Chuan Dian Fragment Research Articles

Tectonic evolution of the Ailaoshan–Red River shear zone and its relationship with the growth of the southeastern Tibetan Plateau

The Ailaoshan–Red River shear zone (ARSZ), which is ∼ 1000 km long and one of the largest boundary strike-slip fault zones in the southeastern margin of the Tibetan Plateau, provides valuable insights into the growth process of the southeastern Tibetan Plateau since the India-Asia collision. During the Late Miocene to Early Pliocene, the ARSZ underwent a kinematic transition from left-lateral strike-slip to right-lateral strike-slip motion. To reveal the mechanism of this kinematic transition and its relationship with the growth process of the southeastern Tibetan Plateau during the Cenozoic, we conducted paleomagnetic and tectonic deformation analyses on both sides of the ARSZ. The results show that the formation of the S-shaped bending and kinematic transition of the ARSZ were controlled by the changes in clockwise rotation rates of the Chuandian Fragment and the Indochina Block. This suggests that since the Oligocene, the growth of the southeastern Tibetan Plateau progressively extended outward from the southern margin of the Lhasa Terrane to the southeastern margin of the Tibetan Plateau, resulting in the sequential initiation of the clockwise rotation of the Shan-Thai Block, Indochina Block, and Chuandian Fragment since the Late Oligocene, and in variations in the rotational rates of these blocks. The different rotational movement of these blocks controlled the tectonic evolution of strike-slip fault systems on the southeastern margin of the Tibetan Plateau.

Complex structural fault system and distributed deformation across the Big Bend of the Red River fault, Yunnan, China

To understand why the 130 km-long restraining bend segment (Big Bend) of the Red River fault (RRF) in Yunnan lacks historical ruptures and has a low geologic slip-rate, deep seismic profiles, relocated earthquakes and GPS-measured velocities are integrated to investigate the fault zone architecture and deformation associated with this segment. The Middle to Late Cenozoic southward extrusion of the Chuan-Dian Fragment, along with the northeastward blocking of the Yunxian Convex, have curved the RRF and its sub-parallel faults towards the southwest, forming the Big Bend. Branch faults split off the Big Bend RRF at depths between the upper lithosphere-mantle and the lower middle crust; splaying upward and sideward, they either connect/reactivate preexisting faults or become blind faults in the middle to upper crust, resulting in seismically active Lancang, Blind Wuliangshan, Qujiang and similar faults on both sides of the Big Bend. Together these faults form a complex fault system that shows a trans-crustal flower structure with a ∼ 350 km width at the surface. Across this fault system GPS-measured dextral-shearing at ∼8 mm/a and horizontal-shortening at ∼3.5 mm/a represent the deep deformation rate of the Big Bend RRF under the flower structure. 85% ± of the deep shearing and almost all of the deep shortening are partitioned onto branch and subsidiary faults bounding and within the flower structure, and only 15% ± of the deep shearing to the Big Bend RRF in the brittle crust, due to the complex fault system architecture and the existence of a large-scale asperity on the main RRF in the brittle crust. Across this fault system the deformation partitioning mode is nearly distributed. Active faulting and prehistoric surface rupture suggest that the Big Bend RRF has the capability to produce large earthquakes at recurrence intervals of millenniums, much longer than the local written earthquake history of 300–500 years.

Upper Crustal Collapse Reconstructed the Topography and Remodeled the Fault System of the Chuandian Fragment in the Southeastern Edge of the Tibetan Plateau, Evidenced by Anisotropy of Magnetic Susceptibility Data Sets

AbstractThe steps of the southeastward stepwise‐descending topography of the Chuandian Fragment (CDF) in the southeastern edge of the Tibetan Plateau coincide with N‐S and NE‐SW trending faults that changed from thrusting to normal activity, indicating that since the Middle‐Late Miocene the CDF maintained an E‐W oriented extensional tectonic environment. However, the anisotropy of magnetic susceptibility (AMS) data sets presented herein, from the Cretaceous and Cenozoic sedimentary strata of the southeastern Tibetan Plateau and its edge, show that since ∼28.0 Ma the CDF remained within a stabilized compressional stress field, oriented NEE‐SWW. A comprehensive analysis of the AMS results, topography, fault systems, and geophysical observations indicate that the northward‐advancing eastern Himalaya syntaxis impeded the southeastward‐flowing viscous lower crust and correspondingly decreased its flux, which could have reduced the thickness of the lower crustal channel beneath the CDF. The original low‐gradient topography of the CDF formed by the viscous lower crustal flow could no longer be supported by the thinned lower crustal channel, and thus gravity drove the collapse of the uplifted CDF. This process reconstructed the topography and remodeled the preexisting fault systems of the CDF, resulting in the coexistence of the E‐W oriented extensional tectonic environment and the stabilized NEE‐SWW oriented compressional stress field of the western part of the CDF, since the Middle‐Late Miocene. Thus, the change in the status of the lower crustal channel related to block interactions provided a major geodynamic setting for shaping the topography of the southeastern edge of the Tibetan Plateau.

