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Article in Journal of Geophysical Research Atmospheres • January 1980
Journal of Geophysical Research Atmospheres 上的文章 • 1980 年 1 月
DOI: 10.1029/JB085iB07p03711
DOI： 10.1029/JB085iB07p03711

2 authors, including:  2 位作者，包括：
Philip Christie  菲利普·克里斯蒂
Schlumberger Gould Research, Cambridge, UK
Schlumberger Gould Research，英国剑桥
66 publications 2,144 CItations
66 出版物 2,144 次引用
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Some of the authors of this publication are also working on these related projects:
本出版物的一些作者也正在从事以下相关项目：

Borehole Seismic and Reservoir Characterisation View project
钻孔地震和储层特征视图项目

Department of Earth and Planetary Sciences, Massachusetts Institute of Technology Cambridge, Massachusetts 02139
麻省理工学院地球与行星科学系 剑桥， 马萨诸塞州 02139

Department of Geodesy and Geophysics, Cambridge University Madingley Rise, Cambridge, England
剑桥大学大地测量学和地球物理学系 英国剑桥 Madingley Rise

Abstract. The North Sea is a major continental basin filled with early Paleozoic to Recent sediments. Though graben formation started in the Triassic, the last major period of extension occurred between the Middle Jurassic and the mid-Cretaceous. Following the faulting and graben formation associated with this extension, subsidence within the central North Sea was widespread and uniform and has created a saucershaped sedimentary basin. Ihis was filled successively by chalks, sandstones, and finally, during most of the Tertiary, by shales and mudstones. We examined the subsidence of six wells down the middle and two on the flanks of the Central Graben. In the period of widespread steady subsidence the water-loaded basement depth in the middle increased by $1100-1400\mathrm{m}$$1100-1400\mathrm{m}$1100-1400m1100-1400 \mathrm{~m}. On the flanks the basement subsided $600-700\mathrm{m}$$600-700\mathrm{m}$600-700m600-700 \mathrm{~m}. We suggest that most of this subsidence results from the thermal relaxation of the lithosphere which was thinned during a Midale Jurassic to mid-Cretaceous stretching of the crust. Assuming a crustal stretching and associated lithospheric thinning of between 50 and $100\mathrm{\%}$$100\mathrm{\%}$100%100 \% in the middle and decreasing on either side, we obtained a good match to the observed amplitude and rate of subsidence. The Middle Jurassic to midCretaceous subsidence which is found within the graben proper we relate to the fault-controlled initial subsidence which occurred during the actual stretching. The measured heat flow is compatible with such a stretching model. Though there is no seismic refraction data across the Central Graben, this model is strongly supported by evidence of a thinner crust under the Viking Graben to the north and the Witchground/Buchan Graben complex to the east. Using the above observetions as the basis for a geological interpretation, we examined the thermal maturity and hydrocarbon potential of certain sedimentary horizons in the northern section of the Central Graben. In analyzing the various wells we extended previous work on the compaction correction to handle overpressuring and mixed lithologies in backstripping studies. Further, we expanded these methods to include the variation of thermal conductivity, and calculations of the degree of thermal maturation of the deposited sediments, through time.
抽象。北海是一个主要的大陆盆地，充满了早古生代至近代的沉积物。虽然地堑的形成始于三叠纪，但最后一个主要的延伸时期发生在中侏罗世和白垩纪中期之间。在与此次延伸相关的断层和地堑形成之后，北海中部的沉降广泛而均匀，并形成了一个碟形沉积盆地。Ihis 先后被白垩岩、砂岩填充，最后，在第三纪的大部分时间里，被页岩和泥岩填充。我们检查了 Central Graben 中间的 6 口井和 Central Graben 两侧的 2 口井的沉降情况。在大范围稳定沉降期间，中间的含水基底深度增加了 $1100-1400\mathrm{m}$$1100-1400\mathrm{m}$1100-1400m1100-1400 \mathrm{~m} 。在侧面，地下室下沉 $600-700\mathrm{m}$$600-700\mathrm{m}$600-700m600-700 \mathrm{~m} 。我们认为，这种沉降大部分是由于岩石圈的热松弛造成的，岩石圈在中侏罗纪至白垩纪中期地壳的拉伸过程中变薄。假设地壳拉伸和相关的岩石圈变薄在 50 到 $100\mathrm{\%}$$100\mathrm{\%}$100%100 \% 中间之间，并且在两侧减少，我们获得了与观察到的沉降幅度和速率的良好匹配。在地堑内发现的中侏罗世至白垩纪中期沉降，我们与实际拉伸期间发生的断层控制初始沉降有关。测得的热流与这种拉伸模型兼容。虽然没有整个 Central Graben 的地震折射数据，但这一模型得到了北部 Viking Graben 和东部 Witchground/Buchan Graben 复合体下较薄的地壳证据的有力支持。 以上述观测结果作为地质解释的基础，我们研究了中格拉本北部某些沉积层的热成熟度和碳氢化合物潜力。在分析各种井时，我们扩展了之前关于压实校正的工作，以处理背带研究中的超压和混合岩性。此外，我们扩展了这些方法，包括热导率的变化，以及沉积物的热成熟度随时间的变化。

