1. PALEOBATHYMETRY 2014
Yousuf Ghouri & Masoom Shani Page 1
Paleobathymetry
The study of the ocean-depth and topography of the ocean floor in the geological past.
Explanation
The determination of ancient water depth is known as paleo-depth. Paleobathymetry is the
paleoenvironmental interpretation most widely used in petroleum exploration because of its
value in determining the depositional history of a basin. Foraminifera are usually used for this
purpose.
Forams as Paleo-depth Indicator
Benthic foraminifera are usually used as Paleo-depth indicator. As bottom dwellers, they provide
information about conditions at the sea floor. Many species live within a relatively limited range
of water depths in patterns normally related to water mass distribution within the basin rather
than directly to bathymetry. Other marine microfossils are occasionally used for more
generalized paleo-depth determinations.
With the advent of geo-history method that requires quantitative paleo-depth data; greater
importance has been placed on the benthic foraminifera as paleo-depth indicator.
A widely used foraminiferal paleo-depth indicator includes trends (species, abundance species,
diversity, test composition, planktonic to benthic ratios) and species depth limits based upon
distributional studies of modern benthic micro fauna.
The application of such ecologic approaches in interpretation of fossils data realized on that has
received some attention as:
Modern distributional pattern are analogous to those of past.
From the study of foraminiferal ecology, it is evident that species distribution is unrelated to
bathymetry but coincides with water-mass, sediments and nutrients boundaries in ocean.
Benthic foraminiferal Paleobathymetry approaches are basically sound aid as benthic faunal
response to climatic oceanography changes are better understood, benthic foraminifera are more
useful indicators of environment.
Depth of Forams Presence
Different Forams present at different depth and show specific environment. The depth at which
different forams are present, are as follows:
Spherical Alveolinids
They found at a depth ranges from 0 to 30 m as shown in fig 1.
2. PALEOBATHYMETRY 2014
Yousuf Ghouri & Masoom Shani Page 2
Elongated Alveolinids
They found at a depth ranges from 30 to 50 m as shown in fig 1.
Nummulites
They found at a depth ranges from 50 to 80 m as shown in fig 1.
Assilina
They found at a depth ranges from 80 to 100 m as shown in fig 1.
Discocyclinids
They found at a depth ranges from 100 to 120 m as shown in fig 1.
Figure 1 : Paleobathymetry and Ocean profile
