WHAT HAPPENED IN THE EARLIER MIOCENE?
THE BRASSO AND TAMANA FORMATIONS
REVISITED
Or
How can I convince you that
quantitative micropalaeontology really is worthwhile?
Dr Brent Wilson FGS
Petroleum Geoscience Programme
The University of the West Indies
St. Augustine
How I looked in 1965, when Batjes
presented his model
Already a lecturer?
What are Foraminifera?
For those who got their degree a geological age ago
• Single celled bugs <1 mm
• Planktonic (float near sea
surface)
• Benthonic (live on seafloor)
• Shelled
• Narrow ecological niches
• Abundant in marine
environments
• Beautiful
Bolivina jiattongi Wilson, 2006
Why the Brasso and Tamana
Formations?
• A point of attack towards basin analysis on
Trinidad
• Good documentation of Brasso forams (Renz,
1948) simplifies systematics
• Easily accessible type locality (Upper Caparo
River)
• A chance conversation with Laurent de Verteuil
• Even uneconomic clays deserve to be
(((((loved)))))
Localities examined, shown on map
courtesy of GSTT’s website
Brasso Formation
1. Guaico-Tamana Road
2. Brasso Village
3. St. Fabien Quarry
Tamana Formation
4. Gasparillo Quarry West
5. Mayo Quarry
1
2
3
5
4
The Brasso Formation I
•
•
•
•
~3800’ (~1170 m) thick (Kugler, 2001)
Inky blue, massive clay (not very photogenic)
Some limestone members
Lateral equivalent of lowest part of conglomeratic MioceneRecent Cunapo Formation
• Shallow-water equivalent of part of Cipero Formation
(a deep water Globigerina Ooooooooooze)
• Deposited in piggy-back basin on advancing thrust sheet
• Partly equivalent to early Middle Miocene Tamana
Formation
Middle
Miocene
Early
Globorotalia fohsi robusta
Globorotalia fohsi lobata
Globorotalia fohsi fohsi
Globorotalia fohsi peripheroronda
Praeorbulina glomerosa
Globigerinatella insueta
Catapsydrax stainforthi
Catapsydrax dissimilis
N12
N11
N10
N9
N8
N7
N6
N5
Age at base (millions of years,
approximate)
Age
Approx. N Zone equivalents
Early to Middle Miocene
(Globigerinatella insueta
through Globorotalia
fohsi robusta planktonic
foraminiferal zones
[N7-N12 of Blow, 1969])
~12.4-18 million years old
Depositional rate ~213 m per
million years
(~0.2 mm yr-1)
Possibly older locally
(Catapsydrax dissimilis
Zone (N5—20.5 million
years old)
Planktonic Foraminiferal Zones
The Brasso Formation II
13.9
14.7
15.3
16
17.2
18
18.6
20.5
Rich Benthonic and Planktonic
Foram Fauna
Renz (1948)—159 species:
mostly benthonics
Wilson (2003)—28 species of
planktonics in
Globigerinatella insueta
through Globorotalia fohsi
fohsi Zones (N8-N10)
alone (Guaico-Tamana
Road, 24 samples)
Wilson (2004)—182 species of
benthonics from GuaicoTamana Road samples
Textularia carrbrowni Wilson, 2006
Little known palaeo-environment
• Renz (1948): 50-600 m
water depth
• Stainforth (1948):
peripheral neritic rim to
deep-water Cipero
Formation (i.e., <200 m)
• Kugler (1953): Neritic
http://www.glossary.oilfield.slb.com/files/OGL98002.gif
Materials and Picking Methods
• 24 samples from Guaico-Tamana Road taken every
outcrop)
5 m (a
BIG
• From Brasso Village, St. Fabien and Gasparillo
West Quarries every 1 m (TINY outcrops)—20
samples at Brasso, 6 at St. Fabien Quarry, 24 at
Gasparillo West
• All foraminifera (planktonics+benthonics) picked
to 200 benthonics, then a further 200 benthonics
• Statistical analyses limited to samples with >100
benthonics
Calculating palaeodepths using the
percentage of planktonic forams
• As water depth increases, percentage of foram
assemblage as planktonics (%P) increases, but rate
of increase differs from area to area
• Off the Nile, D
(1999)
= e(81.9+%P)/24 —de Rijk et al.
