Whitings, a sedimentologic dilemma

Shinn, Eugene A.; Steinen, Randolph P.; Lidz, Barbara H.; Swart, Peter K.

doi:10.1306/212f8f3a-2b24-11d7-8648000102c1865d

Cited by 175 publications

(191 citation statements)

References 0 publications

Supporting

Mentioning

173

Contrasting

Order By: Relevance

“…Precipitation of aragonite takes place along this salinity gradient (42)(43)(44). Some of this precipitation apparently occurs spontaneously (whitings) driven by either inorganic and/or organic mechanisms (43)(44)(45)(46)(47)(48). Although the precise mechanism of generation is still controversial, precipitation of large quantities of aragonite takes place and the consequent release of CO 2 combined with abundant photosynthesis by seagrasses, benthic algae, and cyanobacteria can cause the residual DIC to have elevated ␦ 13 C values.…”

Section: Discussionmentioning

confidence: 99%

Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle

Swart

2008

Proc. Natl. Acad. Sci. U.S.A.

192

119

View full text Add to dashboard Cite

The carbon isotopic (␦ 13 C) composition of bulk carbonate sediments deposited off the margins of four carbonate platforms/ramp systems (Bahamas, Maldives, Queensland Plateau, and Great Australian Bight) show synchronous changes over the past 0 to 10 million years. However, these variations are different from the established global pattern in the ␦ 13 C measured in the open oceans over the same time period. For example, from 10 Ma to the present, the ␦ 13 C of open oceanic carbonate has decreased, whereas platform margin sediments analyzed here show an increase. It is suggested that the ␦ 13 C patterns in the marginal platform deposits are produced through admixing of aragonite-rich sediments, which have relatively positive ␦ 13 C values, with pelagic materials, which have lower ␦ 13 C values. As the more isotopically positive shallowwater carbonate sediments are only produced when the platforms are flooded, there is a connection between changes in global sea level and the ␦ 13 C of sediments in marginal settings. These data indicate that globally synchronous changes in ␦ 13 C can take place that are completely unrelated to variations in the global carbon cycle. Fluctuations in the ␦ 13 C of carbonate sediments measured during previous geological periods may also be subject to similar processes, and global synchroniety of ␦ 13 C can no longer necessarily be considered an indicator that such changes are related to, or caused by, variations in the burial of organic carbon. Inferences regarding the interpretation of changes in the cycling of organic carbon derived from ␦ 13 C records should be reconsidered in light of the findings presented here.isotope ͉ organics ͉ shallow-water platform V ariations in the stable carbon isotopic composition (␦ 13 C) of calcium carbonate sediments throughout geological time have been an invaluable aid in unraveling changes in the global carbon cycle (1, 2). In addition, such variations in ␦ 13 C have provided information on the transfer of carbon between reservoirs during major geological events such as bolide impacts or catastrophic climate changes (3, 4). Generally speaking, increases in the ␦ 13 C of carbonates are considered indicative of increased burial and preservation of isotopically negative organic carbon, whereas decreases in the ␦ 13 C suggest transfer of carbon from the organic into the inorganic reservoir (5-7). Hence, variation in the ␦ 13 C of carbonate material should be a proxy for the amount of buried organic carbon. For example, the ␦ 13 C of the oceanic record has become increasingly more negative over the past 50 million years (Myr) (8, 9), suggesting that as much as 10 20 g of organic carbon have been transferred from the organic to the inorganic carbon reservoir (6).The most reliable archives of changes in the ␦ 13 C of the oceans over the past 100 Myr to 200 Myr are contained in the skeletons of planktic and benthic foraminifera (9, 10). Not only are these organisms relatively diagenetically stable, but the ␦ 13 C values can be corrected for any species-spe...

show abstract

Section: Discussionmentioning

confidence: 99%

Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle

Swart

2008

Proc. Natl. Acad. Sci. U.S.A.

192

119

View full text Add to dashboard Cite

show abstract

“…The seas overlying these muds are well known for episodic, highly turbid events that produce milkywhite coloured waters, historically referred to as "whitings" (Cloud, 1962). Whitings cover from tens to hundreds of km 2 and have an average suspended sediment concentration of 10 mg L −1 (Shinn et al, 1989). These whitings are so distinct that the dramatic white waters have been observed and enumerated from photography taken by astronauts aboard the Space Shuttle (Robbins et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Optics and remote sensing of Bahamian carbonate sediment whitings and potential relationship to wind-driven Langmuir circulation

