Timing of Late Cretaceous shortening and basin development,Little Hatchet Mountains,southwestern New Mexico,USA – implications for regional Laramide tectonics

Laser ablation‐multi collector‐inductively coupled mass spectrometry U‐Pb geochronology, detailed field mapping and stratigraphic data offer improved insights into the timing and style of Laramide deformation and basin development in the Little Hatchet Mountains, southwestern New Mexico, USA, a key locality in the ‘southern Laramide province.’ The Laramide synorogenic section in the northern Little Hatchet Mountains comprises upper Campanian to Maastrichtian strata consisting of the Ringbone and Skunk Ranch formations, with a preserved maximum thickness of >2400 m, and the correlative Hidalgo Formation with a total thickness >1700 m. The Ringbone Formation and superjacent Skunk Ranch Formation are each generally composed of (1) a basal conglomerate member; (2) a middle member consisting of lacustrine shale, limestone, sandstone, and interbedded ash‐fall tuffs; and (3) an upper sandstone and conglomerate member. Basaltic andesite flows are intercalated with the upper member of the Ringbone Formation and the middle member of the Skunk Ranch Formation. The Hidalgo Formation, which crops out in the northern part of the range, is dominantly composed of basaltic andesite breccias and flows equivalent to those of the Ringbone and Skunk Ranch formations. The Laramide section was deposited in an intermontane basin partitioned across intrabasinal thrust structures, which controlled growth‐stratal development. U‐Pb zircon ages from five tuffs indicate that the age range of the Laramide sedimentary succession is ca. 75–70 Ma. U‐Pb detrital‐zircon age data (n = 356 analyses) from the Ringbone Formation and a Lower Cretaceous unit indicate sediment contribution from uplifted Lower and Upper Cretaceous rocks adjacent to the basin and the contemporary Tarahumara magmatic arc in nearby northern Sonora, Mexico. The new ages, combined with published data, indicate that uplift, basin development, and magmatism in the region proceeded diachronously northeastwards as the subducting Farallon slab flattened under northern Mexico and southern New Mexico from Campanian to Palaeogene time.     

Sediment routing in the Zagros foreland basin: Drainage reorganization and a shift from axial to transverse sediment dispersal in the Kurdistan region of Iraq

In the northwestern sector of the Zagros foreland basin, axial fluvial systems initially delivered fine-grained sediments from northwestern source regions into a contiguous basin, and later transverse fluvial systems delivered coarse-grained sediments from northeastern sources into a structurally partitioned basin by fold-thrust deformation. Here we integrate sedimentologic, stratigraphic, palaeomagnetic and geochronologic data from the northwestern Zagros foreland basin to define the Neogene history of deposition and sediment routing in response to progressive advance of the Zagros fold-thrust belt. This study constrains the depositional environments, timing of deposition and provenance of nonmarine clastic deposits of the Injana (Upper Fars), Mukdadiya (Lower Bakhtiari) and Bai-Hasan (Upper Bakhtiari) Formations in the Kurdistan region of Iraq. Sediments of the Injana Formation (~12.4–7.75 Ma) were transported axially (orogen-parallel) from northwest to southeast by meandering and low-sinuosity channel belt system. In contrast, during deposition of the Mukdadiya Formation (~7.75–5 Ma), sediments were delivered transversely (orogen-perpendicular) from northeast to southwest by braided and low-sinuosity channel belt system in distributive fluvial megafans. By ~5 Ma, the northwestern Zagros foreland basin became partitioned by growth of the Mountain Front Flexure and considerable gravel was introduced in localized alluvial fans derived from growing topographic highs. Foredeep accumulation rates during deposition of the Injana, Mukdadiya and Bai-Hasan Formations averaged 350, 400 and 600 m/Myr respectively, suggesting accelerated accommodation generation in a rapidly subsiding basin governed by flexural subsidence. Detrital zircon U-Pb age spectra show that in addition to sources of Mesozoic-Cenozoic cover strata, the Injana Formation was derived chiefly from Palaeozoic-Precambrian (including Carboniferous and latest Neoproterozoic) strata in an axial position to the northwest, likely from the Bitlis-Puturge Massif and broader Eastern Anatolia. In contrast, the Mukdadiya and Bai-Hasan Formations yield distinctive Palaeogene U-Pb age peaks, particularly in the southeastern sector of the study region, consistent with transverse delivery from the arc-related terranes of the Walash and Naopurdan volcano-sedimentary groups (Gaveh-Rud domain?) and Urumieh-Dokhtar magmatic arc to the northeast. These temporal and spatial variations in stratigraphic framework, depositional environments, sediment routing and compositional provenance reveal a major drainage reorganization during Neogene shortening in the Zagros fold-thrust belt. Whereas axial fluvial systems initially dominated the foreland basin during early orogenesis in the Kurdistan region of Iraq, transverse fluvial systems were subsequently established and delivered major sediment volumes to the foreland as a consequence of the abrupt deformation advance and associated topographic growth in the Zagros.     

