New insights on the relative contributions of coastal processes and tectonics to shore platform development following the Kaikōura earthquake

We describe the immediate impact of the 14 November 2016 Kaikōura magnitude 7.8 (Mw) earthquake on shore platforms and cliffs around Kaikōura Peninsula. The earthquake caused an instantaneous uplift of ~1.01 m of the peninsula. We resurveyed seven profiles previously used for erosion monitoring and observed changes in the configuration of the shoreline. The coseismic uplift has fundamentally changed the process regime operating on the platforms and altered the future trajectory of shore platform and cliff development. Our observations highlight the interplay of waves, weathering, biology and tectonics. At this location tectonism strongly modulates the process regime, driving instantaneous changes in morphology and altering rates and patterns of erosion. Finally, the uplift of the Kaikōura coast has implications for changing resilience to climate change and sea level rise. Copyright © 2017 John Wiley & Sons, Ltd.     

Decadal‐scale gravel beach evolution on a tectonically‐uplifting coast: Wellington,New Zealand

Uplift of the shoreline in tectonically‐active areas can have a profound influence on geomorphology changing the entire process dynamics of the coast as the landforms are removed from the influence of the sea. Over decadal timescales it is possible for the landforms to return to their pre‐earthquake condition and this paper examines the re‐establishment of mixed sand and gravel beaches on the coast of Wellington, New Zealand, subsequent to an uplift event in 1855. Over 60 topographic profiles were surveyed, seven sets of aerial photographs from a 67 year period were mapped and sediment size analyses conducted in order to quantify the nature of beach change following uplift, and associated relative sea level fall. These data were supported by surveys using ground penetrating radar. It is found that uplift raised the gravel beaches out of the swash zone thereby removing them from the littoral zone. Intertidal rocky reefs which occur between each embayment were also uplifted during the same event and completely interrupted the longshore transport system. Continued input of gravel material to the littoral zone allowed beaches to re‐establish sequentially along the coast as each embayment was infilled with sediment. This reconnection of the embayments with the longshore drift system is associated with the beach planform being initially drift dominated during infill but then switching to swash alignment once the embayment becomes infilled. This has resulted in shoreline accretion of over 100 m in some places, at rates of up to 4 m/yr, covering shore protection works built in the past few decades. The ability of the shore to adjust back to its pre‐uplift condition appears to be a function of the accommodation space created during uplift and the rate of sediment supply. Copyright © 2012 John Wiley & Sons, Ltd.     

Late Cenozoic uplift along the northern Dead Sea transform in Lebanon and Syria

Evidence of long-term, late Cenozoic uplift, as well as strike-slip faulting, is revealed by topographic and geological features along the northern 500 km of the Dead Sea fault system (DSFS)—the transform boundary between the Arabian and African plates in the eastern Mediterranean region. Macro-geomorphic features are studied using a new, high-resolution (20 m pixel) digital elevation model (DEM) produced by radar interferometry (InSAR). This DEM provides a spatially continuous view of topography at an unprecedented resolution along this continental transform from 32.5° to 38° N. This section of the left-lateral transform can be subdivided into a 200 km long Lebanese restraining bend (mostly in Lebanon), and the section to the north (northwest Syria). Spatial variations in Cenozoic bedrock uplift are inferred through mapping of topographic residuals from the DEM. Additionally, high altitude, low-relief surfaces are mapped and classified in the Mount Lebanon and Anti Lebanon ranges that also provide references for assessing net uplift. These results demonstrate an asymmetric distribution of post-Miocene uplift between the Mt. Lebanon and Anti Lebanon ranges. Antecedent drainages also imply that a major episode of uplift in the Palmyride fold belt post-dates the uplift of the Anti Lebanon region. North of the restraining bend, the Late Miocene surface is preserved beneath spatially extensive lava flows. Hilltop remnants of this paleosurface demonstrate Pliocene-Quaternary uplift and tilting of the Syrian Coastal Range, adjacent to the DSFS north of the restraining bend. This late Cenozoic uplift is contemporaneous with strike-slip along the DSFS. Geometrical relationships between folds and strike-slip features suggest that regional strain partitioning may accommodate a convergent component of motion between the Arabian and African plates. This interpretation is consistent with regional plate tectonic models that predict 10–25° of obliquity between the relative plate motion and the strike of the DSFS north of the restraining bend. We suggest that this convergent component of plate motion is responsible for uplift along and adjacent to the DSFS in the Syrian Coastal Range, as well as within the Lebanese restraining bend.     