• On modern day Trinidad shelf D
= 19.7 +
1.34*%P (Wilson 2007)—only valid down to ~100
m
The Guaico-Tamana Road Outcrop
Grid Reference [Trinidad
Government Cadastral
Coordinates] N1161709
E0701400 links
Planorbulinella trinitatensis
The Guaico-Tamana Road Outcrop
Age determined using
planktonic foraminiferal
index fossils
Praeobulina glomerosa to
Globorotalia fohsi fohsi
Zones (N8 – N10)
Globorotalia praemenardii
Guaico-Tamana Road Outcrop
Sample
Distance above JBW-1 (m)
Percentage Planktonics (%P)
Inferred Palaeodepths using de Rijk et al. (1999)
JBW -24
JBW -23
JBW -22
JBW -21
JBW -20
JBW -19
JBW -18
JBW -17
JBW -16
JBW -15
JBW -14
JBW -13
JBW -12
JBW -11
JBW -10
JBW -9
JBW -8
JBW -7
JBW -6
JBW -5
JBW -4
JBW -3
JBW -2
JBW -1
158
139
134
129
124
117
112
107
101
94
89
84
77
55
50
45
40
35
30
25
20
15
10
0
60.8
71
64.9
78.6
11.6
33.1
27.5
n/a
29.1
18.1
52.6
n/a
n/a
n/a
50.9
64.3
66
62.4
54.8
46.5
n/a
31.5
n/a
n/a
900
Palaeodepth (computed
from de Rijk et al.’s 1999
expression)
800
700
600
500
metres
400
300
200
100
0
0
50
100
150
200
Distance above base of outcrop (metres)
Outlined section anomalous—inner to middle
neritic Probably <50 m—shown by
Pseudononion atlanticum + Elphidium cf.
poeyanum
Measuring
Benthonic Foram Diversity I
• Species Richness (S)
supposedly increases
with water depth
• S is of limited use
– Gives equal weight to
dominant and rare
species, and is
dependent on number
of specimens found (N)
so that SαN
Textularia framptoni Wilson, 2006
Measuring
Benthonic Foram Diversity II
Information Function (H)—a measure independent of N
–
–
–
–
To find H for a sample, first calculate pi=ni/N for each species in it
Then calculate pi*ln(pi) for each species
Add the results and multiply by -1
So, H = -Σ pi*ln(pi)
H typically positively correlated with depth (Murray and Alve,
2000). Should be correlated with %P if change in water
depth is real
Benthonic foram diversity patterns in the
Guaico-Tamana Road outcrop
180
160
140
Distance above JBW-1 (m)
Rise in diversity (H) in lower part
of section, decreasing in higher
(transgression followed by
regression)
H high around sample JBW-7
through 9 (flooding surface)
H significantly correlated with %P
(excluding uppermost
samples)—r = 0.627, p<.05
So, both benthonic H and %P
suggest transgressive-regressive
cycle
H low on flooding surface (JBW-8)
due to stagnation at maximum
flood
JBW-20
120
100
80
60
JBW-8
40
JBW-7
20
JBW-3
0
0
0.5
1
1.5
2
H'
2.5
3
3.5
4
Benthonic Foraminiferal Assemblages
Guaico-Tamana Road outcrop
Age
Late N9 Early N10
Sample
Assemblage
Environment
JBW-24
JBW-23
Assemblage 4
JBW-22
Middle Neritic
JBW-21
JBW-20
JBW-19 Assemblage 3
JBW-18
JBW-17
n/a
JBW-16
Outer Neritic
JBW-15
Middle Neritic
JBW-14
Upper Bathyal (shallow)
JBW-13
n/a
JBW-12
Assemblage 2
JBW-11
JBW-10
Upper Bathyal (shallow)
JBW-9
Upper Bathyal (deep)
JBW-8
JBW-7
JBW-6
Upper Bathyal (shallow)
JBW-5
JBW-4
n/a
n/a
JBW-3
Assemblage I
Outer Neritic
JBW-2
n/a
n/a
JBW-1
N9
Late N8 - Early N9
Four benthonic foraminiferal
assemblages:
•Assemblage 1 ( Brizalina alazanensis),
outer neritic, transgressive phase
• Assemblage 2, Anomalinoides
mecatepecensis, Uvigerina carapitana, U.
subperegrina. upper bathyal (height of
transgression) to middle neritic.
Regression.
• Assemblages 3 and 4, Amphistegina
gibbosa and Textularia framptoni Pseudononion atlanticum - Elphidium cf.
poeyanum respectively, middle
neritic.