Magnetostratigraphy,age and depositional environment of the Lobo Formation,southwest New Mexico: implications for the Laramide orogeny in the southern Rocky Mountains

The Lobo Formation of southwestern New Mexico consists of spatially variable continental successions attributed to the Laramide orogeny (80–40 Myr), although its age and provenance are virtually undocumented. This study combines sedimentological, magnetostratigraphical and geochronological data to infer the timing and origin of the Lobo Formation. Measured sections of Lobo strata at two locations, Capitol Dome in the Florida Mountains and in the Victorio Mountains, indicate significant differences in depositional environments and sediment provenance. At Capitol Dome, where Lobo strata were deposited above a syncline developed in Palaeozoic strata, deposition took place in fluvial, palustrine and marginal lacustrine settings, with alluvial‐fan deposits only at the top of the formation. Combined magnetostratigraphy and a young U–Pb detrital zircon age suggest deposition of the section at Capitol Dome from ~60 to 52 Ma. The Lobo Formation in the Victorio Mountains was deposited in alluvial‐fan and fluvial settings; the age of deposition is poorly bracketed between 66 ± 2 Ma, the weighted‐mean age of two young zircons, and middle Eocene (~40 Ma), the approximate age of overlying volcanic rocks. U–Pb zircon ages from sandstones at the Victorio and Capitol Dome localities indicate that different source rocks provided sediment to the Lobo Formation. Local Proterozoic basement (~1.47–1.45 Ga) dominated the source of the Lobo Formation in the Victorio Mountains, consistent with abundant granitic clasts that are present in the proximal facies there; a diverse range of grain ages suggest that recycled Lower Cretaceous strata provided the dominant source for Lobo Formation sediment at the Capitol Dome locality. The U–Pb data suggest that the depositional systems at the two sites were not connected. Contrasts in depositional setting and detrital zircon provenance indicate that the Palaeogene Lobo Formation in southwest New Mexico was deposited in an assemblage of local depositional settings, possibly in separate structural basins, as a consequence of Laramide tectonics in the region.     

Detrital zircon age spectra of middle and upper Eocene outcrop belts,U.S. Gulf Coast region

Recently reported detrital zircon (DZ) data help to associate the Paleogene strata of the Gulf of Mexico region to various provenance areas. By far, recent work has emphasised upper Paleocene‐lower Eocene and upper Oligocene strata that were deposited during the two episodes of the highest sediment supply in the Paleogene. The data reveal a dynamic drainage history, including (1) initial routing of western Cordilleran drainages towards the Gulf of Mexico in the Paleocene, (2) an eastward shift of the western continental divide, from the Jura‐Cretaceous cordilleran arc to the eastern edge of the Laramide province after the Paleocene and (3) a southward shift, along the eastern Laramide province, of the headwaters of river systems draining to the Mississippi and Houston embayments at some time between the early Eocene and Oligocene. However, DZ characterisation of most (~20 Myr) of the middle Eocene‐lower Oligocene section remains limited. We present 60 DZ age spectra, most of which are from the middle or upper Eocene outcrop belts, with 50–200‐km spacing. We define six to eight distinct groups of DZ age spectra for middle and upper Eocene strata. Data from this and other studies resolve at least six substantial temporal changes in age spectra at various positions along the continental margin. The evolving age spectra constrain the middle and upper Eocene drainage patterns of large parts of interior North America. The most well‐resolved aspects of these drainage patterns include (1) persistent rivers that flowed from erosional landscapes across the Paleozoic Appalachian orogen either into the low‐lying Mississippi embayment or directly into the eastern Gulf; (2) at least during marine regressions, a trunk channel that likely flowed southward along the axial part of Mississippi Embayment and integrated tributaries from the east and west; and (3) rivers that flowed to the Houston embayment in the middle Eocene that likely originated in the Laramide province in central Colorado and southern Wyoming, as Precambrian basement highs in those source areas were being unroofed.     