The Boumerdes (Algeria) earthquake of May 21, 2003 (<Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> = 6.8): Ground deformation and intensity

A destructive earthquake of magnitude M_w = 6.8 hit the region of Boumerdes and Algiers (Algeria) on May 21, 2003. This is among the strongest seismic events of the mediterranean region and the most important event in the capital Algiers since 1716. It caused a widespread damage in the epicentral region, claimed 2271 human lives, injured 10000, about 20000 housing units affected and left about 160000 homeless. The main shock was felt about 250 km far from the epicenter and triggered sea waves of 1–3 m in amplitude in Balearic islands (Spain). Based on field observations and press report an intensity IX (MSK scale) is attributed to the epicentral area. The main shock was followed by many aftershocks among them several are of magnitude greater than 5.0, which added panic to inhabitants. The main shock triggered ground deformation, particularly liquefaction whose features are in different forms and sizes and caused damage and collapse of roads. The focal mechanism determined by worldwide institutions yield a pure reverse faulting with a compressional axis striking NE-SW. The epicenter is located offshore about 7 km from the Boumerdes-Dellys coast. Field observations show 0.7 m of coseismic uplift of shoreline between Boudouaou and Dellys. This uplift is about a half of the extracted coseismic slip from the seismic moment. On the other hand there is no clear surface break onshore, confirming hence, that the causative active fault is offshore. However, the rupture may propagate onshore to the SE near the Boudouaou region where ground cracks showing reverse faulting are observed a long a corridor of about 1 km wide. These fissures may correspond to a diffuse coseismic deformation.     

Fluvial incision and coarse gravel redistribution across the modern Dead Sea shelf as a result of base-level fall

Global eustatic lowstands can expose vast areas of continental shelves, and occasionally the shelf edge and the continental slope. The degree of fluvial connectivity to receding shores influences the redistribution of sediments across these emerging landscapes. Shelf and slope emergence in the Dead Sea since the middle of the 20th century, offers a rare opportunity to examine evolution of stream connectivity in response to continuous base-level decline. We characterize the connectivity evolution of two streams, using high-resolution time series of aerial imagery and elevation models, field mapping, and grain-size analyses. Our rich spatiotemporal dataset of evolving channel geomorphology, sediment transport conditions, and sediment redistribution, allows calculating potential coarse sediment mobility in response to base level decline. Following shelf emergence, alluvial fans first prograded onto the low-gradient shelf under unfavourable conditions for transporting coarse sediment to the regressing shoreline. Then, with shelf and slope emergence, the two adjacent streams evolved differently. The smaller, more arid watershed still maintains its highstand delta progradation on the shelf and is practically disconnected from the receding lake. The larger catchment, heading in wetter environments and having a narrower shelf, has incised the shelf and renewed and gradually intensified the sediment transport from the highstand to the lowstand delta. Sediment mobilization to lowstand shorelines is controlled by the evolution of the channel profile and by the average speed of gravel transport (10s-100s m yr^-1). These findings from the Dead Sea are relevant to fluvial processes operating on continental shelves during glacial maxima. Streams would have commonly stored high proportions of their coarse sediment on the continental shelves rather than efficiently connecting with the lowstand level. Additionally, differences in sediment routing patterns should exist among nearby streams, primarily due to continental margin geometry and watershed hydrology. © 2019 John Wiley & Sons, Ltd.     