2009

View full text Add to dashboard Cite

Abstract.Regions of milky white seas or "whitings" periodically occur to the west of Andros Island along the Great Bahama Bank where the bottom sediment consists of finegrained aragonite mud. We present measurements of inherent optical properties within a sediment whiting patch and discuss the potential for monitoring the frequency, extent, and quantity of suspended matter from ocean colour satellite imagery. Sea spectral reflectance measured in situ and remotely from space revealed highly reflective waters elevated across the visible spectrum (i.e., "whitened") with a peak at 490 nm. Particulate backscattering was an order of magnitude higher than that measured at other stations throughout the region. The whiting also had one of the highest backscattering ratios measured in natural waters (0.05-0.06) consistent with water dominated by aragonite particles with a high index of refraction. Regular periodicity of 40 and 212 s evident in the light attenuation coefficient over the sampling period indicated patches of fluctuating turbidity on spatial scales that could be produced from regular rows of Langmuir cells penetrating the 5-m water column. We suggest that previously described mechanisms for sediment resuspension in whitings, such as tidal bursting and fish activity, are not fully consistent with these data and propose that wind-driven Langmuir cells reaching the full-depth of the water column may represent a plausible mechanism for sediment resuspension and subsequent whiting formation. Optics and remote sensing provide important tools for quantifying the linkages between physical and biogeochemical processes in these dynamic shallow water ecosystems.

show abstract

“…A distinctive and often volumetrically important component of these sediments is carbonate mud (the <63 μm sediment fraction). However, the origins of both aragonitic and Mg-calcite carbonate muds remains a topic of long-standing debate (2,3). Indeed, where attempts have been made to quantify sources of the fine sediment fraction a high proportion remains of unknown origin (e.g., up to 40% in Bahamian sediments and between 28 and 36% in Belize lagoon sediments) (4,5).…”

mentioning

confidence: 99%

Fish as major carbonate mud producers and missing components of the tropical carbonate factory

Perry

Salter

Harborne

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

119

View full text Add to dashboard Cite

Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) calcium carbonate from their guts ("low" and "high" Mg-calcite and aragonite), but that very fine-grained (mostly <2 μm) high Mgcalcite crystallites (i.e., >4 mole % MgCO 3 ) are their dominant excretory product. Crystallites from fish are morphologically diverse and species-specific, but all are unique relative to previously known biogenic and abiotic sources of carbonate within open marine systems. Using site specific fish biomass and carbonate excretion rate data we estimate that fish produce ∼6.1 × 10 6 kg CaCO 3 ∕year across the Bahamian archipelago, all as mud-grade (the <63 μm fraction) carbonate and thus as a potential sediment constituent. Estimated contributions from fish to total carbonate mud production average ∼14% overall, and exceed 70% in specific habitats. Critically, we also document the widespread presence of these distinctive fish-derived carbonates in the finest sediment fractions from all habitat types in the Bahamas, demonstrating that these carbonates have direct relevance to contemporary carbonate sediment budgets. Fish thus represent a hitherto unrecognized but significant source of fine-grained carbonate sediment, the discovery of which has direct application to the conceptual ideas of how marine carbonate factories function both today and in the past. marine teleost | fish intestine | carbonate production M arine carbonates contain unique records of changes in ocean chemistry, biogeochemical cycling, and benthic and pelagic ecology (1), and therefore provide vital information on climate shifts in the geological past. A distinctive and often volumetrically important component of these sediments is carbonate mud (the <63 μm sediment fraction). However, the origins of both aragonitic and Mg-calcite carbonate muds remains a topic of long-standing debate (2, 3). Indeed, where attempts have been made to quantify sources of the fine sediment fraction a high proportion remains of unknown origin (e.g., up to 40% in Bahamian sediments and between 28 and 36% in Belize lagoon sediments) (4, 5). This problem arises in part because, with the exception of inorganic carbonate precipitation (e.g., the carbonate "whiting" controversy) (3, 6-8), the processes of carbonate mud production necessarily invoke the degradation of larger bioclasts (skeletal fragments of marine organisms) to produce mud-grade carbonate, and/or grain recrystallization to produce high Mg-calcite muds (9-11). Thus attempts to determine primary mud sources and production budgets are often hampered because of grain obliteration. The mineralogical composition of the mud fraction of modern tropical carbonate sediment is also very variable between s...

show abstract

Whitings, a sedimentologic dilemma

Cited by 175 publications

References 0 publications

Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle

Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle

Optics and remote sensing of Bahamian carbonate sediment whitings and potential relationship to wind-driven Langmuir circulation

Fish as major carbonate mud producers and missing components of the tropical carbonate factory

Contact Info

Product

Resources

About