Fluvial deposition during transition from flexural to dynamic subsidence in the Cordilleran foreland basin: Ericson Formation,Western Wyoming,USA

The Ericson Formation was deposited in the distal foredeep of the Cordilleran foreland basin during Campanian time. Isopach data show that it records early dynamic subsidence and the onset of basin partitioning by Laramide uplifts. The Ericson Formation is well exposed around the Rock Springs uplift, a Laramide structural dome in southwestern Wyoming; the formation is thin, regionally extensive, and does not display the wedge‐shaped geometry typical of foredeep deposits. Sedimentation in this area was controlled both by activity in the thrust belt and by intraforeland tectonics. The Ericson Formation is ideally situated both spatially and temporally to study the transition from Sevier to Laramide (thin‐ to thick‐skinned) deformation which corresponded to the shift from flexural to dynamic subsidence and the demise of the Cretaceous foreland basin system. We establish the depositional age of the Ericson Formation as ca. 74 Ma through detrital zircon U–Pb analysis. Palaeocurrent data show a generally southeastward transport direction, but northward indicators near Flaming Gorge Reservoir suggest that the intraforeland Uinta uplift was rising and shedding sediment northward by late Campanian time. Petrographic data and detrital zircon U–Pb ages indicate that Ericson sediment was derived from erosion of Proterozoic quartzites and Palaeozoic and Mesozoic quartzose sandstones in the Sevier thrust belt to the west. The new data place temporal and geographic constraints on attempts to produce geodynamic models linking flat‐slab subduction of the oceanic Farallon plate to the onset of the Laramide orogenic event.     

Sediment provenance of the Lulehe Formation in the Qaidam basin: Insight to initial Cenozoic deposition and deformation in northern Tibetan plateau

Unravelling early Cenozoic basin development in northern Tibetan Plateau remains crucial to understanding continental deformation mechanisms and to assessing models of plateau growth. We target coarse-grained red beds from the Cenozoic basal Lulehe Formation in the Qaidam basin by combining conglomerate clast compositions, paleocurrent determinations, sandstone petrography, heavy mineral analysis and detrital zircon U–Pb geochronology to characterize sediment provenance and the relationship between deformation and deposition. The red beds are dominated by matrix-supported, poorly sorted clastic rocks, implying low compositional and textural maturity and short transport distances. Although most sandstones have high (meta)sedimentary lithic fragment contents and abundant heavy minerals of metamorphic origin (e.g., garnet, epidote and chlorite), spatiotemporal differences in detrital compositions are evident. Detrital zircon grains mainly have Phanerozoic ages (210–280 Ma and 390–480 Ma), but Proterozoic ages (750–1000 Ma, 1700–2000 Ma and 2300–2500 Ma) are also prominent in some samples. Analysed strata display dissimilar (including south-, north- and west-directed) paleocurrent orientations. These results demonstrate that the Cenozoic basal deposits were derived from localized, spatially diverse sources with small drainage networks. We advocate that initial sedimentary filling in the northern Qaidam basin was fed by parent-rocks from the North Qaidam-South Qilian belts and the pre-Cenozoic basement within the Qaidam terrane interior, rather than southern distant Eastern Kunlun regions. Seismic and drilling well stratigraphic data indicate the presence of paleohighs and syn-sedimentary reverse faults and noteworthy diversity in sediment thickness of the Lulehe Formation, revealing that the Qaidam terrane exhibited as several isolated depocenters, rather than a coherent basin, in the early stage of the Cenozoic deposition. We suggest the Cenozoic Qaidam basin to have developed in a contractional deformation regime, which supports models with synchronous deformation throughout most of Tibet shortly after the India-Eurasia collision.     

Detrital zircon and apatite constraints on depositional ages,sedimentation rates and provenance: Pliocene Productive Series,South Caspian Basin,Azerbaijan

We used detrital zircon U/Pb geochronology and apatite (U–Th–Sm)/He thermochronology to better constrain depositional ages and sedimentation rates for the Pliocene Productive Series in Azerbaijan. U/Pb analysis of 1,379 detrital zircon grains and (U–Th–Sm)/He analysis of 57 apatite grains—from Kirmaky Valley and Yasamal Valley onshore sections, Absheron Peninsula—yielded two distinct sub‐populations: “young” Neogene grains and “old” Mesozoic, Palaeozoic and Proterozoic/Archean grains. The large numbers of Neogene age grains (around 10% of all grain ages) provided a new absolute age constraint on the maximum depositional age of the Lower Productive Series of 4.0 Myr. These “young” Neogene zircon grains most likely originated from volcanic ash falls sourced from the Lesser Caucasus or Talesh Mountains. In this paper we propose a timescale scenario using the maximum depositional age of the Productive Series from detrital zircon grain U/Pb constraints. Potential consequences and limitations of using apatite (U–Th–Sm)/He dating method in estimating maximum depositional ages are also discussed. These new age constraints for the Lower Productive Series gave much faster sedimentation rates than previously estimated: 1.3 km/Myr in the South Caspian Basin margin outcrops and up to 3.9 km/Myr in the basin centre. The sedimentation rates are one of the highest in comparison to other sedimentary basins and coeval to global increase in sedimentation rates 2–4 Myr. The older group of detrital zircon grains constitutes the majority of grains in all sample sets (~80%). These older ages are inferred to reflect the provenance of the Productive Series sediment. This sediment is interpreted to have been derived from the Proterozoic and Archean crystalline basement rocks and Phanerozoic cover of the East European Craton, Proterozoic/Palaeozoic rocks of the Ural Mountains and Mesozoic sedimentary rocks of the Greater Caucasus. This sediment was likely supplied from northerly sourced drainage that emptied into the South Caspian Basin.     

