Segmentation of the Guyanas continental margin of South America is inherited from the dual-phase Mesozoic rifting history controlling the first-order post-rift sedimentary architecture. The margin is divided into two segments by a transform marginal plateau (TMP), the Demerara Rise, into the Central and Equatorial Atlantic domains. This paper investigates the heterogeneities in the post-rift sedimentary systems at a mega-regional scale (>1000 km). Re-sampling seven key exploration wells and scientific boreholes provides new data (189 analysed samples) that have been used to build a high-resolution stratigraphic framework using multiple biostratigraphic techniques integrated with organic geochemistry to refine the timing of 10 key stratigraphic surfaces and three megasequences. The results have been used to calibrate the interpretation of a margin-scale two-dimensional seismic reflection dataset, and to build megasequence isochore maps, structural restorations and gross depositional environment maps at key time intervals of the margin evolution.

Our findings revise the dating of the basal succession drilled by the A2-1 well, indicating that the oldest post-rift sequence penetrated along the margin is late Tithonian age (previously Callovian). Early Central Atlantic carbonate platform sediments passively infilled subcircular-shaped basement topography controlled by the underlying basement structure of thinned continental crust. Barremian–Aptian rifting in the Equatorial Atlantic, caused folding and thrusting of the Demerara Rise, resulting in major uplift, gravitational margin collapse, transpressional structures and peneplanation of up to 1 km of sediment capped by the regional angular Base Albian Unconformity. Equatorial Atlantic rifting led to margin segmentation and the formation of the TMP, where two major unconformities developed during the intra Late Albian and base Cenomanian. These two unconformities are time synchronous with oceanic crust accretion offshore French Guiana and in the Demerara–Guinea transform, respectively. A marine connection between the Central and Equatorial Atlantic is demonstrated by middle Late Albian times, coinciding with deposition of the organic-rich source rock of the Canje Formation (average total organic carbon 4.21%). The succession is variably truncated by the Middle Campanian Unconformity. Refining the stratigraphic framework within the context of the structural evolution and segmentation of the Guyanas margin impacts the understanding of key petroleum system elements.

Supplementary material: Photographs of sandstone petrography thin sections (Fig. S1); calcareous nannofossil plates (Fig. S2); palynology reports for A2-1 and FG2-1 (Fig. S3); taxonomy description of new species; sample table and organic geochemistry results (Table S1); and nannofossil distribution charts (Table S2) are available at https://doi.org/10.6084/m9.figshare.c.5280490

南美圭亚那大陆边缘的分割继承自控制一阶裂谷后沉积构造的双相中生代裂谷历史。边缘通过转换边缘高原（TMP）将Demerara Rise分为两个部分，分为中部和赤道大西洋域。本文研究了大面积区域（> 1000 km）后裂谷后沉积系统中的非均质性。对七个关键勘探井和科学钻孔进行重新采样提供了新数据（分析的189个样品），这些数据已被用于通过使用多种生物地层技术与有机地球化学相结合来构建高分辨率地层框架，从而完善了10个关键地层表面和三个巨型层序的时间。

我们的发现修改了A2-1井钻探的基础演替的年代，表明沿边缘穿透的最古老的裂谷后层序是铁通时代晚期（以前是卡洛夫时代）。中大西洋早期的碳酸盐台地沉积物被动地填充了亚圆形地壳下面的基底结构所控制的亚圆形地下基底地形。赤道大西洋的Barremian–Aptian裂谷引起Demerara Rise的褶皱和逆冲，导致主要隆升，重力边缘塌陷，超压构造以及高达1 km的沉积物的上倾，该沉积物被区域性有角度的Albian不整合面所覆盖。赤道大西洋裂谷导致边缘分割和TMP的形成，在晚期阿尔比内期和基诺曼尼亚期发生了两个主要不整合面。这两个不整合面分别与法属圭亚那近海和Demerara-Guinea变换中的大洋结壳时间同步。中部和赤道大西洋之间的海洋联系在阿尔比中期晚期被证实，这与Canje组富含有机物的烃源岩的沉积（平均总有机碳含量为4.21％）相吻合。中间的坎帕尼亚不整合面使该断层被截断。在圭亚那边际的结构演化和分段背景下完善地层框架，会影响对关键石油系统要素的理解。中部和赤道大西洋之间的海洋联系在阿尔比中期晚期被证实，这与Canje组富含有机物的烃源岩的沉积（平均总有机碳含量为4.21％）相吻合。中间的坎帕尼亚不整合面使该断层被截断。在圭亚那边际的结构演化和分段背景下完善地层框架，会影响对关键石油系统要素的理解。中部和赤道大西洋之间的海洋联系在阿尔比中期晚期被证实，这与Canje组富含有机物的烃源岩的沉积（平均总有机碳含量为4.21％）相吻合。中间的坎帕尼亚不整合面使该断层被截断。在圭亚那边际的结构演化和分段背景下完善地层框架，会影响对关键石油系统要素的理解。

补充材料：砂岩岩石薄片薄层的照片（图S1）；钙质纳米化石板（图S2）；A2-1和FG2-1的孢粉学报告（图S3）；新物种的分类学描述；样品表和有机地球化学结果（表S1）；和nannofossil分布图（表S2）可在https://doi.org/10.6084/m9.figshare.c.5280490获得