北淮阳地区变质地层序列与构造变形特征

本文较详细阐述了近年来北淮阳地区在变质地层序列与构造变形特征方面研究的新进展。对梅山群的解体与新归属、原庐镇关群的解体与废名、佛子岭岩群的新含义作了简要论述。通过近年来不断深入的构造解剖，阐明了区内由早期伸展构造体制下的褶叠层；主期收缩体制下，以折劈理为标志的叠加向斜；以及晚期多期次自南而北的滑覆逆冲构造的主要特征，将为区内在新的地质背景下开展找矿工作提供了地质依据。     

库车断层相关褶皱的切角检验

库车再生前陆盆地地下构造复杂，正确的构造解释就成为了解盆地成因机理和油气圈闭的关键所在。利用断层相关褶皱几何学理论建立的构造几何模型，对库车地震剖面断层相关褶皱进行了切角检验，结果表明切角实测角度值与理论角度值一致，从而证明了在库车地区所建立的断层相关褶皱构造模型的合理性。     

Strain and vorticity analysis using small-scale faults and associated drag folds

Small-scale faults with associated drag folds in brittle-ductile rocks can retain detailed information on the kinematics and amount of deformation the host rock experienced. Measured fault orientation (α), drag angle (β) and the ratio of the thickness of deflected layers at the fault (L) and further away (T) can be compared with α, β and L/T values that are calculated with a simple analytical model. Using graphs or a numerical best-fit routine, one can then determine the kinematic vorticity number and initial fault orientation that best fits the data. The proposed method was successfully tested on both analogue experiments and numerical simulations with BASIL. Using this method, a kinematic vorticity number of one (dextral simple shear) and a minimum finite strain of 2.5–3.8 was obtained for a population of antithetic faults with associated drag folds in a case study area at Mas Rabassers de Dalt on Cap de Creus in the Variscan of the easternmost Pyrenees, Spain.     

闽西南安砂水库南岸上古生界的多期褶皱特征及其意义

闽西南安砂水库库区省道307的新路段清晰出露了上、下古生界,为研究闽西南地区中生代变形构造提供了良好条件.野外构造观测和构造复原表明上古生界发育3期褶皱:第一期呈NE向展布,两翼相对紧闭,发育特征的轴面片理;第二期呈NW向展布,相对宽缓,发育NW走向的透入性皱纹面理;第三期为近平行第一期褶皱的宽缓褶皱,尺度最大,伴有局...     

Structural analysis of the Mystery Bay area,New South Wales

The Ordovician sedimentary rocks of the southeastern Lachlan Fold Belt in the Mystery Bay area are folded into two approximately coaxial and subhorizontally plunging fold series: F₁ and F₂. Regional domains with internally consistent F₁ and F₂ trends are juxtaposed along strike‐slip faults. Locally developed kink bands commonly have a close spatial relationship with the domain boundaries.

A faulted domain boundary is exposed in coastal rocks at Mystery Bay between north‐northeasterly trending turbidites and northwesterly trending complexly deformed cherts and pelites of the Wagonga Beds. South of the boundary fault, F₁ and F₂ trends in the turbidite succession exhibit a segmented 75° counterclockwise rotation about a near‐vertical axis within a 750 m wide zone parallel with the coast, relative to regional trends preserved farther south. The rotation zone hosts prolific subvertical kink bands and crenulations. The turbidite succession youngs towards the east and hence its present position is incompatible with its projected along‐strike position on the western limb of a major anticline exposing the older Wagonga Beds.

At least three generations of faulting are recognized. Within the coastal Wagonga Beds, a set of post‐F₁ faults is subparallel to the tectonic grain and probably had vertical motion. Two systems of post‐F₂ strike‐slip faults include a conjugate system in coastal outcrops, with offsets indicative of layer‐normal shortening; and a series of northerly trending faults, with probable sinistral displacements, recognized from inland exposures.     

