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In this study, we propose a multiple hypotheses approach to improve interpretations of limited remotely sensed datasets, such as sparsely exposed outcrops, subsurface datasets, or planetary objects using semi‐quantitative scoring and ranking of observable features. This method is demonstrated using an outcrop example from the Broken Beds of the Upper Jurassic–Lower Cretaceous Purbeck Limestone Group exposed along Britain's Jurassic Coast. Four published hypotheses regarding their origin are refined, represented in matrix form, scored and ranked based on carefully selected outcrop features. Semi‐quantitative scoring utilises knowledge of likely processes governing the occurrence of a range of features, some of which might be ignored or down‐played to favour a single hypothesis. Furthermore, by integrating expertise from different sub‐disciplines (e.g. basin analysis, sedimentology, diagenesis), we also consider the combined evidence of multiple features. This new method results in an interpretation that favours a multi‐process origin for the Broken Beds due to evaporite dissolution, overpressure release and tectonic folding, with identified uncertainty, all useful to guide further data collection. [ABSTRACT FROM AUTHOR]

This paper examines how non‐marine thrombolites are formed through a complex, multiphase process of microbial framework construction, erosion, cementation, recrystallization and episodes of internal sedimentation. Recognition of such phases of thrombolite construction provides a framework for the interpretation of the fluctuating environmental conditions leading to their formation. Microbialite frameworks are examined in detail from the Purbeck Limestone Group and their affinities and palaeo‐environmental significance assessed. Three types of thrombolite, one stromatolite and a leolite are described and interpreted. The thrombolite frameworks include: a peloidal mesoclotted type, a thrombolite constructed by the filamentous alga Cladophorites and a type with concentrically laminated micritic mesoclots. Physical and chemical erosion led to extensive early cavity formation within the frameworks. Early calcite rim cements with associated spherulites then developed over the microbial frameworks and these were reworked into cavities. Frameworks were also replaced by chalcedonic quartz and calcite spherulites. Internal sediments comprise peloids, intraclasts and brackish‐water molluscs and ostracods, together with their debris. The thrombolites grew in moderate‐energy to high‐energy shallow, lacustrine, microbial mounds whereas stromatolites occurred in deeper‐water settings. A brackish‐water, lacustrine setting is indicated by the preserved macro‐biota, microbes, absence of charophytes and syndepositional evaporites, and negative stable carbon and oxygen isotope ratios. Strontium isotopes suggest that the carbonate‐rich waters were fed from erosion of Mid–Lower Jurassic limestones on the western basin margin with possible mixing with waters from nearby uplifted Upper Jurassic limestones and with Late Jurassic seawater. The research indicates that non‐marine thrombolites have a complex, multiphase origin resulting in a diverse succession of textures and structures relating to microbially induced and influenced construction, dissolution, cementation, recrystallization and mineral replacement which have not been previously recorded and indicate the major differences between marine and non‐marine thrombolites. [ABSTRACT FROM AUTHOR]

Understanding how carbonate factories influence platform evolution is either based on qualitative conceptual models or quantitative numerical stratigraphic forward models. This study establishes new production depth profiles for four Cenozoic carbonate factories and uses two‐dimensional stratigraphic forward models to explore how interactions between sediment production and transport within carbonate systems influence carbonate platform development. Newly established production/depth profiles are used to model photozoan and heterozoan carbonate grain associations, and the associated carbonate producing factories, and results are compared with well‐studied outcrop successions. Sediment production from photozoan and heterozoan grain associations is also equalized, so that the total sediment production is the same but the depth/production profiles retain their distinctly different form. Thus, the effect of the different production profiles can be assessed. Ramps form when sediment diffusional transport rates are high relative to production rates and flat‐top steep‐margin platforms form when sediment diffusional transport rates are low relative to production rates, whether they are photozoan or heterozoan grain associations. The control exerted by sediment production and transport is expressed as a sediment transport–production ratio where transport ratio is a diffusional sediment transport in two‐dimensions and production ratio is the total sediment production rate which is the product of a production profile that varies in depth and laterally. The transport–production ratio is a key control on the evolution and geometry of carbonate platforms. This is the case with different production profiles (both euphotic and oligophotic) and in mixed grain‐size and mixed transport‐rate systems. Carbonate producing factories significantly influence the rate of sediment production, the depth distribution of sediment production (production profiles), as well as the type of grain sizes produced (influencing resistance to erosion). Thus, different types of carbonate grain associations, and the associated carbonate producing factories, can produce the critical differences between carbonate platform geometries. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the southeastern margin of the Red Sea Rift in western Yemen has been investigated using a multidisciplinary field study of an east-west transect between Al Hudaydah and Sana'a. Slow subsidence of up to 1 km occurred over the area during a 100 m.y. period before rifting. There was a major episode of flood volcanism between ca. 30 and 20 Ma, and important extensional faulting began after the eruption of the volcanic rocks and ceased before middle to late Miocene sediments and volcanic rocks were deposited unconformably on top of rotated fault blocks on the coastal Tihama Plain. Surface uplift has produced the Yemen highlands, whose highest peak reaches an elevation of 3660 m. This is attributed to plume heating and eruption of >3000 m of volcanic rocks. Apatite fission-track ages indicate early to middle Miocene exhumational cooling ages, postdating the major volcanic phase and contemporaneous with rifting. Volcanism was accompanied by emplacement of subvertical dike swarms, which generally strike north-northwest to northwest, broadly parallel to the Red Sea coastline. Major faults indicate northeast-southwest-directed extension. Large granitic sheets and plutons (up to 25 km wide) intruded the volcanic rocks. Approximately 30 km of extension has taken place across a 75-km-wide zone ([Beta] = 1.7) in 6-8 m.y. The relative timing of volcanism followed by extension and uplift does not fit conventional models of passive or active rifting. We suggest that the proto-Red Sea Rift was caused by regional plate stresses that exploited lithospheric weakening caused by the Afar plume. Appreciable doming only occurred after the main episode of volcanism, which suggests that magmas extruded before maximum thermal expansion of the lithosphere took place.