Cover.—The Sechura Desert of northwestern Peru is typical of the hyperarid conditions that exist along 

the west coast of South America where the cold Humboldt (Peruvian) Current generates very little precipitation, especially along the northern coast of Chile and the entire coast of Peru. The tan landscape is 

almost devoid of any vegetation, except for limited areas where sufficient moisture exists to sustain some 

growth. The faint wind streaks show the prevailing southwest-to-northeast wind throughout the desert. 

A low mountain (1,580 ft high) is barely visible on the peninsula that juts into the cold Pacific Ocean. The 

darker area in the desert southeast of Sechura Bay appears to be an oasis area where a hardy variety of 

cotton is possibly grown with the use of irrigation. This photograph demonstrates the importance of elevation by the increase in vegetative cover (darker area along the eastern side of the photograph) as the land 

rises into the Andes Mountains. The west-flowing Cascajal River exits the Andes Mountains, begins to 

cross the Sechura Desert, and apparently disappears beneath the sandy soil of the desert before reaching 

the cultivated field near the coast. The south-flowing Piura River, partially obscured by clouds, can also 

be seen as it traverses the desert. Both of these rivers flow only when there is sufficient precipitation, or 

icemelt/smowmelt from the Andes Mountains.

[Image modified from NASA photograph STS056-075-015, April 1993, available at URL 

<http://earth.jsc.nasa.gov/sseop/efs/geon.htm/>]
The Talara Basin Province of Northwestern Peru:

Cretaceous-Tertiary Total Petroleum System

By Debra Higley

U.S. Geological Survey Bulletin 2206-A

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Posted online August 2004, version 1.0

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: <http://www.usgs.gov/>

This publication is only available online at:

http://pubs.usgs.gov/bul/b2206-a/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not

imply endorsement by the U.S. Government

Although this report is in the public domain, permission must be secured from the individual copyright owners

to reporduce any copyrighted materials contained within this report
iii

Foreword

This report was prepared as part of the World Energy Project of the U.S. Geological Survey. For 

this project, the world was divided into 8 regions and 937 geologic provinces (Klett and others, 

1997). Of these, portions of 128 geologic provinces were assessed for undiscovered petroleum 

resources. The petroleum geology of these provinces is described in a series of reports like the 

one presented here. The primary documentation for these assessments is located in U.S. Geological Survey World Energy Assessment Team (2000). The petroleum geology of these priority 

and boutique provinces is described in the contained series of reports. Province names, codes, 

and boundaries, oil and gas fields, and a geologic map of South America are shown in Schenk 

and others (1999).

The purpose of the World Energy Project is to assess the quantities of oil, gas, and natural gas 

liquids that have the potential to be added to reserves within the next 30 years. These volumes 

either reside in undiscovered fields whose sizes exceed the stated minimum-field-size cutoff 

value for the assessment unit (variable, but must be at least 1 million barrels of oil equivalent 

(MMBOE)) or occur as reserve growth of fields already discovered. One MMBO is equivalent 

to 6 billion cubic feet of gas (BCFG). Field growth (increase through time of estimated recoverable resources) may result from discovery of new productive facies or formations within the 

field, production of a greater percentage of original-oil-in-place through improved secondary or 

tertiary recovery methods, and perhaps a recalculation of reserves that were originally underestimated. Hypothetical assessment units are described to explore the potentials of possible 

new or underevaluated petroleum plays and formations. Analogs from other areas of the world 

are used to determine environments of deposition of source and reservoir rocks, to describe the 

burial history of the area, and to assess possible reservoir properties of formations within the 

hypothetical assessment unit.

The total petroleum system (TPS) constitutes the basic geologic unit of the oil and gas assessment and includes all genetically related petroleum that occurs in shows and accumulations 

(discovered and undiscovered) that (1) has been generated by a pod or by closely related pods 

of mature source rock, and (2) exists within a limited mappable geologic space, along with the 

other essential mappable geologic/geochemical elements (source, reservoir, seal, and overburden rocks) that control the fundamental processes of generation, expulsion, migration, entrapment, and preservation of petroleum (modified from Magoon and Dow, 1994). The minimum 

petroleum system is that part of a total petroleum system that encompasses discovered shows 

and accumulations, along with the geologic space in which the various essential elements have 

been proved by these discoveries.

Graphical depiction of the elements of a total petroleum system and contained assessment units 

is provided in the form of events charts that show the times of (1) deposition of essential rock 

units; (2) trap formation; (3) generation, migration, and accumulation of hydrocarbons; and (4) 

preservation of hydrocarbons. 
iv 

A numeric code identifies each region, province, total petroleum system, and assessment unit; 

these codes are uniform throughout the project and will identify the same type of entity in any 

of the publications. The codes for the regions and provinces are listed in U.S. Geological Survey 

World Assessment Team (2000). The code is as follows: 

Oil and gas reserves quoted in this report are derived from Petroconsultants’ Petroleum Exploration and Production database (Petroconsultants, 1996) and other area reports from Petroconsultants, Inc., unless otherwise noted. Figure(s) in this report that show boundaries of the total 

petroleum system(s), assessment units, and pods of active source rocks were compiled using 

geographic information system (GIS) and graphics software. Political boundaries and cartographic representations were derived, with permission, from Environmental Systems Research 

Institute’s ArcWorld 1:3-million digital coverage (1992), have no political significance, and are 

displayed for general reference only. Center points of oil and gas fields, shown on these figures, 

are reproduced, with permission, from Petroconsultants (1996). The primary source of geochemical data for this report is the GeoMark (1998) database.

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v

Contents

Foreword ....................................................................................................................................................... iii

Abstract.......................................................................................................................................................... 1

Introduction ................................................................................................................................................... 1

Acknowledgments........................................................................................................................................ 2

Province Geology.......................................................................................................................................... 2

Structural and Depositional History ................................................................................................. 2

Exploration History .............................................................................................................................. 8

Petroleum Occurrence .............................................................................................................................. 12

Hydrocarbon Source Rocks............................................................................................................. 12

Maturation and Migration ................................................................................................................ 14

Reservoir Rocks ................................................................................................................................. 15

Traps and Seals.................................................................................................................................. 18

Conclusions ................................................................................................................................................. 18

Selected References.................................................................................................................................. 19

Figures

1. The Talara Basin province (6081) and adjoining provinces, northwestern Peru............... 2

2. North-south stratigraphic cross section across the Talara and 

southern Progreso Basins .......................................................................................................... 3

3. Simplified geologic map of the Talara and Progreso Basin provinces 

and surrounding area................................................................................................................... 4

4. Stratigraphic column of the Talara and southern Progreso Basin provinces.................... 5

5. Total petroleum system events chart for the Cretaceous-Paleogene 

Assessment Unit 60810101, Talara Basin province................................................................. 6

6. Diagrammatic north-south regional cross section across the 

northwestern Talara Basin province......................................................................................... 7

7. Mean estimate of size distributions of undiscovered oil and gas fields 

in the Talara Basin province ..................................................................................................... 10

8. Discovery thirds of known and grown oil field size versus the number 

of oil fields in the Talara Basin province................................................................................. 10

9. Discovery thirds of known recoverable oil and gas versus the number 

of fields for the Talara Basin province .................................................................................... 11

10. History of field discoveries and volumes of known oil-field size 

across the Talara Basin province ............................................................................................ 11

11. Cumulative number of new-field wildcat wells and 

associated completion dates ................................................................................................... 11

12. Field discovery date versus depths of all reservoir intervals ............................................. 11

13. API gravity of oil fields in the Talara (6081) and Progreso (6083) provinces..................... 12
vi

14. API gravity and weight percent sulfur of oils from selected fields 

across the Talara and Progreso Basin provinces, Ecuador and Peru............................... 13

15. The ratio of nickel and vanadium in oils from the Talara and 

Progreso Basin provinces......................................................................................................... 13

16. Distribution of δ13C isotopes for saturated and aromatic hydrocarbons, 

Talara and Progreso Basin provinces..................................................................................... 14

17. Depositional models for the Eocene Mogollon and Clavel (Pariñas) 

Formations, northern Talara Basin province.......................................................................... 16

18. Fluvio-deltaic depositional model of the basal Salina Formation, 

northern Talara Basin province................................................................................................ 17

Tables

1. Background statistics for oil and gas fields in the Talara Basin province, 6081................ 8

2. Assessment results summary for the Cretaceous-Tertiary 

Total Petroleum System (608101), Cretaceous-Paleogene Basin 

Assessment Unit (60810101)........................................................................................................ 9
Abstract

More than 1.68 billion barrels of oil (BBO) and 340 billion cubic feet of gas (BCFG) have been produced from the 

Cretaceous-Tertiary Total Petroleum System in the Talara 

Basin province, northwestern Peru. Oil and minor gas fields 

are concentrated in the onshore northern third of the province. Current production is primarily oil, but there is excellent potential for offshore gas resources, which is a mostly 

untapped resource because of the limited local market for gas 

and because there are few pipelines. Estimated mean recoverable resources from undiscovered fields in the basin are 1.71 

billion barrels of oil (BBO), 4.79 trillion cubic feet of gas 

(TCFG), and 255 million barrels of natural gas liquids (NGL). 

