Sediment marker levels

Berger (12) has identified another sediment marker level in the sediments. This is the level at v hich the proportion of "resistant" planktonic foraminifera show the first significant increase. Berger s estimate of minimum dissolution loss at the Rq level is 10 percent. Adelseck s (11) experimentally determined amount of dissolution necessary to produce the Rq level is approximately 50 percent dissolution. 

The Distribution of Calcium Carbonate Saturation States and Their Relation to Sediment Marker Levels... 

Figure 7). His results indicate that Rq and CSL are close to coincident with the probable uncertainty of their determination. A detailed profile showing the relations among the sediment marker levels and the saturation state of seawater with respect to calcite and aragonite in the Northwest Atlantic Ocean is presented in Figure 8.

An approximate relationship between the degree of undersaturation of seawater with respect to calcite and the extent of dissolution can be established by comparing the saturation state at the various sediment marker levels with estimates of the amount of dissolution required to produce these levels. In Figure 9 the "distance from equilibrium (1 - 2) has been plotted against the estimated percent dissolution of the calcitic sediment fraction. Within the large uncertainties that exist in the amount of dissolution required to produce the FL and Rq levels, a linear relation between the degree of undersaturation and extent of dissolution can be established. The intercept of the linear plot with the FL and Rq levels indicates that approximately 15 percent more material has been lost than Berger s (12) minimum loss estimate of 50% and 10%, respectively. 

Calcium carbonate is accumulating in deep ocean sediments, in which the overlying water is undersaturated with respect to both aragonite and calcite, and sediment marker levels closely correspond to unique saturation states. This indicates that dissolution kinetics play an important role in determining the relation between seawater chemistry and calcium carbonate accumulation in deep ocean basins. It is, therefore, necessary to have knowledge of the dissolution kinetics of calcium carbonate in seawater if the accumulation of calcium carbonate is to be understood. 

Figure 8, A detailed profile of calcite and aragonite saturation states and sediment marker depth in the Northwestern Atlantic Ocean, (Percentages are estimates of the amount of calcite dissolution which must occur to produce a given marker level.)...

The carbonate compensation depth (CCD) occurs where the rate of calcium carbonate dissolution is balanced by the rate of infall, and the calcium carbonate content of surface sediments is close to Owt.% (e.g., Bramlette, 1961). The CCD has been confused with the calcium carbonate critical depth (sometimes used interchangeably with the lysocline discussed next), where the carbonate content of the surface sediment drops below 10 wt.%. A similar marker level in deep-sea sediments is the ACD, below... 

Several fatty acids, specifically 15 0, 17 0 and all branched fatty acids, are produced primarily by both aerobic and anaerobic bacteria [55-57] and the sum of those fatty acids has been used to estimate bacterial contributions [58-61]. A comparison of bacterial markers in plankton, sediment trap and sediment samples showed the lowest values, with little variation, in plankton samples (Fig. 3 b), and the greatest bacterial levels in sediments. The sediment traps, containing partially degraded material, had bacterial marker levels intermediate between the other two sample types, and levels of bacterial markers increased with increasing period of deployment. However, there are conflicting theories concerning the usefulness of these markers and, for that reason, bacterial markers should only be employed with caution. For instance, in a recent paper, Harvey and Macko [57] did not find a correlation between total fatty acids attributed to bacteria and bacterial carbon, and they suggest that bacterial fatty acids only be used as qualitative tools to estimate bacterial contributions. Wakeham [62] also points out that fatty acids of common oceanic bacteria may not be compositionally different from planktonic fatty acids so that bacterial... 

Few data have been published on cationic surfactants in aquatic sediments. Levels from 3 to 67 mg kg-1 were determined in sediment samples from Rapid Creek [54] and 6-69 mg kg-1 concentrations were found in sediment samples from Japan [4]. DTD MAC was reported in digested sewage sludge at levels ranging from 0.15 to 5.87 gkg-1 [22]. Also, cationic surfactants were determined in urban coastal environments and they were reported as markers [18,55]. In our work, concentrations of BAC ranged from 23 to 206 p,gkg 1 in sediment samples from different rivers near to wastewater treatment plants,... 

By virtue of where, when, and how the various organic matter inputs were formed and transported to the underlying sediments, it is possible to exploit specific chemical and isotopic characteristics to make inferences about the sources and composition of sedimentary organic matter. Much of this information is inaccessible at the bulk level. For example, bulk elemental compositions and stable carbon isotopic compositions are often insufficiently unique to distinguish and quantify sedimentary inputs. Abundances and distributions of source-specific organic compounds ( biomarkers ) can help to identify specific inputs. However, this molecular marker approach suffers from the fact that the source diagnostic marker compounds are... 

The majority of patients also had an elevated leukocyte count with modestly elevated levels of aldolase, a marker of muscle injury however, creatine phosphokinase, another indicator of muscle injury, was normal in most patients. This inconsistency between the levels of these two muscle-associated enzymes, previously described in some patients with systemic sclerosis and the toxic oil syndrome (TOS) (see below), is helpful in differentiating EMS from other myopathies (muscle diseases) and from eosinophilic fasciitis (EE) (see below). Approximately one-half of patients had abnormal liver function tests, although the changes were mild. The erythrocyte sedimentation rate, rheumatoid factor, and levels of IgE, complement, and cryoglobulin (all markers of immune dysfunction) were normal in most patients tested. 

Ketones are a class of lipids that were rarely seen in plankton and sediment trap samples from Trinity Bay, although there was a significant level in sediments. This suggests the possibihty of their use as an internal standard in hpid analyses of water column samples. However, they are present in some prymne-siophytes and, in fact, there is much interest in their use as paleotemperatuxe indicators [e.g. 39,40], although methyl and ethyl ketone concentrations respond to nitrogen hmitation as well [41]. Their rarity combined with the fact that they may comprise as much as a quarter of the lipids of some species [42], however, suggests that as a class, ketones could be excellent water column markers in some areas. 

The purpose of this study is to determine variables involved in cementing beach sediment into beachrock. Beachrocks are markers of relative sea level. The process of cementation reflects the geochemistry and temperature conditions of the interstitial waters at the time of cementation. Since the seaward-dipping successions reflect progressive stages of cementation, a geologic history of the shoreline may be unraveled. 

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