Indet
20 m
Guaico-Tamana Road
Near Top of Section:
Hypersaline, Lagoonal
Interlude
hm
JBW-117
JBW-116
JBW-115
JBW-114
h
JBW-113
15 m
h
JBW-112
pm
JBW-111
pm
JBW-110
pm
Log Symbols
fine-grained
sandstone
JBW-109
siltstone
JBW-108
10 m
pm
claystone
h
JBW-107 cc cccccc
c
c c cccc
JBW-106
pm
JBW-105
em
UUUU burrowed horizon
ccc
coquina
Gypsum in some samples near
top of section barren of forams
molluscs
5m
iron concretions
lignite partings
g
JBW-104
p
JBW-103
pm
JBW-102
pm
Minor Residue Components
g euhedral gypsum
JBW-101
(whole
m molluscs
and fragments)
JBW-100
U U UU U UU
JBW-98
0m
Some nearby samples
dominated by Discorbis tholus
or miliolids
p iron pyrites
h
JBW-99
e
m
hematite cemented
lithic fragments
echinoid spines
JBW-97
0
100
200
JBW‐100
JBW‐101
JBW‐102
JBW‐103
JBW‐104
JBW‐105
JBW‐106
JBW‐107
JBW‐108
JBW‐109
JBW‐110
JBW‐111
JBW‐112
JBW‐113
JBW‐114
JBW‐115
JBW‐116
JBW‐117
Total benthonic
foraminifera
JBW‐99
10 15 20 25 30
Mass of residue (grams)
JBW‐98
species
Ammonia cf. catesbyana
Amphistegina gibbosa
Cibicides floridanus
Discorbis tholus
Eponides parantillarum
Hanzawaia carstensi
Lenticulina acutistriata carolina
Lenticulina spp.
Pseudononion atlanticum
Quinqueloculina seminulangulata
Textularia framptoni
5
JBW‐97
0
24
5
18
78
0
0
0
2
0
0
0
0
4
89
9
0
0
0
1
0
0
0
4
0
66
0
3
0
0
1
1
0
0
6
6
127
5
1
0
0
3
1
0
0
1
0
6
0
0
0
0
1
0
0
0
0
22
1
0
4
0
0
3
2
0
58
0
0
0
0
5
1
3
0
0
0
5
0
0
0
0
0
0
6
0
0
0
29
0
0
0
0
1
2
11
109
28
0
1
0
0
0
0
1
34
8
125
1
0
1
0
0
0
0
0
0
0
1
0
0
5
0
0
0
0
5
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
3
0
0
0
1
38
0
0
0
0
0
143
0
4
5
1
43
2
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
0
0
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
2
0
The Brasso Village Section
• Age: Middle Miocene
• Globorotalia fohsi lobata
and Globorotalia fohsi
robusta [N11-N12] Zones
• Section younging to NW
• Patterns not as obvious as
in Guaico-Tamana Road
(outcrop in meander cut
banks only)
Measuring
Palaeo-oxygenation Levels
• Kaiho’s (1994) Benthonic
Foraminiferal Oxygen Index
(BFOI) assesses dissolved
oxygen levels in bottom
waters in bathyal and
abyssal environments
• BFOI = [O/(O + D)] × 100
where O and D are
respectively numbers of oxic
and dysoxic indicators
• Uniformitarianism (“The
key to the past lies in the
present”) allows application
of BFOI to later Cenozoic
Globorotalia mayeri
What is an
Oxygen Minimum Zone (OMZ)?
http://www.galapagosonline.com/Galapagos_Natural_History/Oceanography/Upwelling.jpg
http://earthguide.ucsd.edu/virtualmuseum/images/OceanicOxygenProfile.jpg
• At Brasso Village, complicated
pattern in %P (slight reduction
over time?)
• Overall decrease in S over time
• H shows general decrease over
time
• No significant correlation
between %P, H and BFOI
• Regression brought seafloor in
contact with OMZ
• BFOI constant below OMZ,
low at OMZ core, then
increases above OMZ
• General overall regression
• Succession of foraminiferal
assemblages (oldest first) reflects
changes in palaeo- oxygenation:
•
1 (Uvigerina quesqueyana) upper bathyal,
moderately-oxygenated water beneath OMZ;
•
2 (Siphonina pulchra, Cassidulina laevigata, lesser
Globocassidulina subglobosa) outer neritic,
moderately-oxygenated water below OMZ;
•
3 (Uvigerina subperegrina) occupied outer neritic,
lower margin of OMZ;
•
4 (Brizalina subaenariensis) lived at core of OMZ.
