The Kimmeridgian Alcobaça Formation of the Lusitanian Basin forms a mixed carbonate–siliciclastic unit between basinal deposits of the Abadia Formation, and fluvial–terrestrial strata of the Lourinhã Formation. This study presents >2.5 km of detailed logs of nine outcrop sections of the Alcobaça Formation in its type region. Eight of these sections encircle the Caldas da Rainha Diapir, which was a prominent, emergent, passive salt diapir during the time of deposition. Palaeoenvironments of the unit form a complex mosaic of low- to high-energy, carbonate- or siliciclastic-dominated shallow shelf settings; coastal embayments and lagoons; and coastal plains with rivers, lakes and playas. In the strata, abundant microfauna is often joined by a rich macrofauna, usually dominated by bivalves. Locally, corals, calcareous sponges or oysters form meadows or patch reefs. These autochthonous to parautochthonous remnants of former communities are assigned to 35 benthic macrofaunal associations. The integration of palaeoecological analysis of these associations with microfaunal and sedimentological data provides constraint on their salinity ranges, which range from slightly hypersaline to freshwater. Frequent temporal and spatial salinity fluctuations are attributed to variations in relative sea-level, salt tectonics or climate. The NNE-trending Caldas da Rainha Diapir induced pronounced facies differentiation. Predominantly, non-marine siliciclastic facies in the northwest and carbonate to siliciclastic, marine to brackish facies in the southwest are contrasted by shallow-marine carbonate facies east of the diapir. Comprehensive exposure and well-preserved fossils make the Alcobaça Formation an excellent showcase to demonstrate how biofacies analysis can help to disentangle the interplay of climate changes, sea-level fluctuations and salt tectonics. Based on the improved characterisation of the unit, the Alcobaça Formation is formally defined, and seven members are established.

Lusitanian 盆地的 Kimmeridgian Alcobaça 组在 Abadia 组的盆地沉积物和 Lourinhã 组的河流-陆相地层之间形成了碳酸盐-硅质碎屑混合单元。本研究提供了超过 2.5 公里的 Alcobaça 组在其类型区域的 9 个露头部分的详细测井记录。其中八个部分环绕 Caldas da Rainha Diapir，这是沉积时期一个突出的、涌现的、被动的盐底辟。该单元的古环境形成了一个复杂的马赛克，由低能量到高能量、碳酸盐或硅质碎屑为主的浅陆架环境；沿海海湾和泻湖；以及有河流、湖泊和海滩的沿海平原。在地层中，丰富的微型动物群通常与丰富的大型动物群相结合，通常以双壳类动物为主。在当地，珊瑚，钙质海绵或牡蛎形成草甸或斑礁。这些前群落的原地至近原地残余被分配到 35 个底栖大型动物群落。将这些关联的古生态分析与微动物和沉积学数据相结合，限制了它们的盐度范围，从轻微的高盐度到淡水。频繁的时空盐度波动归因于相对海平面、盐构造或气候的变化。NNE 趋势的 Caldas da Rainha Diapir 诱导了明显的相分化。主要是西北部的非海相硅质碎屑相和西南的碳酸盐到硅质碎屑、海相到半咸水相与底辟以东的浅海相碳酸盐岩相形成对比。全面的曝光和保存完好的化石使阿尔科巴萨组成为展示生物相分析如何帮助解开气候变化、海平面波动和盐构造之间相互作用的绝佳展示。根据该单元的改进特征，正式定义了 Alcobaça 组，并建立了 7 个成员。