Dolomitization and evolution of the Puerto Rico North Coast confined aquifer system
- 出版日期：2000.
- 页数：338 p. :
- 第一责任说明：Wilson R. Ramirez Martinez.
- 分类号：a495.42
- ISBN：0599761326(ebk.) :
MARC全文
02h0023331 20110420154734.0 cr un||||||||| 110411s2000 xx ||||f|||d||||||||eng | AAI9971317 0599761326(ebk.) : CNY371.35 NGL NGL NGL a495.42 Ramirez Martinez, Wilson R. Dolomitization and evolution of the Puerto Rico North Coast confined aquifer system [electronic resource] / Wilson R. Ramirez Martinez. 2000. 338 p. : digital, PDF file. Chairs: Stephen A. Nelson; Ivan P. Gill. ; Source: Dissertation Abstracts International, Volume: 61-04, Section: B, page: 1834. Thesis (Ph.D.) -- Tulane University, 2000. The Lares Limestone and Montebello Member of the Cibao Formation form the lower confined aquifer system of the Puerto Rico North Coast. These extensively cored Neogene limestone units dip from 4° to 6° toward the north, are exposed over a broad area, and have a relatively well-known geologic setting and history.;Dolomite is absent in the exposed sections of the units but is abundant in the subsurface. Dolomitization was apparently limited to the subsurface and seaward portions of the units.;Petrography indicates the following paragenetic sequence: (1) shallow submarine diagenesis, (2) extensive dissolution and/or neomorphism of calcitic and aragonitic allochems, (3) burial compaction and pressure solution, (4) dolomitization, (5) dolomite dissolution and generation of coarse calcite cements. Dolomites are not affected by pressure-solution features, indicating dolomitization after at least 300 m burial. Modern aquifer water is undersaturated with respect to dolomite and high Mg2+ content in the water indicates dissolution of dolomite is occurring, therefore dolomitization occurred after some burial (middle Miocene) and before modern aquifer conditions developed (late Miocene). The dolomites are calcian with CaCO3 mean mole percentage of 56. Average δ18O and δ13C values relative to PDB are +1.0‰ (±0.4‰) and +0.2‰ (±0.5‰) respectively. Mean dolomitic Sr concentration is 360 ppm. Fe and Mn mean concentrations in the dolomites are 266 ppm and 25 ppm respectively. 87Sr/86Sr ranges from 0.708276 to 0.708509 ± 0.000008 in the dolomites and from 0.708199 to 0.708295 ± 0.000008 in the aquifer waters.;These geochemical data are consistent with dolomitization by both marine waters or a mixture of marine and aquifer waters. High concentrations of Fe and Mn indicate non-marine waters. Meteoric fabrics before and after dolomitization suggest meteoric water influences. Sr isotopic ratios are consistent with mixing of marine and aquifer waters.;Although there are other viable explanations, mixing-zone dolomitization in a deep confined aquifer provides the best way to explain all the data obtained. Miocene eustatic sea-level fluctuations probably maintained flow and movement of the mixing zone producing thick dolomitic intervals. Groundwater Puerto Rico. Tulane University. aCN bNGL http://168.160.16.198/umi/detail_usmark.jsp?searchword=pub_number%3DAAI9971317&singlesearch=no&channelid=%CF%B8%C0%C0&record=1 NGL Bs171 rCNY371.35 ; h1 bs1104