广东大亚湾周围地区地壳和上地幔结构的初步研究

在广东大亚湾周围地区,采用地震转换波法取得了该区地壳和上地幔结构的初步研究结果。在大亚湾地区的地壳中只能分出一个中间界面(界面C)和莫霍界面(M)。本区为两层地壳,地壳厚度为28—30公里。地壳和上地幔界面埋深变化不大,深断裂不发育,本区深部构造特征与地震活动性较高的华北地区相比有较大差别。     

Evidence for P wave velocity discontinuities at depths greater than 650 km in the mantle

The arrival times of seismic P waves recorded at long lines of portable seismographs deployed on the shield region of central Australia show evidence of breaks in the travel-time curve at epicentral distances near 30, 39 and 43°. These breaks are additional to those at about 20 and 24° (associated with the 400- and 650-km discontinuities) and imply that the P wave velocity structure of the mantle does not increase smoothly in the depth range 650–1100 km, but rather consists of regions of nearly constant velocity separated by small but significant velocity increases at depths of approximately 770, 980 and 1080 km. These conclusions are in agreement with those previously inferred from first and later arrivals at the Warramunga Seismic Array.     

DEEP STRUCTURE BENEATH THE 1631 CHANGDE,HUNAN M6 EARTHQUAKE AREA DERIVED FROM MAGNETOTELLURIC SOUNDING

In 1631, an earthquake of M_S6 3/4 occurred in the Taiyangshan uplift about 10km north of Changde City, Hunan Province, which is the largest destructive temblor documented in history of South China. With the economic and social development of Changde City and the expansion of the urban, it is necessary to conduct assessment of seismic hazard, including probing the deep structure beneath the region around this historical event. To this end, three magnetotelluric(MT) profiles have been carried out across the Taiyangshan area with 76 sites in 2014. Remote reference, "robust", and phase tensor decomposition techniques were used to process the acquired MT data, and the NLCG two-dimensional inversion was made to image the deep electrical structure in combination with relevant geological and geophysical data available. The images of 3 MT profiles permit to delineate the deep extension of major faults and the deep structural features of the tectonic units in the study area. The largest fault, the Xiaowupu fault shows a steep southwest-dipping with extension of tens of kilometers from the surface to the subsurface. The Shichaipo Fault presents a low-resistivity body around a depth of about 5km. The Huanxian and Dongting Lake Basins show a low-resistivity characteristic from the ground to a depth more than 10km, good-electricity layering, meaning tectonic stability, and corresponding to extensive Cretaceous and Cenozoic strata. The electrical structure of Taiyangshan uplift overall presents a high-resistivity characteristic from the surface to a depth of about 20km, which is the widest in the central Taiyang Mountains. The deep electrical structure of 3 profiles together reveal that the contact between the Dongting Lake Basin and Taiyang Mountains is obviously segmented in NS direction. It is inferred that the Xiaowupu fault is probably the causative feature of the 1631 Changde M_S6 3/4 earthquake. The deep electrical structure nearby the epicenter appears to be complex with alternating high and low resistivity, and the epicenter is located in the high resistivity zone. The low-resistance decoupling in proximity of the fault is likely responsible for the earthquake generation. The Taiyangshan uplift resides in the southwest corner of the Jianghan-Dongtinghu Basin, where differential up and down activity during Quaternary was most intense resulting in big landform contrast, forming the tectonic setting of medium-sized earthquakes in this region.     

