The Geological Society of Korea
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Journal of the Geological Society of Korea - Vol. 55 , No. 3 (Jun 2019)

[ Article ]
Journal of the Geological Society of Korea - Vol. 54, No. 6, pp.615-630
Abbreviation: J. Geol. Soc. Korea
ISSN: 0435-4036 (Print) 2288-7377 (Online)
Print publication date 31 Dec 2018
Received 31 Oct 2018 Revised 11 Dec 2018 Accepted 12 Dec 2018
DOI: https://doi.org/10.14770/jgsk.2018.54.6.615

MATLAB 기반의 프로그램 BasinVis 2.0을 이용한 분지 모델링 : 오스트리아 비엔나 분지의 남부 지역에 대한 사례 연구
이은영1, ; Michael, Wagreich2
1전남대학교 지구환경과학부
2Department of Geodynamics and Sedimentology, University of Vienna

Basin modelling with a MATLAB-based program, BasinVis 2.0: A case study on the southern Vienna Basin, Austria
Eun Young Lee1, ; Michael, Wagreich2
1Faculty of Earth System and Environmental Sciences, Chonnam National University, Gwangju 61186, Republic of Korea
2Department of Geodynamics and Sedimentology, University of Vienna
Correspondence to : +82-62-530-3450, E-mail: eun.y.lee@chonnam.ac.kr

Funding Information ▼

초록

분지 해석은 퇴적분지의 형성과 진화를 이해하기 위한 연구 분야로서 여러 종류의 지구과학 자료들을 종합적으로 분석해야 하며, 분지의 시공간적 발달을 입체적으로 구현하기 위해서는 모델링 기술이 적용된다. 분지해석과 모델링 연구를 위해 2016년 MATLAB 기반의 프로그램 BasinVis 1.0이 공개되었으며 최근에는 새로운 기능과 수정된 사용자 인터페이스를 포함한 BasinVis 2.0이 개발되었다. 이 연구에서는 BasinVis 2.0을 이용한 분지 모델링을 소개하기 위해 비엔나 분지의 남부에서 사례 연구를 수행하였다. 이 연구는 BasinVis 1.0을 이용한 비엔나 분지 중북부의 모델링 연구와 함께 앞으로 수행될 비엔나 분지 전지역의 모델링을 위한 예비 연구로서, 연구 지역의 마이오세 퇴적층과 침강 발달을 시공간적으로 구현하였다. 마이오세 초기의 후반 동안 퇴적과 침강은 북동-남서 방향의 주향이동 단층과 안행성 점완 정단층들을 따라 빠르게 나타난다. 하지만 마이오세 중기부터 후기까지 침강은 급격히 감소한다. 이는 인리형 시스템의 발달에 연관하며, 주향이동 분지의 단기간의 빠른 지구조 침강 패턴과 일치한다. 마이오세 중기의 침강은 주로 주향이동 단층을 따라서 나타나는 반면, 마이오세 중기 후반부터는 북-남 방향의 점완 정단층을 따라 저지대로 퇴적 중심지가 이동되었다. 이는 광역적 고응력장이 북동-남서 방향의 횡인장에서 동-서 방향의 인장으로 변화하는 것과 일치한다. 이 연구에서는 다양한 기능과 기법들이 사례 연구에 적용되었으며, 모델링 결과는 BasinVis 2.0이 분지 모델링 연구에 효과적으로 적용 가능함을 보여준다.

Abstract

Basin analysis is a research field to understand the formation and evolution of sedimentary basins. This task requires various geoscientific datasets as well as numerical and graphical modelling techniques to synthesize results dimensionally in time and space. For basin analysis and modelling in a comprehensive workflow, BasinVis 1.0 was released as a MATLAB-based program in 2016, and recently the software has been extended to BasinVis 2.0, with new functions and revised user-interface. As a case study, this work analyses the southern Vienna Basin and visualizes the sedimentation setting and subsidence evolution to introduce the basin modelling functions of BasinVis 2.0. This is a preliminary study for a basin-scale modelling of the Vienna Basin, together with our previous studies using BasinVis 1.0. In the study area, during the late Early Miocene, sedimentation and subsidence are significant along strike-slip and en-echelon listric normal faults. From the Middle Miocene onwards, however, subsidence decreases abruptly over the area and this situation continues until the Late Miocene. This is related to the development of the pull-apart system and corresponds to the episodic tectonic subsidence in strike-slip basins. The subsidence of the Middle Miocene is confined mainly to areas along the strike-slip faults, while, from the late Middle Miocene, the depocenter shifts to a depression along the N-S trending listric normal faults. This corresponds to the regional paleostress regime transitioning from NE-SW trending transtension to E-W trending extension. This study applies various functions and techniques to this case study, and the modelled results demonstrate that BasinVis 2.0 is effective and applicable to the basin modelling.