Thick‐skinned folding in the eastern Lachlan Fold Belt,Shoalhaven River Gorge,New South Wales

In the Shoalhaven River Gorge, in the eastern Lachlan Fold Belt, the Ordovician quartz‐turbidite succession (Adaminaby Group) is affected by one major phase of deformation with northerly trending, gently plunging, upright, close to tight folds (F₁) characterised by a range in half wavelengths up to 3 km. Several anticlinoria and synclinoria are developed and folds occur in at least four orders; these characteristics are consistent with buckling occurring at several scales and are controlled by the thickness of competent units in the multilayered succession. F₁ folding is thick‐skinned in style with the whole crust probably having been affected by deformation. D₁ occurred during the Silurian to Middle Devonian interval and was associated with crustal thickening and the shallowing of depositional environments over time. Locally, F₁ is overprinted by south‐southeast‐trending, steeply to moderately inclined F₂ that reorients F₁ to recumbent attitudes. D₂ is of Early to Middle Carboniferous age. Both deformations are related to convergence in an intra‐arc to backarc region and occurred inboard of a subduction zone, remnants of which occur in the New England Fold Belt.     

Transected folds with opposite patterns in Terena Formation (Ossa Morena Zone,Portugal): anomalous structures resulting from sedimentary basin anisotropies

The Terena Formation is located in the central part of the Ossa-Morena Zone (OMZ) and outcrops in the core of a latter (D3) first order syncline. This Formation is a Lower Devonian flysch and shows an unusual “Z” shape, with a central sector trending nearly N-S, and the tips trending NW-SE. This central sector is crossed by the cleavage (NW-SE) showing an apparent dextral (clockwise) transection pattern, anomalous and opposite to the regional widespread sinistral (anti-clockwise) transpression. The same sector with cartographic dextral transection, shows at outcrop scale, mesoscopic folds with a sinistral transection. During the Lower Devonian a N-S trending basin was developed as an effect of an early tectonic deformation phase. This trough was filled with turbidites and its elongated geometry determined the shape of the main syncline. We propose that the dextral transection pattern, at cartographic scale, result from the superposition of the NW-SE upright S3 cleavage on this major regional structure controlled by a sedimentary trough. The mesoscopic folds, observed on the upper levels of the sedimentary sequence were not influenced by the topographic anisotropy of the basin, and therefore they developed a left transection, according to the regional deformation mechanisms.

The “Z” shape of the syncline could be explained as a consequence of two major tectonic shear zones situated along the north and south boundaries of the OMZ, respectively the Tomar-Badajoz-Cordoba Shear Zone and the South Iberian Suture, lined by the Beja-Acebuches Ophiolitic Complex. Both shear zones have a sinistral transpressive character and were active during late Variscan tectonic events.     

Flow pattern within a Permian submarine slump recorded by oblique folds and deformed fossils, Ulladulla, south-eastern Australia

The flow pattern within a slump in Permian marine rocks of the southern Sydney Basin, Australia, is recorded by folds and deformed fossils. Abundant brachiopod and bryzoan fossils in the slumped rocks are relatively undeformed, but fossil crinoid stems have been deformed by relative rotation of individual ossicles. Measurement of the strain indicates that the deformation of the crinoids is consistent with flexural flow folding within the slump. Previous models assume that curved slump fold axes remain parallel to the enveloping bedding surface of a slump sheet. Detailed measurements of the orientation of slump folds in this study found fold axes to be oblique to bedding, which is interpreted as a result of folds plunging downward towards the flanks of the slump or slump lobes. In the present model, fold axes are not generally parallel to the strike of the fold axial surface, and this can explain differences between the orientations of slump fold axes and axial surfaces when these are used as directional indicators of slump movement.     

RECENT UNDERTHRUSTS OF TIANSHAN AND POSSIBLE MECHANISM OF THEIR ORIGIN

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变质岩区褶皱构造恢复的方法与实践--以新疆北山高尖地区为例

强烈变形变质地区，构造置换往往导致层理或褶皱变形面消失，从而造成大褶皱形态确定的困难性，采用微片石法、无根褶皱法，构造透镜体法，脉体褶皱法等新方法恢复大褶皱，可以取得良好效果，新疆北山高尖地区石炭系石板山组由于强烈变形变质，区域褶皱不显，为常规方法难以识别的隐性褶皱，曾认为是单斜地层，在区调填图基础上，综合运用上述方法，相互印证，成功恢复了该区一系列近东西向，长达数十千米的紧闭等斜褶皱。