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1.
《Gondwana Research》2011,19(4):674-687
The Bocaina Plateau, which is situated on the eastern flank of the continental rift of southeastern Brazil, is the highest part of the Serra do Mar. Topographic relief in this area is suggested to be closely related to its complex tectono-magmatic evolution since the breakup of Western Gondwana and opening of the South Atlantic Ocean. Apatite fission track ages and track length distributions from 27 basement outcrops were determined to assess these hypotheses and reconstruct the denudation history of the Bocaina Plateau. The ages range between 303 ± 32 and 46 ± 5 Ma, and are significantly younger than the stratigraphic ages. Mean track lengths vary from 13.44 ± 1.51 to 11.1 ± 1.48 μm, with standard deviations between 1.16 and 1.83 μm. Contrasting ages within a single plateau and similar ages at different altitudes indicate a complex regional tectonothermal evolution. The thermal histories inferred from these data imply three periods of accelerated cooling related to the Early Cretaceous continental breakup, Early Cretaceous alkaline magmatism, and the Paleogene evolution of the continental rift of southeastern Brazil. The oldest fission track ages (> 200 Ma) were obtained in the Serra do Mar region, suggesting that these areas were a long-lived source of sediments for the Paraná, Bauru, and Santos basins.  相似文献   

2.
Zircon (ZFT) and apatite (AFT) fission-track low-temperature thermochronology was applied at the Brazilian passive continental margin in order to understand and reconstruct the post-rift evolution since the breakup of southwestern Gondwana. The thermochronological data obtained from samples of both the Precambrian basement and the Paleogene to Neogene sedimentary rocks from the continental rift of southeastern Brazil provided ZFT ages between 148 (15) and 64 (6) Ma, and AFT ages of 81 (8)–29 (3) Ma. These data clearly indicate syn- and post-rift reactivations during the Early Cretaceous, with great emphasis on Paleogene to Neogene times. Integrating the results of older thermochronological studies, the reactivation of the southeastern Brazilian margin can be described in three main phases related to the rift to post-rift evolution of SE Brazil. In general, ZFT and AFT data yield spread values that become younger as samples are closer to the reactivated Neoproterozoic shear zones and might reflect source area exhumation. The analysis of ZFT and AFT data allowed interpretations regarding the main phases that occurred in the study area related to the thermotectonic and tectono-stratigraphic evolution in southeastern Brazil.  相似文献   

3.
Zircon fission track (ZFT), apatite fission track (AFT) and (U–Th)/He thermochronometric data are used to reconstruct the Cenozoic exhumation history of the South China continental margin. A south to north sample transect from coast to continental interior yielded ZFT ages between 116.6 ± 4.7 Ma and 87.3 ± 4.0, indicating that by the Late Cretaceous samples were at depths of 5–6 km in the upper crust. Apatite FT ages range between 60.9 ± 3.6 and 37.3 ± 2.3 Ma with mean track lengths between 13.26 ± 0.16 µm and 13.95 ± 0.19 µm whilst AHe ages are marginally younger 47.5 ± 1.9–15.3 ± 0.5 Ma. These results show the sampled rocks resided in the top 1–1.5 km of the crust for most of the Cenozoic. Thermal history modeling of the combined FT and (U–Th)/He datasets reveal a common three stage cooling history which differed systematically in timing inland away from the rifted margin. 1) Initial phase of rapid cooling that youngs to the north, 2) a period of relative (but not perfect) thermal stasis at ~ 70–60 °C which increases in duration from the south to the north; 3) final-stage cooling to surface temperatures that initiated in all samples between 15 and 10 Ma. The timing and pattern of rock uplift and erosion does not fit with conventional passive margin landscape models that require youngest exhumation ages to be concentrated at or close to the rifted margin. The history of South China margin is more complex aided by weakened crust from the active margin period that immediately preceded rifting and opening of the South China Sea. This rheological inheritance created a transition zone of steeply thinned crust that served as a flexural filter disconnecting the northern margin of the South China block and site of active rifting to the south. Consequently whilst the South China margin displays many features of a rifted continental margin its exhumation history does not conform to conventional images of a passive margin.  相似文献   

