end points are part of an observed continuous stratigraphic
range.
If the fossil record encountered in stratigraphic sections
that we want to correlate and calibrate in time would be
ubiquitous and perfect, i.e., if only time would control
the appearance, range, and disappearance of taxa, then
biostratigraphy would be a straightforward exercise. The
science of biochronology, as developed for the evolutionary first and last occurrence datums of ocean plankton,
would be a matter of systematic bookkeeping on a worldwide scale, only constrained by taxonomic deliberations.
Unfortunately, the paleontological record is highly
imperfect.
Uncertainty factors may be summarized as follows:
1. Quality and quantity of sampling
2. Specimen frequency of fossil taxa
3. Confidence of taxonomic identification
4. Influence of environmental change on the stratigraphic
range of taxa
5. Differential rate of taxon evolution in different parts of
the world
6. Time lag in migration of taxa, where correlation is over
large distances or across major environmental barriers
Hence, biochronology almost always requires careful
calibration with independent geomagnetic reversals and
stable isotope correlation frameworks.
Biochronology is reaching a pinnacle in the massive
fossil event datasets generated with TimeScale Creator
software (http://www.tscreator.org). The method and data
system confidently link all events in the evolutionary
“organic continuum” in an elegant linear time framework,
calibrated to Geologic Time Scale 2012 (see Geologic
Time Scale). A recent calibration of Cretaceous and Cenozoic planktonic foraminifera and calcareous nannofossils
of the temperate to tropical marine realm is by
Anthonissen and Ogg (2012). Syntheses for siliceous,
organic, and other microfossil biostratigraphy are summarized in the appropriate chapters in The Geologic Time
Scale (Gradstein et al., 2012), and detailed and updated
versions of all stratigraphic scales can be accessed as
datasets and graphics at the TimeScale Creator website.
Special mention is made of the detailed and highresolution (deep time) conodont-foraminifera-ammonoid
composite zonation for the Carboniferous, with over
35–40 zones constrained by 36 radiometric dates
employed in timescale building for this period (Davydov
et al., 2012). Particularly in younger parts of the Carboniferous zonal event, resolution is resolved at a
biochronologic scale that provides insight in biota migrations due to the waxing and waning of massive Gondwana
supercontinent glaciations.
Summary
Biochronology attempts to order and scale fossil events
and fossil ranges in linear time.
Bibliography
Anthonissen, D. E., and Ogg, J. G., 2012. Cenozoic and cretaceous
biochronology of planktonic foraminifera and calcareous
nannofossils. In Gradstein, F. M. (ed.), The Geologic Time Scale
2012. Amsterdam: Elsevier, pp. 1083–1128.
Davydov, et al., 2012. for reference see The Geologic Time Scale.
Gradstein, F. M., et al., 2012. The Geologic Time Scale. Amsterdam:
Elsevier.
BIOGENIC BARIUM
Graham Shimmield
Bigelow Laboratory for Ocean Sciences, East Boothbay,
ME, USA
Biogenic barium usually occurs as discrete microcrystals
of the refractory mineral, barite (BaSO 4 ). It may be found
in the water column (in the tests of both live and dead
planktonic species), in benthic foraminifera, in coral skeletons, and in the underlying sediment. The earliest observations of enriched barium (usually identified as barium
concentrations exceeding typical shale or sediment concentrations), and attributed to biological processes, are
the work of Revelle et al. (1955) working in the equatorial
divergence of the Pacific Ocean. Dehairs et al. (1980) and
Bishop (1988) showed that barite (BaSO 4 ) was precipitated in decaying suspended marine particulate matter
(particularly diatoms) in oceanic waters. Some studies
have suggested that biogenic barium may occur in heavy
mineral granules functioning as statoliths in statocyst
organs and within protozoans such as Xenophyophoria
and Loxodes. Biogenic barium distribution and concentration have been studied in benthic foraminifera and corals
as a tracer of bottom water nutrients and upwelling,
respectively.
Biogenic barium in sediments is often found in water
underlying areas of high productivity. Bishop (1988) has
studied the barium content of large and small particles in
the Gulf Stream, and Schmitz (1987) has illustrated the
use of Ba as a tracer of Indian Ocean plate movement
beneath the equatorial upwelling zone on a timescale of
millions of years. Virtually, all ocean basins display
enrichment of biogenic barium where productivity is elevated and with time (paleoproductivity). Shimmield
(1992) suggested that barite-secreting organisms may be
confined to a rather discrete zone within the coastal
upwelling productivity belt, seaward of the shelf break
(under a different nutrient regime), and as a consequence
shallow-water, organic-rich sediments may receive little
biogenic barium, or the sedimentary barite undergoes diagenesis during sulfate reduction (see below). A similar
distribution of biogenic barium was noted by Calvert and
Price (1983) in their work off Namibia.
The refractory nature of barite was remarked on in the
earliest work by Dymond (1981), something he called a
56
BIOGENIC BARIUM
range.