The late Paleozoic through Cenozoic geology of the stable areas of western central Europe is dominated by a series of large epicontinental
晚古生代至新生代地质学中欧西部的稳定地区以一系列大型陆生代为主
Copyright 1980 by the American Geophysical Union.
美国地球物理联盟 1980 年版权所有。
basins. These, for example, the European, Paris, and North Sea basins, are 200 or 300 km wide, up to 600 km long, and in places $5-8\mathrm{km}$$5-8\mathrm{km}$5-8km5-8 \mathrm{~km} deep. It is generally agreed that the sediments have been deposited during a period of widespread general subsidence following active graben formation. The basins are underlain by continental crust, and because the gravity anomalies are small, the subsidence is compensated. Though much is known about their structure as a result of recent exploration for oil, the mode of besin formation and the cause of the subsidence are at present matters of speculation.
盆地。例如，欧洲、巴黎和北海盆地宽 200 或 300 公里，长达 600 公里，有些地方 $5-8\mathrm{km}$$5-8\mathrm{km}$5-8km5-8 \mathrm{~km} 很深。人们普遍认为，沉积物是在活跃的地堑形成后广泛的普遍沉降期间沉积的。这些盆地位于大陆地壳的下方，由于重力异常很小，因此沉降得到了补偿。尽管由于最近的石油勘探，人们对它们的结构了解很多，但 besin 形成的方式和沉降的原因目前仍是猜测的问题。

The North Sea is a typical example of one of these large epicontinental basins. It contains an unfaulted Late Cretaceous to Recent sedimentary fill above a Jurassic through Early Cretaceous graben system (Figure 1) that was also active in the Triassic. Unlike other basins of similar setting on the continental shelves, however, the rate of deposition in the Tertiary appears to increase rather than decrease as the sediments get younger.
北海是这些大型表层盆地之一的典型例子。它包含一个无断层的晚白垩世至近代沉积物填充物，位于侏罗纪至早白垩世地堑系统（图 1）上方，该系统在三叠纪也很活跃。然而，与大陆架上其他类似设置的盆地不同，随着沉积物的年轻化，第三纪的沉积速率似乎会增加而不是减少。

During the recent phase of oil exploration, new well data and seismic sections have been released, and generally accepted summaries of the besic observations are now appearing [Ziegler, 1977, 1978a]. In this paper we examine this information, particularly, the well data both along and across the Central Graben of the North Sea. We remove the sedimentary load allowing for compaction and compare the observed basement subsidence with that predicted by a simple extensional model for the development of the Jurassic and Early Cretaceous faulting. Finally, we discuss the implications of this model for the degree of thermal maturation of certain sedimentary horizons.
在最近的石油勘探阶段，新的井数据和地震剖面已经发布，现在出现了普遍接受的 besic 观测摘要 [Ziegler， 1977， 1978a]。在本文中，我们研究了这些信息，特别是北海中央地堑沿岸和横跨北海的井数据。我们去除了允许压实的沉积载荷，并将观察到的基底沉降与侏罗纪和早白垩纪断层发展的简单延伸模型预测的沉降进行了比较。最后，我们讨论了该模型对某些沉积层位的热成熟程度的影响。

The explanations for the subsidence in the North Sea and other basins and shelves of aimilar type can be separated into two groups. Earlier explanations concentrated upon the effects of graben formation on the crust. These invoke possible upward migration of the Moho with increasing sedimentary load [Collette, 1968; $0^{\prime }$$0^{\prime }$0^(')0^{\prime} Connell and Wasserburg, 1967], creep at the edges after graben formation [Bott, 1976], crustal replacement associated with the formation of an astenolith [Ziegler, 1977], or general flexural subsidence caused by sediment loading following the formation of the graben [Beaumont, 1978].
对北海和其他盆地和大陆架沉降的解释可以分为两组。早期的解释集中在地堑形成对地壳的影响上。这些引发了莫霍河随着沉积负荷的增加而可能向上迁移 [Collette， 1968; $0^{\prime }$$0^{\prime }$0^(')0^{\prime} Connell 和 Wasserburg， 1967]，地堑形成后边缘蠕变 [Bott， 1976]，与星石形成相关的地壳更替 [Ziegler， 1977]，或地堑形成后沉积物负荷引起的一般弯曲沉降 [Beaumont， 1978]。