Modeling shoreline sand waves on the coasts of Namibia and Angola

The southwestern (SW) coast of Africa (Namibia and Angola) features long sandy beaches and a wave climate dominated by energetic swells from the Southsouthwest (SSW), therefore approaching the coast with a very high obliquity. Satellite images reveal that along that coast there are many shoreline sand waves with wavelengths ranging from 2 to 8 km. A more detailed study, including a Fourier analysis of the shoreline position, yields the wavelengths (among this range) with the highest spectral density concentration. Also, it becomes apparent that at least some of the sand waves are dynamically active rather than being controlled by the geological setting. A morphodynamic model is used to test the hypothesis that these sand waves could emerge as free morphodynamic instabilities of the coastline due to the obliquity in wave incidence. It is found that the period of the incident water waves, T_p, is crucial to establish the tendency to stability or instability, instability increasing for decreasing period, whilst there is some discrepancy in the observed periods. Model results for T_p = 7–8 s clearly show the tendency for the coast to develop free sand waves at about 4 km wavelength within a few years, which migrate to the north at rates of 0.2–0.6 km yr^?1. For larger T_p or steeper profiles, the coast is stable but sand waves originated by other mechanisms can propagate downdrift with little decay.     

中国大陆东南缘地震接收函数与地壳和上地幔结构

从2008-2011年,分别在中国大陆东南缘沿海和内陆两条NE向剖面上进行了宽频地震观测,利用记录到的远震波形资料提取得到1446个远震P波接收函数,用H-κ叠加扫描和CCP偏移叠加方法研究了中国大陆东南缘地壳及上地幔过渡带的结构及其变化特征.结合固定台网25个台站的H-κ结果,获得中国大陆东南缘(福建地区)地壳厚度从内陆到沿海逐渐减薄的图像:地壳从闽西北山区的33 km减薄到厦门沿海一带的29 km以下,平均地壳厚度为31.3 km,具有陆地向洋壳过渡的特征;地壳泊松比从内陆到沿海显示出分带特征,闽中西部内陆地区小于0.26,沿海地带高于0.26,且在断裂带的交汇区域表现为相对异常高值.地壳上地幔顶部(0~200 km)的CCP偏移叠加成像结果显示闽江断裂等NW向断裂深切Moho界面,在断裂两侧Moho面急剧抬升或下沉,产状改变,这些特征向内陆地区逐渐变得不明显.闽江等NW向断裂对研究区地壳厚度、地震等有明显控制作用.上地幔尺度(300~700 km)的CCP偏移叠加成像,未见410 km和660 km速度间断面突变和起伏异常,其绝对深度略大于IASP91模型的,上地幔转换带厚度正常(250±5 km),表明中国大陆东南缘上地幔转换带未受欧亚与菲律宾板块碰撞的明显影响,推断中国大陆东南缘及台湾海峡下方不存在俯冲板块,或俯冲前缘未扰动到410 km的深度.     

Holocene and historical earthquakes on the Boconó fault system, southern Venezuelan Andes: Trench confirmation

The Boconó fault system is a major NE-SW, right-lateral strike-slip tectonic feature whose trace extends northeastward for 500 km, from the Tachira depression at the Colombian-Venezuelan border (near the city of Cúcuta) to the town of Morón (located on the Caribbean coast of Venezuela), within the Venezuelan (or Mérida) Andes, and slightly oblique to its main axis. The Boconó fault is morphologically expressed by a continuous straight alignment of longitudinal valleys, linear depressions, pull-apart basins, fault scarps, trenches, sag-ponds, linear ridges and saddles that suggest that this major tectonic feature is active. Moreover, several destructive earthquakes (e.g., 1610, 1812, 1894, 1932 and 1950) affecting the Andean region have been usually attributed to it, without any geological confirmation. Therefore, exploratory trenching on this major fault, the only reliable means of corroborating seismotectonic associations, were carried out at two different sites: slightly north of La Grita and few kilometres north of Cordero (Fundo Mis Delirios); both villages being located between the cities of Mérida and San Cristobal, in the southern part of the Venezuelan Andes. Both trenches revealed that the Boconó fault system has been active during Holocene time. On the one hand, the La Grita trench has particularly demonstrated that: a) the 1610 and 1894 earthquakes occurred along the single trace of the Boconó fault in this region; b) the magnitude of those two earthquakes can be estimated between M = 7.1 and 7.3; c) their return period is about 300 yr; and d) the Holocene oblique-slip rate ranges between 4.3 and 6.1 mm/yr (5.2 ± 0.9 mm/yr) along this segment of the fault system. On the other hand, the Boconó fault at the Mis Delirios trench does not show any deformation associated with the 1610, 1894 or any other historical earthquakes. The complexity of the Boconó fault trace—three active strands have been mapped around the Mis Delrios trench—may account for the lack of such recent ruptures on the excavated strand. However, the occurrence of two to three previous Holocene earthquakes on this fault strand is recorded in the alluvial deposits dug at the trench site.     