Sediment and Water Discharge Assessment on Santiago and Pánuco Rivers (Central Mexico): The Importance of Topographic and Climatic Factors

This study explores the main factors controlling sediment and water discharge in the Santiago and Pánuco Rivers, the two largest rivers of central Mexico. Both Santiago and Pánuco Rivers are sourced in the Central Plateau of Mexico and flow in an opposite direction. Santiago River flows over a tectonically active margin draining to the Pacific Ocean, and Pánuco River flows into the passive margin of the Gulf of Mexico. Mean annual and monthly values of suspended sediment load and water discharge spanning around 50 years were used to evaluate sediment load and water discharge in these two rivers. Our findings indicated that Santiago River delivers to the ocean around 45% more sediment than Pánuco River. However, we found that Santiago River has about half the water discharge of Pánuco River. The high river gradient along Santiago River is likely to enhance the net erosion and sediment transport capacity. Water discharge at Pánuco Basin is higher than in Santiago Basin because the annual rainfall is higher for the former. The difference in sediment and water discharge for both rivers are also related to El Niño Southern Oscillation events. Our results indicated that water discharge in Santiago River increases during El Niño and La Niña events. In contrast, Pánuco River is mostly affected by La Niña events.     

Tectono‐sedimentary Evolution of Early Pennsylvanian Alluvial Systems at the Onset of the Alleghanian Orogeny,Pocahontas Basin,Virginia

Foreland basin strata provide an opportunity to review the depositional response of alluvial systems to unsteady tectonic load variations at convergent plate margins. The lower Breathitt Group of the Pocahontas Basin, a sub‐basin of the Central Appalachian Basin, in Virginia preserves an Early Pennsylvanian record of sedimentation during initial foreland basin subsidence of the Alleghanian orogeny. Utilizing fluvial facies distributions and long‐term stacking patterns within the context of an ancient, marginal‐marine foreland basin provides stratigraphic evidence to disentangle a recurring, low‐frequency residual tectonic signature from high‐frequency glacioeustatic events. Results from basin‐wide facies analysis, corroborated with petrography and detrital zircon geochronology, support a two end‐member depositional system of coexisting transverse and longitudinal alluvial systems infilling the foredeep during eustatic lowstands. Provenance data suggest that sediment was derived from low‐grade metamorphic Grenvillian‐Avalonian terranes and recycling of older Palaeozoic sedimentary rocks uplifted as part of the Alleghanian orogen and Archean‐Superior‐Province. Immature sediments, including lithic sandstone bodies, were deposited within a SE‐NW oriented transverse drainage system. Quartzarenites were deposited within a strike‐parallel NE‐SW oriented axial drainage, forming elongate belts along the western basin margin. These mature quartzarenites were deposited within a braided fluvial system that originated from a northerly cratonic source area. Integrating subsurface and sandstone provenance data indicates significant, repeated palaeogeographical shifts in alluvial facies distribution. Distinct wedges comprising composite sequences are bounded by successive shifts in alluvial facies and define three low‐frequency tectonic accommodation cycles. The proposed tectonic accommodation cycles provide an explanation for the recognized low‐frequency composite sequences, defining short‐term episodes of unsteady westward migration of the flexural Appalachian Basin and constrain the relative timing of deformation events during cratonward progression of the Alleghanian orogenic wedge.     

Role of initial depth at basin margins in sequence architecture: field examples and computer models