New Paleomagnetic results from the Beiya porphyry-skarn gold–polymetallic deposit at the Western Dali faulted-block: Implications for the Cenozoic tectonic rotation of the Chuan-Dian Fragment, Southeastern Tibetan Plateau

The Chuan-Dian Fragment (CDF), in the southeastern Tibetan Plateau, is crucially important for understanding the intra–continental deformation behavior of the blocks between the stable Yangtze craton and the Indian Plate after the Indian-Asian collision. The Beiya porphyry-skarn gold–polymetallic deposit at the northwestern part of the fragment may provide an important paleomagnetic result for understanding the deformation behavior of the CDF. The paleomagnetic study of mineralized and intrusive rocks from the ~35 Ma Beiya deposit reveals a high temperature component with site–mean direction of D = 337.6°, I = 32.6°, k = 74.8, with α95 = 4.4°. Our results show that the Beiya deposit experienced 21.5° ± 3.1° of anticlockwise rotation relative to the stable part of the South China Block since ~35 Ma. The stable part of the Dali faulted-block is deduced to have experienced ~20° clockwise rotation based on a comparison of the fold-axis strike of Triassic strata between the Beiya deposit and surrounding stable area. A best-fit linear regression of the fold-axis strike direction and the tectonic rotation at each sampling site reveals that differential tectonic rotation occurred, accompanied by the horizontal deflection of strata within the CDF.

A Comprehensive Analysis on the Stress Field and Seismic Anisotropy in Eastern Tibet

AbstractWidespread rotations of maximum compressive stress in the upper crust are revealed in eastern Tibet by the focal mechanism stress inversion technique. Because of the good correlation with locations of folds, anticlines, and mountains in the region, the upper crustal stress variation is related to the lateral displacement of upper crust. To compare deformations in upper crust and upper mantle, we use SKS/SKKS splitting measurements to investigate the seismic anisotropy in eastern Tibet. The fast polarization directions subparallel to the strikes of faults in Chuandian fragment and southern boundary tectonic belt. This may indicate that the induced anisotropy mainly resulted from alignment of fault fabrics by strong shearing along strike‐slip faults, while the widespread stress rotations and systemic angular difference between upper crustal stress field and seismic anisotropy suggest that the decoupling of upper crustal deformation from middle‐lower crust by a series of detachments in the process of the crust thickening resulted from the obstruction of eastward expansion by Sichuan Basin.

Cenozoic clockwise rotation of the Chuan Dian Fragment, southeastern edge of the Tibetan Plateau: Evidence from a new paleomagnetic study

Late Eocene-early Oligocene red beds of the Ninglang Formation were sampled from 23 sites in the Yongsheng area, which comprises the northwestern part of the Chuan Dian Fragment (CDF) of the South China Block. The higher temperature components (HTC) were isolated by stepwise thermal demagnetization between ∼300–680°C and they passed the fold test. However, all the HTCs are of normal polarity, which appears to conflict with the frequent occurrence of reversed polarities during the late Eocene-early Oligocene, and therefore the possibility of remagnetization needs to be considered. Widespread secondary hematite was detected in the red beds that further indicates the remagnetization of samples. From the magmatic–metallogenic events in the sampling area, we propose an early Oligocene (∼35Ma) remagnetization event that was most likely related to porphyritic intrusions induced by fluid activity. Comparison of the pole calculated from the remagnetized remanent directions with the ∼35Ma paleomagnetic pole for Eurasia indicated that the degree of clockwise rotation in the Yongsheng area is 17.0±4.1° relative to stable Eurasia. The rotation value is consistent at the 95% confidence level with results obtained from Paleogene and Cretaceous strata in other areas of the CDF. Paleomagnetic data indicate that a consistent clockwise rotation of 20.6±6.3° occurred in different areas in the CDF: at Yongsheng, Zhupeng, Bailu, Dayao, Chuxiong west and Jianchuan. Careful analysis of the paleomagnetic data and the geometrical characteristics of the Ailao Shan–Red River shear zone indicates that the rotation process was separated into two discrete intervals: Approximately 11° of quasi-rigid clockwise rotation occurred between ∼35 and 12.7Ma compared to stable Eurasia, which may have been accompanied by strike-slip movement of the Ziyun-Luodian fault, caused by west-to-east compression induced by the northeastern indention of the Eastern Himalayan Syntaxis. Subsequently, a clockwise rotation of about 10° of the CDF with respect to stable Eurasia is inferred from the paleomagnetic results since 12.7Ma, which is consistent with the change in the geometry of the Ailao Shan–Red River shear zone around the western Chuxiong Basin. The later CW rotation was related to shearing movement of the Xianshuihe–Xiaojiang fault.