Keywords: BasinVis 2.0, basin analysis, basin modelling, subsidence, Vienna Basin
키워드: BasinVis 2.0, 분지 해석, 분지 모델링, 침강, 비엔나 분지

1. Introduction

Sedimentary basins are regions formed due to tectonically induced and prolonged subsidence of the Earth’s surface in which sediments accumulate and be preserved for relatively long geological time periods (Einsele, 2000; Miall, 2000; Leeder, 2011; Allen and Allen, 2013). The internal framework of basins results mainly from the interplay between the volume and rate of sediment supply and the rate of generation and spatial distribution of accommodation. The sediment supply depends on the erosion rate and the provenance type and catchment size, and the generation of accommodation is controlled by tectonic subsidence and uplift, global and regional sea-level change, and compaction. To understand the formation and structure of a basin, therefore, all factors influencing on basin evolution should be considered (Lee et al., 2019). Basin modelling is a method to integrate these factors and visualize the basin formation and evolution dimensionally in time and space by applying numerical and graphical techniques. It is of multidisciplinary nature and often used for hydrocarbon potential and groundwater evaluation.

To allow geoscientists to analyze and visualize basins in a comprehensive workflow within a nonproprietary software environment, BasinVis 1.0 was developed and released as a MATLAB®-based modular open-source tool (Lee et al., 2016). BasinVis 1.0 was particularly aimed at quantitative analyses and 2D and 3D visualization of stratigraphic setting and subsidence of basins based on well data and/or stratigraphic profiles. Recently, the program was extended to improve its user-interfaces and add new functions. The upgraded program is designated as Version 2.0. The new functions of BasinVis 2.0 include the estimation of compaction trends and the applications of the refined decompaction techniques, which are examined using porosity and stratigraphic data acquired from Sites U1459 and U1460 of the International Ocean Discovery Program (IODP). To demonstrate the improved applications of BasinVis 2.0 in basin modelling, this study introduces a case study on the southern part of the Vienna Basin, Austria.

The Vienna Basin is one of the most extensively studied basins by virtue of fundamental geologic research and hydrocarbon exploration over the past 150 years. The Neogene sedimentary succession is documented by numerous boreholes and a dense network of 2D and 3D seismic data, and various aspects of the structural and sedimentary setting of the basin have been analyzed in many publications (e.g., Jiříček and Seifert, 1990; Sauer et al., 1992; Wessely et al., 1993; Kováč et al., 2004; Hinsch et al., 2005; Arzmüller et al., 2006; Strauss et al., 2006; Beidinger and Decker, 2011; Lee and Wagreich, 2016, 2017). The Vienna Basin is located between the Eastern Alps and the Western Carpathians, covering parts of Austria, Slovakia and the Czech Republic in central Europe. However, the basin studies focused mainly on the southern and central parts (Austrian part) of the basin. Recently, in the central and northern parts of the Vienna Basin, crossing the borders of the three countries, a comprehensive study including basin modelling was conducted by Lee and Wagreich (2016, 2017) using BasinVis 1.0. The previously modelled area does not overlap with the area of this study which covers the southern part of the basin. Together with the previous study, this is a preliminary study to prepare for basin-scale evolution modelling of the Vienna Basin.


2. Geologic setting

The Vienna Basin is a Neogene sedimentary basin of about 200 km in length and 55 km in width (Fig. 1), which is subdivided geographically into three parts. The northern part covers the area north of the Kuty graben, and the central part extends from the Kuty graben to the Schwechat depression, including the Zistersdorf depression. The southern part covers the area of the Schwechat and the Mitterndorf depressions (Lankreijer et al., 1995; Lee and Wagreich, 2017). The Vienna Basin is bordered by the Eastern Alps to the west, the Western Carpathians to the northeast and the Pannonian Basin system to the southeast (Fig. 1a). Due to its position, the Vienna Basin has been influenced by the evolution of each of these geologic systems. The Eastern Alps and the Western Carpathians formed by Alpine-type collisional orogeny during the Mesozoic and the Cenozoic (Royden, 1988; Decker and Peresson, 1996; Plašienka et al., 1997). The late Paleogene and Neogene lateral extrusion of the Eastern Alps towards the Pannonian area in the east caused complex and polyphase strike-slip faulting and back-arc-extension linked to the retreating subduction zone (Ratschbacher et al., 1991a, 1991b). This extrusion further resulted in development of Miocene pull-apart basins (e.g., Vienna Basin) and lithospheric extensional rift basins (e.g., Pannonian Basin) (Mann et al., 1983; Royden et al., 1983a, 1983b; Royden, 1985, 1988; Csontos et al., 1992; Horváth, 1993; Decker and Peresson, 1996; Huismans et al., 2001; Hölzel et al., 2010).