Shallow Velocity Structure at the Shagan River Test Site in Kazakhstan

—?During 1997 and 1998, twelve chemical explosions were detonated in boreholes at the former Soviet nuclear test site near the Shagan River (STS) in Kazakhstan. The depths of these explosions ranged from 2.5 to 550 m, while the explosive yield varied from 2 to 25 tons. The purpose of these explosions was for closure of the unused boreholes at STS, and each explosion was recorded at local distances by a network of seismometers operated by Los Alamos National Laboratory and the Institute of Geophysics for the National Nuclear Center (NNC). Short-period, fundamental-mode Rayleigh waves (Rg) were generated by these explosions and recorded at the local stations, resultingly the waves exhibited normal dispersion between 0.2 and 3 seconds. Dispersion curves were generated for each propagation path using the Multiple Filter Analysis and Phase Match Filtering techniques. Tomographic maps of Rg group velocity were constructed and show a zone of relatively high velocities for the southwestern (SW) region of the test site and slow propagation for the northeastern (NE) region. For 0.5?sec Rg, the regions are separated by the 2.1?km/sec contour, as propagation in the SW is greater than 2.1?km/sec and less in the NE region. At 1.0 sec period, the 2.3?km/sec contour separates the two regions. Finally, for 1.5 and 2.0 sec, the separation between the two regions is less distinct as velocities in the NE section begin to approach the SW except for a low velocity region (<2.1?km/sec) near the center of the test site. Local geologic structure may explain the different regions as the SW region is composed predominantly of crystalline intrusive rocks, while the NE region consists of alluvium, tuff deposits, and Paleozoic sedimentary rocks. Low velocities are also observed along the Shagan River as it passes through the SW region of the test site for shorter period Rg (0.5–1.0?sec). Iterative, least-squares inversions of the Rg group velocity dispersion curves show shear-wave velocities for the southwestern section that are on average 0.4?km/sec higher than the NE region. At depths greater than 1.5?km the statistical difference between the models is no longer significant. The observed group velocities and different velocity structures correlate with P-wave complexity and with spatial patterns of magnitude residuals observed from nuclear explosions at STS, and may help to evaluate the mechanisms behind those observations.     

Petrography and uplift history of the Quaternary Takidani Granodiorite: could it have hosted a supercritical (HDR) geothermal reservoir?

