Primary Productivity of Jatigede Reservoir Based on Light and Dark Bottle Method

This research aims to determine the value of primary productivity by using light-dark bottles at different depths in Jatigede Reservoir, Sumedang, West Java. This research was conducted from October 2020 until March 2021 using survey method research. Determination of the research location was done by using the purposive sampling method. Sampling was carried out at five stations and three depths: surface, 0.5 compensation depth, and compensation depth. The results showed that the primary productivity in Jatigede Reservoir ranged from 300.29-1013.47 mgC/m3/day. The results of supporting water quality parameters are light transparency ranging from 38-150 cm, temperature ranging from 26.6-29.7 oC, pH ranging from 6.69-8.7, carbon dioxide (CO2) ranging from 4.4-22.0 mg/ l, dissolved oxygen (DO) ranged from 3.00–6.6 mg/l, Biochemical Oxygen Demand (BOD) ranged from 1.62-16.22 mg/l, ammonia ranged from 0.0004-0.0055 mg/l, nitrate ranged from 0.017-0.044 mg/l and phosphate ranged from 0.06-0.14 mg/l. Based on the value of primary productivity, the waters of the Jatigede Reservoir are categorized as mesotrophic waters.

The carbonate compensation depth in the South Atlantic Ocean since the Late Cretaceous

Deep-sea carbonate deposition is a complex process that is encapsulated in the carbonate compensation depth (CCD)—a facies boundary separating calcareous sediments from non-carbonates. Knowing how the CCD has varied over time is important for understanding and predicting the distribution of seafloor sediments and assessing their role in the global carbon cycle. We focus on the South Atlantic Ocean where the most recent CCD curve is based on Deep Sea Drilling Project (DSDP) Leg 73 sites drilled in 1980 in the South Atlantic Ocean. We compute the South and central South Atlantic CCD from the Late Cretaceous to the present day using updated age models from 45 DSDP and Ocean Drilling Program sites and backtracking with lithology-specific decompaction, eustasy, and dynamic topography. Our models extend further back in time and show more fluctuations than previous reconstructions, with the CCD varying by hundreds of meters during a span of 2–3 m.y. The addition of eustasy and dynamic topography deepens the CCD by as much as 500 m between 74 Ma and 45 Ma, and by ~200 m during the Cenozoic. The central South Atlantic CCD diverges from the average South Atlantic CCD during the Eocene and Miocene, when it was ~1 km shallower. These regional deviations may be due to changes in primary productivity and/or carbonate dissolution leading to reduced carbonate accumulation rates. Our CCD curves highlight the importance of regional processes in carbonate deposition across the South Atlantic and provide improved constraints for the modeling of geochemical cycles.

Supplemental Material: The carbonate compensation depth in the South Atlantic Ocean since the Late Cretaceous

Description of datasets and data sources, Figures S1–S14, and Table S1.<br>

Supplemental Material: The carbonate compensation depth in the South Atlantic Ocean since the Late Cretaceous

