This study used systematic coring, hyperspectral scans, carbonate/siliciclastic analysis, and stable isotope measurements to evaluate environmental controls on large microbial buildup evolution. Buildups initiated on a discontinuous transgressive lag of flat-pebble conglomerate, controlling their spatial distribution and flat-based geometry. The consistent three-phase buildup architecture indicates allogenic forcing by fluctuations in sea level and siliciclastic influx. The initiation of each phase began in a pure carbonate system, with high-energy skeletal-oolitic grainstone interbuildup deposition. Depositional moats formed in the grainstone adjacent to buildups during phases 1 and 2. Buildups developed up to 5.7 m of synoptic relief during phases 1 and 3 prior to being onlapped by siliciclastic sediment. Phase 2 of the buildups intertongued with heterolithic interbuildup sediment, developing only 30 cm of synoptic relief. Lateral variability in phase 2 architecture indicates autogenic controls causing localized differences in microbialite growth rates versus interbuildup accumulation. Phases 1 and 3 display a dense calcitic calcimicrobial rind that surrounds and encloses the top of the buildups. The interior of buildups is composed of decimeter-scale stromatolitic columns, each encased by a calcimicrite rind and exhibiting mottled internal texture due to bioturbation and dolomitization. Interiors of buildups entrapped more carbonate sediment, creating greater porosity, and thus were destructively dolomitized. In contrast, the calcimicrite rinds of columns and the thick rinds surrounding buildups formed as biochemical carbonate precipitates, with minimal porosity, and, therefore, escaped dolomitization. The δ18O and δ13C values of the column and buildup rinds are consistent with late Cambrian seawater, supporting an origin as a precipitate and age as Sunwaptan.

The file contains 11 worksheets: The "Splice" worksheet provides Anhysteretic Remanent Magnetization (ARM@30mT) data obtained from u-channels collected from core sections of holes U1471A, U1471C and U1471D. The experiments were carried out at the Institute of Astronomy and Geophysics of the University of São Paulo using the triaxial cryogenic magnetometer (2G, mod. 755). The "XRF Scan Data" worksheet contains the results obtained by XRF Scan measurements taken at 1 cm intervals directly on the surface of the divided half-core section (each 1.5 m long) using an Avaatech XRF-Scanning generation at the Ocean Discovery Program (IODP) International Gulf Coast Repository at Texas A&M University. Results are displayed in counts per second. The "Benchtop vs. scanner XRF data" worksheet contains data from discrete measurements in conventional XRF performed on 42 samples collected at each 3 cm interval of the central section U1471C-1H-3W (3 to 4.5 mbsf). The samples, taken in 5 g aliquots of core material, were dried and pulverized in an agate mortar. Powder samples were measured in the conventional XRF Rigaku Supermini200 from the University of São Paulo. The worksheet also presents the average of the XRF scan data for the corresponding depth of each discrete sample. The "1st age model (Sr vs LR04)" worksheet contains the Sr/sum data and the tie points obtained by correlating the Sr/sum data with the LR04 curve (Lisiecki and Raymo; 2005). The "Data with 1st age model" worksheet contains the Fe/sum and ln (Fe/Si) data linearly interpolated to a resolution of 1 kry (using the first age model) and their respective spectral analysis through the Multitaper method using Acycle software. The "2nd age model (Fe vs. NHSI)" worksheet shows the Fe/sum data linearly interpolated to 1 kry (using the first age model) and the Fe/sum data filtered using a bandpass in the precession frequency range. The worksheet also presents the tie points obtained by comparing the filtered Fe/sum data with the insolation curve for the Northern Hemisphere. The "Data with 2nd age model" worksheet contains the Fe/sum and ln (Fe/Si) data linearly interpolated to a resolution of 1 kry (using the second age model) and their respective spectral analysis through the Multitaper method using Acycle software. The "3rd age model (U1471 vs. U1467)" worksheet contains the tie points obtained by correlating the Sr/sum curves of records U1471 and U1467 and their respective ages. The "Data with 3rd age model" worksheet contains the Fe/sum and ln (Fe/Si) data linearly interpolated to a resolution of 1 kry (using the third age model) and their respective spectral analysis through the Multitaper method using Acycle software. The "Normalized data (Zmean)" worksheet contains the Fe/sum and ln (Fe/Si) data normalized to the mean equals zero and standard deviation equals one (that is, zero-mean normalization). The "Normalized data (Zmean)" worksheet contains the Fe/sum and ln (Fe/Si) data normalized to the mean equals zero and standard deviation equals one (that is, zero-mean normalization). The "Detrended data (anomaly)" worksheet contains the detrended Fe/sum and detrended ln (Fe/Si) data. Zmean normalized Fe/sum and ln Fe/Si data were linearly interpolated to a resolution of 500 years. The detrended Fe/sum data was obtained by subtracting LR04 from the Fe/sum record and the detrended ln (Fe/Si) data was obtained by subtracting NHSI from the ln (Fe/Si) record. The worksheet also presents the spectral analysis obtained through the Multitaper method using Acycle software.