Of this total resource, 15 percent has been allocated to onshore 

and 85 percent to offshore; volumes are 0.26 BBO and 0.72 

TCFG onshore, and 1.45 BBO and 4.08 TCFG offshore. The 

mean estimate of numbers of undiscovered oil and gas fields is 

83 and 27, respectively. Minimum size of fields that were used 

in this analysis is 1 million barrels of oil equivalent and (or) 6 

BCFG. 

The Paleocene Talara forearc basin is superimposed on a 

larger, Mesozoic and pre-Mesozoic basin. Producing formations, ranging in age from Pennsylvanian to Oligocene, are 

mainly Upper Cretaceous through Oligocene sandstones of 

fluvial, deltaic, and nearshore to deep-marine depositional origins. The primary reservoirs and greatest potential for future 

development are Eocene sandstones that include turbidites 

of the Talara and Salinas Groups. Additional production and 

undiscovered resources exist within Upper Cretaceous, Paleocene, and Oligocene formations. Pennsylvanian Amotape 

quartzites may be productive where fractured. Trap types in 

this block-faulted basin are mainly structural or a combination 

of structure and stratigraphy. Primary reservoir seals are interbedded and overlying marine shales. 

Most fields produce from multiple reservoirs, and production is reported commingled. For this reason, and also because 

geochemical data on oils and source rocks is very limited, 

Tertiary and Cretaceous production is grouped into one total 

petroleum system. The most likely source rocks are Tertiary 

marine shales, but some of the Cretaceous marine shales are 

also probable source rocks, and these would represent separate 

total petroleum systems. Geochemical data on one oil sample 

from Pennsylvanian rock indicates that it was probably also 

sourced from Tertiary shales. 

Introduction

The Talara Basin province is located on the continental shelf along the northern coast of Peru (fig. 1). Its eastern 

limit is delineated by the La Brea–Amotape Mountains of 

the Coastal Range, and the associated uplift that separates 

the basin from the Lancones and Sechura Basins (fig. 1). The 

southeast boundary is east of the La Casita fault and the Paita 

High uplift, between the Talara and Secura Basins; the south 

boundary is the Trujillo Basin. The west boundary of the province is the approximate location of the Nazca Plate subduction 

zone under the South American Plate.

The Pillar of Zorritos is a basement uplift and associated fault zone that is the northern limit of the Talara Basin 

province (figs. 1 and 2). This boundary coincides with the 

southern edge of the Dolores-Guayaquil megashear zone (fig. 

3) and has a complex structural setting that includes transcurrent (wrench) faulting as well as high- and low-angle faults of 

various ages (American International Petroleum Corporation 

(AIPC), no date; Marocco and others, 1995; Pindell and Tabbutt, 1995; Zúñiga-Rivero and others, 1998b, 1999). Location of this megashear and the basin boundary exhibits some 

variation, depending upon who has mapped the fault system. 

Zúñiga-Rivero and others (1999) indicated that the Talara 

Basin province extends northward to their location of the 

Dolores-Guayaquil megashear, which is approximately 50 km 

(30 mi) north of the southern limits shown in figures 1 and 3. 

Talara Basin is one of 10 basins spread over approximately 67 million acres along the west coast of South America 

(Zúñiga-Rivero and others, 1998a). Schenk and others (1999) 

show 13 offshore basins that border and lie west of the coast. 

Maximum width of the Peru continental shelf is about 130 

km (80 mi) (Zúñiga-Rivero and Hay-Roe, 1998). Grossling 

(1976) listed the potential oil and gas prospective areas of 

Peru as including 1,000,000 km2 (400,000 mi2) onshore and 

24,000 km2 (9,300 mi2) offshore. The area of the Talara Basin 

province and the included Cretaceous-Tertiary Total Petroleum 

System (TPS) (608101) and Cretaceous-Paleogene Basin 

The Talara Basin Province of Northwestern Peru: 

Cretaceous-Tertiary Total Petroleum System

By Debra Higley
(60810101) Assessment Unit (AU) is 28,000 km2 (11,000 

mi2); the minimum extent of TPS 608101 is 23,000 km2

(8,900 mi2), which is landward of the dashed line in figure 1. 

About 85 percent of the basin is offshore, and major portions 

are under license for petroleum leases. 

Acknowledgments

Dan Spancers, a petroleum geologist from Denver, provided essential information on oil and gas exploration and 

development in Peru and Ecuador. This document benefited 

from reviews by Christopher J. Schenk, William R. Keefer, 

and Ronald R. Charpentier of the U.S. Geological Survey.

Province Geology

Structural and Depositional History

In many if not all of Peru’s coastal basins, tectonic movements during the Paleozoic established a geologic framework 

that greatly influenced later structural and depositional patterns (Zúñiga-Rivero and others, 1998b). The position, shape, 

and size of 10 offshore Tertiary basins in Peru, including the 

Talara Basin, are substantially controlled by Late Cretaceous–

early Tertiary tectonic activities that involved Paleozoic and 

Mesozoic strata; these strongly affected the region by divid-

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Figure 1 (facing column and above). The Talara Basin province (6081) and adjoining provinces, northwestern Peru. Shown 

are the common boundaries of the basin, the CretaceousTertiary (608101) Total Petroleum System, and the CretaceousPaleogene Basin (60810101) assessment unit. Minimum extent 

of 60810101 is approximated by 1,000-m (3,000-ft) water depth. 

Map projection is Robinson. Central meridian is 0°. 

2 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
ing larger basins into a series of more restricted areas of 

late Tertiary sedimentation (Zúñiga-Rivero and others, 

1998a). 

The Talara Basin province resulted from Paleogene 

tectonic activity. The basin overlies a larger basin that 

records the imprint of Cretaceous tectonic events. This 

older basin also underlies parts of the Neogene structures 

of the adjacent Progreso and Secura-Salaverry Basin 

provinces (figs. 1, 3). These provinces are separated from 

the Talara Basin province by faulted intrusive igneous 

rocks. Talara and these adjoining coastal basins have 

been characterized as forearc basins; they lie seaward 

of the Coastal Range and were identified by Lonsdale 

(1978) as representing a “trench-slope break” or an 

“outer-arc ridge” environmental setting. Kingston (1994) 

believed the basin configurations may be better named 

trench-slope basins. Zúñiga-Rivera and others (1998a), 

however, indicated that the basins, instead of being 

forearc as there was no associated volcanic arc, were 

linear downwarps that filled with clastic sediments from 

the continent combined with shallow- and deep-water 

marine limestones.

Shown in figure 4 are sedimentary strata, major 

periods of erosion and nondeposition, and oil and gas 

source and reservoir rocks in the Talara Basin province 

and the adjoining Progreso Basin province. A northsouth cross section of the offshore Talara and southernmost Progreso Basin provinces (fig. 2) was constructed 

by integrating seismic sections and well data (Raez 

Lurquin, 1999). Shown are structural and stratigraphic 

relations among the Cretaceous and Tertiary sedimentary 

rocks that overlie basement quartzites of the Pennsylvanian Amotape Formation. Lower Tertiary and Cretaceous 

strata are relatively continuous across the cross section. 

It is only the youngest Tertiary rocks (Miocene and Pliocene) that reflect the separation into different sedimentary basins along the coast and offshore (Zúñiga-Rivero 

and others, 1998a). This separation is also visible in the 

Talara Basin province as the Miocene and Pliocene Zorritos, Cardalito, Tumbes, and Mal Pelo Formations occur 

near the northern and southern limits of the basin (fig. 

2). Based on seismic data, thick sequences of Paleozoic 

and Mesozoic strata underlie most of the Peruvian continental shelf and slope, whereas Tertiary sediments show 

more variations in thickness, structural characteristics, 

and areal extent (Zúñiga-Rivera and others, 1998a). 

The northern boundary of the Talara Basin province 

coincides with a part of the right-lateral Dolores-Guayaquil megashear, and the left-lateral Amazonas megashear 

is near the southern boundary, across the north side of the 

Bayovar (Paita) High. General locations of these shear 

zones, shown in figures 1 and 2, are superimposed on the 

generalized geologic map of the region (fig. 3). Surface 

exposures in the Manabi, Progreso, Talara, and Sechura 

Basin provinces are primarily Tertiary and Quaternary 

nonmarine sediments. Modern seismic and sequence-

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Figure 2. North-south stratigraphic cross section across the Talara and southern Progreso Basins (modified from Raez Lurquin, 1999). Approximate location of line of section is shown on figure 1 and as the blue line on the inset map to the left. Not all formations shown are labeled. Section is not to scale. 

