The mechanism for crustal thickening and superposition of several orogens is critical for understanding the growth of mountain ranges. Our study focuses on a trans-orogen crustal cross-section to revisit the Andean tectonic evolution in the Northern Central Andes (5 degrees-8 degrees S). It is based on a review of the geological setting, the definition of long-term tectono-sedimentary successions, and for the first time, a crustal balanced cross-section 895 km long through the entire orogen. We show that the Northern Central Andes were born in the Jurassic, and correspond to the superposition of several orogens representing a minimum total shortening of similar to 207 km. They were built over 180 Ma during three orogenic periods (180-140 Ma; 100-50 Ma; 30-0 Ma), separated by two post-orogenic periods during which most Andean relieves were erased (140-100 Ma; 50-30 Ma). Each postorogenic period was recorded by 1) a major regional erosional unconformity sealed by a widespread marine transgression, and 2) extensional tectonics in the forearc. Crustal shortening was driven by westward South America Plate displacement and continental crustal underthrusting, and not by oceanic subduction. The propagation of the Andean wedge has been controlled by successive inversions of two pre-existing rifts. The sequential restoration of the trans-orogen balanced cross-section, constrained by the sedimentary record, provides a realistic picture of each orogenic and post-orogenic stage. For the first time, the pre-Neogene basins are reconstructed respecting the Andean shortening. The first-order factors that have controlled the complex growth evolution of Northern Central Andes are South America Plate dynamics changes associated with shifts in the geometry of the subducting oceanic slab. Some correlations can be established with Phanerozoic climate changes.

We have mapped gas hydrates, free gas, and bottom-simulating-reflector (BSR) distributions in an area of the Mexican Ridges, central Gulf of Mexico, Mexico, revealing the relationship between these three elements and the tectonostratigraphy. The three elements are more visible when the host rock is a high-porosity sandstone because there is a large seismic impedance contrast between the solid gas hydrates above and the free gas below, which manifests itself on the seismic as a BSR. Gas hydrates are identified in the well as higher resistivity sandstone layers with a strong positive amplitude. When the host rock has a higher shale content with lower porosity, the impedance contrast is lower and the BSR is weak or not visible. The study area in Mexican Ridges is an anticline where gas hydrates and free gas are trapped on the crest after migrating through the dipping layers and faults from synclines that are generated in calcareous shale. The main seal is mass transport complex deposits from the Pliocene; when they are not deposited at the crest of the anticline, there is gas escape to the seafloor in the form of a gas chimney. In this way, we established a complete petroleum system for gas hydrates and free gas on the Mexican Ridges.