The Great Barrier Reef (GBR) located along the northeastern margin of Australia is the largest coral reef system in the world. Modern climatic alterations are quickly changing the GBR ecosystem. To understand the implications of these changes it is important to reconstruct the geological history of GBR. Here we use geochemical and magnetic proxies to evaluate past climatic fluctuations and their consequences on sediment deposition along the GBR margin. IODP Expedition 325 - Hole M0058A, drilled on the uppermost slope at ca. 170 m water depth, reveals the depositional history of the GBR margin during the interval of MIS 7 to 5 and MIS 1. Magnetic and geochemical variations along the core section reveal detailed information on sediment accumulation and on the variations in terrigenous input in relation to sea-level fluctuations and climate change. Sea-level variations influenced margin deposition between MIS 7 and 6 impacting shoreline progradation/retrogradation and siliciclastic redistribution, resulting in a mixture of finer to coarser magnetic assemblages with no significant changes in terrigenous input. At the end of MIS 6 a decline in the deposition of carbonate sediments concomitant with the deposition of fine-grained magnetite-rich terrigenous sediments suggests an intensification of the monsoon in response to global warming trends. Arid periods over NE Australia were established after the glacial/ interglacial transition (the MIS 6-5e) and at the middle Holocene (after the MIS 2-1 transition at ca. 7 ka), which favored dust deposition over the region. Enhanced dust fertilization subsequently promoted primary productivity at these intervals resulting in the presence of biogenic magnetite at Hole M0058A produced by magnetotactic bacteria.

We address the evolution of the shelf architecture of the Northeast Brazilian Equatorial Margin during the Plio-Pleistocene, using a coupled approach of sequence stratigraphy based on 3D seismic data, and cyclostratigraphy based on well-log data. The main purpose of this study is to highlight the major forcing processes that control evolution and architecture of the shelf during the Plio-Pleistocene.Our results reveal nine pronounced seismic sequences within the Plio-Pleistocene series, which are correlated to the long 405-kyr eccentricity cycles. Inside the two youngest 405-kyr cycles, we observe nine Falling Stage System Tracts (FSST) matching the short (97-128 kyr) eccentricity cycles. Finally, we identify three major depositional episodes (mega-sequences) in the Plio-Pleistocene: (i) the first episode (from ~4 to ~2.4 Ma) is characterized by small amplitudes of sea-level variations with low to none erosive structures and the absence of clear transgressive series, (ii) the second phase (from ~2.4 to ~0.9 Ma) records a drastic increase of erosional features as well as the apparition of thicker transgressive series and slope failures, and (iii) the third phase (from ~0.9 to present-day) is characterized by a dramatic change in the shelf geometry, most of the sediments are deposited on the slope during FSST while the outer shelf is greatly exposed and eroded during low sea levels. Our results suggest that long-term increase in amplitude of sea level variation is the main driver of the geometrical changes of the Brazilian shelf. Boundaries of mega-sequences at 0.9 and 2.4 Ma likely reflect major climatic phases at respectively the Intensification of Northern Hemisphere Glaciation and the Mid-Pleistocene Transition. A significant change in the shelf architecture at around 0.4 Ma, acting as a prominent shift in the depositional system from one prograding to another aggrading, is likely related to the substantial sea-level rise together with the long-lasting Marine Isotopic Stage 11. We conclude that changes in the Brazilian shelf geometry during the Plio-Pleistocene was likely paced by orbitally forced sea-level cycles superimposed on long-term trends and phases in the climate and sea level.