If the fossil record encountered in stratigraphic sections
that we want to correlate and calibrate in time would be
ubiquitous and perfect, i.e., if only time would control
the appearance, range, and disappearance of taxa, then
biostratigraphy would be a straightforward exercise. The
science of biochronology, as developed for the evolutionary first and last occurrence datums of ocean plankton,
would be a matter of systematic bookkeeping on a worldwide scale, only constrained by taxonomic deliberations.
Unfortunately, the paleontological record is highly
imperfect.
Uncertainty factors may be summarized as follows:
1. Quality and quantity of sampling
2. Specimen frequency of fossil taxa
3. Confidence of taxonomic identification
4. Influence of environmental change on the stratigraphic
range of taxa
5. Differential rate of taxon evolution in different parts of
the world
6. Time lag in migration of taxa, where correlation is over
large distances or across major environmental barriers
Hence, biochronology almost always requires careful
calibration with independent geomagnetic reversals and
stable isotope correlation frameworks.
Biochronology is reaching a pinnacle in the massive
fossil event datasets generated with TimeScale Creator
software (http://www.tscreator.org). The method and data
system confidently link all events in the evolutionary
“organic continuum” in an elegant linear time framework,
calibrated to Geologic Time Scale 2012 (see Geologic
Time Scale). A recent calibration of Cretaceous and Cenozoic planktonic foraminifera and calcareous nannofossils
of the temperate to tropical marine realm is by
Anthonissen and Ogg (2012). Syntheses for siliceous,
organic, and other microfossil biostratigraphy are summarized in the appropriate chapters in The Geologic Time
Scale (Gradstein et al., 2012), and detailed and updated
versions of all stratigraphic scales can be accessed as
datasets and graphics at the TimeScale Creator website.
Special mention is made of the detailed and highresolution (deep time) conodont-foraminifera-ammonoid
composite zonation for the Carboniferous, with over
35–40 zones constrained by 36 radiometric dates
employed in timescale building for this period (Davydov
et al., 2012). Particularly in younger parts of the Carboniferous zonal event, resolution is resolved at a
biochronologic scale that provides insight in biota migrations due to the waxing and waning of massive Gondwana
supercontinent glaciations.
Summary
Biochronology attempts to order and scale fossil events
and fossil ranges in linear time.
Bibliography
Anthonissen, D. E., and Ogg, J. G., 2012. Cenozoic and cretaceous
biochronology of planktonic foraminifera and calcareous
nannofossils. In Gradstein, F. M. (ed.), The Geologic Time Scale
2012. Amsterdam: Elsevier, pp. 1083–1128.
Davydov, et al., 2012. for reference see The Geologic Time Scale.
Gradstein, F. M., et al., 2012. The Geologic Time Scale. Amsterdam:
Elsevier.
BIOGENIC BARIUM
Graham Shimmield
Bigelow Laboratory for Ocean Sciences, East Boothbay,
ME, USA
Biogenic barium usually occurs as discrete microcrystals
of the refractory mineral, barite (BaSO 4 ). It may be found
in the water column (in the tests of both live and dead
planktonic species), in benthic foraminifera, in coral skeletons, and in the underlying sediment. The earliest observations of enriched barium (usually identified as barium
concentrations exceeding typical shale or sediment concentrations), and attributed to biological processes, are
the work of Revelle et al. (1955) working in the equatorial
divergence of the Pacific Ocean. Dehairs et al. (1980) and
Bishop (1988) showed that barite (BaSO 4 ) was precipitated in decaying suspended marine particulate matter
(particularly diatoms) in oceanic waters. Some studies
have suggested that biogenic barium may occur in heavy
mineral granules functioning as statoliths in statocyst
organs and within protozoans such as Xenophyophoria
and Loxodes. Biogenic barium distribution and concentration have been studied in benthic foraminifera and corals
as a tracer of bottom water nutrients and upwelling,
respectively.
Biogenic barium in sediments is often found in water
underlying areas of high productivity. Bishop (1988) has
studied the barium content of large and small particles in
the Gulf Stream, and Schmitz (1987) has illustrated the
use of Ba as a tracer of Indian Ocean plate movement
beneath the equatorial upwelling zone on a timescale of
millions of years. Virtually, all ocean basins display
enrichment of biogenic barium where productivity is elevated and with time (paleoproductivity). Shimmield
(1992) suggested that barite-secreting organisms may be
confined to a rather discrete zone within the coastal
upwelling productivity belt, seaward of the shelf break
(under a different nutrient regime), and as a consequence
shallow-water, organic-rich sediments may receive little
biogenic barium, or the sedimentary barite undergoes diagenesis during sulfate reduction (see below). A similar
distribution of biogenic barium was noted by Calvert and
Price (1983) in their work off Namibia.
The refractory nature of barite was remarked on in the
earliest work by Dymond (1981), something he called a
56
BIOGENIC BARIUM