Paleogene Thrust Research Articles

Tectonics and gravitational phenomena, part two: The Trnovski gozd-Banjšice-Šentviška Gora degraded plain

The article describes the recent conditions at the Paleogene thrust contact between the External Dinaric Thrust Belt composed of carbonate rocks and the External Dinaric Imbricate Belt composed of flysch rocks, geographically, between the Trnovski gozd (Trnovski gozd plateau) and the Vipava Valley at the northwestern end of the Dinarides. Fossil and recent gravity-related phenomena that indicate the uplift of the southwestern edge of the External Dinaric Thrust Belt and the larger complex in the hinterland are found there. However, these phenomena are not related to the reactivated Paleogene thrust tectonics, but to the Neogene-recent underthrusting as a consequence of the Microadria (Adriatic Microplate) movement towards the Dinarides. Only arguments for these processes are presented in this article.

The importance of structural complexity in the localization of geothermal systems: A case study along the Vallès-Penedès Fault in the Catalan Coastal Ranges (NE Spain)

The Vallès-Penedès Fault is a Neogene normal fault marked by the presence of two established geothermal systems at La Garriga-Samalús and Caldes de Montbuí, within the Catalan Coastal Ranges (NE Spain). The analysis and collation of existing and new geological and geophysical datasets provide the basis for the development of an improved conceptual model that explains the presence and localization of hot geothermal fluid systems at relatively shallow depths (e.g., 60 °C at surface and 90 °C at 1 km). Geothermal flow is concentrated within Paleozoic granodiorites of the immediate footwall of the V-P fault, host rocks that are susceptible to fault-related fracturing, and the generation of both extension and hybrid fracture systems in association with active fault displacements. Flow localization is enhanced further by the presence of fault-related structural complexities, with both systems marked by 300 m wide steps in the main fault trace. These are attributed to relay development and breaching characterizing host rocks by high fracture intensities and fault rock development on a fault that locally has a vertical displacement of over 1.5 km. Accentuated fracturing and deformation are consistent with strain localization predicted by existing models for the development of fault zones along normal faults. The plumbing of the geothermal systems is attributed to up-fault flow in combination with lateral flow controlled by the intersection of the V-P fault with a low-angled Paleogene thrust defining the base of the host-rock granodiorites, with the geothermal systems localized at the distal end of the thrust. Sustained geothermal flow is attributed to groundwater flow circulation associated with seismic pumping and valving of warmer and deeper fluids, and the ingress of groundwater along faults and within fractured basement rocks.

The petrology, geochronology and tectono-magmatic setting of igneous rocks in the Suckling-Dayman metamorphic core complex, Papua New Guinea

Southeastern Papua New Guinea has hosted magmatism throughout the Cenozoic, with the latest phase being concurrent with active extension in the Woodlark Rift. There, the Suckling-Dayman metamorphic core complex (SDMCC) has exhumed middle-crustal rocks in the past few million years along a still-active low-angle normal fault, the Mai'iu Fault. Uplift of the SDMCC has exposed metasedimentary and metaigneous rocks of Late Cretaceous-Pleistocene age that record an evolution from oceanic spreading to subduction, to collision, and finally to subduction-inversion and extensional exhumation. We present new petrographic, whole-rock geochemical and geochronologic (zircon U–Pb LA-ICP-MS) data from the SDMCC to reconstruct its long-term evolution. The dominant footwall-lithology of the SDMCC, the Goropu Metabasalt, has a MORB composition. Detrital zircons from metasedimentary beds intercalated with these basalts yield U–Pb-based maximum estimates for deposition of ~103 and ~72 Ma, suggesting a Late Cretaceous spreading age of the oceanic protolith. Bulk compositions of low-grade tholeiitic meta-gabbroic and -tonalitic rocks (Yau Igneous Complex) that intrude the Goropu Metabasalt reveal both enriched and depleted light rare earth element patterns. Zircon U–Pb ages from the Yau Igneous Complex range between ~60 and ~57 Ma, providing a minimum age for the formation of the Goropu Metabasalt. Much younger syn-extensional granitoids in the mafic footwall of the SDMCC have calc-alkaline to high-K compositions and U–Pb ages on zircon between ~3.7 and ~2.0 Ma. Our data indicate that the Mai'iu Fault had re-activated a Paleogene thrust as an extensional detachment fault by 3.7 ± 0.2 Ma. U–Pb ages of detrital zircons in modern streams draining the footwall of the SDMCC essentially reflect the ages revealed by the Paleocene and Plio-Pleistocene intrusions. Xenocrystic zircons in the Plio-Pleistocene granitoids imply that the crust underlying the metabasaltic carapace of the SDMCC consists chiefly of Australian-continent derived sedimentary rocks.