4.
We evaluated 193 K-Ar ages (10 newly determined) of basaltic and differentiated rocks of the Serra Geral (Paraná) flood-basalt province for indications of magmatism occurring systematically with progressive rifting and complete separation ( ≈130-105 Ma) of South America from Africa. The K-Ar ages represent basalt emplacement between 35° and 19°S covering about 1,200,000 km2. We note that volcanism appears ubiquitous across the province between about 140 and 115 Ma, and that there are no significant age differences within that relate directly to progressive south-to-north tectonism. On the other hand, the oldest samples, about 140–160 Ma, are among those nearest the Brazil coastline (rift margin), perhaps suggesting migration of activity away from the rift with time. Studies of other flood-basalt provinces now indicate short (<3 m.y.) eruption periods, thereby pointing to the need for re-examination of Serra Geral ages by 40Ar-39Ar incremental heating techniques.  相似文献   

5.
We report the first apatite fission-track thermochronologic data for 17 samples from the southern Catalan Coastal Ranges of NE Spain. Thermal histories of Carboniferous metasediments, Late Hercynian intrusions and Lower-Triassic Buntsandstein sediments from three tectonic blocks, Miramar, Prades and Priorat, are derived and interpreted within the geodynamic framework and tectonic evolution of the region. The apatite fission-track ages range from 198±24 to 38±5 Ma and mean fission-track lengths are all <13.3 μm. Samples throughout the study area underwent total track annealing during the Late Hercynian magmatic episode, followed by fast cooling prior to the deposition of Lower Triassic sediments. The Lower Triassic sediments and basement rocks underwent a temperature increase during a first Mesozoic rift phase in Middle Triassic–Early Jurassic times resulting in the complete or near complete annealing of the fission-tracks. During a second Mesozoic rifting stage, in Late Jurassic to Early Cretaceous time, differential tectonic block activity is observed in the three studied tectonic blocks. Subsequently, during Late Cretaceous a long-period of thermal stability, detected in all samples, is related to the post-rift episode. The onset of fast cooling registered in the apatite fission track system during Paleogene times is related to the Pyrenean orogeny. Compressional forces associated with the ongoing southern migration of the convergence forces at the Iberian plate boundaries caused unroofing of about 2–3 km of material of the Prades and northwestern flank of the Priorat block. Extensional collapse in Late Oligocene–Miocene related to the Western Mediterranean rifting triggered the denudation of about 2 km of material from the southeastern flank of the Miramar, Prades and Priorat blocks.  相似文献   

6.
宁武盆地及周缘岩体的抬升剥蚀对于山西地块中—新生代构造演化具有重要的指示意义。本文对宁武盆地及周缘岩体进行裂变径迹分析,磷灰石裂变径迹年龄97～47 Ma,锆石裂变径迹年龄161～141 Ma。裂变径迹记录了早白垩世早期(145～125 Ma)、晚白垩世(85～70 Ma)、古新世晚期—始新世早期(59～53 Ma)和渐新世晚期(28 Ma)的4次抬升剥蚀事件。综合分析山西地块的裂变径迹数据,表明隆起区晚古生代以来发生了多期抬升剥蚀事件。山西地块中—新生代构造演化具有时空差异。周缘岩体样品的裂变径迹年龄大于盆地内沉积地层样品的年龄,指示了周缘山体先于盆地抬升剥蚀。晋东北抬升剥蚀时限早于晋西南。山西裂谷系西南端裂开较早。裂谷系发育具有由南向北扩展的特征,这与地层保留记录相一致。山西地块现今地貌格局是在中生代发育一系列雁行状排列的复背斜和复向斜构造基础上发展而成的。  相似文献   

7.
The crustal structure of the Dabie orogen was reconstructed by a combined study of U–Pb ages, Hf and O isotope compositions of zircons from granitic gneiss from North Dabie, the largest lithotectonic unit in the orogen. The results were deciphered from metamorphic history to protolith origin with respect to continental subduction and exhumation. Zircon U–Pb dating provides consistent ages of 751 ± 7 Ma for protolith crystallization, and two group ages of 213 ± 4 to 245 ± 17 Ma and 126 ± 4 to 131 ± 36 Ma for regional metamorphism. Majority of zircon Hf isotope analyses displays negative εHf(t) values of − 5.1 to − 2.9 with crust Hf model ages of 1.84 to 1.99 Ga, indicating protolith origin from reworking of middle Paleoproterozoic crust. The remaining analyses exhibit positive εHf(t) values of 5.3 to 14.5 with mantle Hf model ages of 0.74 to 1.11 Ga, suggesting prompt reworking of Late Mesoproterozoic to Early Neoproterozoic juvenile crust. Zircon O isotope analyses yield δ18O values of − 3.26 to 2.79‰, indicating differential involvement of meteoric water in protolith magma by remelting of hydrothermally altered low δ18O rocks. North Dabie shares the same age of Neoproterozoic low δ18O protolith with Central Dabie experiencing the Triassic UHP metamorphism, but it was significantly reworked at Early Cretaceous in association with contemporaneous magma emplacement. The Rodinia breakup at about 750 Ma would lead to not only the reworking of juvenile crust in an active rift zone for bimodal protolith of Central Dabie, but also reworking of ancient crust in an arc-continent collision zone for the North Dabie protolith. The spatial difference in the metamorphic age (Triassic vs. Cretaceous) between the northern and southern parts of North Dabie suggests intra-crustal detachment during the continental subduction. Furthermore, the Dabie orogen would have a three-layer structure prior to the Early Cretaceous magmatism: Central Dabie in the upper, North Dabie in the middle, and the source region of Cretaceous magmas in the lower.  相似文献   