Description of datasets and data sources, Figures S1–S14, and Table S1.<br>

Aragonite is calcite’s best friend at the seafloor

&lt;p&gt;Aragonite is about 50% more soluble than calcite in seawater and its pelagic production is dominated by pteropods. Moreover, it could account for a large fraction of marine CaCO&lt;sub&gt;3&lt;/sub&gt; export. The &lt;em&gt;aragonite compensation depth&lt;/em&gt; (ACD, the depth at which accumulation is balanced by dissolution) is generally very close to the &lt;em&gt;aragonite saturation depth&lt;/em&gt;, i.e. within a few hundred metres. Conversely, the &lt;em&gt;calcite compensation depth&lt;/em&gt; (CCD) can be 1-2 kilometres deeper than the &lt;em&gt;calcite saturation depth&lt;/em&gt;. That aragonite disappears shallower than calcite in marine sediments is coherent with aragonite&amp;#8217;s greater solubility, but why is the calcite &lt;em&gt;lysocline&lt;/em&gt;, i.e. the distance between its compensation and saturation depths, much thicker than its aragonite equivalent?&lt;/p&gt;&lt;p&gt;Here, we suggest that at the seafloor, the addition of a soluble CaCO&lt;sub&gt;3&lt;/sub&gt; phase (aragonite) results in the preservation of a predeposited stable CaCO&lt;sub&gt;3&lt;/sub&gt; phase (calcite), and term this a negative priming action. In soil science, priming action refers to the increase in soil organic matter decomposition rate that follows the addition of fresh organic matter, supposedly resulting from a globally increased microbial activity (Bingeman et al., 1953). Using a new 3D model of CaCO&lt;sub&gt;3&lt;/sub&gt; dissolution at the grain scale, we show that a conceptually similar phenomenon could occur at the seafloor, in which the dissolution of an aragonite pteropod at the sediment-water interface buffers the porewaters and causes the preservation of surrounding calcite. Since aragonite-producing organisms are particularly vulnerable to ocean acidification, we expect an increasing calcite to aragonite ratio in the CaCO&lt;sub&gt;3&lt;/sub&gt; flux reaching the seafloor as we go further in the Anthropocene. This could, in turn, hinder the proposed aragonite negative priming action, and favour chemical erosion of calcite sediments.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Reference:&amp;#160;Bingeman, C.W., Varner, J.E., Martin, W.P., 1953. The Effect of the Addition of Organic Materials on the Decomposition of an Organic Soil. Soil Science Society of America Journal 17, 34-38.&lt;/p&gt;

Geomorphometric descriptions of archipelagic aprons off the southern flanks of French Frigate Shoals and Necker Island edifices, Northwest Hawaiian Ridge

This study describes the geomorphometries of archipelagic aprons on the southern flanks of the French Frigate Shoals and Necker Island edifices on the central Northwest Hawaiian Ridge that are hotspot volcanoes that have been dormant for 10−11 m.y. The archipelagic aprons are related to erosional headwall scarps and gullies on landslide surfaces but also include downslope gravitational features that include slides, debris avalanches, bedform fields, and outrunners. Some outrunners are located 85 km out onto the deep seafloor in water depths of 4900 m. The bedforms are interpreted to be the result of slow downslope sediment creep rather than products of turbidity currents. The archipelagic aprons appear to differ in origin from those off the Hawaiian Islands. The landslides off the Hawaiian Islands occurred because of oversteepening and loading during the constructive phase of the islands whereas the landslides off the French Frigate Shoals and Necker Island edifices may have resulted from vertical tectonics due to the uplift and relaxation of a peripheral bulge or isolated earthquakes long after the edifices passed beyond the hotspot. The lack of pelagic drape in water depths above the 4600 m depth of the local carbonate compensation depth suggests that the archipelagic apron off the French Frigate Shoals edifice is much younger, perhaps Quaternary in age, than that off the Necker Island edifice, which has a 50 m pelagic drape. The pelagic drape off the Necker Island edifice suggests that the landslides may be as old as 9 Ma. The lack of pelagic drape off the French Frigate Shoals edifice suggests that the most recent landslides are more recent, perhaps even Quaternary in age. The presence of a chute-like feature on the mid-flank of the French Frigate Shoals edifice appears to be the result of rejuvenated volcanism that occurred long after the initial volcanism ceased to build the edifice.

Reconciling atmospheric CO2, weathering, and calcite compensation depth across the Cenozoic

The Cenozoic era (66 to 0 million years) is marked by long-term aberrations in carbon cycling and large climatic shifts, some of which challenge the current understanding of carbon cycle dynamics. Here, we investigate possible mechanisms responsible for the observed long-term trends by using a novel approach that features a full-fledged ocean carbonate chemistry model. Using a compilation of pCO2, pH, and calcite compensation depth (CCD) observational evidence and a suite of simulations, we reconcile long-term Cenozoic climate and CCD trends. We show that the CCD response was decoupled from changes in silicate and carbonate weathering rates, challenging the continental uplift hypothesis. The two dominant mechanisms for decoupling are shelf-basin carbonate burial fractionation combined with proliferation of pelagic calcifiers. The temperature effect on remineralization rates of marine organic matter also plays a critical role in controlling the carbon cycle dynamics, especially during the warmer periods of the Cenozoic.