Palaeomagnetic results from Palaeogene red beds of the Chuan-Dian Fragment, southeastern margin of the Tibetan Plateau: implications for the displacement on the Xianshuihe–Xiaojiang fault systems

ABSTRACTThe mechanism of deformation associated with the Cenozoic collision of India with Asia along the eastern boundary remains a poorly understood aspect of the tectonic evolution of the southwestern South China Block (SCB). Consequently, we carried out a palaeomagnetic investigation of Palaeogene red beds of the Dayao area of Yunnan Province in order to contribute to understanding the Palaeogene evolution of the SCB. A characteristic higher temperature magnetic component (HTC), with an unblocking temperature from 660°C to 680°C, was determined by principal component analysis (PCA), and positive fold tests indicated that the remanence was a primary magnetization. The mean direction of the HTC from the Dayao area is Ds = 27.8° Is = 33.1° κ = 64.8, α95 = 4.3° after tilt correction. Compared with other palaeomagnetic results from the SCB, our data suggest that the central part of the Chuan–Dian Fragment (CDF) experienced approximately 16.3 ± 4.7° clockwise rotation with respect to East Asia. Rotation of the CDF occurred along the left-lateral Xianshuihe–Xiaojiang Fault Systems (XSF-XJF), which exhibit an arc-shaped curve centred on the Eastern Himalayan Syntaxis. The XSF-XJF was approximated by a circle centred on a Euler pole at Lat. = 26.5° N, Lon. = 97.2° E (α95 = 0.2°), based on 11 reference points selected from the fault system. The clockwise rotation of the CDF resulted in left-lateral shearing along the XSF-XJF system, with a left-lateral displacement of ~200 km. The nature of diverse intense local deformation along the Xianshuihe-Xiaojiang left-lateral strike-slip fault systems is also discussed.

Relationship between the regional tectonic activity and crustal structure in the eastern Tibetan plateau discovered by gravity anomaly

The eastern Tibetan plateau has been getting more and more attention because it combines active faults, uplifting, and large earthquakes together in a high-population region. Based on the previous researches, the most of Cenozoic tectonic activities were related to the regional structure of the local blocks within the crustal scale. Thus, a better understanding of the crustal structure of the regional tectonic blocks is an important topic for further study. In this paper, we combined the simple Bouguer gravity anomaly with the Moho depths from previous studies to investigate the crustal structure in this area. To highlight the crustal structures, the gravity anomaly caused by the Moho relief has been reduced by forward modeling calculations. A total horizontal derivative (THD) had been applied on the gravity residuals. The results indicated that the crustal gravity residual is compatible with the topography and the geological settings of the regional blocks, including the Sichuan basin, the Chuxiong basin, the Xiaojiang fault, and the Jinhe fault, as well as the Longmenshan fault zone. The THD emphasized the west margin of Yangtze block, i.e., the Longriba fault zone and the Xiaojiang fault cut through the Yangtze block. The checkboard pattern of the gravity residual in the Songpan-Garze fold belt and Chuandian fragment shows that the crust is undergoing a southward and SE-directed extrusion, which is coincident with the flowing direction indicated from the GPS measurements. By integrating the interpretations, the stepwise extensional mechanism of the eastern Tibetan plateau is supported by the southeastward crustal deformation, and the extrusion of Chuandian fragment is achieved by Xianshuihe fault.