•
Rates lowest on the Benthonic Foraminiferal
Oxygen Index (BFOI);
5 (middle-neritic with few Uvigerina spp. and
Brizalina spp.) well-oxygenated water above OMZ.
• Note Low H at core of OMZ,
marked by lowest BFOI
Foram Microhabitats in the
Brasso Village Section
• Microhabitats–depths at which foraminifera live in
sediment (Barmawidjaja et al., 1992)
• Epifauna on top of sediment
• Shallow infauna in top 2 cm of sediment
• Deep infauna at >2 cm
• Infaunal taxa dominate where dissolved oxygen
reduced
• 28 species forming >1% of total recovery from
Zones N11-N12 were assigned to microhabitat
groups
Fauna changes from mostly infaunal below OMZ
to mostly epifaunal above
(youngest sample at left)
The OMZ and palaeo-environmental preferences
for some Brasso benthonic foraminifera
Guaico-Tamana Road section
Shallow
Upper OMZ. Dominant Uvigerina subperegrina,
Uvigerina carapitana rare.
Core OMZ. Dominant Brizalina
alazanensis. Uvigerinids rare.
Lower OMZ. Dominant Uvigerina
carapitana, common Cassidulina
carapitana. Uvigerina sub peregrina
rare.
Deep
Oxygen depletion (diagrammatic only)
At Brasso Village:
•B. alazanensis replaced by B. subaenariensis
•U. carapitana replaced by U. quesqueyana
St. Fabien Quarry
• Planktonic forams Indicate
an early Middle Miocene
age (Globorotalia fohsi
fohsi Zone, N10)
• %P suggestive of outer
neritic to upper bathyal
palaeo-depths
• Trend towards deeper
water in the upper part of
the 6 m section
Globigerina bulloides
Trends at St. Fabien Quarry
• Planktonic foram H positively
correlated with %P
• Implies planktonic foram
diversity increased with
palaeo-depth or distance from
shore
• Globigerina praebulloides,
rare in the tropics after the
earliest Early Miocene, is
abundant at St. Fabien
Quarry. Indicates a tropical
refuge due to upwelling of
cool, nutrient-rich water
Globigerina praebulloides
Overview of Tamana Formation
• Four members: Lower Concord Calcareous Silt; Guaracara
Limestone (a series of bioherms); Upper Concord
Calcareous Silt; Los Atajos Conglomerate
• Kugler (2010) – Globorotalia mayeri Zone (N14) age,
overlies Brasso Formation
• Deposited on pop-up structure along southern edge of
Northern Basin
• Kugler (2001): Brasso and Tamana separated on account of
faunal differences
• Biofacies, not formation!
• Guaracara Limestone Member – belongs to Brasso
Formation?
Gasparillo West Quarry
• 24 samples from Upper Concord
Calcareous Silt, 1 m apart
N
• Early Middle Miocene age (N9N10, not N14)
o
10 20'23"N
• Same age as Brasso Formation at
Guaico-Tamana Road
61o25'20"W
250 m
Upper Concord Calcareous Silt Member
• Single transgressive-regressive
cycle
• Oxygen minimum zone
• Maximum depth ~225 m (cf. 475
m at Guaico-Tamana Road)
Gasparillo limestone (Guaracara Limestone Member)
Lower Concord Calcareous Silt Member
Sample Site
Palaeoenvironmental Model,
Gasparillo West Quarry
MRA1
Amphistegina gibbosa
+ Cibicides spp.
MRA23
Cibicides spp.
Cibicidoides
crebbsi
Uvigerina
subperegrina gr.
Time
Uvigerina
subperegrina gr.
Brizalina alazanensis
venezuelana
Time
Guaracara Limestone at Mayo
Quarry
• Limestone-Marl
Alternations in Bioherm
• Yielded abundant forams
• Planktonic Forams
indicate an N10 age
• ?Same age as or
succeeding Gasparillo
West Quarry outcrop
?Upper Concord
Silt Member
OC1-6
OC1-5
OC1-3
OC4
Guaracara
conglomerate
OC2
OC1-2
OC1-1
lower yellow
limestone
Lower Concord
Silt Member
*OC2
*
*
= Mayo limestone
N
Mayo
Village
OC4
OC3
OC1-4
*OC1
OC3
upper yellow
limestone
200 m
OC1
Palaeodepths and palaeoenvironment in
Mayo Limestone
Planktonic forams show a
series of small (~30 m) T-R
cycles (Milankovitch control?)
