Semi-detailed Soil Survey of the LIuidas Vale Area, St. Catherine-St ...

2.4 GEOLOGY
DESCRIPTION OF THE SURVEY AREA
A fairly detailed overview of the formations occurring in the survey area, as
well as their period of deposition and age are given in Table 7. These data
are mainly based on Geological sheet 19 (Mines and Geology Division,
Ministry of Mining and Natural Resources) and on Zans et al. (1962). The
geology of the area is shown in Figure 4. Geology is used as the second entry
in the legend to the soil map, as described in Sub-chapter 4.3. Although
lithology in Jamaica is very important for the soil formation, other factors
like tectonic uplift and original landforms are as important (Pfeffer 1986).
Table 7. Geology of the Lluidas Vale area.
Group/Unit For mation/Lithology Period Age/10*6
(years)
- Recent Alluvium
Inland Basin deposits
White Limestone Newport Fm.
Walderston-Brown's Town Fm.
Somerset Fm.
Troy-Claremont Fm.
Pleistocene-Holocene
Pleistocene
Miocene
Oligocene
Upper Eocene
Middle Eocene
0-1.5
7-26
26-37
37-43
43-48
Yellow Limestone Chapelton Fm. Middle-Lower Eocene 48-53
(Volcanics) Devil's Race Course Fm. Lower Cretaceous 100-120
The oldest formation in the area is of Cretaceous age, i.e. the Mount Diablo
Inker to the north of Ewarton, and is represented by the Devil's Race Course
Formation. This formation mainly consists of lavas and volcaniclastics; a few
banded lavas are overlain by volcanic conglomerates. The rock fragments in
the conglomerates are mainly andesites. Within this formation, there are
four Limestone Members, of which only the Copper Limestone has been
mapped in this area.
In some very small patches, the Cretaceous outcrops are surrounded by
members of the Chapelton Formation (Yellow Limestone Group), which varies
in thickness from 15-150 m. Here, as well as along the southern border of
the survey area, adjacent to the Central Inker, the Albert's Town Member is
mainly found and to a very smzdl extent the Guy's Hik Member.
The Albert's Town member is a sequence of bioclastic calcarenites and marly
kmestone, partly dolomitized in the upper part of the deposit. It is known
for its rich and wide variety of fossils.
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