Province Geology 3
stratigraphic analysis of the Sechura Basin indicate there is a 

relation between tectonic history and submarine fan deposition; these fans originated at a tectonic zone that separates the 

Talara and Sechura basins and is characterized by thrust and 

secondary normal faults (Zúñiga-Rivero and others, 2001).

Isaacson and Diaz Martinez (1995) evaluated the Devonian 

through Permian history of western Bolivia to southern Ecuador 

and distinguished the following four phases as being characteristic of Paleozoic sedimentation across western South America. 

1. Shallow-marine clastic deposition through the Devonian (Lochkovian-Frasnian), with an increase in 

sedimentation during the Early to Middle Devonian 

(Emsian-Eifelian). Lithofacies distribution and sediment thicknesses indicate primarily a western source. 

2. Uppermost Devonian–lower Carboniferous (Famennian-Visean) strata are characterized by glaciomarine 

and fan-deltaic sedimentation. Clasts were derived 

from underlying sedimentary units and andesitic, granitic, and tuffaceous rocks. 

3. A middle-Carboniferous (Serpukhovian-Bashkirian) 

hiatus in sedimentation occurred; its age and duration 

varied across the region. 

4. Siliciclastic and carbonate deposition occurred in late 

Carboniferous–early Permian time (Moscovian?-Artinskian). Intra-arc basins may have existed near presentday coastal Peru. Following the middle-Carboniferous 

hiatus, sedimentation continued in a back-arc region. 

Epeirogeny or magmatic-related tectonics may have 

influenced regional sea-level fluctuations and unconformities between Devonian and Carboniferous strata 

in Peru; during the Devonian, these events would have 

restricted formerly open seaways along eastern Peru, 

western Bolivia, and northern Argentina and Chile 

(Isaacson and Diaz Martinez, 1995). 

The overall shape of the depositional area during Paleozoic and Mesozoic time has not been delineated in detail, but 

the Peruvian coastal region was probably part of an extensive 

basin that covered the whole region and extended farther to 

the east and west; seismic profiles show that the sedimentary 

strata extended westward, all the way to the axis of the PeruChile Trench (Nazca subduction zone on figures 1, 3) (ZúñigaRivero and others, 1998a). 

Late Cretaceous time in northern Peru was marked by 

low volumes of terrigenous sedimentation due to limited 

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Figure 3. Simplified geologic map of the Talara and Progreso Basin provinces and surrounding area. Shown are the generalized locations of the Dolores-Guayaquil megashear zone and the 

Guyana and Amazonas megashears. Oil and gas field centerpoints and the geologic map are modified from Schenk and others (1999) 1:5,000,000-scale map of South America. Source of field centerpoints is Petroconsultants database (1996).

4 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
Andean relief, combined with upwelling and other oceanographic factors (Ziegler and others, 1981). Oceanic crust 

formed during the Early Cretaceous (Aptian-Albian) (Jaillard and others, 1995); Cretaceous mid-oceanic ridge basalt 

(MORB) unconformably overlies the Pennsylvanian basement 

rocks. Between Late Cretaceous and late Eocene time, the oceanic-floored allochthonous terranes of southern coastal Ecuador underwent a complex geologic evolution that included 

island-arc-related and marginal-basin sedimentation, plate and 

intra-plate collisions associated with shear deformation, basin 

subsidence, and several phases of uplift (Jaillard and others, 

1995). 

Thickness of the combined Cretaceous through Tertiary 

stratigraphic sequences across the coastal basins varies from 

about 8,500 to 18,000 m (28,000 to 58,000 ft) (Zúñiga-Rivero 

and Hay-Roe, 1998). Paleogene (66.4 to 23.7 Ma) sediments 

in the Talara Basin province cover more than 23,000 km2

(9,000 mi2) on top of the regional Paleozoic-Mesozoic basin 

(Zúñiga-Rivero and others, 1998b). 

Based on examination of seismic, well, aeromagnetic, 

and gravity data, the creation of the Talara Basin province 

in Paleocene and Eocene time resulted from both subduction of the Nazca Plate under the South American Plate and 

depositional events that were related to transtensional (pullapart) and extensional tectonics (Raez Lurquin, 1999). Origin 

of the eastward-spreading Nazca Plate was the East Pacific 

Rise. It uncoupled in Tertiary time from the continental South 

American Plate and began to form the subduction zone that 

is evidenced by the Peru-Chile Trench, also known as the 

Nazca subduction zone, which is located near the west margin 

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Figure 4. Stratigraphic column of the Talara and southern Progreso Basin provinces. Wavy lines 

and gray zones bracket periods of erosion or nondeposition. Primary reservoir formation names 

are marked with green dots. Possible source-rock intervals are labeled with a small gray box. 

Modified from AIPC (no date), Gonzales Torres (1999), Kingston (1994), Kraemer and others (1999), 

Perupetro (1999), Petroconsultants (1996), and Seranne (1987).

Province Geology 5
of the Talara Basin province. This is a convergent continental margin. Tertiary subduction of the Nazca Plate under the 

South American Plate caused uplift and erosion of the Andes 

Mountains and created an active Peruvian continental borderland with a complex mix of structural and stratigraphic styles. 

Successive systems of clastic sedimentation during Paleocene 

and Eocene time resulted from large-scale synsedimentary 

extensional tectonics represented by high-angle faults that 

delineate horst-and-graben structures; relative movement of 

the faults was directly related to the configuration and movement of basement rocks (Raez Lurquin, 1999). The PaleoceneEocene boundary is marked by an unconformity that underlies 

a thick succession of continental-derived sandstones and conglomerates of the lower Eocene Chacra-Salinas Group (fig. 4) 

(Seranne, 1987). 

The late Paleocene, earliest Eocene, and early-late 

Eocene tectonic events are the most important deformational 

phases that influenced the geologic framework of southern 

coastal Ecuador; they represent progressive accretion to the 

continental margin (Jaillard and others, 1995). Jaillard and 

others (1995) believed that creation of repeated forearc basins 

can be attributed to subsidence from crustal erosion of the 

upper plate; each subsidence event succeeded an important 

compressive phase that must have favored coupling and tectonic erosion. 

New forearc basins that were created in northern Peru 

and southern Ecuador in early-middle Eocene time filled with 

clastic shelf deposits of the Chachra-Salinas Group, which 

is unconformably overlain by coastal to continental coarsegrained sandstones of the middle to early-late Eocene (Jaillard 

and others, 1995) Talara Group (figs. 2, 4). These relations 

record a major Andean orogenic phase that reflects the results 

of collision of coastal Ecuador with the Andean margin (Jaillard and others, 1995). 

During late Eocene through early Oligocene time (about 

38.5 to 33 Ma), there was about a twofold increase in westward 

acceleration of the South America Plate across the mantle, 

triggering the Incaic phase of Andean tectonism that was manifested by thrusting of the eastern and western Andean flanks 

along most of the length of the Andes (Cande and Kent, 1992). 

Onset of the Incaic orogeny is marked by the regionally continuous erosional unconformity at the top of the Talara Group 

in the Talara Basin province, and the base of the Oligocene 

Mancora Formation in the southern Progreso Basin province 

(figs. 2, 4, 5). Uplift of the Andes and Coastal Range mountains 

is associated with both erosion and deposition of considerable volumes of offlapping detritus in both the back-arc and 

forearc regions (Cande and Kent, 1992); this uplift contributed 

to a thick sequence of Oligocene and Eocene sediments in the 

Talara Basin province. The Talara Basin province stratigraphic 

sequence (fig. 4) is primarily Eocene, has an aggregate thickness of as much as 8,500 m (28,000 ft), and overlies more than 

1,500 m (5,000 ft) of Paleocene and as much as 2,045 m (6,700 

ft) of Cretaceous strata (Zúñiga-Rivero and others, 1998b). 

Sebrier and others (1988) believed that evolution of late 

Paleogene-Neogene basins, such as Talara, began during Oli-

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Figure 5. Total petroleum system events chart for the Cretaceous-Paleogene Assessment Unit 60810101, Talara Basin province. Gray and 

turquoise rectangles mark the time sequences of primary events. “P” in the geologic time scale is Pliocene time. MORB is Cretaceous (K) midoceanic ridge basalt on Pennsylvanian (Penn) basement rocks. Compression tectonism of the Andes Mountains during Eocene time (42 million 

years ago) was followed in Oligocene time by partitioning of the Farallon continental plate into the Cocos and Nazca Plates (Handschumacher, 

1976; Marocco and others, 1995; Pilger, 1984). There is no published information available on hydrocarbon source rocks or timing of petroleum 

generation and migration; these interpretations are speculative. Ages of unconformities (wavy black lines) were determined from Sebrier and 

others (1988), Seranne (1987) and the sources (a) through (d) listed below. Letters (a) through (g) refer to the following sources: (a) AIPC (no 

author or date), (b) Jaillard and others (1995), (c) Perupetro (1999), (d) Petroconsultants (through 1996), (e) Zúñiga-Rivero and Hay-Roe (1998), 

and Zúñiga-Rivero and others (1998a), (f) Kingston (1994), (g) Shepherd and Moberly (1981).

