The Stratigraphic Lexicon of Iraq by R.C. van Bellen,
H.V. Dunnington, R. Wetzel and D.M. Morton was published in 1959.
Today, this book continues to serve as one of the foremost sources
of information on the Mesozoic and Cenozoic geology of Iraq and
the Arabian Peninsula. The long life of this book is due to many
Firstly, the authors wrote the comprehensive descriptions
of all the known rock units and biostratigraphic zones in Iraq (as
of 1959) mostly based on direct examination of the data. Therefore
the descriptions continue to be applicable today. Secondly, they
documented and correlated these units from outcrop to the subsurface
across a vast region of some 500 by 1,000 square kilometers. This
region forms a major part of the petroleum habitat in the Middle
Thirdly, and perhaps most surprisingly, they placed
all of these rock units into a regional tectono-stratigraphic framework
that predates Earth Science breakthroughs such as Plate Tectonics
and Sequence Stratigraphy. Geologists who are familiar with the
tectono-stratigraphic evolution of Arabia will immediately recognize
in Plates II to IV and VI (redesigned here as large colored posters)
that these authors had already recognized most of the Mesozoic and
Cenozoic second- and many third-order sea level cycles and main
tectonic unconformities from the Tethyan realm near the Zagros Mountains,
to the stable shelf in western Iraq, Kuwait and Saudi Arabia.
Besides these important achievements, the lexicon
contains a vast array of primary data and insightful interpretations
that are of considerable value today. It is for these reasons that
GeoArabia has located a rare copy of the book and reprinted it with
the sponsorship of the Ministry of Oil of Iraq and Chevron. This
reprint makes every effort to represent the original work without
modifying its technical contents. To the contrary, it adopts several
editing conventions that emphasize the original meaning. The following
discussion identifies the key editing conventions that were applied
to the original book.
Authors: In the present reprint, for each rock
unit, two categories of names are listed under the heading “Authors”.
The first category provides the names of the primary authors who
wrote about the rock unit in reports, journals and books. They are
credited with, for example, first naming the unit, or first defining
it, etc. The names of these primary authors are repeated here from
the original lexicon with minor reformatting (e.g. parenthesis,
punctuation). The second category consists of the names of one or
more of the lexicon’s authors who compiled the description
for the rock unit from the works of the primary authors. In this
reprint the names of the second category of authors are shown in
brackets at the end of the list of primary authors. In the original
lexicon the names of these authors were identified by their initials
at the end of the description of each rock unit: H.V.D [H.V. Dunnington],
D.M.M. [D.M. Morton], R.C.V.B. [R.C. van Bellen] and R.W. [R.
References: In the main text of the lexicon the
title of some papers is given in full although they are repeated
in the section entitled “References”. In this reprint,
only the author and year is given in the text. Throughout this reprint,
references cited in the main text and in the reference list are
restyled to be consistent with GeoArabia’s format (e.g. parenthesis,
punctuation). Several references are made in the text to manuscripts
that were in preparation (sometimes indicated as MS) and these are
shown as “manuscript, then in preparation” in the Reference
list. Where MS followed the names of fossils, the MS was left in
Formal Rock Units: In the original lexicon, the
authors stated which rock units are formal (Tables 1 to 6 and Plates
I to IV and VI); however, they did not capitalize the word “group”,
“formation” and “member” where these terms
followed the names of formal rock units. The formal names of some
rock units also carry a lithological description “Limestone”,
“Shale”, etc. In this reprint all formal units (including
formal lithological descriptions) are capitalised wherever they
For example, the original lexicon shows the formal
“CHIA ZAIRI LIMESTONE FORMATION” as the title for this
rock unit and “Chia Zairi limestone formation”, “Chia
Zairi limestone” or “Chia Zairi formation” in
the text, tables and plates. In this reprint, the name of this rock
unit is written as “Chia Zairi Limestone Formation”,
or “Chia Zairi Limestone” or “Chia Zairi Formation”.