Fig. 1. 
a) Tectonic sketch map of the east Alpine-west Carpathian region, and the structure map of the Vienna Basin showing the faulted pre-Neogene basement surface and location of cross-section A. AT: Austria, SK: Slovakia, CZ: Czech Republic, VBTF: Vienna Basin transfer fault system, KG: Kuty graben, ZD: Zistersdorf depression, GD: Gajary depression, SD: Schwechat depression, MD: Mitterndorf depression (revised from Wessely et al., 1993; Arzmüller et al., 2006; Lee and Wagreich, 2016). b) Depth map of the pre-Neogene basement (base of Neogene fill) from Lee and Wagreich (2016). Location of well Zavod 76 is shown. c) Study area and depth map of the pre-Neogene basement, the latter being a result of this study. Locations of wells (black dots) are shown. d) Geologic cross-section through the Vienna Basin and the adjacent Alpine Foreland Basin (revised from Beidinger and Decker, 2014).

The Vienna Basin is characterized by four distinct tectonic phases (Fig. 2a); 1) Early Miocene piggyback basin, 2) Middle - Late Miocene pull-apart basin, 3) Late Miocene - Pliocene compression and basin inversion, and 4) Quaternary basin formation (Peresson and Decker, 1997a, 1997b; Decker et al., 2005; Strauss et al., 2006; Beidinger and Decker, 2011; Salcher et al., 2012; Lee and Wagreich, 2017).


Fig. 2. 
a) Stratigraphy and evolution of the Vienna Basin in the Miocene (Sauer et al., 1992; Fodor, 1995; Decker, 1996; Peresson and Decker, 1997a; Piller et al., 2007; Hölzel et al., 2010; Hohenegger et al., 2014; Lee and Wagreich, 2016, 2017; Harzhauzer et al., 2018, in press). Horizons mapped in this study area; top of the pre-Neogene basement, top of the Karpatian, top of the early Badenian, top of the late Badenian, top of the Sarmatian, top of the early Pannonian, top of the middle Pannonian, and top of the late Pannonian. b) Paleogeographic and facies models of the Vienna Basin (revised from Sauer et al., 1992); Karpatian, middle Badenian, early Pannonian. Numbers are indicating the paleobathymetry.

1) In the Early Miocene, several E-W trending small sub-basins (piggyback basins; Ori and Friend, 1984) formed on the frontal parts of the N- to NW-propagating thrust belt of the Eastern Alps. The sediments spread mainly in the northern and central parts of the Vienna Basin (Jiříček and Seifert, 1990; Decker, 1996; Kováč et al., 2004; Strauss et al., 2006; Hölzel et al., 2010).
2) At the end of the Early Miocene, the Vienna Basin became a pull-apart structure due to the lateral extrusion of the Eastern Alps (Fodor, 1995; Decker, 1996). The main tectonic elements are NE-SW trending sinistral strike-slip duplexes and en-echelon listric normal faults (e.g., Steinberg fault, Leopoldsdorf fault, Lassee fault system) with a left-stepping geometry (Royden, 1985, 1988; Decker et al., 2005). Growth strata along normal faults indicate synsedimentary faulting during the Middle Miocene (Decker, 1996; Wagreich and Schmid, 2002; Arzmüller et al., 2006; Strauss et al., 2006).
3) In the latest Miocene, the regional stress field switched from N(NW)-directed to E-W-directed compression (Decker and Peresson, 1996; Peresson and Decker, 1997a, 1997b). This phase is characterized by the gradual structural inversion with an uplift of more than 200 m in the Vienna Basin, which caused sediment deformation and erosion (Decker, 1996; Strauss et al., 2006).
4) Since c. 250 - 300 ka, the Vienna Basin has been reactivated by NE-SW extension at a releasing bend which is along the slow moving sinistral strike-slip faults and corresponding to the Vienna Basin transfer fault system (VBTF) (Decker et al., 2005; Beidinger and Decker, 2011; Salcher et al., 2012). The small Quaternary basins are developed and filled mainly by fluvial sediments unconformably overlying Miocene sediments (Decker et al., 2005; Hinsch et al., 2005; Salcher et al., 2012).