6 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
gocene time, about 28–26 Ma, after a long period of relative 

quiescence following the 42-Ma late Eocene compressive 

episode. The entire area then emerged until the formation, 

during latest Oligocene-Miocene (fig. 5), of new forearc basins 

that were subsequently filled by fine-grained shallow-marine 

sandstones and shales (Jaillard and others, 1995). Late Oligocene is characterized by initiation of intermontane basins 

with reactivation of Andean tectonism that ended in latest 

Miocene (about 7 Ma); structural analysis of these Neogene 

and Paleogene basins shows that their evolution was controlled 

by regional tectonic stress (Jaillard and others, 1995; Marocco 

and others, 1995). Synsedimentary folding and fracturing 

show that there was a clockwise rotation of the direction of 

stress in the Neogene; this explains variations in the behavior 

of the faults that border the basins and the different stages 

of their evolution (Jaillard and others, 1995; Marocco and 

others, 1995). A trough at the northern border of the Talara 

Basin province may have been created in Neogene time by 

opening of the Gulf of Guayaquil along the Guayaquil-Dolores megashear (Shepherd and Moberly, 1981) at the southern 

boundary of the Progreso Basin province (figs. 1, 3). 

Upper Eocene Lagunitos Group strata unconformably 

overlie the Talara Group and are overlain by the Oligocene 

Mancora and Heath Formations (fig. 4). The Neogene sedimentologic history of the bounding Progreso Basin province 

began with an Oligocene transgressive cycle and associated 

deposition of the Mancora and Heath Formations (AIPC, no 

date). These formations were also present in the Talara Basin 

province, except where removed by erosion (figs. 2, 4). Deposition was followed by peneplanation of the Heath Formation 

and subsequent deposition of the Miocene Zorritos Formation 

in the northern part of the province; this was associated with a 

period of block faulting (AIPC, no date).

Normal faulting is an important aspect of the structural style of the Talara Basin province, as are low-angle 

gravitational slide faults and large vertical transcurrent faults 

(Zúñiga-Rivero and others, 1998b). Complex structural features of the offshore Talara and southern Progresso Basin 

provinces include extensive growth faulting with associated 

rollover-type folding (AIPC, no date). Bianchi (2002) mapped 

faults in the offshore area of the Litoral field (fig 1), where the 

major faults are oriented approximately north-south. Seismic 

and subsurface data indicate that the faulting is most intense 

in the eastern (onshore) portions of the northern basins and 

decreases in a seaward direction (Zúñiga-Rivero and others, 

1998a). Figure 6 shows some of the complex faulting in a 

regional north-south cross section in the northwestern Talara 

Basin province. Location of the cross section is in the area of 

the La Brea–Pariñas to Tunal oil fields in figure 1. Fault movement during times of deposition and erosion resulted in variable thicknesses of formations across the region. The primary 

target for reservoirs is the upper Eocene Verdun Formation 

(Montagna and others, 1999), which is represented by the 

close-set lines above the Talara Group in figure 6.

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Figure 6. Diagrammatic (not to scale) north-south regional cross section across the northwestern Talara Basin province (modified from Montagna and others, 1999, reprinted by permission of author, 6/24/02). Shown are vertical and lateral offsets of formations that resulted from fault 

(falla) movement; arrows show relative movement. The Pleistocene Tablazo Formation unconformably overlies Oligocene and older formations. 

Unlabeled vertical lines are wells. 

Province Geology 7
Exploration History

For many centuries, Peruvians used oil seeps, such as 

those near the La Brea–Pariñas oil field (fig. 1), largely to 

seal joints in wooden boats and also for fuel to light their 

homes. The Spaniards used pitch to caulk their ships and to 

waterproof ropes. Discovery of the first field in the province, 

La Brea–Pariñas, was in 1869; production is reported commingled from Eocene formations and the Cretaceous Ancha 

and the Pennsylvanian Amotape Formations (Petroconsultants, 

1996). Production within the basin has been mostly from 

Eocene sandstones (38 fields). One field, the Piedra Redonda 

(fig. 1), produces from sandstone of the Oligocene Mancora Formation, and two fields include production from the 

Paleocene Balcones and Mesa Formations (Petroconsultants, 

1996). Four fields record production from Cretaceous and 

Pennsylvanian formations (Petroconsultants, 1996). The Litoral field (discovered in 1960) (fig. 1) has about 44 MMBO of 

commingled production from the Eocene Salina, Clavel (also 

known as Pariñas), Terebratula, and Basal Salina Formations 

(Bianchi, 2002). Background statistics for oil and gas fields in 

the province are listed in table 1.

Talara Basin province cumulative production exceeds 

1.68 BBO (Perupetro, 1999) and 1.95 trillion cubic feet of gas 

(TCFG) (Petroconsultants, 1996) (table 1); offshore wells have 

produced about 285 MMBO. The Petroconsultants database 

did not contain production information on the La Casita gas 

field (fig. 1). Daily production from offshore wells is about 

15 thousand barrels (Raez Lurquin, 1999). Forty-two oil and 

(or) gas fields are located in the basin; known recoverable oil 

and gas for these fields is 2.90 billion barrels of oil equivalent 

(BBOE) (modified from Petroconsultants, 1996). 

Zúñiga-Rivero and others (1998a, 1998b) listed cumulative production of 1.6 billion barrels of light crude and an 

estimated 3.5 TCF of associated gas, mainly in the central and 

northern parts of the onshore sector; this estimate includes 

wells in the shallow offshore (out to the 370-ft water depth) 

that have cumulative production of about 280 MMB of light 

crude and about 700 BCF of gas. Zúñiga-Rivero and others 

(1998a, 1998b) generalized known recoverable (estimated ultimate potential) reserves and resources are greater than 2 BBO 

or 25 TCFG for the offshore Talara Basin province. 

Gonzales and Alarcon (2002) estimated the volume of 

generated, migrated, trapped, and recoverable hydrocarbons 

for the Talara Basin province. The hydrocarbon source rocks 

used in their analysis were shales and limestones of the Cretaceous Redondo Formation (fig. 4); the characteristics of the 

Redondo Formation in the hydrocarbon-generation area of 

their model included a thickness of 473 m, specific grain density of 2.525 g/cm3, 1.4 percent total organic carbon (TOC), 

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8 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
vitrinite reflectance (Ro) of 1.11 percent, a hydrogen index of 

91, and 1,625 ppm of extracted hydrocarbons. Gonzales and 

Alarcon (2002) published the following estimates:

1. Volume of thermally mature source rock in the hydrocarbon generation area of the Talara Basin province is 

8.27×1017 cm3, 

2. Total volume of generated hydrocarbons is 2.75×105

MMBO and 2.25×104 TCFG. 

3. Total trapped oil and gas of 2.48×105 MMBO and 

2.03×103 TCFG, calculated using a 30 percent expulsion efficiency and 30 percent emplacement efficiency 

in reservoirs.

4. Total volume of recoverable oil and gas is 2.48×104

MMBO and 162.4 TCFG, based on a 10-percent recovery factor.

5. Volumes of lost hydrocarbons are 3.72×103 MMBO 

and 2.4 TCFG, based on 15 percent of the hydrocarbons lost from traps due to migration along faults and 

other processes.

6. Total volume of recoverable hydrocarbons from the 

Talara Basin province, including current production, is 

3.72 BBO and 9.344 TCFG. Production through 2000 

is 1.5 BBO and 3.5 TCFG (Gonzales and Alarcon, 

2002).

7. Volume of remaining recoverable hydrocarbons 

(excluding current production) is 2.22 BBO and 5.844 

TCFG. 

8. Remaining recoverable hydrocarbons are 70 percent 

onshore, or 1.554 BBO and 4.09 TCFG, and 30 percent 

offshore, or 666 MMBO and 1.75 TCFG.

USGS estimated mean recoverable oil, gas, and natural 

gas liquids (NGL) resources from undiscovered fields in the 

basin are 1.71 BBO, 4.79 TCFG, and 255 million barrels of 

NGL (table 2). Minimum size of fields used in this analysis is 

1 MMBO, or 6 BCFG. Figure 7 shows the proposed frequency 

distribution of undiscovered oil and gas fields within the 

province. The mean estimate is 83 undiscovered oil fields and 

27 undiscovered gas fields. Ranges in undiscovered resource 

distributions from table 2 show the USGS estimates for undiscovered oil, gas, and natural gas liquids (NGL) resources for 

the Talara Basin province that have the potential to be added 

to reserves within the next 30 years (USGS World Energy 

Assessment Team, 2000). These estimates for TPS 608101 

used data from Petroconsultants (1996), GeoMark (1998), and 

referenced publications in the analyses of the areal and temporal distribution of drilling and production. Estimated mean 

recoverable oil and gas resources from undiscovered onshore 

(15 percent) and offshore (85 percent) fields are 257 MMBO 

and 719 BCFG, and 1.45 BBO and 4.08 TCFG, respectively. 

