Supporting information for

Reconstruction of the Cenozoic deformation of the Bohai Bay Basin, North China

Yinbing Zhua, Shaofeng Liua,*, Bo Zhanga, b, Michael Gurnisb, Pengfei Maa

a State Key Laboratory of Geological Processes and Mineral Resources and School of

Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing

100083, China

b Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125,

United States

Contents of this file

Methods for the calculation of isostatic subsidence

Supporting Figures S1 to S5

Supporting Tables S1 and S2

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Methods for the calculation of isostatic subsidence

The theoretical water-loaded subsidence due to continental thinning and thermal

contraction was calculated with the following equations described by Jarvis and

McKenzie (1980) and White (1994):

S (t )=A (1−1β )−BQ (t ) (1)

where S (t ) is the theoretical water-loaded subsidence; A and B are crustal thinning and

lithospheric mantle thinning factors, respectively; β is the stretching factor and Q(t ) is a

measure of the difference between the perturbed and equilibrium temperature structure. A

, B, β and Q(t ) can be calculated with the following equations:

β=exp (∫0

∆t

G(t)dt ) (2)

A=tc (ρm−ρc )/(ρa−ρw ) (3)

B=α ρm/( ρa−ρw) (4)

Q ( t )=∫0

L

[T ( z ,t )−T (z ,∞)]dz (5)

∂T∂ t

+G (L−z ) ∂T∂ z

=κ ∂2T∂ z2 (6)

Given the strain rate, G ( t ), calculated from the reconstruction model, Eq. (1) can be

solved iteratively to yield S ( t ). The symbols and values for the parameters used in the

study are listed in Table S2.

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Supporting Figures

Fig. S1. A schematic diagram showing the relationship between the observed tectonic subsidence (the subsidence driven by lithospheric extension, thermal contraction, and dynamic topography, excluding the effect of the sediment load), water-loaded isostatic subsidence (the subsidence driven by lithospheric extension and thermal contraction), and dynamic topography.

The observed tectonic subsidence (OTS) obtained from well-log data using the back-

stripping method (Steckler & Watts, 1978; Watts & Ryan, 1976) includes the

contribution of dynamic topography over the period of basin formation. Therefore, the

initial dynamic topography (DTi) should be considered when we compare the observed

basin subsidence with the predicted total surface topography (the combined effect of

water-loaded isostatic subsidence and dynamic topography):

OTS+DT i=WIS+DT (7)

Especially at the beginning of basin formation, both the initial observed tectonic

subsidence (OTSi) and the predicted water-loaded isostatic subsidence (WISi) are 0:

OTSi=WISi=0 (8)

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Fig. S2. Comparison between the predicted isostatic topography (ignoring dynamic topography) with ±2σ envelopes (blue line), and the observed tectonic subsidence (orange line) at six wells across the BBB.

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Fig. S3. Comparison between the predicted total surface topography (blue line) with ±2σ envelopes, and the observed tectonic subsidence (orange line) at six wells across the BBB. The predicted total surface topography in this figure was calculated assuming thin crustal and lithospheric thicknesses of 32 km and 100 km at 65 Ma, respectively.

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Fig. S4. Predicted evolution of the dynamic topography for the BBB and adjacent areas at 63 Ma (a), 51 Ma (b), 40 Ma (c), 33 Ma (d), 24 Ma (e) and present (f) (according to Ma, Liu, Gurnis, & Zhang, 2019; Liu et al., in preparation). The area outlined in black is the BBB.

Fig. S5. Predicted evolution of the dynamic topography for the BBB. The dynamic topography of each region in the basin has the same trend with time, and its spatial distribution does not differ much (less than ~50 m) at each moment (Fig. S4). The blue line in the figure shows the change in the dynamic topography in the middle of the basin, which presents an overall upward trend from 65 Ma to the present day with a downward trend between 48-37 Ma.