During the Early Miocene, according to Sauer et al. (1992) and Kováč et al. (2004), the sediment succession in the north was deposited in a fully marine environment, while the central part of the basin was characterized by deposition of huge freshwater to brackish lacustrine-deltaic formations supplying sediments from the Alps. The southern basin part was fully continental during this time (Fig. 2b). From the Middle Miocene to the Late Miocene, a broad paleo-Danube delta complex on the western flank of the Vienna Basin carried a massive sediment load from the Alpine Foreland Basin into the Vienna Basin. Small deltaic systems that entered from the southern and northern corners of the basin deposited sediments from areas of the Eastern Alps and the Western Carpathians into the basin (Sauer et al., 1992) (Fig. 2b).


3. Data and Methods
3.1 Data

The study area covers an area of 37 x 37 km2 in the southern part of the Vienna Basin including the Schwechat depression (Fig. 1c). The sedimentary fill was analyzed using the sediment thickness and stratigraphic data of 38 wells collected from Hölzel (2009) which were provided by OMV E&O Austria. The base depths of the Neogene fill (the depths of the pre-Neogene basement) in the wells were supplemented by using data from the published maps of the Vienna Basin (e.g., Wessely et al., 1993). Because the Alps-Carpathians-Pannonian system was influenced by the Central Paratethys from Oligocene to Miocene times, which was a partly enclosed sea to the north of the Alpine mountain belt, this study uses the regional Central Paratethys chronostratigraphy and regional and local zonations for the Vienna Basin (Piller et al., 2007; Hohenegger et al., 2014; Harzhauser et al., 2018, in press). The well data were arranged for seven successive time steps (Fig. 2a); a) Karpatian (c. 17.2 - 15.97 Ma), b) early Badenian (c. 15.97 - 13.82 Ma), c) late Badenian (c. 13.82 - 12.83 Ma), d) Sarmatian (c. 12.83 - 11.62 Ma), e) early Pannonian (c. 11.62 - 10.5 Ma), f) middle Pannonian (c. 10.5 - 9.8 Ma), g) late Pannonian (c. 9.8 - 7.8 Ma). In the studied well data, the boundary between the late Karpatian and the underlying piggyback sediments is unclear. However, because the study area has thin deposition of lower Karpatian and only sparse deposition during Ottnangian - Eggenburgian time (Jiříček and Seifert, 1990; Sauer et al., 1992; Hölzel et al., 2010), the lowermost unit is defined as Karpatian in this study.

3.2 Subsidence analysis

This study provides two subsidence analysis models which are total subsidence as well as tectonic subsidence (Fig. 3a). In a basin evolution study, the total subsidence represents total depth (depth of basement or total thickness of accumulated sediments) of a sedimentary basin through geologic time. It results from the contribution of various factors including tectonics, sedimentary load, paleobathymetric variation and global sea-level change (Allen and Allen, 2013; Lee et al., 2019).


Fig. 3. 
a) Process of total and tectonic subsidence analysis. Gray dotted line: sediment accumulation curve at present (relative to a fixed datum of paleobathymetry and sea-level variation), blue solid line: total subsidence curve calculated by decompaction technique, green solid line: tectonic subsidence curve calculated by backstripping technique (revised from Lee et al., 2019). b) Concept of compaction and decompaction processes of a stratigraphic unit with exponential compaction trend and equation (revised from Lee et al., 2019). c) Schematic model of successive thickness reduction of sedimentary layers compacted by burial and faulting.

Total subsidence analysis starts with the division of the stratigraphic column for thickness and age range, and then decompacts each compacted sedimentary layer’s thickness successively (decompaction technique). The decompaction process is basically the calculation of the thickness of a sedimentary layer at any time and depth in the past using the appropriate compaction trend (Fig. 3b and c). The equation for compaction trend is typically arranged as an exponential porosity decrease with depth (Athy, 1930; Sclater and Christie, 1980; Bond and Kominz, 1984);

=0exp(-y/c)

where ∅: porosity at depth y, ∅0: initial porosity when the layer near surface, c: compaction coefficient. The total amount of restored thickness of accumulated layers provides the base for the total subsidence analysis (Lee et al., 2019).

Tectonic subsidence stands for the amount of subsidence induced by the tectonic driving force (Watts and Steckler, 1979). To identify the tectonic component in basin subsidence, tectonic subsidence analysis performs an isostatic balance between a lithospheric column through the sedimentary basin and a column in which the sediment load has been removed and has been replaced with water. This process is called the backstripping technique (Watts and Ryan, 1976), which is a technique for progressively removing the sedimentary load from a sediment accumulation history (total subsidence) and correcting for compaction, paleobathymetry and sea-level change (Fig. 3a). Incorporating the various effects results in the Airy-isostasy compensated 1D tectonic subsidence (Z) at any geologic time t in the past (Steckler and Watts, 1978; Watts and Steckler, 1979; Sclater and Christie, 1980; Bond and Kominz, 1984);

Zt=Stρm-ρsρm-ρw+Wdt-SL(t)ρmρm-ρw

where S(t): sediment layer thickness at any time t evaluated by decompaction, ρw, ρm and ρs: densities of water, mantle and mean sediment, Wd(t): paleobathymetry at any time t, ∆SL(t): sea-level change at any time t (Lee et al., 2019).

