image by symetric ridges (attributed to thick 
sandstone beds) alternating with smooth areas (more 
silty strata). This is attributed to the early 
Miocene. At this level, no indication reveals if 
the arrangement of the ridges is related to tectonic 
imbrications or to a fan delta sedimentation process 
with further uplift. Undated series are refrered to 
as MP on the map. They correspond to a very flat 
rough surface, in slightly datted light gray level 
on the image. This is the case for the detritai 
series in the NW area of the foothills along the 
western flank of the Central Range. The light gray 
siltstones of the turbiditic sequence (Pga) sampled 
in the Quezon area are of late Paleocene to late 
Eocene age (C. Muller, 1984). On the images, the 
same characteristics (plain area with a slightly 
rough surface and no erosional feature) can be 
observed east of the Bulantao Range. Therefore, 
these terrains are attributed to the same sequence. 
All these units are equivalent to the detritai 
Crocher formation in northern Borneo (Sabah region). 
The ophiolitic complex (0) forms the highest 
relief of the Central Range. The ophiolites are 
most probably of early Cretaceous age compared to 
those dated in Sabah (North Borneo). The Unit 
referred to as M on the map occurs as a very flat 
area, with alluvial deposit aspects. Since 
ophiolites can be observed in the field, the lack of 
relief on Landsat images suggests a melange. 
Therefore, an argillaceous matrix would produce the 
flat appearance while the ophiolites would be too 
small to be detectable. 
In central and southern North Palawan (Aborlan 
River, Ulugan Bay and north of it up to the 
Malampaya Sound) thick clastic series of late 
Cretaceous age (Muller, in preparation) are exposed. 
They are strongly tectonized and locally slightly 
metamorphosed. These alternating sand and 
siltstones with some thin graphitic layers were 
deposited along the former Chinese continental 
margin. On both MSS and radar documents two main 
photofacies correspond to this sequence: 
1. The UKS-unit forms high mountains with 
brilliant surface (around Cleopatra Needle). 
2. The UKM-unit occurs as strongly dissected and 
highly fractured plateau with a velvety appearence 
(region of Roxas). 
These differences on satellite imagery can be 
linked to local differences in the degree of 
metamorphism and/or to the greater amount of 
sandstones in the area of Cleopatra Neddie which are 
more resistant to erosion. The crests outlined in 
the western part correspond to particularly thick 
sandstone beds: The St. Paul shelf limestones 
(Pgb), of late Oligocene-early Miocene age, occur as 
a wide plateau on the image. In the area of Ulugan 
Bay they are present also as small elongated slices 
trending N20E, perpendicular to the first 
compressional phase. The same formation is known 
from offshore wells NW off Palawan. Offshore from 
South Palawan this carbonate platform is covered by 
overthrust accretionary wedge. 
Massive granodiotite intrusions, considered as 
late Miocene in age in comparison with Sabah, occur 
at Linapacan Island, Mount Capoas and Cleopatra 
Neddie. It is not excluded that there are some other 
small intrusions in this region. These formations 
form high relief but elevation induces artefacts in 
vegetation so that their boundaries cannot be drawn 
precisely. 
In North Palwan, Permian to Jurassic formations 
occur from Bay Point to Cabuli Island. On MSS 
imagery this is rendered by a very peneplanated 
surface, that is homogeneous in medium grey so that 
only very few morphological features can be of help 
in evaluating lithological or structural changes. 
In the field, early Jurassic limestones and 
sandstones (Frontaine) and Cretaceous detritics are 
tectonically imbricated with radiolarites (with 
slate and tuff intercalations) of Triassic age. 
Paleozoic is mentioned at Bacuit Island, Miniloc 
Island and north of El Nido. Two series are 
described: limestones (with fusulinas, algae, 
crinoids) and a clastic sequence (sandstone, tuffs, 
calcareous sandstones). 
3.2 Tectonic features 
It is quite difficult to detect the oldest 
structural features as reactivations by further 
tectonic phases have alterated them. Hence, mainly 
in the northern part of Palawan, the superimposition 
of at least three folding events plus the strong 
peneplanation make imbricated structures impossible 
to perceive on a 1:500 000 scale. The same problem 
occurs with the very thin early to middle Miocene 
imbrications. 
Abnormal contacts can easily be mapped when the 
difference in hardness and colour of the two 
juxtaposed units is great (as ophiolites and 
detrital) but their vergence can be deduced only 
from field observations. 
Regional fracture analysis reveals five domains of 
main directions: 
- South of Quezon: Due to the nature of the rocks 
(mainly ophiolites and elastics) fracturation is 
very badly expressed. The main trends are N40-N170, 
N60, N30, N135. 
- Between Queron and Ulugan Bay: Major trends are 
N45-N60, N160. 
- Cleopatra unit: N10, N37, N65, N105. 
- Roxas unit: N20-30, N60-70. 
- North or Malampaya sound: N-S, N30, N60, N120. 
The young N-S fault direction was more distinctly 
detected by remote sensing interpretation compared 
with previously published maps. 
The Ulugan fault, a major fault in the strongly 
N-S sheared zone, is clearly recognized in the 
bathymetry, coastal line and on aerial photographs. 
However, there is no clear evidence of this fault on 
satellite imagery. This might be due to sub-recent 
conglomerates and alluvial deposits which conceal 
its manifestation. 
The Rizal fault separates two lithological units 
(referred to as UKM and UKS) and is outlined by a 
broad rectilinear thalweg. Bent crests interpreted 
as folded beds in its vicinity confirm the 
hypothesis of a left lateral shear zone. This might 
be interpreted as a satellite of the Ulugan Fault to 
which it runs parallel. At Imuruan Bay some 
complications occur due to the interference with 
N30E right lateral strike slip faults or reverse 
faults. 
A very dense fracturation pattern with a N30E 
direction affects the UKM unit. It seems to be 
linked to the N67E compression of the second 
tectonic phase. 
The N60E trending major fractures which affect 
south and central Palawan may be interpreted as 
tension fractures of this second tectonic event. 
South of Cleopatra Needle, strong deviations of 
the drainage pattern suggest a major fracture zone 
trending N100E. This element, unshown on previous 
maps, could be related to the second tectonic event 
(as sinistral shear zone) reactivated during the 
third one (as a dextral shear zone). Many 
hypotheses require further field observations. 
The folding processes can be evidenced only in the 
"UKS unit". Here, herring bones and bed-tracks 
reveal an axial intense and penetrative folding 
which could be related to the first folding event. 
The Curvature of the main ridges and their asymmetry 
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C0NCLUSIC 
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Floyd, 
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Fontaine, 
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News Let1 
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la marge 
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of the P 
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