A delay in the onset of sedimentation during fault‐related subsidence at a basin margin can occur in both extensional settings, where footwall tilting may cause a diversion of drainage patterns, and in strike‐slip basins, where a source area may be translated along the basin margin. The ‘initial depth’ created by this delay acts as pre‐depositional accommodation and is a partly independent variable. It controls the geometry of the first stratal units deposited at the basin margin and thus modifies the response of the depositional system to subsequent, syndepositional changes in accommodation. In systems with a sharp break in the depositional profile, such as the topset edge in coarse‐grained deltas, the initial depth controls the foreset height and therefore the progradational distance of the topset edge. The topset length, in turn, influences topset accommodation during cyclical base level variations and therefore is reflected in the resulting stacking patterns at both long‐ and short‐term time scales. In the simplified cases modelled in this study, it is the relationship between the initial depth and the net increase in depth over the interval of a relative sea‐level cycle (ΔH) that governs long‐ and short‐term stacking patterns. In situations where the initial depth is significantly larger than ΔH, the topset accommodation of the first delta is insufficient to contain the volume of sediment of younger sequences formed during subsequent relative sea‐level cycles. Therefore, the depositional system tends to prograde over a number of relative sea‐level cycles before the topset area increases so that the long‐term stacking pattern changes to aggradation. Stacking patterns of high‐frequency sequences are influenced by a combination of topset accommodation available and position of the short‐term relative sea‐level cycles on the rising or falling limb of a long‐term sea‐level curve. This determines whether deposits of short‐term cycles are accommodated in delta topsets or foresets, or in both. Variations in stacking pattern caused by different initial depths may be misinterpreted as due to relative sea level or sediment supply changes and it is necessary to consider initial bathymetry in modelling and interpretation of stacking patterns, especially in fault‐bounded basins.     

Decoding post-orogenic sediment recycling and dispersal using detrital zircon core and rim ages

Detrital zircon (DZ) geochronology has become a popular tool in provenance studies during the past two decades. However, similar zircon crystallization ages from different source regions greatly hamper the interpretation of sediment dispersal and recycling processes. The Alleghenian–Ouachita–Marathon (AOM) foreland and vicinity in North America is a region where some dominant DZ age groups could come from both the southern Appalachians in the eastern United States and the Gondwanan terranes in Mexico. In this study, we present 1045 new DZ U–Pb ages and 81 DZ core–rim age pairs in lower Permian sandstone in the Permian Basin and Miocene sandstone in the eastern Gulf of Mexico (GOM). These new data were integrated with published DZ single U–Pb age and core–rim ages from syn- to post-orogenic strata in the Permian Basin, Marathon foldbelt, southern Appalachian foreland basin and eastern GOM to interpret the sediment-dispersal models in the AOM foreland and eastern GOM. Our models show that during the Leonardian Stage, sediments derived from the Appalachians were first delivered to the US midcontinent and then recycled to the Permian Basin; during the Miocene, sediment from the Appalachians fluxed to the eastern GOM, with no longshore mixing from the western GOM. These models based on the integration of single U–Pb and core–rim ages are consistent with published results that used other methods, including zircon single U–Pb age, zircon Hf isotopic data, zircon (U–Th)/He age, sedimentology and stratigraphy. Our results demonstrate that although some limitations exist, zircon core–rim age is a powerful tool, adding an extra constraint on the interpretation of sediment-dispersal systems. This tool is particularly applicable to the post-orogenic stage, during which the sediment pathways are more complicated because of the dominant input from distal sources. Insights gained in this study imply that this novel strategy of using core and rim ages could be integrated with other methods to better understand sediment dispersal.     

Reorganization of continent-scale sediment routing based on detrital zircon and rutile multi-proxy analysis

The duration and extent of sediment routing systems are intrinsically linked to crustal- to mantle-scale processes. Therefore, distinct changes in the geodynamic regime may be captured in the detrital record. This study attempts to reconstruct the sediment routing system of the Canning Basin (Western Australia) during the Early Cretaceous to decipher its depositional response to Mesozoic-Cenozoic supercontinent dispersal. Specifically, we reconstruct source-to-sink relationships for the Broome Sandstone (Dampier Peninsula) and proximal modern sediments through multi-proxy analysis of detrital zircon (U–Pb, Lu–Hf and trace elements) and detrital rutile (U–Pb and trace elements). Multi-proxy comparison of detrital signatures and potential sources reveals that the majority of the detrital zircon and rutile grains are ultimately sourced from crystalline basement in central Australia (Musgrave Province and Arunta region) and that proximal sediment supply (i.e., Kimberley region) is negligible. However, a significant proportion of detritus might be derived from intermediate sedimentary sources in central Australia (e.g., Amadeus Basin) rather than directly from erosion of crystalline basement. Broome Sandstone data are consistent with a large-scale drainage system with headwaters in central Australia. Contextualization with other broadly coeval drainage systems suggests that central Australia acted as a major drainage divide during the Early Cretaceous. Importantly, reorganization after supercontinent dispersal is characterized by the continuation of a sediment pathway remnant of an earlier transcontinental routing system originating in Antarctica that provided a template for Early Cretaceous drainage. Review of older Canning Basin strata implies a prolonged denudation history of central Australian lithologies. These observations are consistent with the long-lived intracontinental tectonic activity of central Australia governing punctuated sediment generation and dispersion more broadly across Australia and emphasize the impact of deep Earth processes on sediment routing systems.     