To estimate the appropriate compaction trend in the Vienna Basin, this study evaluated porosity values using seismic velocity data of well Zavod 76 in the Vienna Basin (Fig. 4a). Seismic velocity data of the well were analyzed by recognizable correlations between seismic velocity-density and density-porosity. A relation between seismic velocity and bulk density defined by Gardner et al. (1974) is used;


Fig. 4. 
a) Compaction trend for the Vienna Basin. Porosity values were evaluated from seismic velocity data at well Zavod 76 (see Figure 1b for location). b) Main menu of BasinVis 2.0 showing four main stages and subsidiary functions. c) Input parameters for this study.

ρ=aVP0.25

where ρ: bulk density, Vp: seismic velocity, a: coefficient. The bulk density is a function of the average density of the rock types making up the formation and the relative volumes occupied;

ρ=ρs1-+ρV

where ρs: average density of rock matrix, ρv: average density of fluid in pore space (Allen and Allen, 2013; Lee and Wagreich, 2017). Based on the porosity-depth relation from well Zavod 97, this study estimated the compaction trend using the function of the ‘Compaction Trend Estimation’ window in BasinVis 2.0;

=40.2exp(-y6096)

where ∅: porosity at depth y, 40.2: initial porosity when the layer near surface, 6096: compaction coefficient (Fig. 4a).

For the tectonic subsidence analysis of the study area, regional paleobathymetric variations were assumed from Sauer et al. (1992) (Fig. 2b). This study has not incorporated eustatic sea-level changes in the calculations, since the basin was separated from the world ocean around the early Late Miocene and the regional sea-level changes in the Paratethys were only partially in accordance with global sea-level cycles (Haq et al., 1987; Steininger and Wessely, 1999; Hohenegger et al., 2014; Harzhauser et al., 2018).

3.3 BasinVis 2.0

BasinVis 2.0 is implemented entirely in MATLAB® version 9.3 (R2017b) and requires the ‘Symbolic Math’ and ‘Curve Fitting’ Toolboxes (Math, Statistics, and Optimization package). By running the ‘mainwindow.m’ script in the program folder, BasinVis 2.0 is started and opens the main program window (Fig. 4b) as a central hub accessing to all functions and process stages.

In the ‘Setup’ stage, this study defined the extent of the study area and the stratigraphic unit names and ages (Fig. 4c), and input the stratigraphic information of well data with coordinates relative to the defined study area. In the ‘Stratigraphic Visualization’ window, this study visualizes 2D and 3D models of basement surface, sediment distribution, isopach and sedimentation rate of each stage. To evaluate realistic sedimentation rate during the time of deposition, sedimentation rate in this study is based on initial thickness of each stage which is decompacted using the compaction trend. In the ‘Subsidence’ stage, after inputting parameters for subsidence analysis (Fig. 4c), BasinVis 2.0 computes numerical subsidence analysis of individual wells in the study area. The results are interpolated and visualized for 2D and 3D models of total subsidence depth, total subsidence rate, tectonic subsidence depth and tectonic subsidence rate of each stage (Lee et al., 2016).

Because the collected well data are distributed sparsely and irregularly over the study area (38 well sites in 37 × 37 km2), this study integrates the data with MATLAB® 3D surface plotting functions provided by BasinVis 2.0. An adopted method to reconstruct the surface in the study area is the Ordinary Kriging (OK) spatial interpolation which originated from the field of geostatistics (Li and Heap, 2008). The OK estimator incorporates the covariance structure between known data points to predict the depth at arbitrary surface locations (Cressie, 1988, 1993). Therefore, surfaces reconstructed using OK result in an entirely smooth surface that inter- and extrapolates the data points over the study area.


4. Results
4.1 Visualization of basement structure

The pre-Neogene basement (base of Neogene fill) of the study area is visualized in 3D surface model (Fig. 5a), and it is compared with a structure map of the Vienna Basin (Fig. 5b). In the 3D basement surface model, the arrangement of prominent highs and depressions is recognizable and dissected by NE-SW trending sinistral strike-slip duplexes and en-echelon listric normal faults. The Schwechat depression and Marchfeld depression show relatively deep subsided depocenters, which are bound by fault blocks of the Leopoldsdorf fault, the Markgrafneusiedl fault and the Lassee fault system. However, the Quaternary basins (Mitterndorf Basin, Aderklaa Basin, Obersiebenbrunn Basin and Lassee Basin) located in this study area do not appear on the basement model.