8.
Southern Africa's topography is distinctive. An inland plateau of low relief and high average elevation is separated from a coastal plane of high relief and low average elevation by a steeply dipping escarpment. The origin and evolution of this topography is poorly understood because, unlike high plateaus elsewhere, its development cannot be easily linked to present day compressional plate boundary processes. Understanding the development of this regional landscape since the break-up of Gondwana is a first order step towards resolving regional epeirogenesis. We present data that quantifies the timing and extent of exhumation across the southern Cape escarpment and coastal plane, using apatite fission track analysis (AFTA) of 25 outcrop samples and 31 samples from three deep boreholes (KW1/67, SA1/66, CR1/68). Outcrop fission track (AFT) ages are Cretaceous and are significantly younger than the stratigraphic ages of their host rocks, indicating that the samples have experienced elevated paleotemperatures. Mean track lengths vary from 11.86 to 14.23 μm. The lack of Cenozoic apatite ages suggests that major cooling was over by the end Cretaceous. The results for three boreholes, situated seaward (south) of the escarpment, indicate an episode of increased denudation in the mid-late Cretaceous (100–80 Ma). An earlier episode of increased denudation (140–120 Ma) is identified from a borehole north of the escarpment. Thermal modelling indicates a history involving 2.5–3.5 km of denudation in the mid-late Cretaceous (100–80 Ma) at a rate of 175 to 125 m/Ma. The AFT data suggest that less than 1 km of overburden has been eroded regionally since the late Cretaceous (< 80 Ma) at a rate of 10 to 15 m/Ma, but do not discount the possibility of minor (in relative amplitude) episodes of uplift and river incision through the Cenozoic. The reasons for rapid denudation in these early and mid-Cretaceous episodes are less clear, but may be related to epeirogenic uplift associated with an increase in mantle buoyancy as reflected in two punctuated episodes of alkaline intrusions (e.g. kimberlites) across southern Africa and contemporaneous formation of two large mafic igneous provinces (~ 130 and 90 Ma) flanking its continental margins. Because Cenozoic denudation rates are relatively minimal, epeirogenic uplift of southern Africa and its distinct topography cannot be primarily related to Cenozoic mantle processes, consistent with the lack of any significant igneous activity across this region during that time.  相似文献   

9.
Despite the generalized occurrence of colluvial deposits in the humid tropical areas of southeastern Brazil, regional correlation is difficult because the deposits are discontinuous, and chronological data are very scarce and scattered. For the first time, colluvial deposits in the Bocaina Plateau are described, including 18 radiocarbon ages from 12 profiles. The plateau is located on the eastern flank of the Continental Rift of Southeastern Brazil and is the highest part of the Serra do Mar, with elevations up to 2000 m above sea level. Because the Bocaina Plateau is part of the summit surfaces of southeastern Brazil, it was subjected to specific climatic conditions during the Quaternary. Colluvial deposits on the lower hillslopes and edges of amphitheatres can show complex sequences with up to three intercalated dark humic horizons, corresponding to Late Pleistocene and Holocene phases of morphodynamic activity and pedogenesis. Ages of palaeosols vary from 650±50 a BP to 36 880±980 a BP. Landforms and colluvia on the Bocaina Plateau are very similar to those found on the opposite flank of the continental rift, on the Campos do Jordão Plateau. Ages of buried soils point to similar soil formation and colluviation episodes in the two plateaus. As in Campos do Jordão, the succession of erosive, depositional and pedogenetic processes on the altos campos hillslopes is probably related to late Quaternary climate changes.  相似文献   