30
20
Benthonic forams indicative of photic
zone (Amphistegina spp., Elphidium
spp.)
10
B
AB1
AB2
AB3
AB4
AB5
AB6
C
AB7
0
OC1
base
OC2
OC3
OC4
top
Amphistegina n. sp., drawing by Annalize
McLean
A
Group A
60
Group B
AB5
AB6
AB7
40
AB1
AB2
AB3
AB4
Benthonic forams indicative of photic
zone (Amphistegina spp., Elphidium spp.)
20
0
OC1
base
B 40
OC2
OC3
top
Group D
Group C
30
OC4
AB5
AB6
AB7
20
10
AB1
AB2
AB3
AB4
0
OC1
base
C
OC3
OC2
OC4
top
Asterigerinata dominicana
Group A, (Outcrops 1,3,4) Elphidium
poeyanum, Nonionella basiloba,
Asterigerinata dominicana, Bolivina plicatella
mera: Group B, (Outcrop 2) Amphistegina
sp., Rosalina subaraucana
Elphidium dominicense
10
AB1
AB2
AB3
AB4
AB5
AB6
Amphistegina – intolerant of turbidity
Elphidium – tolerant of nutrient
enrichment associated with river outflow.
AB7
5
0
base
OC1
OC3
OC2
D 15
AB4
AB1
OC4
top
Hanzawaia carstensi
Rosalina subaraucana
AB2
AB7
10
AB5
5
AB6
AB3
0
base
OC1
OC2
OC3
OC4
top
Variations in fauna: control by depth or some factor
associated with variation nutrient supply. Control by
changing distance from shore ?
Assemblage A
Assemblage B
Assemblage C
Assemblage D
Several Hundred Kilometers
Assemblage A
Assemblage B
Assemblage C
•In Mayo Quarry,
fluctuations in fauna
uncorrelated with
change in palaeodepth
shown by planktonic
forams
•Model from
Whitsuntide Islands,
•Western Australia.
•Upper figure, depth
control
•Lower figure, distance
from shore
A Warning!
“There is something
fascinating about science.
One gets such wholesale
returns of conjecture from
out of a trifling investment
of fact.” (Mark Twain)
“We all know that we do not
need a complete data set to
write an acceptable
(hi)story. A nice story can
equally well be written on
the basis of a very few data
and a fair amount of
imagination.” (C. W Drooger,
1993, Radial Foraminifera;
Morphometrics and Evolution, p. 19)
Tectonic or eustatic control on transgressiveregressive cycles in Brasso and Tamana
Formations? I
• Catuneanu (2006) suggests eustatically controlled
transgressive-regressive cycles have tabular
sedimentary sequences (equal creation of
accommodation throughout basin) but basin rim
lacks proximal conglomerate
• In tectonically controlled cycles, sedimentary
sequences wedge-shaped, basin has proximal rim
of conglomerate from uplift of source areas
Tectonic or eustatic control on transgressiveregressive cycles in Brasso Formation? II
• Geometry of Brasso
sequences unknown
• Rim of conglomerate
(Cunapo Formation)
• Transgressions in
Brasso Formation at
least partly
tectonically driven
7m
Diapir of Brasso Formation within limestone of
Tamana Formation, Mayo Quarry
Tectonic or eustatic control on transgressiveregressive cycles in Brasso Formation? III
• Pulses of loading-induced subsidence can explain
transgressions
• Difficult to reconcile regressions with erosional
unloading of the hinterland
• Eroded sediment would continue to load and
depress proximal foredeep within piggy-back basin
(cf. Varban and Plint, 2008)
• More research at the basin analytical level required
Conclusions
•
At least 2 T-R cycles in the Brasso Formation:
•
1. N8-N10 (Guaico-Tamana Road, St. Fabien Quarry)
2. N11-N12 (Brasso Village)
Transgressions tectonically induced at least in part
•
Earlier cycle found in Upper Concord Silt (not a true member?)
