Time-rock unit

The relationship between time units, time-rock units, and rock units is as follows ... 

Time Units Time-Rock Units Rock Units... 

A time-rock unit has been defined as a succession of strata bounded by theoretically uniform time pianes, regardiess of the local lithology of the unit. Fossil evidence usually provides the basis for the estabiishment of time planes. Ideal time-rock units would be bounded by completely independent time planes, however, practically the establishment of time-rock units depend on whatever evidence is available. 

This system for keeping track of these important units is used as the basis for the standard geologic lime and the evolution of the animal life on earth. (See also Tables 2-26 and 2-27.) Table 2-28 gives the relationship between geologic time and important physical and evolutionary events that are used to aid in the identification of rock units in relative geologic time [26]. 

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. 

Figure 8.35. Porosity versus time-temperature index of maturity (TTI) for various carbonate rock units. The TTI values are based on Lopatin s (1971) method. The onset and end of oil generation (the "oil generation window") in terms of TTI units are from Waples (1980). The log linear equations of best fit between porosity and TTI data are also shown. = porosity. (After Schmoker, 1984.)...

Rock unit Neutron density (p.u.) Sonic transit time (ps/ft) Density (g/cm )... 

Many authors reported paragenetic relationships that allow the relative timing of saddle dolomite precipitation within a given rock unit to be determined. There is general agreement among these... 

Stratigraphy distinguishes rock units and time units. A rock unit, such as a stratum or a formation, possesses a variety of physical characteristics that enable it to be recognized as such, and, hence, measured, described, mapped and analysed. A rock unit is sometimes termed a lithostratigraphical unit. 

Fig. 2 Time-scale divisions utilized in this paper, orogenies and major rock units referred to in text...

The types of rocks that comprise a collapse structure depend on the types of rock that are cut by the structure, the amount of underlying material removed by solution and rock units overlying the structure at the time of development. Blocks of sandstone, siltstone, shale and carbonates may be found in the collapse. Sandstone emd some siltstones are the common uranium hosts. Well-known pipe-like bodies include Woodrow Pipe, New Mexico, Orphan mine, Arizona, and Temple Mountain, Utah, all in the U.S.A. 

We will now estimate the front velocity using the method of Guy (1984). Let us consider, in one dimension, the conservation of element i in a rock column (x = xt to x = x2) of unit section which contains a propagating front at the time-dependent position s(t). The discontinuity is handled by breaking the column at s = s(t). The amount of element i in the rock column only changes by fluid exchange through both ends of the column, hence... 

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