A newly recognized thrust and nearby asymmetric anticline crop out 40 km north of Memphis, Tennessee, and they deform Eocene through Quaternary strata. These east–west-striking, south-verging structures are peripheral to the New Madrid seismic zone (NMSZ) of central North America, the source of M7+ earthquakes in 1811–1812. The thrust dips ∼20° N and has 55 m of throw in Eocene strata. An angular intraformational unconformity indicates most deformation was Eocene. The anticline’s limbs dip 7° N and 22° S and fold Eocene and Pleistocene strata. Pleistocene sediments are dropped at least 4 m into a graben along the fold axis. Holocene sediment is ponded upstream from the fold axis, suggesting Holocene activity. Based on outcrops, well logs, and seismic reflection, we interpret the anticline as a fault-tip fold above a splay of the thrust fault. We interpret these thrusts in the context of a previously published sandbox model of a restraining bend uplift, which we apply here to the Reelfoot Rift fault complex. Using the eastern rift margin as the strike-slip fault of the sandbox model, the periphery of the model uplift has an east–west-striking, south-verging oblique-slip thrust where the actual thrust and anticline crop out. These results suggest that young thrust faults may be common along the periphery of the NMSZ and similar active intraplate restraining bends, that the eastern margin of the Reelfoot Rift may have been a principal strike-slip fault of the restraining bend, and that the seismic zone was active as early as Eocene.

中文翻译：

---

美国中部新马德里地震带的新近认识的第四纪地表断层和褶皱外围及其对板内地震带弯曲模型的启示

在田纳西州孟菲斯市以北40公里处，出现了一种新近认识到的逆冲和附近的不对称背斜，它们通过第四纪地层使始新世变形。这些东西向，向南延伸的结构位于北美中部的新马德里地震带（NMSZ）的外围，后者是1811至1812年M7 +地震的源头。推力倾角约为20°N，在始新世地层中有55 m的抛射。角形内不整合表明大部分变形是始新世。背斜的四肢倾角分别为北纬7°和南纬22°，并且使始新世和更新世地层褶皱。沿褶皱轴将更新世的沉积物降落到a沟中至少4 m。全新世沉积物聚集在褶皱轴的上游，表明全新世活动。基于露头，测井和地震反射，我们将背斜解释为逆冲断层之上的断层褶皱。我们在先前发布的约束弯曲隆起沙盘模型的背景下解释这些推力，在此我们将其应用于Reelfoot Rift断层复合体。使用东部裂谷边缘作为沙盒模型的走滑断层，模型隆升的外围具有东西向，南向倾斜的斜推力，实际的推力和背斜就出现了。这些结果表明，年轻的逆冲断层可能在ＮＭＳ periphery的外围和类似的活动板内约束弯曲中很常见，Reelfoot裂谷的东缘可能是该约束弯曲的主要走滑断层，并且地震带始于始新世。在这里我们将其应用于Reelfoot Rift断层复合体。使用东部裂谷边缘作为沙盒模型的走滑断层，模型隆升的外围具有东西向，南向倾斜的斜推力，实际的推力和背斜就出现了。这些结果表明，年轻的逆冲断层可能在ＮＭＳ periphery的外围和类似的活动板内约束弯曲中很常见，Reelfoot裂谷的东缘可能是该约束弯曲的主要走滑断层，并且地震带始于始新世。在这里我们将其应用于Reelfoot Rift断层复合体。使用东部裂谷边缘作为沙盒模型的走滑断层，该模型隆起的外围具有东西向，南向倾斜的斜推力，实际的推力和背斜都出现了。这些结果表明，年轻的逆冲断层可能在ＮＭＳ periphery的外围和类似的活动板内约束弯曲中很常见，Reelfoot裂谷的东缘可能是该约束弯曲的主要走滑断层，并且地震带始于始新世。