The rate of subsidence in most basins de-
大多数流域的沉降速率 de-

Fig. 1. The sites of nine selected wells from the central North Sea on a chart of the major graben (heavy lines) and the Tertiary sedimentary contours (light lines) from Ziegler [1977, 1978a]. The political boundaries are shown as dashed lines. Seismic reflection profiles $A{A}^{\prime }$$A{A}^{\prime }$AA^(')A A^{\prime} and $B{B}^{\prime }$$B{B}^{\prime }$BB^(')B B^{\prime} are discussed in the text.
图 1.Ziegler [1977， 1978a] 的主要地堑（粗线）和第三纪沉积等值线（轻线）图表上从北海中部选定的 9 口井的地点。政治边界显示为虚线。地震反射剖面 $A{A}^{\prime }$$A{A}^{\prime }$AA^(')A A^{\prime} ， $B{B}^{\prime }$$B{B}^{\prime }$BB^(')B B^{\prime} 将在正文中讨论。
creases rather than accelerates with age [sleep, 1971]. This rules out any mechanism of longterm subsidence involving Moho migration. Further, the widespread period of subsidence in most basins lasts for more than $100\mathrm{m}.\mathrm{y}$$100\mathrm{m}.\mathrm{y}$100m.y100 \mathrm{~m} . \mathrm{y}. This is much longer than the time constant of shallow effects in the crust or the flexural response of a rigid lithosphere. Thus though these crustal phenomena probably occur in one form or another, and, in particular, the isostatic loading of the sediment is important in permitting large accumulations in these basins, these phenomena are not the basic cause of the overall subsidence.
折痕而不是随着年龄的增长而加速 [SLEEP， 1971]。这排除了任何涉及 Moho 迁移的长期沉降机制。此外，大多数流域的广泛沉降时间超过 $100\mathrm{m}.\mathrm{y}$$100\mathrm{m}.\mathrm{y}$100m.y100 \mathrm{~m} . \mathrm{y} 。这比地壳中浅层效应的时间常数或刚性岩石圈的弯曲响应要长得多。因此，尽管这些地壳现象可能以这样或那样的形式发生，特别是沉积物的等静压负荷对于允许这些盆地中大量堆积很重要，但这些现象并不是整体沉降的根本原因。

More modern explanations are based on the observations of Sleep [1971], Watts and Ryan [1976], Steckler and Watts [1978], and Keen [1979], who have shown that the subsidence of these basins is remarkably similar to that of the deep sea floor [Parsons and Sclater, 1977]. To account for this observation, Sleep [1971] proposed a model which resembled those which have been so successful in the oceans. When the temperatures of the continental crust and lithosphere are raised, the lithosphere expands, and crust is eroded. When the lithosphere cools, the upper surface returns to a depth below its original position. Though this satisfactorily explains the subsidence which will be at an exponentially decaying rate dependent upon the thickness of the lithosphere, there is a space problem. No more sediment can be deposited than was removed by erosion in the first place. For instance, in the North Sea there is no evidence of the 5 km of Jurassic erosion necessary to produce the Cretaceous and Tertiary sediment fill. There have been some attempts involving thermal
更现代的解释是基于 Sleep [1971]、Watts 和 Ryan [1976]、Steckler 和 Watts [1978] 以及 Keen [1979] 的观察，他们表明这些盆地的沉降与深海海底的沉降非常相似 [Parsons 和 Sclater， 1977]。为了解释这一观察结果，Sleep [1971] 提出了一个模型，该模型类似于在海洋中如此成功的模型。当大陆地壳和岩石圈的温度升高时，岩石圈会膨胀，地壳会受到侵蚀。当岩石圈冷却时，上表面恢复到低于其原始位置的深度。虽然这令人满意地解释了沉降，沉降将以指数衰减的速度取决于岩石圈的厚度，但存在空间问题。沉积物不能比最初通过侵蚀去除的沉积物更多。例如，在北海，没有证据表明产生白垩纪和第三纪沉积物填充所需的 5 公里侏罗纪侵蚀。已经有一些涉及热的尝试
doming and phase changes to account for these space problems [Haxby et al., 1976], but these mechanisms are ad hoc, and it is difficult to justify them in a simple extensional setting [McKenzie, 1978a].
圆顶和相变来解释这些空间问题 [Haxby et al.， 1976]，但这些机制是临时的，很难在简单的扩展环境中证明它们的合理性 [McKenzie， 1978a]。