10.
A single zircon geochronological study of gneisses from the Obudu Plateau of southeastern Nigeria, using the evaporation technique, indicates that zircons recorded several Precambrian high-grade metamorphic events (Eburnean and Pan-African). Igneous and multifaceted metamorphic zircons yielded 207Pb/206Pb ages of 2062.4 ± 0.4 Ma, 1803.8 ± 0.4 Ma and 574 ± 10 Ma, respectively and confirm for the first time that granulite-facies metamorphism affected the basement of southeastern Nigeria, resulting in the formation of charnockites and granulitic gneisses. The Pan-African high-grade event was coeval with the formation of granulites in Cameroon, Togo and Ghana and resulted from collisional processes during continental amalgamation to form the Gondwana supercontinent. The sources of the sediments, which were deposited at ≈605 Ma and metamorphosed at 574 Ma, comprise older igneous and metamorphic protoliths (including inherited xenocrystic zircons up to 2.5 Ga in age). The Palaeoproterozoic zircons seem to have survived Pan-African melting.  相似文献   

11.
The Curitiba Basin, Paraná, lies parallel to the west side of the Serra do Mar range and is part of a continental rift near the Atlantic coast of southeastern Brazil. It bears unconsolidated and poorly consolidated sediments divided in two formations: the lower Guabirotuba Formation and the overlying Tinguis Formation, both developed over Precambrian basement. Field observations, water well drill cores, and interpretations of satellite images lead to the inference that regional tectonic processes were responsible for the origin of the Basin in the continental rift context and for morphotecatonic evolution through block tilting, dissection, and erosion. The structural framework of the sediments and the basement is characterized by NE–SW-trending normal faults (extensional tectonic D1 event) reactivated by NE–SW-trending strike–slip and reverse oblique faults (younger transtensional tectonic D2′ to transpressional tectonic D2″ event). This tectonic event, which started in the Paleogene and controlled the basin geometry, began as a halfgraben and was later reactivated as a pull-apart basin. D2 is a neotectonic event that controls the current morphostructures. The Basin is connected to the structural rearrangement of the South American platform, which underwent a generalized extensional or trantensional process and, in late Oligocene, changed to a compressional to transpressional regime.  相似文献   

12.
To constrain the post-Pan-African evolution of the Arabian–Nubian Shield, macro-scale tectonic studies, paleostress and fission track data were performed in the Eastern Desert of Egypt. The results provide insights into the processes driving late stage vertical motion and the timing of exhumation of a large shield area. Results of apatite, zircon and sphene fission track analyses from the Neoproterozoic basement indicate two major episodes of exhumation. Sphene and zircon fission track data range from 339 to 410 Ma and from 315 to 366 Ma, respectively. The data are interpreted to represent an intraplate thermotectonic episode during the Late Devonian–Early Carboniferous. At that time, the intraplate stresses responsible for deformation, uplift and erosion, were induced by the collision of Gondwana with Laurussia which started in Late Devonian times. Apatite fission track data indicate that the second cooling phase started in Oligocene and was related to extension, flank uplift and erosion along the actual margin of the Red Sea. Structural data collected from Neoproterozoic basement, Late Cretaceous and Tertiary sedimentary cover suggest two stages of rift formation. (1) Cretaceous strike-slip tectonics with sub-horizontal σ1 (ENE/WSW) and σ3 (NNW/SSE), and sub-vertical σ2 resulted in formation of small pull-apart basins. Basin axes are parallel to the trend of Pan-African structural elements which acted as stress guides. (2) During Oligocene to Miocene the stress field changed towards horizontal NE–SW extension (σ3), and sub-vertical σ1. Relations between structures, depositional ages of sediments and apatite fission track data indicate that the initiation of rift flank uplift, erosion and plate deformation occurred nearly simultaneously.  相似文献   

13.
贵州碳酸盐岩红色风化壳次生石英的裂变径迹测年研究   总被引：12，自引：1，他引：11  
贵州位于青藏高原东南缘,由于缺乏沉积记录其新生代的地质演化历史还不很明晰,而广泛分布于云贵高原的碳酸盐岩红色风化壳可能蕴涵着重要的地质演化信息.本文对贵州多个原位碳酸盐岩红色风化壳中产出的晶体形态较好的石英进行了裂变径迹方法测年.结果显示,石英的裂变径迹年龄数据呈现出较大的变化范围,从 1 Ma到 25 Ma,且远远地小于其三叠纪和寒武纪的母岩年龄;结合贵州 25 Ma到 1 Ma的区域地质演化历史,裂变径迹年龄值可以排除石英来源于母岩碎屑、成岩过程的次生形成以及火山活动产生的热水沉淀或交代形成的可能性,而只能推断为该晶体形态较好的石英于碳酸盐岩风化作用产生的富硅流体中沉淀形成;各剖面石英的年龄值与新生代的青藏高原夷平期、华南红土期、贵州构造稳定期乃至世界范围内的风化气候期有着良好的对应关系,说明次生石英裂变径迹测年具有很好的可行性和可靠性.  相似文献   

