Table_2_Selective Recording of Tectonic Forcings in an Oligocene/Miocene Submarine Channel System: Insights From New Age Constraints and Sediment Volumes From the Austrian Northern Alpine Foreland Basin.XLSX

Detailed characterization of variations in sediment architecture, flux, and transport processes in peri-orogenic basins offers insights into external climatic or tectonic forcings. We tested how four well-known tectonic/erosional events in the Oligocene/Miocene Alpine source area are recorded in the sediment-accumulation rates (SARs) of the deep marine sink in the Northern Alpine Foreland Basin (NAFB): exhumation of the Lepontine Dome (starting at 30 Ma) and the Tauern Window (23-21 Ma), erosion of the Augenstein Formation (∼21 Ma), and the visco-elastic relaxation of the European Plate. The Upper Austrian NAFB offers a unique opportunity to investigate external forcings on sedimentary infill due to the large amount of data on the Alpine hinterland and foreland. Deep-marine sedimentation, forming the Puchkirchen Group and the basal Hall Formation, was controlled by a basin-axial submarine channel (3–5 km wide, >100 km length). Two basin-wide unconformities were recognized in seismic-reflection data: the Northern Slope Unconformity (NSU) and the Base Hall Unconformity (BHU). We combine biostratigraphic and chemostratigraphic analyses of 316 drill-cutting samples from three wells with a large 3D-seismic-reflection data set (3300 km2, >5 km depth) to determine age and duration of the unconformities and to calculate spatially averaged SARs for the submarine channel and its overbanks, separately. Deepening of the basin, recorded by the NSU, occurred between 28.1 and 26.9 Ma. The Puchkirchen Group (26.9–19.6 Ma) is characterized by constant SARs (within standard deviation) in the channel [432–623 (t/m2/Ma)] and on the overbanks [240–340 (t/m2/Ma)]. The visco-elastic relaxation of the European Plate results in low SARs on the overbanks [186 (t/m2/Ma)], a decrease in sediment grain size in channel deposits and a decrease in sea level at the BHU (19.6–19.0 Ma). In the upper Hall Formation (19.0–18.1 Ma), clinoforms prograding from the south filled up the basin [1497 (t/m2/Ma)] within 1 Myrs. We conclude that only two of the tectonic signals are recorded in this part of the deep-marine sink, erosion of Augenstein Formation and visco-elastic relaxation of the European Plate; the exhumation of the Tauern Window and Lepontine Dome remain unrecorded.

造山带周缘盆地内沉积构型、沉积物通量与搬运过程的精细表征，可为揭示外部气候或构造驱动因素提供重要研究视角。本研究针对渐新世/中新世阿尔卑斯物源区的四大典型构造/侵蚀事件，探究其在阿尔卑斯前陆盆地北部（Northern Alpine Foreland Basin，NAFB）深海沉积汇区的沉积物堆积速率（sediment-accumulation rates，SARs）记录特征：莱蓬蒂穹窿（Lepontine Dome）的剥露作用（起始于30 Ma）、陶恩窗（Tauern Window）的剥露作用（23~21 Ma）、奥根斯坦组（Augenstein Formation）的侵蚀作用（约21 Ma），以及欧洲板块的粘弹性松弛过程。上奥地利境内的阿尔卑斯前陆盆地北部拥有阿尔卑斯内陆与前陆地区的大量实测数据，为探究沉积充填的外部驱动因素提供了独特契机。形成普赫基尔群（Puchkirchen Group）与哈尔特组底部段（basal Hall Formation）的深海沉积作用，受盆轴向海底峡谷（宽3~5 km，长>100 km）控制。通过地震反射数据，本研究识别出两期全盆地范围不整合面：北坡不整合面（Northern Slope Unconformity，NSU）与哈尔特组底不整合面（Base Hall Unconformity，BHU）。本研究整合了三口钻井的316件钻井岩屑样品的生物地层与化学地层分析结果，结合覆盖面积达3300 km²、探测深度超5 km的大型三维地震反射数据集，明确了两期不整合面的形成时代与持续时长，并分别计算了海底峡谷及其堤岸的空间平均沉积物堆积速率。北坡不整合面（NSU）所记录的盆地加深事件，发生于28.1~26.9 Ma期间。普赫基尔群（26.9~19.6 Ma）的沉积物堆积速率呈现稳定特征（处于标准差范围内）：海底峡谷区为432~623 t/(m²·Ma)，堤岸区为240~340 t/(m²·Ma)。欧洲板块的粘弹性松弛作用导致堤岸区沉积物堆积速率偏低（186 t/(m²·Ma)），同时引发峡谷沉积的沉积物粒度降低，并在哈尔特组底不整合面（BHU）处造成海平面下降（19.6~19.0 Ma）。在上覆哈尔特组（19.0~18.1 Ma）中，由南部向前推进的前积斜层体在1百万年内充填了整个盆地，沉积物堆积速率达1497 t/(m²·Ma)。本研究最终得出结论：该深海沉积汇区仅记录了两大构造信号——奥根斯坦组（Augenstein Formation）的侵蚀作用与欧洲板块的粘弹性松弛；陶恩窗与莱蓬蒂穹窿的剥露作用并未留下相关记录。