Detrital thermochronologic record of burial heating and sediment recycling in the Magallanes foreland basin,Patagonian Andes

The Patagonian Magallanes retroarc foreland basin affords an excellent case study of sediment burial recycling within a thrust belt setting. We report combined detrital zircon U–Pb geochronology and (U–Th)/He thermochronology data and thermal modelling results that confirm delivery of both rapidly cooled, first‐cycle volcanogenic sediments from the Patagonian magmatic arc and recycled sediment from deeply buried and exhumed Cretaceous foredeep strata to the Cenozoic depocentre of the Patagonian Magallanes basin. We have quantified the magnitude of Eocene heating with thermal models that simultaneously forward model detrital zircon (U–Th)/He dates for best‐fit thermal histories. Our results indicate that 54–45 Ma burial of the Maastrichtian Dorotea Formation produced 164–180 °C conditions and heating to within the zircon He partial retention zone. Such deep burial is unusual for Andean foreland basins and may have resulted from combined effects of high basal heat flow and high sediment accumulation within a rapidly subsiding foredeep that was floored by basement weakened by previous Late Jurassic rifting. In this interpretation, Cenozoic thrust‐related deformation deeply eroded the Dorotea Formation from ca. 5 km burial depths and may be responsible for the development of a basin‐wide Palaeogene unconformity. Results from the Cenozoic Río Turbio and Santa Cruz formations confirm that they contain both Cenozoic first‐cycle zircon from the Patagonian magmatic arc and highly outgassed zircon recycled from older basin strata that experienced burial histories similar to those of the Dorotea Formation.     

Importance of predecessor basin history on sedimentary fill of a retroarc foreland basin: provenance analysis of the Cretaceous Magallanes basin,Chile (50–52°S)

An integrated provenance analysis of the Upper Cretaceous Magallanes retroarc foreland basin of southern Chile (50°30′–52°S) provides new constraints on source area evolution, regional patterns of sediment dispersal and depositional age. Over 450 new single‐grain detrital‐zircon U‐Pb ages, which are integrated with sandstone petrographic and mudstone geochemical data, provide a comprehensive detrital record of the northern Magallanes foreland basin‐filling succession (>4000‐m‐thick). Prominent peaks in detrital‐zircon age distribution among the Punta Barrosa, Cerro Toro, Tres Pasos and Dorotea Formations indicate that the incorporation and exhumation of Upper Jurassic igneous rocks (ca. 147–155 Ma) into the Andean fold‐thrust belt was established in the Santonian (ca. 85 Ma) and was a significant source of detritus to the basin by the Maastrichtian (ca. 70 Ma). Sandstone compositional trends indicate an increase in volcanic and volcaniclastic grains upward through the basin fill corroborating the interpretation of an unroofing sequence. Detrital‐zircon ages indicate that the Magallanes foredeep received young arc‐derived detritus throughout its ca. 20 m.y. filling history, constraining the timing of basin‐filling phases previously based only on biostratigraphy. Additionally, spatial patterns of detrital‐zircon ages in the Tres Pasos and Dorotea Formations support interpretations that they are genetically linked depositional systems, thus demonstrating the utility of provenance indicators for evaluating stratigraphic relationships of diachronous lithostratigraphic units. This integrated provenance dataset highlights how the sedimentary fill of the Magallanes basin is unique among other retroarc foreland basins and from the well‐studied Andean foreland basins farther north, which is attributed to nature of the predecessor rift and backarc basin.     

Neotectonic basin and landscape evolution in the Eastern Cordillera of NW Argentina,Humahuaca Basin (~24°S)

The intermontane Quebrada de Humahuaca Basin (Humahuaca Basin) in the Eastern Cordillera of the southern Central Andes of NW Argentina (23°–24°S) records the evolution of a formerly contiguous foreland‐basin setting to an intermontane depositional environment during the late stages of Cenozoic Andean mountain building. This basin has been and continues to be subject to shortening and surface uplift, which has resulted in the establishment of an orographic barrier for easterly sourced moisture‐bearing winds along its eastern margin, followed by leeward aridification. We present new U–Pb zircon ages and palaeocurrent reconstructions suggesting that from at least 6 Ma until 4.2 Ma, the Humahuaca Basin was an integral part of a largely contiguous depositional system that became progressively decoupled from the foreland as deformation migrated eastward. The Humahuaca Basin experienced multiple cycles of severed hydrological conditions and subsequent re‐captured drainage, fluvial connectivity with the foreland and sediment evacuation. Depositional and structural relationships among faults, regional unconformities and deformed landforms reveal a general pattern of intrabasin deformation that appears to be associated with different cycles of alluviation and basin excavation in which deformation is focused on basin‐internal structures during or subsequent to phases of large‐scale sediment removal.     