The Quaternary Takidani Granodiorite (Japan Alps) is analogous to the type of deep-seated (3–5 km deep) intrusive-hosted fracture network system that might support (supercritical) hot dry/wet rock (HDR/HWR) energy extraction. The I-type Takidani Granodiorite comprises: porphyritic granodiorite, porphyritic granite, biotite-hornblende granodiorite, hornblende-biotite granodiorite, biotite-hornblende granite and biotite granite facies; the intrusion has a reverse chemical zonation, characterized by >70 wt% SiO₂ at its inferred margin and <67 wt% SiO₂ at the core. Fluid inclusion evidence indicates that fractured Takidani Granodiorite at one time hosted a liquid-dominated, convective hydrothermal system, with <380°C, low-salinity reservoir fluids at hydrostatic (mesothermal) pressure conditions. ‘Healed’ microfractures also trapped >600°C, hypersaline (35 wt% NaCl_eq) fluids of magmatic origin, with inferred minimum pressures of formation being 600–750 bar, which corresponds to fluid entrapment at 2.4–3.0 km depth. Al-in-hornblende geobarometry indicates that hornblende crystallization occurred at about 1.45 Ma (7.7–9.4 km depth) in the (marginal) eastern Takidani Granodiorite, but later (at 1.25 Ma) and shallower (6.5–7.0 km) near the core of the intrusion. The average rate of uplift across the Takidani Granodiorite from the time of hornblende crystallization has been 5.1–5.9 mm/yr (although uplift was about 7.5 mm/yr prior to 1.2 Ma), which is faster than average uplift rates in the Japan Alps (3 mm/yr during the last 2 million years). A temperature–depth–time window, when the Takidani Granodiorite had potential to host an HDR system, would have been when the internal temperature of the intrusive was cooling from 500°C to 400°C. Taking into account the initial (7.5 mm/yr) rate of uplift and effects of erosion, an optimal temperature–time–depth window is proposed: for 500°C at 1.54–1.57 Ma and 5.2±0.9 km (drilling) depth; and 400°C at 1.36–1.38 Ma and 3.3±0.8 km (drilling) depth, which is within the capabilities of modern drilling technologies, and similar to measured temperature–depth profiles in other active hydrothermal systems (e.g. at Kakkonda, Japan).     

Converted T Phases Recorded on Hawaii from Polynesian Nuclear Tests: A Preliminary Report

v--vWe present a preliminary study of T waves from Polynesian nuclear tests at Mururoa, recorded on digital stations of the Hawaii Volcano Observatory network, following their conversion to seismic waves at the southern shore of the Island of Hawaii, and subsequent propagation to the recording stations. We show that seismograms are composed of several packets, which can be interpreted as resulting from TMP and TMS conversions, and which feature distinct spectral characteristics. As the distance from the shoreline to the station increases, the relative importance of the several wave packets changes; a prominent shadow for TMP is found at 8-12 km from the shore. This pattern is affected by the local crustal structure; in a favorable case, propagation in deep, low-attenuation layers resulted in a clear record as far as 76 km from the shoreline. While these results are generally robust, they can be moderately affected by a change of location of the source inside Mururoa Atoll.     

Complex Archean lower crustal structure revealed by COCORP crustal reflection profiling in the Wind River Range,Wyoming

A COCORP deep crustal reflection profile across the Wind River uplift crosses exposed Archean rocks and resolves an unusual complex deep crustal structure at a depth of 24–31 km in an area where depth relations in Precambrian rocks can be inferred. The different levels of exposure across the beveled plunge of the Wind River uplift reveal supracrustal rocks at shallower levels with migmatites and pyroxene granulites at deeper levels. For the first time, deep crustal structure from reflection profiling may be interpreted in terms of exposed basement geology. A folded, multilayered deep structure shown by relfection data resembles multiply folded pyroxene granulite interlayered with granitic gneiss exposed in the central Wind River uplift; isoclinal folding is suggested in the folded layered seismic structure. Earlier seismic reflection studies suggested a simpler lower crust. These data indicate that lower crustal structure may have a complexity similar to deeply eroded Precambrian granulite-facies rocks. If this seismic feature represents folded metamorphic rocks, it seems unlikely that this Archean crust could have been thickened by underplating after 2.7 b.y. B.P. and the crust would have to be at least 30 km thich when this structure was formed.     