The Andean foreland basin formed throughout the Cenozoic in a retro-arc setting in front of the advancing orogen. A 2,500-km-long segment of this basin system passes through eastern Perú and Bolivia and is comprised of, from north to south, the Marañon, Ucayali, Madre de Dios, Beni and Chaco Basins. The Andean foreland basin contains substantially thick units of Cenozoic sediments, which overlie Mesozoic and Paleozoic successions and Precambrian crystalline basement. In the deeper parts of the foreland basin, no wells have penetrated the full, pre-Andean sedimentary section and the sheer thickness of the sediments makes it difficult to seismically image crystalline basement in some areas. Thus, the thickness of the pre-Andean sediments and the existence of basins that pre-date the Andean Orogeny are partly obscured. Areally extensive gravity and magnetic data sets have been used to build a structural and tectonic framework for the area. Gravity and magnetic 2D forward modelling and 3D inverse gravity modelling, constrained by seismic interpretation and well data, enabled base Cretaceous and top crystalline basement horizons to be derived. This approach allowed lateral extrapolation of the detailed but localised seismic interpretation into areas without seismic coverage and it also extended this interpretation by including the depth to top crystalline basement. The results of this analysis indicate the presence of large pre-Cretaceous depocentres underlying the Andean foreland basin. These include a major depocentre extending from the central Marañon Basin north-northeastwards across the Iquitos Arch, two depocentres underlying the Madre de Dios Basin and four depocentres beneath the Beni/Chaco basins. 2D Forward Modelling Two-dimensional gravity and magnetic modelling was performed using GM-SYS TM (Geosoft Inc.). The aim of the 2D modelling was to test and refine the structural interpretation and to investigate the depth to base Cretaceous and top crystalline basement, and hence the preCretaceous sedimentary thickness. By adequately defining the depths to these two horizons, the 2D modelling results could be used as constraints for the 3D gravity inversions that followed. The sedimentary section was divided into two main units: Cenozoic/Cretaceous sediments and pre-Cretaceous sediments. This means that this study only resolves pre-Andean depocentres of Jurassic age and older. An analysis of almost 20 well density logs in the Marañon, Ucayali and Madre de Dios basins indicate that, while there was some variability, there are no obvious, large-scale density steps within the tested Cenozoic and Cretaceous sediments. Therefore, it was deemed sensible to model these sediments as a single layer with a density equal to the average density seen in the wells (2.33 g/cc). Density logs indicate a clear density increase in the pre-Cretaceous sediments to an average density of 2.56 g/cc. Five 2D models were constructed for the study area. Where possible these models were constrained by well and seismic data and followed the best available gravity and magnetic data. Figure 1 shows the results from one of the 2D models across the Marañon Basin. A number of basement grabens and a half-graben have been modelled between 170 and 480 km along the profile (Figure 1). These structures show some correlation with upper Paleozoic features seen in the seismic interpretation, and they presumably formed as a result of pre-Cretaceous extensional tectonics (Sempere et al., 2002; Spikings et al., 2016). North of 480 km along the profile, the basement starts to shallow, and consequently we see a thinning of the pre-Cretaceous section. A positive gravity anomaly at 600 km along the profile is generated by a basement structural high where pre-Cretaceous sediments are absent or at least very thin. This structure has been identified as the Iquitos Arch (Roddaz et al., 2005; Wesselingh et al., 2006; Barragan et al., 2008; Hermoza et al., 2009;) and is thought to represent the Andean forebulge in this area. A gravity low between 610 and 675 km along the profile is presented here as being due to the presence of a small, pre-Cretaceous basin with a maximum basement depth of around 6.5 km. 3D Gravity Inversions Three-dimensional gravity inversions were performed using a modified version of the iterative technique of Cordell and Henderson (1968). Here, the subsurface is represented as an array of vertical rectangular prisms, and their gravity effect is calculated at the surface; the mismatch between the observed gravity anomaly and the modelled gravity anomaly is used to iterate the model. Separate inversions, constrained by outcrop data and by well, seismic, and 2D model depths were performed to produce base Cretaceous and top crystalline depth surfaces for the foreland areas of Perú and Bolivia. The difference between these two surfaces indicates the thickness of pre-Cretaceous sediments (Figure 2). Although thick, localised accumulations of pre-Cretaceous sediments can be seen beneath the foreland basin of Perú and Bolivia, the thickest sediments are to be found in the central Marañon Basin of Perú and in parts of the Beni and Chaco basins of Bolivia. A number of basement arches appear to separate these pre-Cretaceous depocentres. A number of less well-known depocentres have been revealed by the gravity inversion. These include the small basins seen to the northeast of the Marañon Basin and Iquitos Arch in northeast Perú, and a possible northeastward continuation of the Madre de Dios Basin towards the Bolivia/Brazil border. Discussion The thickest accumulations of pre-Cretaceous sediments follow the NW–SE to N–S trend of the Andean front, being located directly east or northeast of it (Figure 2). Therefore, the Paleozoic and Mesozoic subsidence pattern in Peru and Bolivia must have been controlled, besides by basement heterogeneity, by tectonic processes related to the South American active plate margin. Thus, the pre-Cretaceous subsidence pattern observed replicates to a large extent the geometry of this long-lasting plate boundary and the strike of the present-day Andean Belt. The significant thickness of pre-Cretaceous sediments (Figure 2) and their stratigraphic inventory (McGroder et al., 2015) suggest that the development of the pre-Andean basins was a long-lasting process that spanned the entire Phanerozoic. By implication, the present-day size of the pre-Cretaceous basins in the study area does not necessarily correspond to their original extent. Some basement arches (e.g., the Iquitos Arch) were formed in a Neogene forebulge setting (Roddaz et al., 2005; Wesselingh et al., 2006; Barragan et al., 2008; Hermoza et al., 2009), whereas others (e.g., the Fitzcarrald Arch) may have originated because of latest Paleozoic contractional events (House et al., 2000). In both cases, they did not exert any control on pre-Permian depositional systems. Our data confirm a possible extension of thick Upper Paleozoic sedimentary successions, hosting the most important source rocks in southern Peru and Bolivia, into central and northern Peru. We can speculate that the extensive Mesozoic overburden in this area, which is primarily comprised of a thick Cretaceous succession, might have partly deteriorated the Paleozoic petroleum systems.