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Supporting Tables

Table S1 Balanced cross-section data used in the reconstruction model

Section ID

5.1 (N2m1)

12 (N1m2) 23.3 24.6

(N1g)27.4

(E3d1)30.3

(E3d2)32.8

(E3d3)36

(E3s1)38

(E3s2)42

(E2s3)50.5 (E2s4)

65 (E1-2k) Total Section

Direction Source

1 1.82 0.79 1.58 0.85 5.11 4.5 14.65 143.00 (1)2 0 0.2 1.6 1.8 3 13.3 17.1 37.00 143.00 (2)3 1.87 2 2.23 0.34 3.87 1.92 12.23 148.00 (3)4 1.64 1.45 2.36 1.75 1.97 1.06 10.23 148.00 (3)5 2.3 5.8 1.3 2.5 5.2 14.1 31.20 143.00 (2)6 0.1 0.07 0.82 0.99 148.00 (4)7 0.45 5.31 3.88 9.64 148.00 (4)8 3.86 9.42 4.48 17.76 90.00 (4)9 2.69 4.63 3.58 10.90 90.00 (4)10 0.19 0.06 0.51 1.58 4.24 0.82 2.93 1.45 11.78 149.00 (5)11 0.44 0.35 1.32 1.4 0.44 1.59 0.75 6.29 149.00 (6)12 0 0.46 0.53 1.13 3.14 0.15 2.93 1 9.34 149.00 (5)13 2.46 0.37 0.24 2.34 0.98 4.18 0.9 11.47 140.00 (7)14 2.32 0.49 0 2.31 0.25 5.49 0.92 11.78 140.00 (7)15 6.15 1.47 0.28 0.55 8.45 139.00 (8)16 2.19 1.99 2.26 1.71 0.48 3.56 12.19 70.00 (9)17 0.39 1.37 0.15 0.58 2.68 3.22 8.39 70.00 (9)18 0.25 0.75 -0.03 0.91 4.34 6.22 70.00 (9)19 0.32 1.74 2.98 1.63 6.67 70.00 (9)20 1.25 1 1.47 1.96 5.68 70.00 (9)21 0.43 0.75 2.45 0.52 0.78 4.93 150.00 (10)22 0.7 -0.1 2.07 3.12 5.14 10.93 120.00 (11)23 1.52 -1.41 2.17 4.03 6.41 12.72 30.00 (11)24 2.15 -1.52 4.82 8.94 12.95 27.34 90.00 (11)25 0.67 -0.45 4.35 9.03 13.72 27.32 90.00 (11)

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26 0.2 0.4 1.3 3.4 11.6 16.90 90.00 (12)27 1.1 0.3 4.6 1.3 15.8 23.10 90.00 (12)28 0.67 0.58 3.47 4.72 145.00 (13)29 0.35 0.9 1.02 2.27 145.00 (13)30 2.64 2.88 7.62 8.05 21.19 143.00 (14)31 0.27 0.80 1.60 1.33 4.00 143.00 (15)32 0.46 1.37 2.74 2.28 6.85 145.00 (16)33 0.3 1.34 4.57 1.36 7.57 143.00 (16)34 0.72 1.65 0.89 1.25 3.95 1.36 9.82 145.00 (16)35 0.29 3.33 1.78 3.18 4.71 2.90 16.18 145.00 (16)36 0.27 0.58 0.22 0.53 1.07 1.33 4.00 143.00 (15)

References: (1) Mao (2014); (2) He et al. (2018); (3) Liu (2015); (4) Dong, Qi, Yang, and Yuan (2013); (5) Zhang, Wu, Li, Xiao, and Qi (2017); (6) Tang, Wan, Zhou, Jin, and Yu (2008); (7) Sun (2008); (8) Xin (2015); (9) Zhou (2010); (10) Zhan (2013); (11) Hou (2010); (12) Zhao (2015); (13) Hou (2007); (14) Q. Li (2014); (15) Yang (1984); (16) J. Li (2011). Note: Numbers from 5.1 to 65 in column headings are in Ma, corresponding to the base age of the Cenozoic stratigraphic units in the basin (see Table 1 for details). The numbers in the table are in km, indicating the extended (positive) or shortened (negative) distance of cross-sections between two ages. For example, in section 3, the number in column ‘23.3’ is 1.87, and there is no number between 0 and 23.3, which means that section 3 extended 1.87 km from 0 to 23.3 Ma; similarly, the number in column ‘65’ is 1.92, and there is no number in column ‘50.5’, which means that section 3 extended 1.92 km from 42 to 65 Ma, and so on. Some references do not provide specific numbers on the extended (or shortened) distance of balanced cross-sections but provide figures of balanced cross-sections. The extended (or shortened) distance of these balanced cross-sections was measured using ImageJ software (https://imagej.nih.gov/ij/). The section direction is the azimuth (degree) counter-clockwise from east. See Fig. 2 for section locations.