14.
Apatite fission track thermochronology reveals that uplift and erosion occurred during the mid‐Cretaceous within the Bathurst Batholith region of the eastern highlands, New South Wales. Apatite fission track ages from samples from the eastern flank of the highlands range between ca 73 and 139 Ma. The mean lengths of confined fission tracks for these samples are > 13 μm with standard deviations of the track length distributions between 1 and 2 μm. These data suggest that rocks exposed along the eastern flank of the highlands were nearly reset as the result of being subjected to palaeotemperatures in the range of approximately 100–110°C, prior to being cooled relatively quickly through to temperatures < 50°C in the mid‐Cretaceous at ca 90 Ma. In contrast, samples from the western flank of the highlands yield apparent apatite ages as old as 235 Ma and mean track lengths < 12.5 μm, with standard deviations between 1.8 and 3 μm. These old apatite ages and relatively short track lengths suggest that the rocks were exposed to maximum palaeotemperatures between approximately 80° and 100°C prior to the regional cooling episode. This cooling is interpreted to be the result of kilometre‐scale uplift and erosion of the eastern highlands in the mid‐Cretaceous, and the similarity in timing of uplift and erosion within the highlands and initial extension along the eastern Australian passive margin prior to breakup (ca 95 Ma) strongly suggests these two occurrences are related.  相似文献   

15.
A fossil partial annealing zone of fission tracks in zircon is described from high pressure–low temperature (HP–LT) rocks of the Phyllite–Quartzite Unit (PQ) on the island of Crete, Greece. Correlation of regional trends in fission track age populations with independent thermobarometric and microstructural data, and with new experimental annealing results, allows a calibration of this low temperature thermochronological method to a degree hitherto not available from other field examples.The zircon fission track (FT) ages of samples from the PQ across Crete range from original detrital signature through reduced to completely reset. The annealing is the result of a single heating period related to the HP–LT metamorphism with near-peak temperatures lasting for only a few million years some time between 24±1 and 20±1 Ma. In eastern Crete, where rocks have experienced temperatures of 300±50 °C and pressures of 0.8±0.3 GPa, zircon FT ages range from 414±24 to 145±10 Ma. Ages above 300 Ma occur mostly near the east coast of the island in rocks which have not been heated to above ca. 280 °C and probably represent a pre-Variscan source. Track lengths are already indicative of a substantial annealing at this temperature. Most of the zircon FT ages from eastern Crete scatter within error around the stratigraphic age. Samples with apparent zircon FT ages significantly younger than the depositional age are only observed in areas where temperatures exceeded ca. 320 °C. Towards the west, a sudden decrease to very young ages ranging from 17±2 to 18±1 Ma reflects a complete resetting at ca. 350 °C. Short tracks, however, are still observed. Throughout the central and western part of the island, ages are consistently below 22 Ma. Thermobarometric data for this area indicate maximum temperatures of 400±50 °C and pressures of 1±0.3 GPa. Only samples from western Crete, which have been exposed to 400±50 °C, show exclusively long tracks. Consequently, the high temperature limit of the zircon partial annealing zone (ZPAZ) appears to be between 350 and 400 °C.A significant influence of elevated confining pressure on the stability of fission tracks in zircon is ruled out by the results of annealing experiments at 0.5 GPa and at different temperatures, which fit the curves previously obtained by other authors at ambient pressure.  相似文献   

16.
Using low‐temperature thermochronology on apatite and zircon crystals, we show that the western Reguibat Shield, located in the northern part of the West African Craton, experienced significant cooling and heating events between Jurassic and present times. The obtained apatite fission track ages range between 49 and 102 Ma with mean track lengths varying between 11.6 and 13.3 μm and Dpar values between 1.69 and 3.08 μm. Zircon fission track analysis yielded two ages of 159 and 118 Ma. Apatite (U–Th)/He uncorrected single‐grain ages range between 76 and 95 Ma. Thermal inverse modelling indicates that the Reguibat Shield was exhumed during the Early Cretaceous, Late Cretaceous, Palaeocene–Eocene and Quaternary. These exhumation events were coeval with regional tectonic and geodynamic events, and were probably driven by a combined effect of plate tectonics and mantle dynamics.  相似文献   

