Conference Agenda

Many sedimentary basins worldwide host extensive evaporite deposits, which through salt tectonic processes can form a variety of complex salt structures and diapirs. Many of these basins also host extensive networks of igneous intrusions. It thus seems inevitable that, in some scenarios, magma intruded into a sedimentary basin will interact with salt. However, we do not know how the interaction of hot magma with salt, or the presence of crystallised intrusions within salt, may impact halokinesis and basin evolution. Here, we use 3D seismic reflection data from the Santos Basin, offshore Brazil to characterise the structure of, and relationships between, 38 igneous sills emplaced below, within, or above a Lower Cretaceous evaporite layer. Salt movement initiated soon after deposition, primarily driven by gravity-driven extension, and continued throughout most of the Cenozoic but with different kinematics and degree of salt rise and diapirism throughout the study-area. In the area hosting the sills, Late Cretaceous-Cenozoic deformation was dominated by continued extension with limited salt rise and diapirism. Conversely, in the area where no sills are recognized, Late Cretaceous-Cenozoic salt tectonics was characterized by passive/active diapirism and localized shortening. We suggest this magmatism occurred in the Turonian-to-Santonian, separating the major Albian-Cenomanian and Cenozoic periods of salt movement, locally inhibiting diapirism and thereby changing the mode of basin deformation. We attribute this local change in salt diapirism to: (i) crystallisation of igneous sills, which locally increased the mechanical strength of salt and overburden, limiting salt rise and acting as buttresses to lateral salt movement; and (ii) melting and assimilation of weak evaporite layers, which usually act to lubricate salt movement, into the magma. These results shed light into the mechanics and impacts of interaction between two common and important structural processes in sedimentary basins, are relatively well studied separately but whose interaction is often overlooked.

The evolution of passive continental margins is a consequence of continental rifting followed by continental breakup and the formation of new oceanic crust. One key question is how the lithospheric thermal field of passive margins evolves and how this would affect the rheological configuration of the lithosphere. To contribute to this discussion, we numerically modeled the thermal-rheological state for two continental margins of North and South Atlantic; SW African passive margin with the breakup age of ~130 Ma, and the Norwegian passive margin with the breakup age of ~55 Ma. Despite a very comparable crustal configuration, the lithospheric mantle differs significantly in the two areas. The lithospheric mantle beneath the oceanic crustal parts of the young North Atlantic is remarkably thinner than the older counterpart of the South Atlantic. Our results indicate that the thermal field and the lithospheric strength are influenced by the age of the adjacent ocean and the depth to the oceanic thermal lithosphere-asthenosphere boundary increasing with thermal cooling age of the newly formed oceanic lithosphere. Accordingly, the Norwegian model is significantly hotter and mechanically weaker than the SW African model in the oceanic crustal domain and the distal margin.

The Cretaceous Songliao basin in Northeast China and several strongly inverted, smaller satellite basin remnants east of it represent one of the world largest lacustrine basin system. While the burial and thermal evolution of the Songliao basin is well studied, the development of the eastern area with exhumed basement highs and basin remnants is less understood. Therefore, an integrated evaluation of the thermal history of both the basement highs and the basin remnants has been performed using low-T thermochronology and burial/thermal modelling based on vitrinite reflectance data, respectively.

We present new apatite and zircon (U-Th)/He and apatite fission track results from an area of ca. 100,000 km² covering largely the eastern part of the satellite basin system in order to elucidate the post Jurassic thermal history of the basement highs bordering the sub-basins. The low-T thermochronometers show mostly Late Cretaceous - early Paleogene apparent ages, younger than the Early Cretaceous sedimentary record in the related satellite basins. These age constraints are in harmony with the thermal modelling of vitrinite reflectance data from the basins, which indicates that the maximum burial depth occurred in mid-Cretaceous. The following major basin inversion leads to erosion from ca. 110 ca. 40 Ma. The modelling indicated that in the Jiamusi Uplift the central part experienced deeper erosion than marginal areas. Combining the above modelling results, we suggest a single united down warped basin in the continent margin that formed in the Early Cretaceous. The Late Cretaceous - Paleogene exhumation of the Jiamusi Uplift, gradually destroyed the formerly continuous, 1.6 to 4.8 km thick sedimentary cover and only basin remnants have preserved.

Calculating the arithmetic mean in particle (grain) size, a_m, with the phi scale (Folk, 1964: 81), is quite complicated. Its calculation, therefore, should be done in the numeric, or arithmetic way, where the sizes for the percentiles are directly given:

- - For the sizes, with the greatest frequencies, the values of 25; 50 and of 75 weight %, are included in the calculation.

- - 5 and 95 wt. % are suggested as the ends from the graph. With this, 90 % of the total particle-size data go into the calculation.

- - The percentiles for 5; 10; 16; 25; 40; 50; 60; 75; 84; 90 and 95 wt. % are common magitudes for further calculations. They are distributed over the graph at distances from the neighbouring values in such a way that they can be considered well covered over the curve, and we obtain:

a_m = (d₅ + d₁₀ + d₁₆ + ... + d₉₅) / n ,

where:

a_m = arithmetic mean in particle-size diameter [mm];

d₅; d₁₀; d₂₅; d₉₅ = percentiles for diameters from screened material [mm];

n = total number of data ( n = 11).

For the calculation, sizes from 0 to 5 % and from 95 to 100 % of the graphical presentation remain disregarded.

Afterward, the result from a_m can be converted into the phi value, which normally, is shown on the standard particle-size diagram, too.

Folk, R.L. (1964): A review of grain-size parameters. - Sedimentology, 6 (1966): 73 - 93; Amsterdam.

Bahuklat River is one of the most important rivers in Sistan and Balouchestan province, which passes through the Bahuklat area into the Oman Sea. In order to evaluate the displacement of the meanders and the effect of river regeneration plans on its morphology from the Shirgoaz dam to the Oman Sea, geometric characteristics of the meanders and the textural properties of the river channel sediments have been studied. The effect of human interference on river morphology during field surveys based on aerial photos and satellite imagery in a 12-year period has been investigated. The river sediments are remarkably fine grained, with poorly sorted and positive skewness. The average curvature coefficient of the Bauchalkat River in the studied area is 1.38, indicating a twisting and roughness of the river route. The highest frequency of the central angle of the meander arc is in the range of 85 to 158 degrees, which is related to the pattern of the developed meander. The curvature radius of the arches studied in the Bahukalat River varies from 100 to 810 meters. Between the radius of curvature and Meander Valley length, the experimental relation (R_C=17.4L_V^0.73) is established. The R_C/λ curve versus curvature coefficient in the Bauchalkat river shows that the R_C/λ value is minimized in a 1/3 curvature. The existing facilities along the Baqulakat River route and the margin of the river include Baqulakat diversion dam, Jor village levees, Rimdan bridge, Bahtokalat fountain, flood strap walls, levees and cultivation in the riverside, which during the change in the channel duct and the velocity of the flow of water leads Changes in the morphology of the Bauchalkat channel have been made. In order to protect the agricultural land, the villagers have built up levees in the riverside area. During flood events, due to the erodability of the soils of the area, flood deviations sometimes occur and cause damage. Following this, the morphology of the river has also been changed so that the displacement of the Meander rings occurs, and sometimes crevasse splays are formed after the broken up of the embankments. It seems that the presence of suitable vegetation and shrubs on the overbank of the Bauchalkat River has increased the marginal resistance of the river to erosion, so that the lateral erosion, followed by the migration and lateral displacement of the Meander rings, has decreased.