Incised Valley in the Taim Swamp Area

The research data presented here allow us to describe the trajectory of river paleo-channels that corroborate the hypothesis of The Taim Swamp as being the remnant of an Incised Valley. The database consists of: a grid of 2D seismic lines acquired in the north cell of The Mirim Lagoon, a 2.5D grid of GPR (Ground Penetrating Radar) acquired over the area of the Holocene coastal barrier, and finally drill holes collected on the Holocene coastal barrier. The seismic data in SGY format has a total length of 510 km and was obtained by a subbottom profiler system (GeoAcoustics) at a frequency of 3.5 kHz, and comprising a GeoPulse 5430A transmitter, a GeoPulse5210A receiver, a 132B 4-mount transducer array, a GeoPro processor system, and a SonarWiz seismic data acquisition software. These data were acquired using a DGPS Trimble® ProXRS (datum: WGS84) and analyzed in a Geographic Information System (GIS). The three-dimensional (2.5D) high-resolution stratigraphic GPR survey was performed in the north part of The Taim swamp area, in a total length of 72,4 km. The method employed consisted of a 2.5D grid (Radan™ format), forming two united blocks. The utilized GPR system was composed of a GSSI™ (Geophysical Survey Systems, Inc.) SIR-3000 data collector for bistatic aerial antennas 80 MHz (Subecho SE-70 – Radarteam Sweden AB). According to Barboza et al. (2014a), the GPR profiles were collected using the Common Offset method. A high pass (150 MHz), low pass (20 MHz), stacking (32), and gain filters were applied during the time of data acquisition. The drill holes were made using a percussion drilling system (SPT – Standard Penetrating Test). The SPT integrates percussion and water circulation; however, this method does not preserve sedimentary structures. After penetrating 55 cm by water circulation, a percussion sampler was used to recover a cylindrical sample (45 cm length and a diameter of 3.8 cm) every 1 m of drilling penetration. The percussion enabled an evaluation of the compaction of all the sampled lithologies. The total of two drill holes were positioned using a DGPS Trimble® ProXRS (datum: WGS84) and analyzed in a Geographic Information System (GIS). For the seismic and GPR sections' interpretation is used the seismostratigraphy method (Payton, 1977) adapted for GPR (Neal, 2004). The method is based on reflections termination (onlap, downlap, toplap, and truncations), geometry, and pattern of reflections (Mitchum and Vail, 1977; Abreu et al., 2010; Barboza et al., 2014b; Neal et al., 2016).

本研究提供的科研数据可用于刻画河流古河道（river paleo-channels）的演化轨迹，佐证了塔伊姆沼泽（The Taim Swamp）为侵蚀河谷（Incised Valley）残留体的假说。本数据集包含三类核心数据：其一为米林潟湖北区块采集的二维地震测线网格；其二为全新世海岸砂坝（Holocene coastal barrier）区域采集的2.5D探地雷达（Ground Penetrating Radar, GPR）网格；其三为全新世海岸砂坝区域获取的钻孔岩芯。
格式为SGY的地震数据总长度达510 km，由GeoAcoustics公司的海底剖面仪系统采集，工作频率为3.5 kHz，配套设备包括GeoPulse 5430A发射机、GeoPulse 5210A接收机、132B型4单元换能器阵列、GeoPro处理系统及SonarWiz地震数据采集软件。本次数据采集采用Trimble® ProXRS差分全球定位系统（DGPS），基准面为WGS84，并通过地理信息系统（Geographic Information System, GIS）完成全流程数据分析。
本次三维（2.5D）高分辨率层序探地雷达测量覆盖塔伊姆沼泽北部区域，总测线长度为72.4 km。数据采集采用2.5D网格形式（Radan™格式），划分为两个拼接区块。所用探地雷达系统搭载GSSI™（Geophysical Survey Systems, Inc.）SIR-3000数据采集器，搭配80 MHz双站机载天线，型号为Subecho SE-70——产自瑞典Radarteam Sweden AB公司。根据Barboza等人（2014a）的研究，本次探地雷达剖面采用共偏移距法（Common Offset method）采集，并在数据采集阶段应用了高通滤波（截止频率150 MHz）、低通滤波（截止频率20 MHz）、32次叠加及增益滤波等预处理流程。
钻孔作业采用冲击钻探系统，即标准贯入试验（Standard Penetration Test, SPT）。该方法结合了冲击作业与水循环作业，但无法保留沉积物的原生沉积构造。在通过水循环钻进55 cm后，每钻进1 m便使用冲击取样器获取圆柱形岩芯样品（长度45 cm，直径3.8 cm）。通过冲击作业可评估所有取样岩性的压实程度。本次共完成2个钻孔，定位采用Trimble® ProXRS差分全球定位系统（DGPS），基准面为WGS84，并通过地理信息系统完成数据分析。
针对地震与探地雷达剖面的解释，采用了适配探地雷达的地震地层学方法（seismostratigraphy method，Payton, 1977; Neal, 2004）。该方法基于反射终止类型（上超、下超、顶超及削蚀）、反射几何形态与反射特征开展分析（Mitchum与Vail, 1977; Abreu et al., 2010; Barboza et al., 2014b; Neal et al., 2016）。