Deformation around a detached half-graben shoulder during nappe stacking (Northern Calcareous Alps, Austria)

This study describes the inversion of a rift-related graben shoulder during emplacement and transport of a major thrust sheet in the external part of the western Northern Calcareous Alps (NCA). Structural fieldwork was carried out along the Lechtal thrust, separating the tectonically deeper Allgäu thrust sheet from the Lechtal thrust sheet. An irregularly shaped Early Jurassic normal fault and an adjacent basin are present in the immediate footwall of the Lechtal thrust. The Early Jurassic age of the basin formation is indirectly established by thickness differences in the syntectonic deposits. Scaly fabric and small-scale drag folds document top S to top SW kinematics at the normal fault. During Alpine orogeny the Lechtal thrust is forced to recess around the graben shoulder in the footwall. A transpressive, dextral tear-fault develops in the hanging wall to compensate for lateral differences of shortening. The normal fault is too steep for inversion, and a shortcut thrust across the half-graben shoulder developed at a shallower angle. It transports the detached half-graben shoulder into the neighbouring basin. Albian to Paleogene transport of the Lechtal thrust sheet caused deformation below the Lechtal thrust, creating a shear zone with isoclinal folds, break thrusts, boudinaged beds and development of S–C fabric. Kinematic analyses of S–C fabrics and small-scale fold axes along the Lechtal thrust show consistent top NW to top N shortening directions in accordance with Cretaceous to Paleogene thrust directions in the NCA.

Jurassic–Cretaceous granitoids and related tectono-metallogenesis in the Zapug–Duobuza arc, western Tibet

The Zapug–Duobuza magmatic arc (ZDMA), located along the southern edge of the south Qiangtang terrane in western Tibet, extends east–west for ~400km. Small scattered granite and porphyry intrusions crop out in the ZDMA, but a large amount of granite may be buried by Late Cretaceous to Paleogene thrusting. Two stages of magmatism have been identified, at 170–150Ma and 130–110Ma. The widely distributed Middle–Late Jurassic granite intrusions in the ZDMA exhibit SrNd isotopic characteristics similar to those of ore-bearing porphyries in the Duolong giant CuAu deposit, and their εHf(t) values mostly overlap those of other porphyry CuMo deposits in the ZDMA and the Gangdese zone. The SrNdHf isotopic geochemistry suggests variable contributions of mantle and Qiangtang crustal sources, and indicates the presence of two new ore districts with potentials for CuAu, Fe, and PbZn ores, located in the Jiacuo–Liqunshan and Larelaxin–Caima areas. Except for the Duolong ore-forming porphyries, which show significant contributions of mantle components intruded into an accretionary mélange setting, the Early Cretaceous granites in other areas of the belt are of mostly crustal origin, from sources in Qiangtang felsic basement and Permo-Carboniferous strata, indicating the weak ore-forming potential of skarn-type Fe and PbZn deposits. The ephemeral but deep Bangong Co–Nujiang ocean in the Early Jurassic evolved into a shallow compressional marine basin in the Middle–Late Jurassic, possibly transitioning to northward flat subduction of oceanic crust at this time. The subducted slab broke off in the Early Cretaceous, initiating a peak in arc magmatism and metallogenesis at 125–110Ma.

Tectonic controls of the right-lateral Burro Negro tear fault on Paleogene structure and stratigraphy, northeastern Maracaibo Basin

The northeastern Maracaibo Basin in western Venezuela was deformed by Paleogene thrusting and an associated tear fault (Burro Negro right-lateral strike-slip fault zone), related to Paleogene oblique collision between the Caribbean and South American plates. Two different tectonic models have been previously proposed for the thick Paleogene depocenter located along the northeastern margin of the Maracaibo Basin. The first model proposes that the depocenter is a foreland basin controlled by southwestward-directed overthrusting during a late Paleocene–middle Eocene oblique collision between the Caribbean and South American plates. The second model, supported by data presented in this study, proposes that the asymmetric Paleogene Maracaibo sedimentary wedge was controlled by strike-slip displacement along a right-lateral tear fault, separating southeast-directed thrust sheets to the east (Lara nappes) from a more stable platform area to the west (Maracaibo Basin).Regional seismic lines recorded to 5 s two-way traveltime reveal the structure of the asymmetric Paleogene depocenter in the northeastern part of the Maracaibo Basin. The approximately 100-km (62-mi)-long Burro Negro fault is a right-lateral strike-slip fault separating less deformed, inner- to outer-shelf rocks of the western Maracaibo Basin from highly deformed, deep-marine rocks of the eastern Maracaibo Basin. Seismic lines northeast of the Burro Negro fault zone show elongate, subsurface basins bounded by partially inverted reverse and strike-slip faults filled with about 3 km (1.8 mi) of Oligocene and Miocene clastic marine sedimentary rocks. Structural highs of Eocene rocks are characterized at depth on seismic reflection lines by chaotic seismic reflections that underlie the more coherently stratified Oligocene and Miocene subbasins. We interpret these structural highs as steeply dipping fault zones and shale diapirs activated during Eocene–Oligocene oblique plate convergence.The geology and overall structural configuration of the northeastern Maracaibo Basin and the Burro Negro fault zone support its origin as a right-lateral tear fault. In our model, the Burro Negro fault zone accommodated southeastward migration of the thrust front in the deep-water area east of the fault in the present-day Falcn region. The Paleogene clastic wedge of the Maracaibo Basin exhibits many common features of a classic foreland basin, including onlap onto an arch or forebulge located near the center of the present-day Lake Maracaibo. This paleogeographic coincidence of the Burro Negro fault zone and the Maracaibo shelf edge suggests that the paleotrend of the South American passive margin prior to collision was serrated in map view. West-to-east migration of the Caribbean–South America oblique collision formed progressively younger, parallel tear faults to the east of the Maracaibo Basin that may have formed by the same tectonic process as the Burro Negro fault zone.