Lateral variability in clinoform trajectory,process regime,and sediment dispersal patterns beyond the shelf‐edge rollover in exhumed basin margin‐scale clinothems

Sediment supply rate and accommodation regime represent primary controls on the depositional architecture of basin margin successions, but their interaction is commonly inferred from 2D dip profiles and/or with limited constraints on sedimentary facies. In this study, three parallel (>40 km long) 2D depositional oblique‐dip profiles from outcrops of the lower Waterford Formation (Karoo Basin, South Africa) have been correlated. This data set provides a rare opportunity to assess the lateral variability in the sedimentary process record of the shelf‐to‐slope transition for eight successive clinothems over a 900 km² area. The three profiles show similar shelf‐edge rollover trajectories, but this belies significant along‐margin variability in sedimentary processes and down‐dip sediment supply. The depositional architecture of three successive clinothems (WfC 3, 4 and 5) also show along‐shelf physiographic differences. The reconstructed shelf‐edge rollover position is not straight, and a westward curve to the north coincides with an area of greater sand supply to the slope beyond a shelf dominated by wave and storm processes. All the clinothems thicken northwards, indicating an along‐margin long‐term increase in accommodation that was maintained through multiple shoreline transits across the shelf. The origin of the differential subsidence cannot be discriminated confidently between tectonic or compaction processes. The interplay of basin margin physiography, differential subsidence rate and process regime resulted in significant across‐strike variability in the style and timing of sediment dispersal patterns beyond the shelf‐edge rollover. This study highlights the challenge for accurate prediction of the sediment partitioning across the shelf‐edge rollover in subsurface studies.     

Provenance of Oligocene lithic and quartz arenites of the East Carpathians: Understanding sediment routing systems on compressional basin margins

We present new sedimentological, petrographical, palaeontological and detrital zircon U–Pb data on late Oligocene–early Miocene sedimentary rocks of the thin-skinned thrust belt of East Carpathians. These data were acquired to reconstruct the sedimentary routing system for two compositionally different turbidite fans made of the regionally extensive Kliwa and Fusaru formations. On the eastern margin of the Moldavides foreland basin, large low-gradient river systems draining the East European Platform provided well-sorted quartz-rich sand forming deltas on wide shallow shelves and thick Kliwa submarine fans. Due to the westward subduction of a thinned continental plate, the western basin margin was characterized by short, steep-gradient routing systems where sediment transport to deep water was mainly through hyperpycnal flows. The Getic and Bucovinian nappes of the East Carpathians and the exhumed Cretaceous–Early Palaeogene orogenic wedge fed Fusaru fans with poorly sorted lithic sand. The Fusaru fans trend northwards in the foredeep basin having an elongate depocentre, interfingering and then overlapping on the distal part of the Kliwa depositional system due to the eastward advance of the Carpathian fold-and-thrust belt. A smaller sediment input is supplied by southern continental areas (i.e. Moesian Platform, North Dobrogea and potentially the Balkans). In general, the sandstone interfingering between distinct basin floor fan systems is less well documented because the facies would be similar and there are not many systems that have a distinct sediment provenance like Kliwa and Fusaru systems. This case study improves the understanding of regional palaeogeography and sedimentary routing systems and provides observations relevant here or elsewhere on the interfingering turbidite fan systems.     

Late Triassic tectonic inversion in the upper Yangtze Block: Insights from detrital zircon U–Pb geochronology from south‐western Sichuan Basin

The Sichuan Basin and the Songpan‐Ganze terrane, separated by the Longmen Shan fold‐and‐thrust belt (the eastern margin of the Tibetan Plateau), are two main Triassic depositional centres, south of the Qinling‐Dabie orogen. During the Middle–Late Triassic closure of the Paleo‐Tethys Ocean, the Sichuan Basin region, located at the western margin of the Yangtze Block, transitioned from a passive continental margin into a foreland basin. In the meantime, the Songpan‐Granze terrane evolved from a marine turbidite basin into a fold‐and‐thrust belt. To understand if and how the regional sediment routing system adjusted to these tectonic changes, we monitored sediment provenance primarily by using detrital zircon U‐Pb analyses of representative stratigraphic samples from the south‐western edge of the Sichuan Basin. Integration of the results with paleocurrent, sandstone petrology and published detrital zircon data from other parts of the basin identified a marked change in provenance. Early–Middle Triassic samples were dominated by Neoproterozoic (~700–900 Ma) zircons sourced mainly from the northern Kangdian basement, whereas Late Triassic sandstones that contain a more diverse range of zircon ages sourced from the Qinling, Longmen Shan and Songpan‐Ganze terrane. This change reflects a major drainage adjustment in response to the Late Triassic closure of the Paleo‐Tethys Ocean and significant shortening in the Longmen Shan thrust belt and the eastern Songpan‐Ganze terrane. Furthermore, by Late Triassic time, the uplifted northern Kangdian basement had subsided. Considering the eastward paleocurrent and depocenter geometry of the Upper Triassic deposits, subsidence of the northern Kangdian basement probably resulted from eastward shortening and loading of the Songpan‐Ganze terrane over the western margin of the Yangtze Block in response to the Late Triassic collision among Yangtze Block, Yidun arc and Qiangtang terrane along the Ganze‐Litang and Jinshajiang sutures.     