Uplift of the Emei Shan, western Sichuan Basin: Implication for eastward propagation of the Tibetan Plateau in Early Miocene

The Emei Shan stands on the southeast side of the Longmen Shan. It marks the southeastern most edge of the eastern margin of the Tibetan Plateau (EMTP) and towers above the Sichuan Basin to its east, with the highest peak being 3099m. A large number of structural and thermo-chronological studies have been published focused on the Longmen Shan orogen, which is considered to be the northern part of the EMTP. However, for the southern part of the EMTP where the Emei Shan lies, its tectonics and uplift history are still poorly understood. This paper dates five granite samples from the Emei Shan batholith using the apatite fission track (AFT) method. The boundary faults of the Emei Shan and structural deformation in adjacent region are also investigated and mapped in detail. (1) In Miocene time, compressional stress from the eastward extrusion of the EMTP caused large-scale thrusting and mountain uplift along narrow Longmen Shan in northern EMTP, in contrast to southern EMTP where a broad and gentle Yaan−Emei Shan fold belt absorbed most of the stress. By Pliocene time, the southeastward extrusion of the Tibetan Plateau caused the transpressional stress and rotated the Chuandian fragment along the Xianshuihe−Xiaojiang fault belt. As a consequence, the Emei Shan region was intended northeastwards into the Sichuan Basin, bounded by two strike-slip faults on its north and southeast sides. (2) The AFT results show the Emei Shan uplifted since ∼25–20Ma ago. The threshold and main stage of uplift of the Emei Shan possibly lagged behind the Longmen Shan of approximately 5Myr. As the leading edge of fold belt, uplift of the Emei Shan indicated the eastward propagation of the EMTP was time-transgressive from Late Oligocene to Middle Miocene.

The Cenozoic rotational extrusion of the Chuan Dian Fragment: New paleomagnetic results from Paleogene red-beds on the southeastern edge of the Tibetan Plateau

Paleomagnetic studies were conducted on the Eocene and Oligocene strata at the western part of the Chuan Dian Fragment in order to describe the crustal deformation induced by continuous penetration of the Indian plate into Eurasia during the late Cenozoic. High-temperature magnetic components with unblocking temperatures of ~680°C were isolated, and positive fold and/or reversal tests reveal the primary nature of the magnetization. The tilt-corrected site-mean directions obtained from the Oligocene and middle-early Eocene strata are, respectively, Ds=200.9°, Is=−31.3°, k=52.8, α95=7.7° and Ds=29.7°, Is=32.0°, k=44.9, α95=5.6°. Comparison of these results with previous paleomagnetic data from the Chuan Dian Fragment shows that the western and central parts of the Chuan Dian Fragment experienced ~20° integral clockwise rotation relative to East Asia since the middle Miocene. However, the eastern part of the Chuan Dian Fragment has experienced different rotational deformation relative to East Asia since the Pliocene, because of the intense regional crustal deformation and activity on fault systems. The eastern boundary of the Chuan Dian Fragment was bounded by the Yuanmou-Luezhijiang left lateral strike-slip fault prior to the Pliocene, and then substituted by the Xiaojiang left lateral strike-slip fault since the Pliocene, due to the eastwards spreading of the clockwise rotational movement of the Chuan Dian Fragment. The evolutionary characteristics of the Ailaoshan-Red River and Xianshuihe-Xiaojiang strike-slip faults were controlled by the difference between the clockwise rotational extrusion velocities of the Chuan Dian Fragment and the Indochina Block.

Block rotation: Tectonic response of the Sichuan basin to the southeastward growth of the Tibetan Plateau along the Xianshuihe‐Xiaojiang fault

AbstractGPS field and seismic data show that the southeastern margin of the Tibetan Plateau is tectonically and seismically active. This activity is due to the southeastward extrusion of the Chuandian fragment, a large crustal block rotating clockwise around the northeastern syntaxis of the Himalayas. The eastern boundary fault of this fragment is defined by the left‐lateral Xianshuihe‐Xiaojiang fault, which abruptly truncates the Sichuan basin of the Yangtze block. Our paper presents evidence indicating that the Sichuan basin experienced right‐lateral shear along its margin, including the Longmen Shan fault belt, as shown by the presence of a large number of interference deformation features, including S‐shaped and Z‐shaped folds and faults, aligned in an en echelon pattern. This study hypothesizes that the Sichuan basin experienced counterclockwise rotation, dragged by the left‐lateral movement along the Xianshuihe fault, and it is this rotation that was the underlying cause of the 12 May 2008 Wenchuan Ms 7.9 earthquake. During the rotation, the Sichuan basin decoupled along a subhorizontal decollement fault zone that developed along Triassic gypsum‐ and coal‐bearing rocks, at a mean depth of ~5000 m, below which the Paleozoic rocks experienced much more intense deformation than the overlying Mesozoic rocks, suggesting that the lower part of the basin experienced a larger‐scale rotation relative to the uppermost part of the basin. Based on thermal data from the western margin of the Sichuan basin and from along the Xianshuihe fault, the counterclockwise bending/rotation of the Sichuan basin initiated in late Cenozoic time (~13 Ma).