Travis and others (1975) estimated the offshore potential 

at 1 BBO, but believed that the onshore portion had low potential for future discoveries. Kingston’s (1994) estimated offshore potential of 1.2 BBO and 1.4 TCFG was based on comparing the areal distribution of possibly productive areas in the 

onshore to that of the offshore. The southernmost parts of the 

onshore and offshore basin areas appear to be gas prone, but 

oil resources could be present in unexplored areas according 

to Zúñiga-Rivero and others (1998b, 1999). Offshore Peru has 

excellent potential for gas-hydrate resources based on work by 

Miller and others (1991); these potential resources were not 

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Table 2. Assessment results summary for the Cretaceous-Tertiary Total Petroleum System (608101), Cretaceous-Paleogene Basin Assessment 

Unit (60810101) (USGS World Energy Assessment Team, 2000).

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids; MFS, minimum field size assessed (in MMBO or 

BCFG); Prob., probability, including both geologic and accessibility probabilities of at least one field equal to or greater than the MFS. Results shown are fully 

risked estimates. All liquids in gas fields are included under the natural gas liquids (NGL) category. F95 represents a 95-percent chance of at least the amount 

tabulated. Other fractiles are defined similarly. Fractiles are additive under the assumption of perfect positive correlation. Shading indicates not applicable]

Province Geology 9
assessed in the present study. 

Twenty oil fields and one gas field have known recoverable resources of 1 MMBOE and greater. Twenty oil and two 

gas fields have grown recoverable resources of greater than 1 

million barrels of oil equivalent (MMBOE) (fig. 8). Figure 8 

shows the field-size distribution, based on periods of discovery 

for known oil resources, versus the number of fields in each 

size range. Grown oil fields versus the number of fields in 

each size range are also displayed. Assigning a growth factor 

to fields (fig. 8) resulted in little or no change in field size for 

those that were discovered early in the history of exploration and are already mature; the second third of discovered 

fields exhibits a slight increase in field size, and the latest 

third exhibits the greatest increase. Discovery-history curves 

in mature basins commonly show that the largest fields are 

discovered early in the history of exploration and field size 

tends to decrease through time. In the Talara Basin province, 

the largest field is La Brea–Pariñas (1869) with grown recoverable oil and gas resources greater than 1 BBO and 1 TCFG. 

Two other large fields that were discovered early in the history of exploration were Los Organos–El Alto and Lobitos, 

which have discovery dates of 1901 and grown recoverable oil 

resources of about 350 MMBO. The irregular distribution of 

discovery thirds reflects the frontier aspect of exploration in 

the basin. There are only nine fields that have cumulative production greater than 1 MMBOE, and 39 with known recoverable reserves plus resources of greater than 1 MMBOE. 

Figure 9 shows the known recoverable reserves and 

resources of oil and gas based on data from Petroconsultants 

(1996); these are divided into the first, second, and third discovery-thirds of all fields regardless of field size. Three of 

the four largest fields were discovered early in the history of 

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Figure 7. Mean estimate of size distributions of undiscovered oil 

(green) and gas (red) fields in the Talara Basin province. Distributions 

are based on grown oil and gas assessments from the USGS World 

Energy Assessment Team (2000).

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Figure 8. Discovery thirds of known and grown oil field size (MMBO) versus the number of oil fields in the Talara Basin province. 

10 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
exploration in the basin, but there is an irregular distribution 

of known recoverable reserves and resources for fields. The 

smallest oil and gas fields were mainly found in the latter 

two-thirds of the exploration history. Figure 10 shows the 

discovery year for each field versus the known recoverable 

oil field size for fields in the Talara Basin province; minimum 

known field size cutoff is 1 MMBO. Some fields, such is La 

Brea–Pariñas, were originally two separate fields that were 

later merged into one; discovery date of the earliest was used. 

Although the three largest fields were discovered early in the 

history of exploration in the basin (1869, 1901, and 1901), the 

next field, Portachuelo (Mirador), was not discovered until 

1931. A noticeable increase in exploration began about 1950, 

expanded further around 1960, but was then followed by a 

decrease in new field discoveries. This trend is mirrored by the 

linear trends in cumulative number of new-field wildcat wells 

versus field discovery year (fig. 11). There are currently more 

than 12,000 onshore wells. Low rates of drilling until about 

1945, and the discoveries of the Malacas (1947) and Chimenea 

(1950) fields, were followed by a steady and stable increase 

in exploration to the early 1980s, with a subsequent slight 

decrease in drilling rate. Figure 12 shows discovery dates 

for fields versus the reservoir depth(s). Because most fields 

produce from multiple reservoirs, the chart shows a range of 

depths for most of them. Maximum and median drill depths 

were 1,500 m (4,900 ft) and 2,570 m (8,430 ft), respectively, 

for the 39 oil plus oil and gas fields (table 1) (Petroconsultants, 

1996). ����������������

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Figure 9. Discovery thirds of known recoverable oil and gas, in 

millions of barrels of oil equivalent (MMBOE), versus the number of 

fields for the Talara Basin province. Known recoverable reserves and 

resources data modified from the Petroconsultants database (1996) 

were divided into the first, second, and third thirds of discovered 

fields. 

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Figure 10. History of field discoveries and volumes of known oilfield size across the Talara Basin province (Petroconsultants, 1996). 

A sharp increase in the volume of known recoverable hydrocarbons 

generally indicates a major field discovery or combined effects of 

numerous field discoveries, as started in about 1949. Minimum field 

size is 1 million barrels of oil (MMBO) recoverable.

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Figure 11. Cumulative number of new-field wildcat wells and associated completion dates (Petroconsultants, 1996). Increased exploration 

frequently follows discovery of large fields, such as after the 1955 discovery date of Pena Negra field. More than 143 million barrels of oil 

(MMBO) have been produced from the field (Chavez and Rodriquez, 

2002).

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Figure 12. Field discovery date versus depths in meters of all reservoir intervals.

Province Geology 11
Petroleum Occurrence

Hydrocarbon Source Rocks

There is little published geochemical information on 

potential hydrocarbon source rocks in the Talara Basin province. Pindell and Tabbutt (1995) indicated that there are five 

main Mesozoic-Cenozoic settings for source-rock deposition 

and preservation in the Andean basins of South America. 

One of these settings may be appropriate for the Talara Basin 

province. This is along the Andean forearc in areas where terrigenous sedimentation at various times was slow due to low 

Andean relief (Ziegler and others, 1981) and where upwelling 

and other oceanographic factors presumably produced conditions that concentrated organic matter in marine shales. A possible example is the Upper Cretaceous (Campanian) Redondo 

Shale (fig. 2). 

Probable Cretaceous hydrocarbon source rocks in the 

Talara Basin province are the Albian Muerto Limestone and 

the marine shales of the Campanian Redondo Formation (fig. 

4) (AIPC, no date; Perupetro, 1999; Zúñiga-Rivero and others, 

1998a, 1998b). Gonzales and Alarcon (2002) proposed that the 

Cretaceous Redondo Formation is the primary hydrocarbon 

source rock in the basin and included the Cretaceous Muerto 

and Oligocene Heath Formations as potential source rocks. 

Perupetro (1999) indicated that potential Tertiary hydrocarbon 

source rocks are shales of the Eocene San Cristobal Formation (lower Eocene of the Salina Group), the Chacra Group 

(lower Eocene Echinocyamus and Clavel (Pariñas) Formations), the lower Talara (middle Eocene), and the Chira-Heath 

(upper Eocene–lower Oligocene) Formations. Kraemer and 

others (2001) believed that the Heath Formation is the primary 

source rock in the southern Progreso Basin province (fig. 4). 

Lower Eocene Palegreda neritic marine shales and the Paleocene Balcones Shale (Mal Paso Group) are also believed to be 

important organic-rich source rocks in the Talara Basin province by AIPC (no date) and Zúñiga-Rivero and others (1998a, 

1998b). Gonzales and Alarcon (2002) however, indicated that 

the Balcones Formation—as well as the Eocene Chira, Salina, 

and San Cristobal Formations and the Paleocene Petacas 

Formation—were not of source-rock quality based on TOC, 

hydrocarbon indices, and other data. Shales of the Cretaceous 

Monte Grande Formation are primarily of terrestrial (type-III 

kerogen) origin and are potential sources of dry gas; there is 

no evidence of dry gas generation in the basin (Gonzales and 

Alarcon, 2002).