Records of element ratios obtained from the Maldives Inner Sea sediments provide a detailed view on how the Indian Monsoon System has varied at high-resolution time scales. Here, we present records from International Ocean Discovery Program (IODP) Site U1471 based on a refined chronology through the past 550,000 years. The record's high resolution and a proper approach to set the chronology allowed us to reconstruct changes in the Indian Monsoon System on a scale of anomalies and to verify their relationships with established records from the East Asian Monsoon System. On the basis of Fe/sum and Fe/Si records, it can be demonstrated that the Asia continental aridity tracks sea-level changes, while the intensity of winter monsoon winds responds to changes in Northern Hemisphere summer insolation. Furthermore, the anomalies of continental aridity and intensity of winter monsoon winds at millennial-scale events exhibit power in the precession band, nearly in antiphase with Northern Hemisphere summer insolation. These observations indicate that the insolation drove the anomalies in the Indian Summer Monsoon. The good correspondence between our record and the East Asian monsoon anomaly records suggests the occurrence of anomalous widespread arid events in Asia.

Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island that recently formed as part of the discontinuous North Malé Atoll rim. Understanding the formation of Malé Island is relevant in predicting its future in the context of accelerating rates of sea-level rise in the next centuries due to anthropogenic global warming. Analyses of two boreholes up to 35 m-long, published information from additional boreholes drilled on Malé Island and a high-resolution multi-beam bathymetric survey acquired along its upper slopes and deep surroundings were available for this study. Two distinct sedimentary units were recovered from the boreholes. Facies analyses of the lower unit reveal an overall deepening coralgal reef that accumulated probably during the previous interglacial (Marine Isotope Stage = MIS 5e) and which was subsequently altered by meteoric diagenesis during a 100 kyr-long time of exposure. The upper unit consists of Holocene unconsolidated coralgal accumulation, unconformably overlying the lower karstified coralgal MIS 5e unit. The upper unit, protected behind a karstified late Pleistocene reef, was initiated at ~8200 yr BP and vertically grew 25 m-high until 6510 yr BP in the northern part of the Malé Island area, which at the time was a karstified limestone island with a central geomorphological depression. The narrow, 30 to 35 m-deep, newly formed central faro lagoon started to fill ~ 5500 yr BP, when a reef initiated on top of the southern highest Pleistocene karstified reef and sea-level rise stalled. The infilling of the faro lagoon was completed ~ 4500 yr BP. An island formed that was flanked on its south side by a shallow lagoon and surrounded by a reef flat. Through several phases of land reclamation since the 1950s, the shallow lagoon was infilled and the reef flat buried with sand and rubble to form Malé Island as it is known today.

The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m amplitude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is anchored in only two palaeo reefs (Barbados, Great Barrier Reef). Here, the authors present the analysis of a coralgal reef that thrived along the south-east Papua New Guinea Peninsula outer shelf during this initial pulse. In the cone of a piston core, a shallow Goniastrea retiformis coral colony was retrieved at 111 m below present sea-level and uranium/thorium dated to 19.4 ka BP. This colony had been buried beneath the debris of a proximal coralgal reef before its partial drowning at 14.5 ka BP. Seismic survey data suggest that the reef edifice was established directly on the eroded top of a lowstand shelf-edge delta, partially drowned and then back-stepped towards the south-east in response to three distinct deglacial sea-level pulses and stepwise increases of water column turbidity.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

In 1842, Darwin identified three types of reefs: fringing reefs, which are directly attached to volcanic islands; barrier reefs, which are separated from volcanic islands by lagoons; and ring reefs, which enclose only a lagoon and are defined as atolls. Moreover, he linked these reef types through an evolutionary model in which an atoll is the logical end point of a subsiding volcanic edifice, as he was unaware of Quaternary glaciations. As an alternative, starting in the 1930s, several authors proposed the antecedent karst model; in this model, atolls formed as a direct interaction between subsidence and karst dissolution that occurred preferentially in the bank interiors rather than on their margins through exposure during glacial lowstands of sea level. Atolls then developed during deglacial reflooding of the glacial karstic morphologies by preferential stacked coral-reef growth along their margins. Here, a comprehensive new model is proposed, based on the antecedent karst model and well-established sea-level fluctuations during the last 5 million years, by demonstrating that most modern atolls from the Maldives Archipelago and from the tropical Pacific and southwest Indian Oceans are rooted on top of late Pliocene flat-topped banks. The volcanic basement, therefore, has had no influence on the late Quaternary development of these flat-topped banks into modern atolls. During the multiple glacial sea-level lowstands that intensified throughout the Quaternary, the tops of these banks were karstified; then, during each of the five mid-to-late Brunhes deglaciations, coral reoccupied their raised margins and grew vertically, keeping up with sea-level rise and creating the modern atolls.