Fig. 5. 
a) 3D basement (base of Neogene fill) surface model of the study area. b) 2D basement surface model with faults and structural elements. Major faults, depressions and Quaternary basins are labeled. Contour lines (500 m; solid line), well locations (black dots and lines), major faults (bold solid line) and faulted displacement (gray range) are shown.

4.2 Reconstruction of sedimentation setting

The basin fill of the study area is visualized in 3D sediment distribution surface, 2D isopach map (Fig. 6) and 2D sedimentation rate map (Fig. 7) in seven successive time steps. The isopach maps of sediment thickness show the position of major faults (e.g., Leopodsdorf fault, Markgrafneusiedl fault, Lassee fault system) to understand the geometrical trend of Miocene sedimentation.


Fig. 6. 
Sedimentation setting model of the study area. 3D sediment distribution surface (above) and 2D sediment thickness isopach (below) of each stage; a) Karpatian (17.2 - 15.97 Ma), b) early Badenian (15.97 - 13.82 Ma), c) late Badenian (13.82 - 12.83 Ma), d) Sarmatian (12.83 - 11.62 Ma), e) early Pannonian (11.62 - 10.5 Ma), f) middle Pannonian (10.5 - 9.8 Ma), g) late Pannonian (9.8 - 7.8 Ma). Studied wells and contour lines (500 m) are shown in 3D surface models. The major faults and contour lines (200 m) are shown in 2D isopach maps. The top depth of the late Pannonian unit is assumed as 0 m.


Fig. 7. 
2D sedimentation rate map of the study area, based on initial (decompacted) thickness of each stage; a) Karpatian (17.2 - 15.97 Ma), b) early Badenian (15.97 - 13.82 Ma), c) late Badenian (13.82 - 12.83 Ma), d) Sarmatian (12.83 - 11.62 Ma), e) early Pannonian (11.62 - 10.5 Ma), f) middle Pannonian (10.5 - 9.8 Ma), g) late Pannonian (9.8 - 7.8 Ma). The major faults and contour lines (200 m/Ma) are shown.

In the Karpatian stage, the overall sediments show a high thickness (up to 1,800 m; Fig. 6a) compared to the other time intervals, with a high sedimentation rate (up to 1600 m/Ma; Fig. 7a). The sediments accumulated mainly along the Markgrafneusiedl fault and Lassee fault system which consists of strike-slip faults and negative flower structures activated along the southwestern margin of the Vienna Basin. The major depocenters are located at/near the Marchfeld depression and Mitterndorf depression. The lower Badenian sediments are of 200 - 600 m in thickness with a sedimentation rate of around 200 m/Ma (Figs. 6b and 7b). Relatively thick depositional packages are recorded in the Schwechat depression and Mitterndorf depression. During the late Badenian, the sedimentation is NE-SW trending and thick along the Lassee fault system (Fig. 6c). Sedimentation rate is overall 400 - 800 m/Ma in the study area, and a depocenter at the Marchfeld depression shows up to 1,000 m/Ma in sedimentation rate (Fig. 7c). Surface geometries of sediment distribution in the Karpatian - Badenian follow locations and displacement of major fault systems, while the Sarmatian to Pannonian sediments show no indication of fault structure. The Sarmatian sediments attain a varying thickness between 200 - 800 m with a depocenter at the Schwechat depression along the Leopoldsdorf fault (Fig. 6d). The depositional package at the depocenter is 600 - 800 m in thickness with a high sedimentation rate of up to 800m/Ma (Fig. 7d). The lower Pannonian sediments are distributed overall with a thickness round 200 m (Fig. 6e) and a sedimentation rate of 200 m/Ma (Fig. 7e). A small depocenter is recorded near the Marchfeld depression. The middle Pannonian sediments attain a varying thickness between 0 - 600 m, and the sedimentation rate is high along the Leopoldsdorf fault but only thin deposits occur at the Mitterndorf depression (Fig. 6f). There are two thicker deposition packages characterized by high sedimentation rates, recorded in the northwestern and northeastern corners of the study area (Fig. 7f). During the late Pannonian, several shallow and small depocenters with ~200 m/Ma in sedimentation rate are distributed in the study area (Figs. 6g and 7g).