Tectonic-sedimentary evolution of the frontal part of the Ukrainian Carpathian nappe structure

For the first time in the Ukrainian Carpathians, the depths and tectono-sedimentation processes in the north-eastern part of the Outer Carpathian Basin (Skyba and Boryslav-Pokuttya units) have been restored on the base of sedimentological and microfaunistic studies. It was established that in the Cretaceous-Eocene time, the deep-water (near Calcite Compensation Depth) turbidite and similar sedimentation (turbidites with Bouma textures, grainites, debris-flow deposits), which periodically alternated with (hemi)pelagic sedimentation (red, green and black shales) was dominant here. Sedimentation took place on the continental margin of the the Carpathian branch of the Tethys, where deep-water fans were formed. Cretaceous-Eocene background red and green shales are enriched in buried in situ benthic foraminifera which are similar in taxonomic composition and morphological features to the microfauna of the Carpathian-Alpine and Atlantic regions (deep-water agglutinated foraminifera), which indicate lower bathyal – abyssal depths of flysch sedimentation. Latest Eocene Globigerina Marl horizon contains the foraminiferal assemblage with plankton dominance, which indicates a general shallowing of the Outer Carpathian Basin (middle-upper bathyal conditions above a calcite compensation depth). Oligocene – lowermost Miocene Menilite-Krosno and Polyanytsia formations were accumulated in the Skyba and Boryslav-Pokuttya sub-basins. In the Miocene, shallow-water molasses were accumulated here. Probably, the tectonic uproot of flysch deposits from its substrate and their synsedymentary thrusting towards the platform caused a significant shallowing of the Skyba and Boryslav-Pokuttya sub-basins starting from the latest Eocene. These processes reflected the growth of the Carpathian frontal nappes at the final orogen formation stage.

Sedimentary and volcanic record of the nascent Izu-Bonin-Mariana arc from IODP Site U1438

The oldest known, intact sedimentary record of a nascent intraoceanic arc was recovered in a ∼100-m-thick unit (IV) above ca. 49 Ma basaltic basement at International Ocean Discovery Program Site U1438 in the Amami Sankaku Basin. During deposition of Unit IV the site was located ∼250 km from the plate edge, where Izu-Bonin-Mariana subduction initiated at 52 Ma. Basement basalts are overlain by a mudstone-dominated subunit (IVC) with a thin basal layer of dark brown metalliferous mudstone followed by mudstone with sparse, graded laminae of amphibole- and biotite-bearing tuffaceous sandstone and siltstone. Amphibole and zircon ages from these laminae suggest that the intermediate subduction-related magmatism that sourced them initiated at ca. 47 Ma soon after basement formation. Overlying volcaniclastic, sandy, gravity-flow deposits (subunit IVB) have a different provenance; shallow water fauna and tachylitic glass fragments indicate a source volcanic edifice that rose above the carbonate compensation depth and may have been emergent. Basaltic andesite intervals in upper subunit IVB have textures suggesting emplacement as intrusions into unconsolidated sediment on a volcanic center with geochemical and petrological characteristics of mafic, differentiated island arc magmatism. Distinctive Hf-Nd isotope characteristics similar to the least-radiogenic Izu-Bonin-Mariana boninites support a relatively old age for the basaltic andesites similar to detrital amphibole dated at 47 Ma. The absence of boninites at that time may have resulted from the position of Site U1438 at a greater distance from the plate edge. The upper interval of mudstone with tuffaceous beds (subunit IVA) progresses upsection into Unit III, part of a wedge of sediment fed by growing arc-axis volcanoes to the east. At Site U1438, in what was to become a reararc position, the succession of early extensional basaltic magmatism associated with spontaneous subduction initiation is followed by a rapid transition into potentially widespread subduction-related magmatism and sedimentation prior to the onset of focused magmatism and major arc building.