Summary The southern Portuguese margin recorded significant extension and subsidence during the Jurassic, resulting in the formation of the Algarve basin. Recent studies have revealed the existence of oceanic crust, of potentially Jurassic age, underlying significant portions of the Gulf of Cadiz to the south and west of the Algarve basin, but the exact relationship between this basin and the oceanic crust is still ambiguous. In this study we integrate data derived from field outcrop studies, interpretation of commercial seismic, and gravity and magnetic modelling to better understand the transition from the rifted continental crust underlying the Algarve basin to the oceanic crust of the Gulf of Cadiz. This integrated approach reveals that the Gulf of Cadiz oceanic crust is related to the WSW-ENE trending Jurassic passive margin of southern Portugal, and is separated from the Algarve Basin by a domain of highly thinned continental crust.

Abstract The Colombian Caribbean Margin, offshore the Guajira Peninsula, results from the complex interaction of the Caribbean oceanic, South American, and Nazca tectonic plates through geologic time. The Chichibacoa–Rancherias Basin (CRB) is located at the boundary of the Caribbean and South American tectonic plates, and extends from the shelf northward into deepwater. The basement of the CRB is characterized by lateral terrane accretion within a major transpressional province, involving the Caribbean plate arc, accreted terranes of transitional crust, and continental crust. The tectono-stratigraphic framework of the CRB is made up of 10 Paleogene and Neogene depositional sequences we define as SQ 1 to SQ 10 and an earlier Cretaceous (Maastrichtian to Campanian) sequence we define as SQ 0. Each of these sequences records an average time span of 5–10 My, representing major second- to third-order sequences. The definition and classification of the basin involved the application of high-resolution biostratigraphy from exploratory wells, U–Pb zircon isotopes (core), and a systematic calibration of seismic profiles using wells and biostratigraphic data. U–Pb zircon geochronology is used to constrain the age and nature of the basement in the CRB, which consists of Cretaceous meta-sedimentary rocks ranging in age from 67 My to 82 My (SQ 0). Analysis and interpretation of the data reveals that the CRB displays different structural styles of deformation, distinctive basement types, and sedimentary basin fills. The CRB is bounded by normal faults with strike-slip component. Locally, the strike-slip faults are inverted during the deformation of the accretionary prism of the Southern Caribbean Deformed Belt (SCDB). According to the structural reconstructions, gravimetric and magnetics modeling and basement sample analysis, the CRB lays over continental crust. Along the northern edge of the CRB, the SCDB shows two styles of deformation. The landward segment is characterized by structural inversion of pre-Eocene and probably Oligocene depocenters. Gravity and magnetic data indicate that this zone has a Cretaceous meta-sedimentary basement, which differs from the CRB, which is underlain by continental crust basement. The seaward structural segment (younger) exhibits well-developed thrust faults and duplexes associated with the Miocene and Pliocene deformation.