Thermal modeling of the Southern Alps,New Zealand

Finite-element modeling of the thermal regime across the Southern Alps of New Zealand has been carried out along two profiles situated near the Franz Josef and Haast valleys. The modeling involves viscous deformation beneath the Southern Alps, including both uplift and erosion, and crustal/lithospheric thickening, as a result of crustal shortening extending to 20 mm/y of a 25-km thick crust. Published uplift rates and crustal thickness variations along the two profiles are used to constrain the modeled advection of crustal material, and results are compared with the recent heat flow determinations, 190±50 mW/m² in the Franz Josef valley and 90±25 mW/m² in the Haast valley. Comparisons of the model with published K–Ar and fission track ages, show that the observed heat flow in the Franz Josef valley is consistent with observed zircon fission track ages of around 1 Ma, if the present-day uplift rate is close to 10 mm/y. Major thermal differences between the Franz Josef and Haast profiles appear to be due to different uplift and erosion rates. There is weak evidence that frictional heating close to the Alpine fault zone is not significant. The modeling provides explanations for the distribution of seismicity beneath the Southern Alps, and predicts a low surface heat flow over the eastern foothills due to the dominant thermal effect of crustal thickening beneath this region. Predicted temperatures at mid-crustal depth beneath the zone of maximum uplift rate are 50–100°C cooler than those indicated in previously published models, which implies that thermal weakening of the crust may not be the main factor causing the aseismicity of the central Southern Alps. The results of the modeling demonstrate that the different types of reset age data in the region within 25 km of the Alpine fault are critical for constraining models of the deformation and the thermal regime beneath the Southern Alps.     

Longshore variations in nearshore wave processes at magilligan point,northern ireland

Magilligan Point is a recurved cuspate foreland at the mouth of Lough Foyle. Two wave regimes intersect in the estuary mouth and the manner of their interplay controls shoreline changes. Ocean swell waves from the N and NE are refracted around the recurve, losing both height and energy longshore. Width of the surf zone decreases and waves tend to steepen, although both these changes and wave refraction owe something to nearshore geometry. Angle of wave approach becomes more acute and a westerly flowing longshore current moves sand S and SW along the beach. Estuary waves from the S and SW are wind-driven with high-frequencies and steepnesses. They generate a northeasterly current which returns material N, but dies out as the waves become obliterated by nearshore attenuation and breaking of swell. It is possible to identify a time-averaged null-point where shoreline wave power is balanced, although this tends to shift over short periods causing rapid morphological changes. The existence of two independent, but counteractive cells ensures the long-term maintenance of the foreland, without requiring major or continuous supplies of fresh sediment.     

Quantitative relationships between uplift and relief parameters for the Southern Alps,New Zealand,as determined by fission track analysis

The Southern Alps mountain chain, New Zealand, has formed as a consequence of late Cenozoic collision of the continental parts of the Pacific and Australia plates. Fission track analysis has yielded estimates of the amount, age of initiation, and rate of late Cenozoic rock uplift for 82 surface samples taken from transects across the Southern Alps. The mean surface, summit and valley elevations in the vicinity of each of the rock sample sites have also been measured. Regression of the geomorphic variables on the uplift variables has been used to establish quantitative relationships between uplift and geomorphology. There are strong and consistent linear associations between uplift and the elevations of the mean surface, summits and valleys. The preferred regression models have uniform slope but varying elevation response between transects. Substitution of space for time has allowed the evolution of landforms to be studied. To the east of the Main Divide, elevation and relief are proportional to, and closely related to, the age of initiation of rock uplift (‘uplift age’) and the amount of rock uplift (r² > 0·8). Mean surface uplift was delayed for ～2 Ma after the start of rock uplift, a result of the stripping of a soft cover rock succession that, prior to rock uplift, overlaid the harder greywacke basement. Inter-transect variations in regression response and x-intercept are inferred, therefore, to reflect the variable preuplift thickness of cover rocks. However, the regular regression slope for the transects reflects the consistent nature of the interaction between uplift and the erodibility of greywacke basement. Uplift of the mean surface proceeded at 0·4 km/km and 0·4 km/Ma of rock uplift, while the rock uplift rate was 0·8 km/Ma. Summit elevations have increased at a rate of 0·6 km/Ma and valley elevations have increased at 0·2 km/Ma. Regression lines relating mean surface, summit and valley elevations to rock uplift and uplift age diverge from common intercepts; it is concluded, therefore, that the mountains east of the Main Divide have continued to increase in elevation and relief and change in form over time since the start of mean surface uplift. Mountain elevation has little relationship with late Cenozoic mean rock uplift rates of 0·8–1·0 km/Ma or inferred contemporary rock uplift rates (r² ～ 0·3). In contrast, to the west of the Main Divide, elevation is shown to be closely related to rock uplift rate (r² > 0·3). In contrast, to the west of the Main Divide, elevation is shown to be closely related to rock uplift rate (r² > 0·8). Transects with higher rock uplift rates support higher topography. Landforms are therefore in a stable equilibrium with rock uplift rate, and the landscape contains no residual evidence of the total amount of rock uplift, or the age of uplift. Lithological variation appears to have no relationship with elevation.     