AIPC (no date) evaluated the total organic carbon (TOC) 

of 151 samples of Tertiary shales collected from outcrops and 

well cuttings at locations between Zorritos (just north of the 

Talara Basin province) and Talara (near the Portachuelo oil 

field) (fig. 1). Eighty-one Eocene shales ranged from 0.11 percent to 1.92 percent TOC, 15 Mancora Shale samples ranged 

from 0.08 percent to 4.95 percent TOC, 35 Heath shales were 

0.24 percent to 3.86 percent TOC, 13 Zorritos shales varied 

from 0.22 percent to 13.12 percent TOC, and 7 Cardalitos 

shales ranged from 0.15 percent to 1.62 percent TOC. Gonzales and Alarcon (2002) indicated that geochemical analyses of 

13 shale and limestone samples that ranged in age from Early 

Cretaceous (Albian) to Oligocene age showed TOC contents 

ranging from 1.1–1.3 percent. Values above 1 percent TOC are 

potential source rocks, whereas those below this have low to 

marginal potential.

Distribution of API gravity of oils for fields in the Talara 

and Progreso Basin provinces is shown in figure 13. Although 

they have a similar distribution, Talara Basin province oils 

tend to be slightly heavier than those of the Progreso Basin 

province. Weight percent sulfur and API gravity of oils are 

both influenced by migration history, biodegradation, evaporation and mixing of oils, and other geologic and geochemical 

factors. Biodegradation can result in an increase in sulfur as 

the microorganisms preferentially eat light-chain hydrocarbons that have a lower percent of sulfur, which caused some 

of the scatter in figure 13. Many of the Tertiary oils, particularly those with API gravity less than 23, exhibit some biodegradation, commonly with a second phase of hydrocarbon 

migration, based on examination of gas chromatogram/mass 

spectrometer charts. Three biodegraded Tertiary oil samples 

are shown in green in figure 14. The oil sample on the far left 

also has a second phase of migration. Figure 14 shows API 

gravity versus weight percent sulfur for oils from the Progreso 

and Talara Basin provinces. Sulfur content of the 20 oils analyzed in the Talara Basin province ranges from 0.03 to 0.26 

percent, with a median of 0.06 percent (table 1) (GeoMark, 

1998). There is one sample population for the analyzed oils of 

the Talara Basin and Progreso Basin provinces. The one Pennsylvanian Amotape Formation oil is grouped with the Tertiary 

oils in the Talara Basin province. Pennsylvanian Amotape Formation reservoir rocks are mostly quartzite, and any associated 

Paleozoic shales would probably be overmature for hydrocarbon generation. This Pennsylvanian oil from the Portachuelo 

field may have been sourced from Tertiary shales and migrated 

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Figure 13. API gravity of oil fields in the Talara (6081) and Progreso 

(6083) provinces. Light oil is commonly characterized by an API of 

31°–55°, medium-grade oil by 22°–31°, and heavy oil by less than 22°.

12 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
along fault and fractures into the Amotape, or it could be associated with mixing of oils from several source rocks. Field oil 

production is from the Upper Cretaceous Redondo and the 

Eocene Salina Formations and is reported as commingled. 

Zúñiga-Rivero and others (1999) stated that the Amotape 

Formation can be a commercial reservoir in areas where it is 

highly fractured and capped by the Cretaceous Redondo Shale. 

Because the overlying Muerto, Tablones, and Redondo Formations contain probable source rocks, these would be likely 

sources for oil in Amotape reservoirs.

Concentrations of nickel (Ni) and of vanadium (V) in 

hydrocarbons can be influenced by depositional environment 

(marine versus nonmarine), shale versus carbonate source 

rocks, migration history, and by factors that remove lighter 

chain hydrocarbons and result in concentration of Ni and V on 

the longer chain atoms, onto which these elements are preferentially attached. However, the ratio of Ni to V in oils is quite 

stable through time. Because Ni and V atoms exhibit similar 

chemical properties, they, and the hydrocarbon molecules that 

contain them, are generally influenced similarly through their 

burial history. Median values are 5.5 ppm Ni and 4.0 ppm V 

for the 20 oil samples analyzed in the Talara Basin province. 

Ratios of nickel and vanadium for the analyzed oils (figs.15A, 

15B) show one sample population that includes Paleocene and 

Eocene oils for the Talara Basin province and probable Tertiary oils of the Progreso Basin province. Visual examination 

of groups of oil samples could indicate several sets of Talara 

Basin province source rocks, but this is misleading. Each 

“group” of three or more Tertiary samples in the Talara Basin 

province is a mix of Eocene and Paleocene oils, as opposed to 

them being segregated by formation. The Pennsylvanian Amotape Formation oil (figs. 14, 15) is grouped among the Tertiary 

oils, which suggests that it was probably sourced from the 

same marine shales. 

The Talara Basin province oils were from source rocks 

of similar origin, such as shales deposited in a marine setting, based on the distribution of data in figures 15A and 15B. 

Probable exceptions to this are the three oil samples located in 

the upper left corner of figure 15A and upper right corner of 

15B. Although these oils are from an unknown, but probable 

Tertiary, source having similar V concentrations to the other 

Tertiary oils, the Ni content is much greater at 27 to 31 ppm. 

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Figure 14. API gravity and weight percent sulfur of oils from 

selected fields across the Talara and Progreso Basin provinces, 

Ecuador and Peru (GeoMark, 1998). Based on the distribution of data, 

there appears to be one oil population for these provinces. Scatter in 

data can result partly from analytical methods and from biodegradation of oils from Tertiary reservoirs. Three Tertiary oils that indicate 

biodegradation are shown in green.

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Figure 15. The ratio of nickel and vanadium (Ni/V) in parts per million 

(ppm), in oils from the Talara and Progreso Basin provinces. The Ni/V 

ratio tends to be constant through time and can indicate different age 

and lithology of source rocks. Distribution of data for A and B show 

one sample population for oils from the Talara and Progreso Basin 

provinces. Talara Basin province samples are generally less than or 

equal to 10 ppm Ni and 30 ppm V; one sample from a Paleocene reservoir contains about 7 ppm Ni and almost 60 ppm V. The one Pennsylvanian Amotape oil is characteristic of a Tertiary source. Talara 

samples that contain greater than 25 ppm nickel are probably also a 

Tertiary source, based on other geochemical data. Isolation of these 

samples may represent a more terrigenous source for these than for 

the other samples.

Petroleum Occurrence 13
This may be due to a difference in depositional environment. 

These oils could have been sourced from nonmarine or mixed 

marine-nonmarine shale that contained a greater initial ratio of 

nickel to vanadium. Mixing of oils from several source rocks 

may also have influenced the Ni and V contents of these oils, 

as well as other oils. Gas chromatograms of the same three oils 

exhibit an early stage of biodegradation followed by a second 

pulse of migration of hydrocarbons into the reservoir. These 

secondary hydrocarbons show minor to extensive biodegradation, as indicated by concentration of heavier chain hydrocarbons relative to lighter ones. Conversely, the sample located 

near 60 ppm V in figure 15A is highly biodegraded oil from 

the Salina Group in Tunal field (fig. 1). Gas chromatograms 

in the Talara and Progreso samples exhibit some loss of lightchain hydrocarbons, whether due to leakage upward along 

fault systems or from biodegradation and concentration of 

heaver relative to lighter hydrocarbons. Many also show two 

pulses of hydrocarbon migration with relatively non-degraded 

secondary oils. This is indicated in figure 13 by the median 

API gravity of 32° for Talara Basin province oils; most oils 

listed in the GeoMark database are light to medium gravity. 

The 13C distribution of saturated and aromatic hydrocarbons from oils across the Talara and Progreso Basin provinces 

is shown in figure 16. Oils were identified using data from 

the GeoMark (1998) and Petroconsultants (1996) databases. 

Shown is one sample population for all analyzed oils in the 

Talara and Progreso Basin provinces. The two Progreso Basin 

oils in figures 15A and 15B are unidentified but are probably 

Eocene in age. The 20 Talara oil samples are primarily from 

the Eocene Talara, Clavel (Pariñas), and Chacra Sandstones, 

and the Mogollon and Basal Sandstones of the Salina Group. 

One oil sample is listed in the GeoMark database as being 

from the Pennsylvanian Amotape Formation in the Portachuelo field (fig. 1). Grouping of this one sample (fig. 16) with 

the other mostly Eocene samples indicates that it is derived 

from Tertiary source rocks. 

Maturation and Migration

Paleozoic through Tertiary source rocks across Colombia, 

Ecuador, and Peru became thermally mature for oil generation during the Neogene phases of basin development (Pindell 

and Tabbutt, 1995). Maturation of source rocks within the 

entire stratigraphic column probably began during Miocene 

time, when the sediments across the Talara Basin province 

approached their maximum thickness. Kingston (1994), however, believed that the section was thick enough by the end of 

Eocene time for source rocks to have generated hydrocarbons. 