17.
The Amapá Block, southeastern Guiana Shield, represents an Archean block involved in a large Paleoproterozoic belt, with evolution related to the Transamazonian orogenic cycle (2.26 to 1.95 Ga). High spatial resolution dating using an electron-probe microanalyzer (EPMA) was employed to obtain U–Th–Pb chemical ages in monazite of seven rock samples of the Archean basement from that tectonic block, which underwent granulite- and amphibolite-facies metamorphism. Pb–Pb zircon dating was also performed on one sample.Monazite and zircon ages demonstrate that the metamorphic overprinting of the Archean basement occurred during the Transamazonian orogenesis, and two main tectono-thermal events were recorded. The first one is revealed by monazite ages of 2096 ± 6, 2093 ± 8, 2088 ± 8, 2087 ± 3 and 2086 ± 8 Ma, and by the zircon age of 2091 ± 5 Ma, obtained in granulitic rocks. These concordant ages provided a reliable estimate of the time of the granulite-facies metamorphism in the southwest of the Amapá Block and, coupled with petro-structural data, suggest that it was contemporaneous to the development of a thrusting system associated to the collisional stage of the Transamazonian orogenesis, at about 2.10–2.08 Ga.The later event, under amphibolite-facies conditions, is recorded by monazite ages of 2056 ± 7 and 2038 ± 6 Ma, and is consistent with a post-collisional stage, marked by granite emplacement and coeval migmatization of the Archean basement along strike-slip shear zones.  相似文献   

18.
Zircon and apatite fission track ages were obtained on two granulite samples that were recovered from the sea floor in the ocean–continent transition area of the Galicia margin (North Atlantic) using the French submersible Nautile. Zircon ages indicate that the rocks cooled through about 250°C in Carboniferous to Early Permian time (307 ± 42 Ma and 287±35 Ma). Hence, the granulites do not represent the prerift lower crust but were in an upper crustal position long before rifting started. Apatites yielded Early Cretaceous ages (126 ± 6.7 Myr and 129 ± 13.4 Myr), indicating cooling through 90 ± 30°C coeval with the main rifting phase that preceded continental breakup. We assume that the granulite samples originate from a tectonic breccia cropping out near one of the sample locations. This breccia formed along a synrift detachment accommodating continental breakup and final exhumation of the Galicia margin's peridotite ridge.  相似文献   

19.
This study presents the first suite of apatite fission‐track (AFT) ages from the SE part of the Western Sudetes. AFT cooling ages from the Orlica‐?nie?nik Dome and the Upper Nysa K?odzka Graben range from Late Cretaceous (84 Ma) to Early Palaeocene–Middle Eocene (64–45 Ma). The first stage of basin evolution (~100–90 Ma) was marked by the formation of a local extensional depocentre and disruption of the Mesozoic planation surface. Subsequent far‐field convergence of European microplates resulted in Coniacian–Santonian (~89–83 Ma) thrust faulting. AFT data from both metamorphic basement and Mesozoic sedimentary cover indicate homogenous Late Cretaceous burial of the entire Western Sudetes. Thermal history modeling suggests that the onset of cooling could be constrained between 89 and 63 Ma with a climax during the Palaeocene–Middle Eocene basin inversion phase.  相似文献   

20.
The Cenozoic evolution history of Guizhou Province, which is located on the southeastern flank of the Qinghai-Tibet Plateau, is unclear because of the lack of sedimentation records. The red weathering crusts widespread on the Yunnan-Guizhou Plateau may bear critical information about their evolution history. This work firstly determined the ages of four red weathering crusts in eastern, central and northern Guizhou. The material used in fission track dating is well-crystallized quartz occurring in many in-situ weathering crusts of carbonate rocks. The results showed that the fission track ages of quartz vary over a wide range from 1 to 25 Ma in the four profiles, significantly younger than the ages of the Triassic and Cambrian parent rocks. In combination with the evolution history of the regional geology during the period from 25 to 1 Ma, the ages of quartz can exclude the possibility that the origin of quartz has nothing to do with primary clastic minerals in parent rocks, authigenesis during diagenesi  相似文献   

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