Early Cretaceous uplift and erosion of the northern Appalachian Basin, New York, based on apatite fission track analysis

The thermal history of outcropping Devonian sediments of the northern Appalachian Basin, New York, has been investigated using fission track analysis of detrital apatites from 57 sandstone samples. Based on lengths and apparent age measurements using fission tracks in apatite it is concluded that Lower Devonian sediments presently at the surface in the Catskill region were cooled rapidly from temperatures higher than about 110°C during Early Cretaceous times (120–140 Ma ago). In the western part of New York (Wellsville-Buffalo) data from late Devonian sediments are consistent with cooling at the same time as that identified for the Catskill region but from lower temperatures, in the range of approximately 80–110°C, the maximum temperature these sediments experienced since deposition. For a pre-uplift paleogeothermal gradient of 25–35°C/km, the confined track length data indicates uplift and erosion of 2–3 km for western New York and greater than 3–4 km for the Catskill region, a differential uplift pattern which is consistent with the historical stratigraphic data from the region. This conclusion is at variance with earlier interpretations put forth by others.Rapid broad scale uplift and erosion of the scale identified imply that large volumes of sediment could have been supplied from the northern Appalachian Basin during the Early Cretaceous. This timing for the dominant post-Devonian cooling phase in the basin is not accounted for by recent models of the tectonic evolution of the Appalachian Orogen but is compatible with the change from carbonate to siliciclastic deposition in the Atlantic coastal plain. It is suggested that this style of broad regional uplift without significant deformation is characteristic of a tectonic regime associated with, and subsequent to, continental rifting.Apatite fission track analysis is shown to be a basic tool in providing fundamental limits for thermal history assessment in regional tectonic problems.     

京津唐及邻区地壳结构的中新生代构造运动响应

以华北地块作为实施“国际地壳与上地幔模型计划（IGCP-474）”示范区,我们综合京津唐及邻区的8条宽角反射地震剖面地壳速度结构, 计算了该区域不同构造域上、中及下地壳平均速度和厚度.利用格里金插值技术构建上、中、下地壳平均速度、厚度和底界深度在空间上变化图像.这些图像指示出,京津唐及邻区发育沿近东西和北东两个方向展布的隆起与拗陷,发育受北东向断裂控制的断隆和断坳.这些地质构造的形成与该区域发生在中生代以来的构造运动密切相关,推断京津唐及邻区在中新生代至少发生三期较强烈的构造运动.结合区域构造研究成果得出,近东西向展布的隆起和拗陷形成于三叠纪,北东向展布的隆起和拗陷形成于侏罗纪,受北东向断裂控制的断隆和断坳则形成于白垩纪以来.由于中地壳为壳内低速层,与上、下地壳的变形规律截然不同,以塑性变形为主,造成中地壳在隆起部位厚度大、速度低,拗陷部位厚度小、速度高,其厚度较大的部位地壳强度整体降低,在后期构造运动中易发生断裂变形,进而控制京津唐及邻区现今地震活动.