Young, active conjugate strike–slip deformation in West Sichuan: evidence for the stress–strain pattern of the southeastern Tibetan Plateau

The active kinematics of the eastern Tibetan Plateau are characterized by the southeastward movement of a major tectonic unit, the Chuan-Dian crustal fragment, bounded by the left-lateral Xianshuihe–Xiaojiang fault in the northeast and the right-lateral Red River–Ailao Shan shear zone in the southwest. Our field structural and geomorphic observations define two sets of young, active strike–slip faults within the northern part of the fragment that lie within the SE Tibetan Plateau. One set trends NE–SW with right-lateral displacement and includes the Jiulong, Batang, and Derong faults. The second set trends NW–SE with left-lateral displacement and includes the Xianshuihe, Litang, Xiangcheng, Zhongdian, and Xuebo faults. Strike–slip displacements along these faults were established by the deflection and offset of streams and various lithologic units; these offsets yield an average magnitude of right- and left-lateral displacements of ∼15–35 km. Using 5.7–3.5 Ma as the time of onset of the late-stage evolution of the Xianshuihe fault and the regional stream incision within this part of the plateau as a proxy for the initiation age of conjugate strike–slip faulting, we have determined an average slip rate of ∼2.6–9.4 mm/year. These two sets of strike–slip faults intersect at an obtuse angle that ranges from 100° to 140° facing east and west; the fault sets define a conjugate strike–slip pattern that expresses internal E–W shortening in the northern part of the Chuan-Dian crustal fragment. These conjugate faults are interpreted to have experienced clockwise and counterclockwise rotations of up to 20°. The presence of this conjugate fault system demonstrates that this part of the Tibetan Plateau is undergoing not only southward movement, but also E–W shortening and N–S lengthening due to convergence between the Sichuan Basin and the eastern Himalayan syntaxis.

Paleomagnetic versus GPS determined tectonic rotation around eastern Himalayan syntaxis in East Asia

Northward indentation of the Indian Plate has brought about significant tectonic deformation into East Asia. A record of long-term tectonic deformation in this area for the past 50 M yr, particularly the vertical axis rotation, is available through paleomagnetic data. In order to depict rotational deformation in this area with respect to Eurasia, we compiled reliable paleomagnetic data sets from 79 localities distributed around eastern Himalayan syntaxis in East Asia. This record delineates that a zone affected by clockwise rotational deformation extends from the southern tip of the Chuan Dian Fragment to as far as the northwestern part of the Indochina Peninsula. A limited zone that experienced a significant amount of clockwise rotation after an initial India–Asia collision is now located at 23.5°N, 101°E, far away from an area (27.5°N, 95.5°E) where an intense rotational motion has been viewed by a snapshot of GPS measurements. This discrepancy in clockwise rotated positions is attributed to southeastward extrusion of the tectonic blocks within East Asia as a result of ongoing indentation of the Indian Plate. A quantitative comparison between the GPS and paleomagnetically determined clockwise rotation further suggests that following an initial India–Asia collision the crust at 30°N, 94°E paleoposition was subjected to southeastward displacement together with clockwise rotation, which eventually reached to present-day position of 23.5°N, 101°E, implying a crustal displacement of about 1000 km during the past 50 M yr.

Paleomagnetic study of Cretaceous rocks from Pu'er, western Yunnan, China: Evidence of internal deformation of the Indochina block