4.3 Total and tectonic subsidence model

This study visualizes 3D subsidence depth models and 2D subsidence rate maps of total subsidence and tectonic subsidence at the seven successive time steps (Figs. 8 and 9). The subsidence rate maps show the position of major faults (e.g., Leopodsdorf fault, Markgrafneusiedl fault, Lassee fault system) to understand the geometrical trend of Miocene subsidence.


Fig. 8. 
Total subsidence model of the study area. 3D subsidence depth surface (above) and 2D subsidence rate map (below) of each stage; a) Karpatian (17.2 - 15.97 Ma), b) early Badenian (15.97 - 13.82 Ma), c) late Badenian (13.82 - 12.83 Ma), d) Sarmatian (12.83 - 11.62 Ma), e) early Pannonian (11.62 - 10.5 Ma), f) middle Pannonian (10.5 - 9.8 Ma), g) late Pannonian (9.8 - 7.8 Ma). Studied wells and contour lines (500 m) are shown in 3D depth models. The major faults and contour lines (200 m/Ma) are shown in 2D rate maps.


Fig. 9. 
Tectonic subsidence model of the study area. 3D subsidence depth surface (above) and 2D subsidence rate map (below) of each stage; a) Karpatian (17.2 - 15.97 Ma), b) early Badenian (16.1 - 13.82 Ma), c) late Badenian (13.82 - 12.83 Ma), d) Sarmatian (12.83 - 11.62 Ma), e) early Pannonian (11.62 - 10.5 Ma), f) middle Pannonian (10.5 - 9.8 Ma), g) late Pannonian (9.8 - 7.8 Ma). Studied wells and contour lines (200 m) are shown in 3D depth models. The major faults and contour lines (50 m/Ma) are shown in 2D rate maps.

Total and tectonic subsidence are considerably fast during the Karpatian, especially along the Markgrafneusiedl and Lassee fault systems (Figs. 8a and 9a). The areas with high subsidence rates (~1,600 m/Ma in total subsidence and ~800 m/Ma in tectonic subsidence) are near/at the Marchfeld depression and the Mitterndorf depression which are bound by the en-echelon fault system and structural ridges consisting of the southwestern transtensional system of the Vienna Basin. After this fast subsidence, both the total and tectonic subsidence decrease markedly during early Badenian time (Figs. 8b and 9b). During the late Badenian, relatively high total and tectonic subsidence commence along the Lassee fault system (600 - 800 m/Ma in total subsidence rate and up to 400 m/Ma in tectonic subsidence rate) showing a NE-SW trend, and also partly along the Leopodsdorf fault (Figs. 8c and 9c). From the Sarmatian onwards, the subsidence decreases overall in the study area (Figs. 8d and 9d). However, relatively high total and tectonic subsidence rates (400 - 600 m/Ma in total subsidence rate and 150 - 200 m/Ma in tectonic subsidence rate) are indicated in the hanging wall region of the Leopoldsdorf fault and along the Markgrafneusiedl fault. The subsidence during the early Pannonian shows a slight NE-SW trending along the Lassee fault system, and relatively high total subsidence rates (around 200 m/Ma) are recorded at the Mitterndorf depression and the northwestern and northeastern parts of the study area (Figs. 8e and 9e). The northwestern part of the study area subsides significantly during the middle Pannonian (up to 800 m/Ma in total subsidence rate and up to 300 m/Ma in tectonic subsidence rate), which is connected with the Schwechat depression along the Leopoldsdorf fault, while the Marchfeld depression and Mitterndorf depression subside slowly (0 - 200 m/Ma in total subsidence rate and 0 m/Ma in tectonic subsidence rate) during this time (Figs. 8f and 9f). During the late Pannonian, there are no strong subsidence trends or features (Figs. 8g and 9g). Several areas with 200 m/Ma in total subsidence rate are recorded, which partly correspond to the Mitterndorf depression at the southwestern corner of the study area.


5. Discussion

Using functions of BasinVis 2.0, this study visualizes the basement surface, sedimentation setting and subsidence evolution of the study area and analyzes the basin evolution of the Miocene pull-apart structure in the southern part of the Vienna Basin, Austria.

The subsidence during the Karpatian is significant along the Markgrafneusiedl fault and Lassee fault system, which reflects the development of a pull-apart basin system between two left-stepping segments occurred in the Vienna Basin at the end of the Early Miocene (Fig. 10). The faults and structural styles are dominated by NE-SW trending sinistral strike-slip duplexes and en-echelon listric normal faults, and growth strata by synsedimentary faulting are indicated in seismic sections (Strauss et al., 2006; Hölzel et al., 2010; Harzhauser et al., in press).


Fig. 10. 
A seismic section through the study area (see Figure 1c for location; revised from Beidinger and Decker, 2011). Quaternary basins (Obersiebenbrunn Basin, Lassee Basin) are overlying the Markgrafneusiedl fault and the negative flower structure of Lassee fault system.