Northern Tunisia Thrust Belt: Deformation Models and Hydrocarbon Systems

The integrated use of the geological, geophysical, and geochemical data of northern Tunisia onshore and offshore led to an inversion model from the Tethyan rifting and subsequent evolution of the North African passive margin to the Late Cretaceous–Tertiary orogeny, inducing the fold and thrust belt and associated foreland deformations. Respective deposits characterize each tectonic cycle; Triassic synrift and Jurassic–Cretaceous open-marine series are related to the Mesozoic opening, and Paleogene–Neogene clastic sequences are closely controlled by the Tertiary shortening. For hydrocarbon prospectivity and despite its early stage of exploration, this domain could be considered as an emerging area with encouraging ingredients, particularly three fractured carbonate reservoirs, two sandy reservoirs, five source rocks, and numerous potential structural and stratigraphic traps. The main feature in this area is the close relationship between the Tertiary tectonics and the evolution of the petroleum systems. Hence, the Numidian turbidites identified both as reservoir and source rock were deposited in a foredeep directly generated by the Paleogene thrusting and later displaced as far-traveled nappes above the Ypresian fractured limestones defined also as a source rock and reservoir. The maturity of these source rocks is closely related to the nappes displacement, which assumes the overburden and increases the heat flow. Fracturing is also generated by these events.

Paleogene Thrust Tectonics In Northwestern Venezuela: Petroleum System Implications: ABSTRACT

Oil exploration in northeastern Perija Mountains, northwestern Maracaibo basin, has been difficult, mainly due to the various tectonic events that have strongly deformed this area. This study is an attempt at better understanding the effect of a Paleogene thrusting event on the petroleum system development in the area. Subsidence analysis interpretation at both sides of the NNE directed Tigre fault (which separates the northern Perija Mountains from the rest of the Maracaibo basin) suggests the onset of a foreland basin during, at least, Paleocene-Early Eocene time. Continuous sedimentation occurred from Late Cretaceous to Early Eocene, as long as it kept pace with subsidence, in the west block of the fault, while the east block acted as an obstacle against the thrust-sheet movement, delaying its subsidence. Sedimentation for this time is associated with a thick unit of mainly paralic sediments west of that fault and thinner continental (fluvial) to shallow marine sediments, with an intra-Paleocene/Early Eocene unconformity, east of it. So, this tectonic event, associated with convergence from the north, caused a south-verging thrust sheet giving rise to differences in the evolution of the petroleum system on both sides of the Tigre fault, mainly regarding the existence of source rocks andmore » their generation/migration of hydrocarbons, preservation time and critical moment. Finally, in order to evaluate the oil exploration opportunities in northeastern Perija mountains, it is advisable that any integrated interpretation of the petroleum system processes (generation-migration-accumulation) take into account this tectonic event.« less

Interpretive Structural Cross Section from the Central Diablo Range to the San Joaquin Valley, California