In tropical and sub‐tropical mixed siliciclastic–carbonate depositional systems, fluvial input and in situ neritic carbonate interact over space and time. Despite being the subject of many studies, controls on partitioning of mixed sediments remains controversial. Mixed sedimentary records, from Ashmore Trough shelf edge and slopes (southern Gulf of Papua), are coupled with global sea‐level curves and anchored to Marine Isotope Stage stratigraphy to constrain models of sediment accumulation at two different timescales for the past 130 kyr: (i) 100 kyr scale for last glacial cycle; and (ii) millennial scale for last deglaciation. During the last glacial cycle, carbonate production and accumulation were primarily controlled by sea‐level fluctuations. Export of neritic carbonate to the slopes was initiated during re‐flooding of previously exposed reefs and continued during Marine Isotope Stage 5e and 1 interglacial sea‐level highs. Siliciclastic fluxes to the slope were controlled by interplay of sea level, shelf physiography and oceanic currents. Heterogeneous accumulation of siliciclastic mud on the slope, took place during Marine Isotope Stage 5d to Marine Isotope Stage 3 sea‐level fall. Siliciclastics reached adjacent depocentres during Marine Isotope Stage 2. Coralgal reef and oolitic–skeletal sand resumed at the shelf edge during the subsequent stepwise sea‐level rise of the last deglaciation. Contemporaneous, abrupt siliciclastic input from increased precipitation and fluvial discharge illustrates that climate controlled deglacial sedimentation. Siliciclastic input persisted until ca 8.5 ka. Carbonate accumulation waned at the shelf edge after ca 14 ka, whereas it increased on the slopes since ca 11.5 ka, when previously exposed reef and bank tops were re‐flooded. When comparing the last sea‐level cycle sedimentation patterns of the southern Gulf of Papua with other coeval mixed systems, sea level and shelf physiography emerge as primary controls on deposition at the 100 kyr scale. At the millennial scale, siliciclastic input was also controlled by climate change during the unstable atmospheric and oceanic conditions of the last deglaciation.

The morphological architecture and distribution of modern and ancient carbonate systems has been shown to follow spatial-self-organization, however, limited studies describe the morphometrics of microbial carbonates. Upper Cambrian microbial-build-ups outcropping in Central Texas, are exposed laterally (plan view), enabling a study of their morphological architecture and spatial distribution. Drone imagery was acquired to capture the outcrop features and develop a digital terrain model (cm scale resolution) for a bedding plane outcrop (600 x 200 m in size). Four scales of microbial growth (S1- few m, S2- few m, S3- few tens of m, and 54- few hundreds of m) were identified and mapped. A series of morphometric analysis including Ripley's k, univariate, multi-variate, and grouping were conducted and results demonstrate that, the scales S1, S2, and S3 display clustering and the spatial organization of microbial-buildups is naturally organized and not random. Further, as the size of the build-ups increases (from S1-S4), the anisotropy (length/width) increases, their shape becomes oblong, and they become aligned (S2-S4) with the inferred regional winds and tide-associated currents (NE-SW according to the present geography). The S1 scale does not align itself with the regional currents; instead, the build-ups behaved as a baffle during growth, and modified the currents locally, leading to preferential alignment at the edges within S2. As the scales increases in sizes (S2, S3, S4), there is competition for space, and due to regional currents, the larger scales preferentially align parallel to high-energy currents. The trends and spatial relationships identified in this study are particularly relevant and provide a scenario for sub-seismic scale heterogeneities for subsurface microbial hydrocarbon reservoirs.

Morphological features on low-latitude continental shelves have recorded past sea level fluctuations. This study aims to recognize and interrogate, on the Rio Grande do Norte (RN, NE Brazil) outer shelves, specific seabed morphologies that could have been produced by the punctuated relative sea level rise of the last deglaciation. These sea floor morphologies, imaged by single-beam bathymetric data from two areas of the North and East outer Shelves, ~ 160 km apart, reveal terraces, submerged paleo-shorelines, reefs, and incised valleys, which act as regional archives of past sea levels. The North and East outer shelves, covered by carbonate sediments, display steep gradients (~ 0.5°), variable widths (up to 13 km), and are bound between a well-defined shelf break at 75 m water depth and a beachrock ridge at 25 m. A steep step on the sea floor occurs between depths of 60 and 70 m in both areas. Though interrupted by the Açu Incised Valley, two distinct continuous terraces, 3 and 4 km in width, at depths of 49 m (± 5 m) (T1n) and 33 m (±3 m) (T2n), respectively, extend for 60 km along the North Shelf. Three nearly continuous terraces occur along the East Shelf on either the north or south sides of the Natal Canyon. A first, 6 km wide, lower terrace occurs at a depth of 54 m (± 4 m) (T1e). A second terrace, 2 km wide, at 40 m (± 2 m) (T2e), and a third 2 km wide upper terrace at 30 m (±2 m) (T3e) are also found. Patch reefs scattered over the terraces rise in average to 3 m in height. Based upon their depth occurrences, the established limited neotectonics in the study areas, and correlations with well-established archives from other morphological features of similar outer shelves, we hypothesize that these reefs and terraces were likely formed during the last deglacial interval spanning from the end of the MWP-1A (70–60 m), through the MWP-1B (50–40 m), and to subsequent punctuated millennial sea level rise events (30–25 m) occurring prior to the 8.2 kyr cooling event.