The thickness of sedimentary rocks in the Talara Basin province exceeds 8,000 m (26,000 ft) for mid-Cretaceous carbonates and sandstones, combined with conglomerates through 

clays of Paleocene and Eocene age (Raez Lurquin, 1999). 

Hydrocarbon generation during Eocene time was possible 

for Cretaceous source rocks, but Eocene source rocks may 

not have been buried deep enough for this to have occurred. 

Gonzales and Alarcon (2002) placed the onset of hydrocarbon 

generation and migration as late Eocene, based on their model 

of hydrocarbon generation, migration, and accumulation for 

shales and limestones of the Cretaceous Redondo Formation. 

Onset of migration and emplacement was probably in 

Miocene time, soon after the start of Late Eocene or Miocene 

hydrocarbon generation, because of the proximity of probable 

source to reservoir rocks. Faulting and fracturing across the 

Talara Basin province would have enhanced vertical migration 

of hydrocarbons. Gas chromatograms of Paleocene oils from 

several fields that are scattered across the basin give evidence 

of two or more stages of migration; minor to extensive biodegradation is overprinted by later migrated oil that is nonbiodegraded or exhibits minor biodegradation of light-chain 

hydrocarbons. Gas chromatographic–mass spectrographic data 

plus the presence of active seeps indicate that active migration 

is still occurring in the basin. Median API gravity is 31.8° for 

36 oils across the basin (table 1).

Zúñiga-Rivero and others (1998b) concluded that (1) 

much or all of the hydrocarbon migration occurred following 

a mild compressive phase because the areal distribution of oil 

and gas is indicative of original entrapment in anticlinal or 

domal closures; and (2) subsequent normal faulting modified 

the structure and also redistributed the hydrocarbons to some 

extent, possibly assisting in the second pulse of migration. 

Sanz (1988) believed that lateral migration of hydrocarbons 

was limited in onshore Talara Basin province fields; the oil 

was generated in shales immediately adjacent to and overlying the reservoir. Sanz (1988) did not present any geochemical 

evidence, however, to support this opinion, which was based 

on analyses of well and outcrop samples. The northern portion 

of the Talara Basin province is extensively faulted, providing 

potential conduits for vertical migration of hydrocarbons. It 

is likely, however, that there was a mix of vertical and lateral 

migration of hydrocarbons.

Gonzales and Alarcon (2002) indicated, based on magnetic, gravimetric, seismic, and geochemical data, that (1) 

hydrocarbon migration was primarily from Cretaceous source 

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Figure 16. Distribution of δ13C isotopes for saturated and aromatic 

hydrocarbons, Talara and Progreso Basin provinces (GeoMark, 1998). 

Clustering of data indicates that sampled oils from the Talara and Progreso Basin provinces have a common source rock.

14 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
rocks deeper in the basin, laterally toward faults, and 20–600 

m vertically along the faults into the mostly structural traps; 

(2) subsequent vertical migration along fault systems, and lateral migration distances, were 10–50 km, based on the above 

geophysical and geochemical data and on changes in API 

gravity of oil in reservoirs that are progressively farther away 

from the kitchens, and (3) there were several periods of migration, based partly on early biodegradation of oils followed by 

later non-biodegraded oils. 

Reservoir Rocks

There are more than 40 oil and (or) gas fields in the 

Talara Basin province (table 1), with production from as many 

as a dozen formations per well; and all production is reported 

commingled (Petroconsultants, 1996). The primary reservoirs 

are Eocene-age nearshore-marine sandstones. Three fields 

that produce oil and gas from quartzites of the Pennsylvanian 

Amotape Formation also have oil from Eocene and (or) Cretaceous sandstones; a fourth field, the now-abandoned Zorro 

field, produced about 100,000 BO from only the Amotape Formation. Oil and gas in four other fields is from sandstones of 

the Cretaceous Redondo Formation and the Cretaceous Ancha 

and Petacas Formations of the basal Mal Paso Group. One 

field produces gas from the Oligocene Mancora Formation. 

Reservoirs are mainly sandstones in the following formations:

• Pennsylvanian Amotape Formation fractured quartzites,

• Upper Cretaceous Redondo Shale, and the Upper Cretaceous Ancha and Petacas Formations of the Mal Paso 

Group,

• Paleocene sandstones of the Mesa and Balcones Formations, upper Mal Paso Group,

• Lower to middle Eocene Chacra and Salinas Groups 

(including the Basal Salina, San Cristobal, Mogollon 

(Manta), Ostrea (Tangue, Pardo), Palegreda, Clavel 

(Pariñas), and Echinocyamus Formations), 

• Middle and upper Eocene Talara Group (including the 

Terebratula, Hélico, and Talara (Pozo, southern basin, 

Media and underlying Yapato in the north) Formations), 

• Upper Eocene Verdun Formation of the Lagunitos 

Group,

• Oligocene Mancora Formation.

Quartzites of the Amotape Formation are unconformably overlain by Cretaceous limestones, sandstones, and 

shales, which in turn are in unconformable contact with Tertiary rocks. The thick sequence of Upper Cretaceous through 

Eocene strata in the Talara Basin province accumulated primarily in fluvial to deltaic depositional environments, with 

some offshore marine turbidites (AIPC, no date). Although 

the pre-Neogene strata are laterally continuous through the 

basins, the vertical sequence is also cut by internal unconformities (Zúñiga-Rivero and Hay-Roe, 1998) (figs. 2, 4). Eroded 

Mesozoic and Paleozoic strata were the initial source of clastic 

detritus; petrographic analysis confirms that the sandstones 

are quartz rich with a small proportion of volcanic material 

(Raez Lurquin, 1999). The source of Paleocene and Eocene 

sediments was from the northeast to southeast; the origins 

were highlands that resulted from compressional uplift of the 

Andes and other mountainous areas (Perupetro, 1999; Pindell 

and Tabbutt, 1995; Raez Lurquin, 1999). Sandstones interfinger westward with marine and nonmarine shales (Pindell 

and Tabutt, 1995), creating stacked sandstone reservoirs with 

interbedded shale seals and potential source rocks. ZúñigaRivero and others (1998a) indicated their stratigraphic and 

structural interpretations are based on approximately 13,037 

line-km (8,100 line-mi) of seismic profiles that have been run 

in the basin, of which 88 percent is offshore in water depths of 

as much as 5,000 m (1,500 ft). Early onshore seismic surveys 

were generally of poor quality due mainly to a thick cover of 

calcareous shallow-marine Pleistocene deposits, but modern 

marine seismic surveys have generated fair to excellent data 

(Zúñiga-Rivero and others, 1998a).

The Paleocene-Eocene sedimentary sequence is entirely 

clastic (fig. 4) and is characterized by shallow-marine, deltaic, 

and fluvial sandstones, marine shales, and turbidites; underlying sediments are about 75 percent clastic but include some 

thick and widespread oolitic, reefy, and micritic limestones 

that were considered by Zúñiga-Rivero and others (1998b) 

to be the most important hydrocarbon source rocks. Eocene 

strata include littoral and beach sandstones, and (in places) 

coarse conglomerates, as well as turbidite channel sandstones 

(Zúñiga-Rivero and others, 1998b). Sandstone and conglomerate grains show a high degree of roundness and a sorting that 

is characteristic of the most resistant rocks, indicating several 

phases of recycling before the final sedimentation (Raez Lurquin, 1999). 

Bianchi (2002) listed porosity and permeability ranges 

for the following formations (Note: no information was provided on sources of data or number or types of analyses): 

1. Hélico Formation sandstones, 12–15 percent porosity, 

2–5 millidarcies (mD) permeability, 

2. Clavel (Pariñas), 11–19 percent porosity, 60–120 mD 

permeability, 

3. Manta (Mogollon) 8–11 percent porosity, 0.15 mD permeability, and 

4. Basal Salinas Sand, 11–16 percent porosity, 14–20 mD 

permeability. 

Porosity of reservoir intervals for the Mogollon Formation in the Pena Negra field (fig. 1) ranges from 9 to 10.6 percent, and water saturation is 45.1 to 46.3 percent (Chavez and 

Rodriquez, 2002). The Eocene Hélico Formation in the field 

area consists of a lower conglomeratic sandstone and an upper 

fine- to medium-grained sandstone (Robles Chavez and Lopez 

Chavez, 2002). The depositional environments were three 

separate sets of deep-water marine turbidites, with the better 

quality sandstones present within the channel systems; grain 

size decreases from east to west. These channel sandstones are 

laterally discontinuous, resulting in compartmentalization of 

Petroleum Occurrence 15
the reservoir. The Hélico Formation has a vertical thickness of 

152 m (500 ft); its average porosity is 12 percent in the PN3 

offshore platform of the Pena Negra field.