Stratigraphic inversion of siliciclastic basin fills: a note on the distinction between supply signals resulting from tectonic and climatic forcing

Rates of accommodation and sediment supply are the principal controls on stacking patterns in siliciclastic basin fills. Stratigraphic inversion is aimed at reconstruction of these controls from the detrital record. Efforts to ‘explain’ siliciclastic basin fills have been focused on analysis and numerical modelling of sequence geometry in response to changes in accommodation, whereas comparatively few studies have attempted to address the role of sediment supply. The compositional and textural properties of siliciclastic basin fills are linked with the evolution of drainage basins through the principle of climatic–physiographic control of sediment production and supply. Application of this principle leads to a method of compositional analysis for distinguishing sequences controlled by high-frequency changes in the rate of accommodation from sequences controlled by high-frequency variations in the rate of sediment supply (order of 10 kyr). This method does not require detailed time control. Changes in rate and type of sediment supplied to depositional systems in response to environmental perturbations in drainage basins are explored in greater detail by means of a numerical model of sediment production under various scenarios of climatic and tectonic forcing. Simulation experiments suggest that drainage basins respond differently to high-frequency tectonic and climatic perturbations. Synthetic time series of cyclically forced sediment production display different types of asymmetric variations in grain size, accumulation rate and residence time of sediments in response to tectonic and climatic forcing. The results also highlight the role of vegetation as the principal modulator of climate forcing, and show that the nonlinear response to climate change may frustrate any attempts at providing broad generalizations of the system's responses. The modelling results confirm the usefulness of a combined analysis of sediment composition and sequence geometry, and the mathematically rich behaviour of the system suggests that further development of this approach is likely to increase our ability to reconstruct forcing mechanisms and initial boundary conditions from the detrital record.     

Testing long-term patterns of basin sedimentation by detrital zircon geochronology, Centralian Superbasin, Australia

Detrital zircon geochronology of Neoproterozoic to Devonian sedimentary rocks from the Georgina and Amadeus basins has been used to track changes in provenance that reflect the development and inversion of the former Australian Superbasin. Through much of the Neoproterozoic, sediments appear to have been predominantly derived from local sources in the Arunta and Musgrave inliers. Close similarities between the detrital age signatures of late Neoproterozoic sedimentary rocks in the two basins suggests that they were contiguous at this time. A dominant population of 1.2–1.0 Ga zircon in Early Cambrian sediments of the Amadeus Basin reflects the uplift of the Musgrave Inlier during the Petermann Orogeny between 560 and 520 Ma, which shed a large volume of detritus northwards into the Amadeus Basin. Early Cambrian sedimentary rocks in the Georgina Basin have a much smaller proportion of 1.2–1.0 Ga detritus, possibly due to the formation of sub‐basins along the northern margin of the Amadeus Basin which might have acted as a barrier to sediment transfer. An influx of 0.6–0.5 Ga zircon towards the end of the Cambrian coincides with the transgression of the Larapintine Sea across central Australia, possibly as a result of intracratonic rifting. Detrital zircon age spectra of sedimentary rocks deposited within this epicontinental sea are very similar to those of coeval sedimentary rocks from the Pacific Gondwana margin, implying that sediment was transported into central Australia from the eastern continental margin. The remarkably consistent ‘Pacific Gondwana’ signature of Cambro‐Ordovician sediments in central and eastern Australia reflects a distal source, possibly from east Antarctica or the East African Orogen. The peak of the marine incursion into central Australia in the early to mid Ordovician coincides with granulite‐facies metamorphism at mid‐crustal depths between the Amadeus and Georgina basins (the Larapinta Event). The presence of the epicontinental sea, the relative lack of a local basement zircon component in Cambro‐Ordovician sedimentary rocks and their maturity suggest that metamorphism was not accompanied by mountain building, consistent with an extensional or transtensional setting for this tectonism. Sediments deposited at ～435–405 and ～365 Ma during the Alice Springs Orogeny have detrital age signatures similar to those of Cambro‐Ordovician sedimentary rocks, reflecting uplift and reworking of the older succession into narrow foreland basins adjacent to the orogen.