All along the eastern border of the Andes lie foreland basins that are among the most prolific hydrocarbon provinces of the world. Their Cenozoic evolution was controlled by the Andean uplift and its consequences on deformation and sedimentation. In turn, the Andean uplift results from the interplay between the subducting Nazca oceanic plate and the South American continental plate. Although the process exists all along the margin, the subducting plate is not regular including bathymetric anomalies and segments that result in different response in the deformation and active volcanism of the overriding plate. In the Maranon Basin of Peru, evidences allow documenting the consequences of a topographic anomaly subduction on the thermal regime and deformation of the Andean foreland during the Neogene. In this basin, a maturity anomaly is difficult to explain by considering only the present day thermal regime. However, it spatially coincides with the trace of a lost subducting ridge, the Inca Plateau. Other features like differential uplift and erosion can be related to the same event in the area. We review the consequences of oceanic ridge subduction along the Andean margin. Their effects on the deformation and volcanism of the forearc and arc regions have been extensively described. Their influence on the present day foreland topography is testified by the existence of giant alluvial fans and displaced terraces. Their effect on magmatism and ore deposits formation has also been demonstrated. The example illustrated here shows that their influence on thermal regime, deformation, erosion and ultimately on petroleum systems must also be taken into account in the search for hydrocarbons in subduction related basins.

In the Central to Northern Andes transition zone (Ecuador and Northern Peru), several Tertiary intermontane basins have been preserved (e.g. Bagua Basin in Peru, Zumba, Nabon, Loja, Malacatos- Vilcabamba, Giron and Cuenca basins in Ecuador). The analysis of these intermontane basins showed similarities in their sedimentological evolution and ages of infilling; however structurally, three groups can be separated: the Cuenca and Giron-Santa Isabel basins related to dextral movement of allochtonous terranes sutures (Raspas- Peltetec; Calacali-Pallatanga-Palenque). The Loja and Vilcabamba-Malacatos basins are associated to N-S sutures activation (Las Aradas- Zamora). The third group includes the Bagua Basin and others small piggyback basins purely related to the eastward migration of the main fold and thrust deformation front of the Central Andes during the Upper Miocene. Exploration point of view, the Miocene intermontane basins often contain a thick sequence of lacustrine and/or shallow marine deposits that could host potential source rocks. Indeed, coal layers are described and were traditionally exploited for domestic use. Nevertheless, the Miocene basin fill could at depth have triggered the activation of Mesozoic and older petroleum systems. In the area of the Bagua Basin exists two potential petroleum systems. The Jurassic (Aramachay Fm) and Cretaceous (Goyllarisquizga Gp and Inca Fm) sequences have an excellent source rock potential. One oil seep sample hosted in the Upper Cretaceous reservoirs was collected in the Bagua Basin. According to its geochemical characterization it is from a marine source rock, kerogene type II and a Pre-Cretaceous age has been postulated.

Precise knowledge of the timing of deformation in the Subandean zone of the Andean Plateau is a prerequisite for deciphering the late Neogene growth of the Andean Plateau. In this paper, we report new apatite fission-track (AFT) and vitrinite reflectance (Ro) data for a regional balanced cross section of the Camisea Basin in the central Peruvian Subandean zone, adjacent to the northern Andean Plateau. The balanced cross section shows that the structure of this basin is characterized by a broad internal passive roof duplex and external thrust-related anticlines. The balanced cross-section restoration shows 53 km (39%) of total horizontal shortening. We sampled Paleozoic to Cenozoic sedimentary strata for AFT and Ro analyses along the similar to 4-km-thick vertical profile of the Mainique back thrust (passive roof thrust), the innermost preserved Subandean structure. Young components of AFT ages are spread between ca. 6 Ma and ca. 24 Ma. A break in the slope in the AFT ages determines the geometry of the Miocene partial annealing zone and the exhumation of the Mainique back thrust at ca. 6 Ma. Sequential restoration calibrated by AFT and Ro data indicates that the last similar to 23 km horizontal shortening were accommodated by the Camisea thrust system over the past similar to 6 m.y., giving a mean shortening rate of 3.8 mm/yr. Using this shortening rate for the first similar to 30 km horizontal shortening, we calculate that the Andean shortening transfer into the Peruvian Subandean zone initially started at ca. 14 Ma. This result suggests that the transfer of shortening from the northern Andean Plateau to the Subandean zone occurred prior to the removal of dense lithosphere previously reported to have occurred between ca. 10 Ma and ca. 7 Ma. We rather propose that the late Neogene growth of the northern Andean Plateau mostly resulted from a continuous crustal shortening combined with lower-crustal flow.