Although Late Cambrian microbial build‐ups were recognized in the Point Peak Member of the Wilberns Formation in Central Texas (USA) nearly 70 years ago, only a few studies focused specifically on the build‐ups themselves. This study focuses on the interpretation of the regional (15 measured sections described in literature representing an area of 8000 km2) and local (field and drone photogrammetry studies in a 25 km2 area from within south Mason County) microbial build‐up occurrence, describes their growth phases and details their interactions with the surrounding inter‐build‐up sediments. The study establishes the occurrence of microbial build‐ups in the lower and upper Point Peak members (the Point Peak Member is informally broken up into the lower Point Peak and the upper Point Peak members separated by Plectotrophia zone). The lower Point Peak Member consists of three <1 m thick microbial bioherms and biostrome units, in addition to heterolithic and skeletal/ooid grainstone and packstone beds. One, up to 14 m thick, microbial unit associated with inter‐build‐up skeletal and ooid grainstone and packstone beds, intercalated with mixed siliciclastic–carbonate silt beds, characterizes the upper Point Peak member. The microbial unit in the upper Point Peak member displays a three‐phase growth evolution, from an initial colonization phase on flat based, rip‐up clast lenses, to a second aggradation and lateral expansion phase, into a third well‐defined capping phase. The ultimate demise of the microbial build‐ups is interpreted to have been triggered by an increase of water turbidity caused by a sudden influx of fine siliciclastics. The lower Point Peak member represents inner ramp shallow subtidal and intertidal facies and the upper Point Peak member corresponds to mid‐outer ramp subtidal facies. Understanding the morphological architecture and depositional context of these features is of importance for identifying signatures of early life on Earth.

Logging data are measurements of physical properties of the formation surrounding a borehole, acquired in situ after completion of coring (wireline logging) or during drilling (Logging-While-Drilling, LWD). The range of data (resistivity, gamma radiation, velocity, density, borehole images,…) in any hole depends on the scientific objectives and operational constraints.

Abstract The upper Cambrian Wilberns Formation in central Texas records deposition on a low‐gradient shelf within a mixed carbonate–siliciclastic tidal‐flat system that changes offshore to subtidal shelf and open‐marine oolitic skeletal shoals with large microbial mounds. Siliciclastic sediment is interpreted to have been delivered to the tidal flat by aeolian processes because of the narrow range in grain size and paucity of clay. Tidal influence is dominant as evidenced by reversing currents and desiccation on the tidal flat, and megaripples with reversing current indicators in offshore shoals. Intraclastic conglomerates were deposited in broad channels on the tidal flats during storm surges. Microbialite deposition is interpreted to be controlled by accommodation favouring amalgamated thin biostromes developed in the tidal flat vs. larger mounds with greater synoptic relief in the offshore, and current energy resulting in preferential elongation of offshore mounds in a NE–SW orientation. Intertidal mounds and biostromes grew in the presence of significant siliciclastic flux and trapped it within their structure, whereas offshore large buildups incorporated little siliciclastic component. Oolite and skeletal grainstone formed in tide agitated shoals associated with large subtidal microbial mounds. Storms extensively recycled and redistributed skeletal and oolitic sands from the offshore shoals across the shelf as thin sand sheets. Spatial mixing of siliciclastic and carbonate sediment occurred across the tidal flat and shelf. Low‐frequency and intermediate‐frequency stratigraphic cycles were driven by shifts in the shoreline and changes in rate of siliciclastic flux in response to relative sea‐level fluctuation. Random facies stacking and the lack of metre‐scale cyclicity are interpreted to reflect stratigraphic incompleteness and an episodic signal introduced by storms.