Where the authors refer to the “Chia Zairi limestones”
the term limestones is not capitalized.
Informal Rock Units: All rock units that are indicated
as informal are not capitalized except for the name of localities;
for example, Mosul marble, etc. The authors noted that: “In
order to stress the informality of the beds, distinguished in certain
formations (e.g. Dammam Formation, Lower Fars Formation) the unit
term bed has been capitalized as Bed. Article 1, Remark (c) of the
rules in Ashley et al. (1939) prohibits capitals for the initial
letters of terms designating units.” In the present edition
this convention was reversed so that all units, beds, etc. are not
Moreover, each formal unit contains a subsection
listing its informal or obsolete synonyms that are again not capitalized.
For the cited synonyms the encompassing quotations were not consistently
applied in the original and these were removed where appropriate.
This was possible because the formal rock units are capitalized
here. Also the word “part” is here positioned immediately
after the relevant rock unit (instead of in parenthesis after it)
to emphasize that the authors meant that the correlation is partial
to the formal rock unit that is being described.
Qualifiers of Stages: In the reprint the use (or
suppression) of capitalization of the qualifiers “upper, late,
middle, lower, and early”, where they appear before the name
of a stage (age) or period (system) was not modified. Accordingly
the apparent inconsistency of using, for example, “Upper Aptian”
and “late Aptian” (sometimes late-Aptian”) was
not modified. Nor were these terms switched to reflect time (late,
mid, early) or stratigraphic position (upper, middle, lower). Thus
phrases that mix time and position like, for example, “late
Upper Campanian” or sometimes “uppermost Campanian”
remain as in the original. In the reprint the respective position
of units and ages occurring at contacts is written “Upper
Unit/Lower Unit” or “Younger Age/Older Age”. Also
the informal “Middle” Cretaceous (capitalized “Middle”
in the original lexicon) was not decapitalized. Finally the term
“Maestrichtian” is spelled here as “Maastrichtian”.
Combining Paragraphs: The page size of the original
lexicon is about half that of this edition’s page size and,
in places, it consists of many short paragraphs or single sentences.
In this reprint, for the benefit of conciseness, related short paragraphs
are combined. Also some sentences have been repositioned to sections
where they retain their context.
Combining “Location and Thickness”
Sections: For the formally defined rock units this edition combines
the sections entitled “Location” and “Thickness”,
into a “Location and Thickness” section. This is because
the thickness of a rock unit is usually a single numeric entry and
derived from the depths cited in the well or outcrop under “Location”.
The phrase “Brief description of type section” was deleted
as in all cases it now refers to the indented discussions under
the sections on lithology, fossils, age, underlying and overlying
formations and detail of contact. Furthermore, where appropriate,
this reprint provides all thicknesses in both meters and feet (1.0
m = 3.28 ft).
Tables 1–7: Tables 1–6 (pages 15-22)
were not numbered in the original lexicon. They are here positioned
close to where they appeared in the original text. In the original
lexicon the names of wells are cited by operating company (B.O.D.,
B.P.C., I.P.C., M.O.D., etc.) followed by the well name (e.g. Kirkuk
Well No. 109). In the present reprint the names of wells are shortened
to just well name and number (e.g. Kirkuk-109). The new Table 7
(pages 238-239) consists of a list of all the wells cited in the
text, operating company of that time, and coordinates (where known).
Also, where possible, phrases with several named wells and name
places are listed alphabetically. Where coordinates are cited the
word “lat.” and “long.” were removed as
the numeric coordinates are followed by E (east) and N (north).
Capitalization and Nameplaces: Where geographic
features are considered well known then their descriptor was capitalized;
for example, Shield (as in Arabian Shield). Other examples are Depression,
Mountain, River, Valley, Village, etc. The words foraminifera, ostracoda,
etc. were decapitalized and not italicized. Throughout the text
the Arabian Gulf was substituted for the Persian Gulf.