The Andes and the Amazon River have been neighbouring geographical and geological features for at least the past 10 million years. However, the nature of the interactions between them remains unclear. The western margin of South America has been convergent since similar to 100 Ma, but only during the last 30 million years has there been an adjacent subduction orogen of the extent observed today. Instead, the configuration of the Amazon River evolved from 11 Ma and has remained largely unchanged at least for the past 6 million years. In this chapter we review the available data on the history of deformation, palaeoelevation and exhumation of the northern Central Andes, Northern Andes and adjacent sub-Andean basins in order to compare these data sets with the evolution of the Amazon drainage basin. The available data are far too scarce to propose definitive patterns, but do allow us to pose testable hypotheses on the interaction between the Andes, evolution of sub-Andean zones and the Amazon River. Deformation in the Andes began prior to the establishment of the modern Amazon drainage network and patterns. Although the modern Amazon is very young it appears to be closely related to the development of the Andes. This interrelated history of Amazon River and Andes is inferred from the acceleration in the denudation rates of the Eastern Cordillera, which coincides with the moment that Andean palaeoelevations became significant and began to constitute an orographic barrier and trap to moisture-bearing winds. However, this acceleration could also be related to the development of a denser drainage network in the Andean headwaters. All these factors, together with the presence of orogen-perpendicular basement highs, may have prompted a greater and more focused water and sediment influx towards the Amazon lowlands, producing a river directed to its present-day delta plains in the Atlantic Ocean. As previously proposed, the synchronous development of intense deformation in the sub-Andean basins appears to be related to changing mechanical conditions in the foreland sedimentary wedge that prompted deformation to migrate to the lowlands.

The Fitzcarrald Arch corresponds to a NE-SW-trending widespread dissected relief of about 400,000 km(2) located to the east of the sub-Andean thrust front. Analyses of drainage maps demonstrate that this regional uplift controls the modern Amazonian drainage network. During the Miocene, the Fitzcarrald Arch did not exist and this area corresponded to the subsiding foredeep of the Amazonian foreland basin. Analyses of the Miocene deposits outcropping within the Fitzcarrald Arch area indicate that deposition was controlled by tidal current and consisted of tide-dominated deltas and estuaries. The tidal Miocene deposits were followed by fluvial conglomerate and sandstone sediments, probably Pliocene to Pleistocene in age. Modelling of the vitrinite reflectance data shows that the uplift of the Fitzcarrald Arch began in Pliocene times; this date is further confirmed by sedimentary evidence such as provenance and a change of palaeocurrent directions from the Pliocene and Pleistocene record. Geophysical data show that the Fitzcarrald Arch uplift superimposed on the eastern part of the Nazca Ridge flat slab segment. The flat subduction process linked to the buoyancy of the Nazca Ridge has been active since similar to 4 Ma. Thus, the coincidence of the initiation of flat slab subduction with the Pliocene uplift of the Fitzcarrald Arch implies that the flat subduction of the Nazca Ridge is the cause of uplift. The Nazca Ridge flat subduction is the process responsible for the modern configuration of the Amazon drainage basin and may be one of the decisive factors that triggered large-scale modification of the Amazonian landscape inducing drastic biota changes in the Amazonian basin during the last 4 million years.