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Table S2 Parameters used in subsidence computationsSymbol Parameter Value

L Lithospheric thickness 125 km

t c Crustal thickness 40 km

ρw Sea water density 1.03103 kg/m3

ρc Crust density (at 0 )℃ 2.8103 kg/m3

ρm Mantle density (at 0 )℃ 3.33103 kg/m3

ρa Asthenosphere density (at 1333 )℃ 3.2103 kg/m3

T m Asthenosphere temperature 1350 ℃

T 0 Surface temperature 0 ℃

α Thermal expansion coefficient 3.2810-5 ℃-1

κ Thermal diffusivity 110-6 m2/s

∆ t Stretching duration

G Strain rate

T Temperature

z Vertical coordinate (see Fig. 1 in Jarvis & McKenzie, 1980)

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References

Dong, M., Qi, J., Yang, Q., & Yuan, F. (2013). Characteristics of extension amounts and their temporal and spatial distribution of the Cenozoic of Huanghua Depression in Bohai Bay Basin. JournalofPalaeogeography,15, 327-338. https://doi.org/10.7605/gdlxb.2013.03.028

He, D., Cui, Y., Shan, S., Xiao, Y., Zhang, Y., & Zhang, C. (2018). Characteristics of geologic framework of buried-hill in Jizhong depression, Bohai Bay Basin. ChineseJournalofGeology,53, 1-24. https://doi.org/10.12017/dzkx.2018.001

Hou, X. (2007). TheanalysisofMesozoic-CenozoicbasinevolutionintheeastareaofLinqingDepression(Master's thesis), China University of Petroleum (East China), Qingdao.

Hou, X. (2010). ThedevelopmentcharacteristicsofstructuresinversioninJiyangDepressionanditsrelationshipwiththeevolutionofsuperimposedbasin(Doctoral dissertation), China University of Petroleum (East China), Qingdao.

Jarvis, G. T., & McKenzie, D. P. (1980). Sedimentary basin formation with finite extension rates. EarthandPlanetaryScienceLetters,48, 42-52. https://doi.org/10.1016/0012-821x(80)90168-5

Li, J. (2011). ThestructuralevolutionofLinqingandtheeffectonitsNeopaleozoic. (Master's thesis), China University of Petroleum (East China), Qingdao.

Li, Q. (2014). CenozoictectonicevolutionofBohaiBayBasinanditsimplicationsonthePacificPlatesubduction. (Master's thesis), China University of Geosciences (Beijing), Beijing.

Liu, H. (2015). RelationshipsbetweenCenozoicextensionandstrike-slipofRaoyangSaginJizhongDepression. (Master’s thesis), China University of Petroleum (East China), Qingdao.

Ma, P., Liu, S., Gurnis, M., & Zhang, B. (2019). Slab horizontal subduction and slab tearing beneath East Asia. GeophysicalResearchLetters. https://doi.org/10.1029/2018gl081703

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Steckler, M. S., & Watts, A. B. (1978). Subsidence of the Atlantic-type continental margin off New York. EarthandPlanetaryScienceLetters,41, 1-13. https://doi.org/10.1016/0012-821x(78)90036-5

Sun, Y. (2008). CenozoicstructuralcharacteristicsanditscontroltomigrationandaccumulationofhydrocarboninBozhongdepression. (Doctoral dissertation), Daqing Petroleum Institute, Daqing.

Tang, L., Wan, G., Zhou, X., Jin, W., & Yu, Y. (2008). Cenozoic geotectonic evolution of the Bohai Basin. GeologicalJournalofChinaUniversities,14, 191-198. https://doi.org/10.16108/j.issn1006-7493.2008.02.001

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