vertebrate hemoglobins in in erlebrute animals. They also suggest ihal the gene duplication believed 10 lie responsible fix the divergence ot die or- and /(-chains took place in ihe Devonian period at the time of the appearance ol early amphibians and die dominance of (is.lt. 

The other trends of decreasing epoch mass with decreasing age of continental sedimentary carbonates (Figure 10.46B) for Cambrian to early Devonian and Devonian to early Triassic strata correlate very well with the continental freeboard curve (relative elevation of continents with respect to sea level) (Figure 10.47) for the cratonic interior of the United States and southern Canada. The preserved mass... 

Taylor, T. N., Remy, W., Hass, H. Kerp, H. (1995). Fossil arbuscularmycorrhizae from the Early Devonian. Mycologia, 87, 560-73. 

Retallack G. J. (1997) Early forest soils and their role in Devonian global change. Science 276, 583—585. 

Early Devonian paleosols have abundant traces of true roots, including woody tap roots of a variety... 

ElickJ. E., DrieseS.E., and MoraC. I. (1998) Very large plant root traces from the Early to Middle Devonian imphcations... 

For the strontium isotope record, the present is the key to the Cambrian in between, the Sr/ Sr ratio is seen to fall in roller-coaster fashion through the Paleozoic and early Mesozoic to a minimum in the Late Jurassic, and then to rise in steps to the present (Figure 3(a)). The Late Ordovician, Late Devonian (Figure 3(b)), and P-Tr events occurred just after local minima in Sr/ Sr and thus mark times of significant change in the strontium cycle. In contrast, the Tr-J event follows a local maximum value in the ratio, and marks a time of declining Sr/ Sr. The K-T event occurred contemporaneously with a local maximum in the ratio, on both the multimillion and 10 -year timescales (MacLeod et al., 2001 Figures 3(a) and (c)). 

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