Cretaceous red sandstones and siltstones were collected at 31 sties for paleomagnetic investigation from the Jingxing and Nanxin Formation around Pu'er (23.0°N, 101.0°E), western part of Yunnan province, China, in order to examine quantitative amount of tectonic deformation of the Simao Terrane due to collision of India with Asia. After stepwise thermal demagnetization, the high-temperature component magnetization with unblocking temperature of around 680 °C is isolated. Positive field tests show that the high-temperature component magnetization from 25 sites is primary for the Cretaceous formations. A tilt-corrected mean direction is D = 59.9°, I = 45.2° with α 95 = 5.1°, corresponding to a paleopole at 35.8°N, 173.1°E with A 95 = 5.6°. Comparison with Cretaceous paleomagnetic pole of the whole China block indicates that amount of clockwise rotation in the Pu'er area is evaluated to be 46 ± 9° with respect to the whole China block, which is consistent with large amount of rotation in the Mengla and Jinggu areas (47° and 66°) in the central part of the Simao Terrane. Clockwise rotation of the central part is larger by more than 20° compared to the Yunlong and Yongping areas of northern part of the Simao Terrane, suggesting that the Simao Terrane experienced internal deformation. The southward displacement of the Pu'er area expected from inclination data is 7.5 ± 6.6° with respect to the Chuan Dian fragment, which is a similar estimate to other areas in the Simao Terrane and the Indochina block. While the Simao Terrane displaced southward by 800 km together with clockwise rotation of 30° as a whole, further clockwise rotation occurred in the central part.

Palaeomagnetic evidence for southward displacement of the Chuan Dian fragment of the Yangtze Block

SUMMARY Cretaceous red sandstones of the Feitianshan Formation and the Xiaoba Formation were sampled at 33 sites from the Dadeli and Mishi synclines of Xichang (27.9 ◦ N, 102.3 ◦ E). The study area is a part of the Chuan Dian fragment bounded by the Xianshuihe‐Xiaojiang and the Red River fault systems, which in turn constitute the southwestern part of the Yangtze Block. Almost all the samples give a characteristic palaeomagnetic direction with unblocking temperatures up to 680 ◦ C. The primary nature of magnetization is ascertained by a positive fold test with a 99 per cent confidence level for the Dadeli Syncline. The tilt corrected overall mean direction of the 33 sites is D = 3.7 ◦ , I = 41.5 ◦ (α 95 = 3.4 ◦ ), with a corresponding palaeopole at 85.2 ◦ N, 241.7 ◦ E(A95 = 3.5 ◦ ). This pole occupies the near-sided position with respect to the estimate of the Cretaceous pole of the Sichuan Basin, indicating that the Xichang area experienced a significant southward displacement. Combined with earlier reported palaeomagnetic data from the Chuan Dian fragment, a significant southward displacement of 6.7 ◦ ± 3.5 ◦ in latitude is estimated for the whole fragment with respect to the Sichuan Basin since the Late Cretaceous. Extrusion dynamics in the Asian continent due to its collision with India brought about the southward displacement of the Chuan Dian fragment. Declination data indicate that the southern part of the Chuan Dian fragment was subjected to clockwise sense rotation of up to 45 ◦ . This significantly large tectonic rotation probably occurred during extrusion of this

Paleomagnetic evidence for post-Cretaceous internal deformation of the Chuan Dian Fragment in the Yangtze block: a consequence of indentation of India into Asia

Paleomagnetic samples of Paleocene–Eocene red sandstones were collected at 36 sites from the Jiangdihe-4 and Zhaojiadian formations around the Yongren (26.1°N, 101.7°E) and Dayao areas (25.7°N, 101.3°E). These areas are located in the Chuxiong basin of the Chuan Dian Fragment, southwestern part of the Yangtze block. After stepwise thermal demagnetization, a high-temperature component with unblocking temperature of about 680 °C is isolated from 26 sites. The primary nature of this magnetization is ascertained through positive fold and reversal tests at 95% confidence level. The tilt-corrected mean paleomagnetic directions for the Yongren and Dayao areas are D=17.2°, I=26.6° with α 95=5.8° and D=16.5°, I=31.1° with α 95=4.8, respectively. Easterly deflected declinations from this study are consistent with those reported from other areas of the Chuxiong basin, indicating its wide presence in the Cretaceous–Eocene formations of the said basin. Comparison with declination values expected from the Cretaceous–Eocene APWP of Eurasia indicates that the magnitude of clockwise rotation systematically increases toward the southeast within the Chuxiong basin as well as in the Chuan Dian Fragment. This trend of the differential tectonic rotation in the Chuan Dian Fragment is consistent with curvature of the Xianshuihe–Xiojiang fault system. Deformation of the Chuxiong basin can fairly be associated with the formation of eastward bulge in the southern part of the Chuan Dian fragment. During southward displacement, the Chuan Dian Fragment was probably subjected to tectonic stresses as a result interaction with the Yangtze and Indochina blocks, which resulted into east–west extension and north–south shortening.