In this chapter we present a synthesis of the Cenozoic evolution of the Amazonian foreland basin system, based on a review of the estimated ages, lithology and sedimentary structures, palaeontological content, and inferred depositional environments of sedimentary units in the basin. In addition, we have calculated maximum sedimentation rates for the Cenozoic formations of the northern Peruvian foreland basin and integrated these with existing data on sedimentation rates, subsidence analysis, migration of depocentre and depositional environments. Based on this information we propose a model for the Cenozoic evolution of the Amazonian foreland. The sedimentary architecture of this foreland basin indicates that Cenozoic evolution was marked by several periods, which were roughly synchronous and of similar effect, along the entire Amazonian foreland basin system. Tectonic loading of the Andes of Colombia, Ecuador, Peru and northern Bolivia, and development of the Amazonian foreland, was initiated during Late Cretaceous-Paleocene times and followed by an unloading stage during the Early-Middle Eocene period. The Middle-Late Eocene marine transgression and the increase in sedimentation rates, associated with westward migration of the depocentre, were all indicative of a renewed phase of tectonic loading of the Peruvian Western Cordillera and the Ecuadorian and Colombian Eastern Cordillera. Subsequent Oligo-Miocene increase in sedimentation rates and further migration of the depocentres towards the present-day sub-Andean zone, are all indicative for a thrust-induced uplift and loading of the Eastern Cordilleras of Peru, Bolivia and Colombia. This Oligo-Miocene loading stage maintained high subsidence rates that favoured the sedimentation of aggradational floodplain and coastal plain and tidally influenced deposits. Nevertheless, the processes that controlled the Early-Middle Miocene marine ingressions remain to be determined. Late Miocene ongoing thrust tectonic loading of the Eastern Cordillera, initial structuring of the sub-Andean zone and the onset of the main phase of Andean surface uplift induced flexural subsidence in the foredeep depozones of the entire Amazonian foreland basin. This process also drove the Late Miocene marine transgressions that characterized the filled stage of the Ecuadorian, Peruvian and Bolivian Amazonian foreland basin system. Valley incisions and full relief development in the hinterland during the Late Miocene-Pliocene provided increased sediment supply and overfilled the Amazonian foreland basin system. Finally, the flat-slab subduction of the Nazca ridge induced Pliocene (similar to 4 Ma) uplift of the Fitzcarrald Arch and subdivided the Amazonian foreland basin into the northern and southern Amazonian foreland basins.

The 400 000 km(2)-wide Fitzcarrald Arch constitutes a wide topographic high of the Amazon Basin against the central Andes. In order to constrain its formation mechanisms and in particular to test its relationships to the Nazca ridge subduction, a quantitative geomorphology analysis of the Arch is performed using hypsometric integrals, elongation and azimuths of 7th- and 5th-order catchments. They all express a trend from high maturity to low maturity from NW towards SE. This maturity gradient coupled with the local drainage direction demonstrate that the Fitzcarrald Arch is not a 'classical' alluvial fan, since its apex is located 100 km east to the Subandean Thrust Front and the corresponding sedimentary pile is lacking. Nor is the Arch the superficial expression of an inherited transfer zone, because its geomorphic shape is radial and it does not diverge from a symmetry axis; moreover, such a reactivated structure is not found at depth on seismic profiles. In addition, our data show that underlying geomorphic control on catchment initiation and development has progressed from NW to SE, which in combination with the observation of crustal doming by Espurt et al. [Espurt, N., Baby, P., Brusset, S., Roddaz, M., Hermoza, W., Regard, V., Antoine, P.O., Salas-Gismondi, R., Bolanos, R., 2007. How does the Nazca Ridge subduction influence the modern Amazonian foreland basin? Geology 35, 515-518.] suggests that this relief is caused by the eastward sliding of the buoyant Nazca ridge beneath the South American lithosphere. (C) 2008 Elsevier B.V. All rights reserved.