Abstract An interpretation of the structure of the Central Diablo Range and its relation to the northern San Joaquin Valley is presented. The interpretation recognizes the need to separate in time and space at least three tectonic events: (1) formation of the basin of deposition of the Great Valley Sequence (GVS), (2) Paleogene convergence to produce the Diablo Range antiform, and (3) Late Cenozoic convergence to produce the present topography of the Range. The basin of deposition for the GVS was formed on two separate portions of the Foothills Terrane Arc. The Jurassic and Lower Cretaceous portion of the GVS, which has only been recognized in the Range, was deposited on oceanic crust on the west side of the Foothills Terrane Arc in a distal setting. The proximal Upper Cretaceous portion of the GVS was deposited on Foothills Terrane Arc after ductile deformation of the Arc substrate and tectonic stripping of the Arc superstructure. The ductile deformation within the Arc occurred synchronously with deposition of the distal portion of the GVS. It is suggested that the Arc superstructure detached in the Lower Cretaceous, slid slowly southwestward during the late Lower Cretaceous and Upper Cretaceous, and now forms the tectonic wedge beneath the Diablo Range, which has been interpreted by Wentworth and others (1984) from reflection seismic data. The Central Diablo Range is an anticline expressed by GVS and younger sedimentary rocks dipping "radially" away from a core of Franciscan Formation. Everywhere the GVS is separated from the Franciscan core by a complex fault zone (Jayko and others, 1987) called the "Coast Range Thrust." This "thrust" was initiated by gravity driven slumping of the GVS into the Franciscan trench, perhaps during the Late Cretaceous as a part of the detachment of the arc superstructure. The anticline was created in essentially its present form by Paleogene thrusting of the distal GVS and Franciscan package northeastward over the proximal GVS in the northern San Joaquin Valley on a gentle southwestward dipping thrust plane. Thrusting continued, perhaps intermittently, on the same thrust structures through the middle Miocene. The present elevation of the range is due to a reactivation of these same structures after deposition of the Plio-Pleistocene Tulare Formation. More than 2,600 feet of structural relief developed on the base of the Tulare Formation between the San Joaquin Valley and the Diablo Range during the latest Cenozoic at the latitude of the Panoche Hills. The interpretation is presented on a conceptually balanced cross section constructed along Garzas Creek. Potential hydrocarbon traps are indicated.

Tectonic implications of canyon directions over the Northeast Atlantic Continental Margin

The basis of this study is a new bathymetric map of the northeast Atlantic compiled from previously published maps made from conventional echosounder data, plus all Sea Beam data acquired on board the R/V JEAN CHARCOT since 1977. As most of the Sea Beam data have been obtained on the continental margin from Porcupine Seabight to the south of the Iberian Peninsula, a precise picture of the continental slope is given. A statistical analysis of the canyons, based on 750 measurements, reveals that many of the canyons present sharp changes in their direction, indicating a structural control mainly linked to the late Hercynian trends, especially around the Iberian Peninsula. Nevertheless, the paths of canyons may merely reflect recent gravity processes, as in the Porcupine Seabight. Canyons locally follow the directions of listric and associated transecting faults (Permian to Triassic and upper Jurassic to lower Cretaceous), as on the Celtic margin, and every type of tectonic lineament—for example, the North Pyrenean Paleogene thrust front which fringes the Gouf of Cap Breton. A comparison of diagrams for the northern and southern Bay of Biscay margin (especially trends predating the opening) is compatible with a 25° rotation of Iberia with respect to Europe.

Pericollisional Strike-Slip Basins in Western Cordillera, Canada: ABSTRACT

The late Mesozoic-Paleogene evolution of the Canadian Cordillera was dominated by accretion of elongate crustal blocks against the North American craton. Geologic and paleomagnetic evidence suggest that these exotic terranes dispersed from volcanic arcs and oceanic platforms and approached North America along anastomosing right-lateral faults with great cumulative displacement. Obduction of oceanic allochthons was followed by transpressive thickening and regional metamorphism of the cratonic margin in the mid-Jurassic. Strike-slip motion and emplacement of plutonic rocks continued near relict sutures and reactivated deep faults. Sedimentary basins related to strike-slip faults formed by elongation of accreted terranes (Stikinia and Wrangellia) and by shear within the eformed cratonic margin zone (Rocky Mountain Trench). Subsidence is reflected by northwest-southeast stretching along pull-apart structures, and by massive influx of turbidites from incipient collision zones and relict arc relief. It was interrupted and outlived by rotation of blocks, folding of basin sediments, and vigorous progradation of deltaic-fluvial clastics from rising collision belts. Transition from predominant transtension to prevailing transpression is diachronous from basin to basin. Near the Stikine-Wrangellia collision zone (Bowser basin), it occurred in the Late Jurassic; along the Stikine-Wrangellia border it occurred in the mid to Late Cretaceous. Only small nonmarine basins developed in the Rocky Mountain Trench system, which, in its southernmost part, was closed com letely during Paleogene thrust faulting. The strike-slip basins of the western Canadian Cordillera were subject to high regional heat flow and also suffered from widespread intrusion of Paleogene granitoids. Therefore, they are generally poor oil and gas prospects. End_of_Article - Last_Page 473------------