The space problem and the long-term subsidence are resolved if the basins are created by extension over a broad region. Such extension removes the space problem, since light crust is replaced by more dense asthenosphere and there is no necessity for uplift before subsidence. In fact, the maximum amount of sedimentary fill that can be obtained without invoking uplift and erosion occurs after infinite extension and is between 15 and 20 km . The lithosphere can extend either by stretching or by rigid breakup and the intrusion of hot material from below. Thus two plausible models can be developed from this explanation, and in the case of large amounts of extension they are indistinguishable.
如果盆地是通过在广阔的区域上扩展而形成的，那么空间问题和长期沉降就得到了解决。这种延伸消除了空间问题，因为轻质地壳被更致密的软流圈所取代，并且在沉降之前不需要隆起。事实上，在不引发隆起和侵蚀的情况下可以获得的最大沉积填充量发生在无限延伸之后，在 15 到 20 公里之间。岩石圈可以通过拉伸或刚性破裂以及来自下方的热物质的侵入来延伸。因此，从这个解释中可以发展出两个合理的模型，在大量扩展的情况下，它们是无法区分的。

Many authors, for example, Artemjev and Artuskov [1971], Voight [1974], Lowell et al. [1975], and Morton and Black [1974], have invoked stretching to account for the normel faulting and crustal thinning observed in rifted regions. Recently, McKenzie [1978a] has examined both the short-and long-term consequences of such a model and has demonstrated that it can account for the present deformation and heat flow in the Aegean [McKenzie, 1978b]. In this mathematical development, extension occurs instantaneously, resulting in a rapid breakup of the brittle crust and ductile flow in the subcrustal lithosphere, permitting the asthenosphere to rise beneath the thinned portion of the crust. Grabens bounded by low-angle listric normel faults are created during extension and give rise to fault-controlled subsidence. When faulting ceases, the hot asthenosphere cools, and the basin subsides in a widespread steady manner. After a time, which is dependent upon the anount of stretching, the basin subsides at the same rate as the deep ocean floor.
许多作者，例如 Artemjev 和 Artuskov [1971]、Voight [1974]、Lowell 等人 [1975] 以及 Morton 和 Black [1974]，都援引了拉伸来解释在裂谷地区观察到的正常断层和地壳变薄。最近，McKenzie [1978a] 研究了这种模型的短期和长期后果，并证明它可以解释爱琴海目前的变形和热流 [McKenzie， 1978b]。在这个数学发展中，延伸是瞬间发生的，导致地壳下岩石圈中的脆性地壳和延性流动迅速破裂，从而允许软流圈在地壳的变薄部分下方上升。以低角度 listric normel 断层为界的地堑是在延伸过程中形成的，并引起断层控制的沉降。当断层停止时，炽热的软流圈冷却，盆地以广泛稳定的方式下沉。一段时间后，取决于伸展的作用，盆地以与深海海底相同的速度下沉。

An alternative explanation has been developed from the generally accepted idea that the ocean crust is created by numerous dykes and flows. Simple models based on this concept have been used to account for the dyke swarms found on continents. Burke [1975] proposed that such intrusion processes are important in continental breakup and in the formation of inland basins, and Royden et al. [1980] have considered the thermal consequences of this proposel. During periods of rapid extension there is much block faulting and graben formation. Vertical dykes are injected, and heat is brought rapidly to the surface. Though there is fault-controlled sub-
从普遍接受的观点中，已经发展出另一种解释，即洋壳是由许多堤坝和水流形成的。基于这个概念的简单模型已被用来解释在大陆上发现的岩脉群。Burke [1975] 提出这种侵入过程在大陆分裂和内陆盆地的形成中很重要，Royden 等人 [1980] 考虑了这一提议的热后果。在快速伸展期间，有很多块状断层和地堑形成。注入垂直堤坝，热量迅速到达表面。虽然有故障控制的分

TABLE la. Comparison of the Amplitude of FaultControlled Initial and Thermal Subsidence
TABLE la.断层控制初始沉降和热沉降幅度的比较

Initial and thermal subsidence values are in kilometers. WF is water-filled subsidence.
初始沉降值和热沉降值以千米为单位。WF 是充满水的沉降。
SF is sediment-filled subsidence.
SF 是充满沉积物的沉降。