•
Both cycles show presence of oxygen minimum zone
–
•
Environmental preferences of some foraminifera elucidated,
especially as palaeo-oxygen indicators
Trinidad was a refuge for Globigerina praebulloides—due to
upwelling
A Suggestion
“Knowing is not enough. We must apply.”
Johann Wolfgang von Goethe
“If basin analysis on Trinidad is to attain its
full potential, then it must make abundant
use of fully quantitative and statistical
micropalaeontology.” – B. Wilson
Convinced? ☺
Acknowledgements
(in no order of preference or importance)
• Professor Richard Dawe of UWI for invaluable mentorship
• Mr Barry Carr-Brown and Dr John Frampton
(BioStratigraphic Associates) for discussions
• Ms Ann Ramsook (Petrotrin) for encouragement
• Dr Laurent de Verteuil (Latinum) for the location of the
Guaico-Tamana Road outcrop
• Mrs Jacqueline Attong-Wilson of UWI for fieldwork
assistance
• The UWI Research and Publications Fund—for the cash to
photograph the bugs
Selected References I
•
•
•
•
•
•
•
•
•
Barmawidjaja, D. M., Jorissen, F. J., Puskaric, S., & van der Zwaan, G. J. (1992).
Microhabitat selection by benthic foraminifera in the northern Adriatic Sea. Journal of
Foraminiferal Research, 22, 297-317.
de Rijk, S., Troelstra, S. R., & Rohling, E. J. (1999). Benthic foraminiferal distribution in
the Mediterranean Sea. Journal of Foraminiferal Research, 29, 93-103.
Kaiho, K. (1994). Benthic foraminiferal dissolved-oxygen index and dissolved-oxygen
levels in the modern ocean. Geology, 22, 719-722.
Keller, G. (1985). Depth stratification of planktonic foraminifers in the Miocene ocean. In
J. P. Kennett (Ed.), Geological Society of America Memoir 163. The Miocene Ocean:
Paleoceanography and Biogeography, 177-196.
Kugler, H. G. (1953). Jurassic to recent sedimentary environments in Trinidad. Bulletin
de l'Association Suisse des Géologiques et l’Ingéneurs du Pétrole, 20(59), 27-60.
Kugler, H. G. (2001). Treatise on the Geology of Trinidad. Part 4: Paleocene to Holocene
Formations. Basel, Switzerland: Museum of Natural History, 309 p.
Renz, H. H. (1948). Stratigraphy and fauna of the Agua Salada Group, State of Falcón,
Venezuela. Mem. Geol. Soc. America No. 32, 219 p.
Stainforth, R. M. (1948). Description, correlation, and paleoecology of Tertiary Cipero
marl formation, Trinidad, B. W. I. AAPG Bulletin; 32, 1292-1330
Varban, B. L.. & PLint, A. G., Sequence stacking patters in the Western Canada
foredeep: influence of tectonics, sediment loading and eustacy on deposition of the
Upper Cretaceous Kaskapau and Cardium Formations. Sedimentology, 55, 395-421.
Selected References II
•
•
•
•
•
•
Wilson, B. (2003). Foraminifera and Paleodepths in a Section of the Early to Middle
Miocene Brasso Formation, Central Trinidad. Caribbean Journal of Science, 39, 209-214.
Wilson, B. (2004). Benthonic Foraminiferal Paleoecology Across a TransgressiveRegressive Cycle in the Brasso Formation (Early-Middle Miocene) of Central Trinidad.
Caribbean Journal of Science, 40, 126-138.
Wilson, B. (2005). Planktonic Foraminiferal Biostratigraphy and Paleo-Ecology of the
Brasso Formation (Middle Miocene) at St. Fabien Quarry, Trinidad, West Indies.
Caribbean Journal of Science, 41, 797-803.
Wilson, B. (2006). Depths, paleodepths and the percentage of foraminiferal assemblages
comprising planktonics in Trinidad. Forams 2006 Anuario do instituo de Geosciencias
UFJR, 29, 373-374.
Wilson, B. (2006). Four new species of benthonic foraminfiera from the Miocene of
Trinidad, West Indies, and their paleobiogeographic importance. Revue de
Paleobiologie, 25, 519-524.
Wilson, B. (2007). Benthonic foraminiferal paleoecology of the Brasso Formation
(Globorotalia fohsi lobata and Globorotalia fohsi robusta [N11-N12] Zones), Trinidad,
West Indies: A transect through an oxygen minimum zone. Journal of South American
Earth Sciences, 23, 91-98.
Any questions?