The subsidence abruptly decreased during the early Badenian and this condition continued until the Late Miocene. This corresponds to the tectonic subsidence patterns of strike-slip basins which are mainly episodic, short-lived (typically <10 Ma) and end abruptly (Xie and Heller, 2009; Lee et al., 2019). The slow subsidence of the early Badenian becomes faster and wider with NE-SW trending along the Lassee fault system. In Hölzel et al. (2008), the tectonic subsidence rate of the early Badenian (Upper Ladenid Zone) is higher than the rate of late Badenian in the southern Vienna Basin. However, the tectonic subsidence pattern is not observed in the models of this study. This can result from different methodological details (e.g., chronostratigraphy, compaction trend, unit boundary).

Different from the largely varying geometries in the sediment surface models of the Karpatian to the Badenian, the sediment surfaces from the Sarmatian are less influenced by fault systems. This geometric change demonstrates the cease of synsedimentary faulting and related growth strata in the study area. According to Arzmüller et al. (2006), the Vienna pull-apart structures are filled mainly with upper Karpatian and Badenian sediments, which are blanketed by Sarmatian and Pannonian successions without major depositional breaks (Fig. 10).

The area of Sarmatian sedimentation and subsidence shifts to the Schwechat depression along the N-S trending Leopoldsdorf fault, and this continues until Pannonian times. This corresponds to the E-W trending extensional subsidence during the Sarmatian - Pannonian (late Middle - Late Miocene) described in the northern and central parts of the Vienna Basin (Lee and Wagreich, 2017). During late Pannonian times, several minor depocenters and subsiding areas are found in the study area; some of them are located at/near the positions of Quaternary basins (Fig. 10). Because Quaternary deposits have not been separated consistently from the Pannonian sediments in well data (Lee and Wagreich, 2016), the areas are possibly related to Quaternary subsidence (300 - 500 m/Ma in tectonic subsidence rate; Lee and Wagreich, 2017).

This case study presents the Early to Late Miocene basin evolution of the study area, successively and dimensionally in time and space. The results demonstrate that the basin evolution of the southern Vienna Basin is strongly coupled with changes of the regional paleostress regime and structural setting (especially, faults and depressions). Comparing our results to previously published studies conducted in the Vienna Basin (e.g., Jiříček and Seifert, 1990; Lankreijer et al., 1995; Arzmüller et al., 2006; Hölzel et al., 2008; Lee and Wagreich, 2016), they match mostly those of preceding works but provide partly different models. For better understanding of the basin evolution in the Vienna Basin, the differences need to be analyzed in the further studies. However, the previous works differ in some of their methodological details. They used largely the same Central Paratethys chronostratigraphy and local zones, however without recent age refinements (e.g., Hohenegger et al., 2014; Harzhauser et al., 2018, in press). Additionally, in the subsidence analysis, they did not use compaction trend estimated from onsite data, but empirical porosity-depth relation from literatures for specific lithologies. And some previous studies focused only on the pull-apart evolution or part of Miocene succession, which excluded the subsidence effect by compaction of underlying sediments. Although the time factor and compacted depth are the most influential parameters in basin modelling, there are methodological differences between studies. To avoid this methodological issue and understand the basin evolution comprehensively, a basin-scale evolution modelling of the Vienna Basin is being prepared.


6. Conclusions

This study applies various analysis techniques to a case study on the Vienna Basin to introduce the basin modelling using BasinVis 2.0. The 3D basement surface model, 2D/3D sedimentation setting model and 2D/3D subsidence evolution model in seven successive stages during the Miocene are visualized in the study area and analyzed to understand the internal setting and basin evolution of the Miocene pull-apart structure in the southern part of the Vienna Basin. The results show that the basin evolution was strongly coupled with changes of the regional paleostress regime and structural setting. They match closely results of preceding works but provide partly different models, which are the basis of further studies in the Vienna Basin. This case study demonstrates that the functions and techniques of BasinVis 2.0 are effective to understand the sedimentation setting, subsidence and structural geometric evolution throughout basin history and applicable to the basin modelling.


Acknowledgments

This research was supported by Korea Research Fellowship program funded by the Ministry of Science and ICT through the National Research Foundation of Korea (2017H1D3A1A01054745) and a part of the project titled 'International Ocean Discovery Program (IODP)’ funded by the Ministry of Oceans and Fisheries, Korea. Special thanks go to two reviewers for their constructive comments and Johannes Novotny, a co-developer of BasinVis 2.0, for his excellent skills and knowledge in scientific visualization.


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