Bianchi (2002) indicated that the Clavel (Pariñas) Formation is fluviodeltaic and transport directions were mainly 

toward the northwest and southwest. Clavel (Pariñas) Formation reservoirs within the Lobitos and Providencia fields are 

composed of fluviodeltaic sandstones with interbedded shales 

and clay (fig 17); reservoirs are extensively faulted, with 

hydrocarbons trapped in horsts, grabens, and other structures 

(Lopez and others, 2002). The thickness of the Clavel (Pariñas) Formation in the Lobitos and Providencia fields is about 

180 and 305 m (600 and 1,000 ft), respectively; the depth to 

the top of the formation varies from 825 to 1,280 m (2,700 to 

4,200 ft) in Lobitos and 395 to 580 m (1,300 to 1,900 ft) in 

Providencia; permeability and porosity in reservoirs ranges 

from 30 to 50 mD, and 12 to 18 percent, respectively (Lopez 

and others, 2002). Results are based largely on analysis of 

scattered geophysical well logs across the field areas, within 

which more than 800 wells have been drilled. 

The Mogollon Formation in the northern half of the 

Talara Basin province ranges in thickness from about 180 to 

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Figure 17. Depositional models for the Eocene Mogollon (A, B) and Clavel (Pariñas) (C) Formations, northern Talara Basin province. 

The Mogollon Formation has a progressive southward decrease in depositional energy, from reworked conglomerates in fluviodeltaic channels, to shales beyond the submarine fans (modified from Chavez Cerna and Rodriques Rios, 2002). Line of cross section is 

marked by N and S. Fluviodeltaic systems of the Clavel (Pariñas) Formation exhibit westward decrease in depositional energy with 

associated decrease in sediment grain size; primary reservoirs are distributary channel sandstones (modified from Lopez Chavez 

and others, 2002). Yellow is onshore, dark purple is igneous intrusions, and green and red dots are oil and gas field centerpoints, 

respectively.

16 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
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Figure 18. Fluviodeltaic depositional model of the basal Salina Formation, northern Talara Basin province (Gonzales Torres, 1999; reprinted by permission of author, 6/24/02). Sediment transport direction 

and source of these (gray, green, and yellow) stacked lobes was primarily from Paleozoic and Cretaceous rocks of the Alto de Negritios. Offshore contour interval is 100 ft. Blue line corresponds to the 

coastline, and the red line segregates lease blocks. 

Petroleum Occurrence 17
640 m (600 to 2,100 ft) and is composed of shale, sandstone, 

and conglomerate that originated in fluviodeltaic to submarine 

depositional environments; transport directions were from the 

northeast and depositional energy decreased seaward and to 

the south (fig. 17) (Chavez and Rodriquez, 2002). The formation is extensively fractured, with faults oriented primarily 

east-northeast in the area of the Tunal and Pena Negra fields 

(fig. 1); the field axes are oriented mainly northeast-southwest 

and some production is bounded by the faults (Benito and 

Arispe, 2002). 

Gonzales Torres (1999) indicated that Basal Salina sandstones in the northern third of the basin (1) consist mostly 

of turbidite fans and incised valley fill that prograde to the 

southwest, northwest, and northeast, (2) are part of a complex 

stacked fluviodeltaic sequence that was deposited in early 

Eocene and late Paleocene time, and (3) were sourced primarily by erosion of Paleozoic and Cretaceous rocks of the Alto 

de Negritos (Negritos High) (fig. 18). In general, grain size 

and depositional energy increases southward along this progradational sequence (Gonzales Torres, 1999). The system 

extends more than 50 km (30 mi) north of the Alto de Negritos 

(fig. 18). Gonzales Torres (1999) also indicated that reservoirs 

in the Basal Salina Formation contributed almost 40 percent of 

new petroleum production in the Talara Basin province during 

the last 15 years. 

The Neogene sedimentary history of the southern Progreso Basin province and northern Talara Basin province 

followed an Oligocene transgressive cycle and deposition of 

fluvial and marine sandstones and shales of the Mancora and 

Heath Formations (AIPC, no date; Kraemer and others 1999, 

2001). There is no known Neogene production from the Talara 

Basin province (fig. 4).

Traps and Seals

Late Oligocene and Miocene time is characterized by 

separation of the Nazca Plate from the South American Plate, 

with active subduction at the Peru-Chile trench and creation 

of the Neogene portion of the southern Progreso Basin province, located at the north border of the Talara Basin province 

(Jaillard and others, 1995). The region, in middle Miocene 

time, experienced block faulting, mostly extensional tectonics, 

and renewed growth of the Andes Mountains east of Talara. 

Although earlier tectonic activity affected patterns of folding, 

faulting, and deposition across the basin, the middle to late 

Tertiary extensional regime was associated with high-angle 

normal faulting that trapped and redistributed hydrocarbons, 

causing development of the current fault-block reservoirs 

(Zúñiga-Rivero and others, 1998a, 1998b). Structurally, the 

area is a system of faulted blocks—the size of the blocks is 

nonuniform and can vary from 100 to 1,500 acres or more 

(Raez Lurquin, 1999). Structural trap types are generally 

moderate- to high-angle normal faults, low-angle gravitational 

slide faults, and transcurrent faults (AIPC, no date; Petroconsultants, 1996; Zúñiga-Rivero and others, 1998b). Based on 

seismic interpretations, normal faulting appears to decrease 

westward from the intensely faulted onshore area of the basin 

(Zúñiga-Rivero and others, 1999).

Seismic records indicate a variety of trapping features for 

Talara and bounding basins that include rollovers and updip 

closures against faults, and stratigraphic pinch-outs (turbidite 

channel deposits) and onlap onto old highs (Zúñiga-Rivero and 

others, 1998a). Sediment sources are primarily from the east, 

northeast, and southeast (Perupetro, 1999; Pindell and Tabbutt, 

1995), and depositional patterns associated with these fluvial, 

shoreline, turbidite, marine and other facies strongly influence 

types and locations of seals. Zúñiga-Rivero and others (1998b) 

indicated that marine shales segregated and sealed both shallow and deepwater sandstone beds. Interbedded and overlying 

marine shales are the primary reservoir seals. Some units are 

composed of multiple sandstones separated by shales. Lateral 

seals are (mainly normal) fault offsets, and lateral depositional 

or erosional pinch-outs of the mostly marine sandstones into 

shales (Zúñiga-Rivero and others, 1998b). 

Conclusions

The Paleogene Talara Basin province overlies an older 

regional basin. Movement through time of the continental 

plates resulted in a complex block-faulted basin, characterized by normal faults, low-angle gravitational slide faults, and 

large vertical transcurrent faults. Complex structural features 

of the offshore Talara Basin province include extensive growth 

faulting with associated rollover-type folding. Seismic and 

subsurface data indicate that the faulting was most intense in 

the eastern (onshore) portion of the basin and decreased in a 

seaward direction.

Oil geochemical studies indicate that there is one Tertiary 

hydrocarbon source rock for Tertiary production in the Talara 

Basin province, as evidenced by distributions of (1) ratios of 

Ni/V, (2) saturated versus aromatic 13C, and (3) API gravity 

versus weight percent sulfur among approximately 20 analyzed oils. Gas chromatograms for many of these oils indicate 

an early stage of biodegradation and (or) water washing followed by a second phase of migration into reservoirs. This 

biodegradation resulted in some scatter in the geochemical 

data. 

Possible Tertiary hydrocarbon source rocks are marine 

shales of the (1) Balcones Formation (lower Paleocene), (2) 

the San Cristobal, Palegreda, Clavel (Pariñas), and Echinocyamus Formations of the lower Eocene Chacra-Salina Group, 

(3) the upper Eocene Talara Formation, (4) the upper Eocene 

Chira Formation, and (5) the Oligocene Heath Formation. 

Shales of the Cretaceous Monte Grande Formation are primarily of terrestrial (type-III kerogen) origin and are potential 

sources of dry gas, although there is no evidence of dry gas 

generation in the Talara Basin province. Probable Cretaceous 

hydrocarbon source rocks are the Albian Muerto Limestone 

and marine shales of the Campanian Redondo Formation, 

18 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System
which are also potential source rocks for the unconformably 

underlying Pennsylvanian Amotape Formation. Geochemical 

data on one oil sample from the Amotape quartzite indicate 

that it has a Tertiary source. Pennsylvanian shales would probably be overmature for hydrocarbon generation. 

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Manuscript approved for publication May 12, 2004

Published in the Central Region, Denver, Colorado

Editing—Richard W. Scott, Jr.

Page layout, photocomposition—Adam Redmon

Section 508 compliance—David G. Walters

Webmaster—Tracy A. Pinto

Graphics by the author

20 The Talara Basin Province of Northwestern Peru: Cretaceous-Tertiary Total Petroleum System