GSA Today Archive |
|
GSA Today, v. 9, no. 2, February 1999
|
|
Table of Contents
Science Article: (View Abstract)
Hypercalcification: Paleontology Links Plate Tectonics and Geochemistry to Sedimentology
by Steven M. Stanley, Lawrence A. Hardie
 |
Warning! 2.02 MB
file size. View entire
issue (pdf format) ...
... or right-click (option-click for Macs) to download. |
 |
Note: This file requires Acrobat
Reader to view or print. Reader can be downloaded free from Adobe.
|
also ...
| In Memoriam |
2 |
| History of Geology Award |
3 |
| Executive Director Position |
3 |
| Award Nominations |
7 |
| Memorial Preprints |
7 |
| SAGE Remarks |
8 |
| Biggs Award |
9 |
| GeologyCo-Editor |
9 |
| Student Research Grants |
10 |
| Washington Report |
12 |
| GSA On the Web |
12 |
| GSAF Update |
14 |
| 1999 Section Meeting -- Rocky Mountain |
17 |
| 1999 Section Meeting -- North-Central |
23 |
| Shlemon Mentors Workshops |
23 |
| Penrose Conference Report: Ophiolites and Oceanic Crust |
30 |
| GSA Meetings |
33 |
| Bulletin and Geology Contents |
34 |
| 1999 GeoVentures |
35 |
| Classifieds |
38 |
Return to GSA Today Archives
top
Hypercalcification: Paleontology Links Plate Tectonics
and Geochemistry to Sedimentology
by Steven M. Stanley, Lawrence A. Hardie
ABSTRACT
During the Phanerozoic Eon, the mineralogies of nonskeletal marine cements and
oolites have oscillated on a 100-200 m.y. scale between aragonite ± high-Mg calcite
(aragonite seas) and low-Mg calcite (calcite seas). Oscillations in the carbonate
mineralogy of dominant reef-building and sediment-producing organisms are in harmony
with the oscillations for nonskeletal carbonates. These oscillations, together
with synchronous oscillations in the mineralogy of marine potash evaporites, can
be explained by secular variation in the Mg/Ca ratio of seawater driven by changes
in the spreading rates along midocean ridges. The temporal patterns for biocalcification
have come to light through a focus on (1) simple taxa that exert relatively weak
control over the milieu in which they secrete their skeletons, and (2) taxa that
hypercalcify-i.e., secrete massive skeletons or are exceptionally productive,
for example, in forming voluminous chalk deposits. Most major reef-building and
sediment-producing taxa belong to both of these categories. It appears that the
Mg/Ca ratio of seawater has not only controlled Phanerozoic oscillations in hypercalcification
by simple taxa, such as calcareous nannoplankton, sponges, and bryozoans, but
has strongly influenced their skeletal evolution.
Return to GSA Today Archives
top
|