The Neogene evolution of the Ene and southern Ucayali basins of the Subandes has been controlled by two stacked thrust wedges that differ in terms of tectonic styles. The lower thrust wedge is formed by deep‐seated décollements within the basement related to thick‐skinned foreland structures inherited from an Early Carboniferous thrust system. Seismic reflection data show that this Paleozoic compressional system has been eroded and unconformably covered by Late Carboniferous clastic sediments. It generated an irregular Paleozoic sedimentary architecture controlling the Neogene thrust propagation. The upper thin‐skinned thrust wedge developed within this Paleozoic sedimentary series and constitutes the Subandean zone. Cross‐section balancing shows an along‐strike homogenous horizontal shortening of ∼56 km (∼30%) across the Ene−southern Ucayali thrust system. This amount of shortening was vertically partitioned onto the two stacked thrust wedges. The N‐S thickness variations of the Paleozoic sedimentary prism controlled the eastward propagation of the upper thrust wedge. The southern thickening of the Paleozoic series generated major décollements and the shortening excess is of 7 km (16%) in comparison to the north. Consequently, the northern lack of shortening onto the upper thrust wedge was transferred to the Early Carboniferous compressional structures of the lower thrust wedge. We suggest that this vertical partitioning of the shortening was accommodated by a regional oblique ramp: the Tambo transfer zone. This geometrical analysis of the Ene−southern Ucayali thrust system provides new perspectives for future hydrocarbon exploration in this region.

The subduction of an aseismic ridge has important consequences on the dynamics of the overriding upper plate. In the central Andes, the Nazca Ridge subduction imprint can be tracked on the eastern side of the Andes. The Fitzcarrald arch is the long-wavelength topography response of the Nazca Ridge flat subduction, 750 km inboard of the trench. This uplift is responsible for the atypical three-dimensional shape of the Amazonian forelland basin. The Fitzearrald arch uplift is no older than Pliocene as constrained by the study of Neogene sediments and geomorphic markers, according to the kinematics of the Nazca Ridge subduction.

The subandean Ucayali Basin is an active fold and thrust belt propagation, which constitutes part of the wedge-top depozone of the Peruvian Amazonian retroforeland basin system. In the North, the Ucayali Basin is limited from the Marañón basin by the NW-SE overthrust Contaya Arch. In the east, the Ucayali Basin reaches the NNW-SSE trend of the Brazilian Moa Divisor structure, which disappears progressively to the south on the northern flank of the Fitzcarrald Arch.

From north to south, the Central Andes present significant variations in morphology, deformation and stratigraphic units. They have been ascribed to Palaeozoic and Jurassic paleogeographies (Gil et al., 2001) and geometry of the Nazca plate subduction (Pilger, 1984 ; Pardo-Casas & Molnar, 1987 ; Allmendinger & Gubbels, 1996 ; Norabuena et al., 1999). The retroforeland basin system of the Central Andes orogen constitutes a favoured area to study the tectonic-sedimentation coupling. Figure 1: The morphological/structural configuration in Andean Cordillera, showing the retroforeland basin system of the Central Andes orogen. The A and B represent the schematic regional cross-sections location. The purpose of this study is to present two regional cross-sections, in northern and southern Peru, and their sequential restorations (Figs 1 and 2) illustrating mean latitudinal variations of the Central Andean retroforeland basin system from Eocene to Present day. This study has been carried out from a multi disciplinary approach

The sub-Andean Huallaga basin is part of the modern retroforeland basin system of Peru. It corresponds to a thrust-and-fold belt superimposed on inverted and halokinetic structures and is characterized by Eocene–Pliocene, thick synorogenic series that have controlled the burial history of petroleum systems. Sedimentological analysis and a sequentially restored cross-section based on seismic data and new field studies show three sequences of synorogenic deposits. The Eocene (Lower Pozo member) developed in shoreface environments, when the basin morphology corresponded to a foresag depozone linked to an orogenic unloading period. The Middle Eocene sequence (Upper Pozo member) developed in shallow marine environments and recorded a change in Andean geodynamics and the retroforeland basin system. The basin morphology corresponded to a foredeep depozone linked to an orogenic loading period. This configuration remained until the Middle Miocene (Chambira Formation). The Middle Miocene–Pliocene sequence recorded the onset of the modern sub-Andean Huallaga basin that became a wedge-top depozone. Thrust propagation occurred in a deltaic environment, which evolved progressively to an alluvial system linked to the modern Amazon River.