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首页> 外文期刊>Facies >Degrading windward patch reefs and processes influencing composition, mineralogy, and stable-isotope record of peri-reefal sediment, San Salvador Island, Bahamas
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Degrading windward patch reefs and processes influencing composition, mineralogy, and stable-isotope record of peri-reefal sediment, San Salvador Island, Bahamas

机译：降解迎风贴片珊瑚礁和过程影响组成，矿物学和稳定同位素记录Peri-Reefal沉积物，圣萨尔瓦多岛，巴哈马

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摘要

Patch reefs and their surrounding skeletal-peloidal-intraclast grainstone facies are very abundant on modern (sub-) tropical carbonate platforms. Compared to the barrier and fringing reef facies, the processes influencing composition, mineralogy, and stable-isotope record of peri-reefal sediment have received much less attention, despite a potentially significant volume of such sediment in many Phanerozoic carbonate platforms. To better understand the evolution and sedimentary record of patch-reef settings, this study investigates the patch-reef biota (scuba diving surveys) and composition (petrography), mineralogy (X-ray diffraction) and stable-isotope record (mass spectrometry) of peri-reefal sediments at East Beach on the northeastern, windward margin of San Salvador Island, the Bahamas. The macroalgae-dominated ecology is assessed, and a decadal decline in stony coral coverage with a shift to more opportunistic, stress-tolerant species is documented. The most common stony corals on these shallow-water (3-5 m) patch reefs are Diploria strigosa, Porites astreoides, and P. porites, and Halimeda lacrimosa dominates among green algae. Peri-reefal sediment is pure carbonate sand composed of roughly equal volumes of aragonite and high-Mg calcite (HMC), with mean MgCO3 content in HMC of 15.2%. The bulk-sediment isotope record shows very limited variation (delta C-13 between + 2.3 parts per thousand and + 3.2 parts per thousand, and delta O-18 between - 0.8 parts per thousand and - 0.6 parts per thousand) and this is consistent with similar modern settings. A lack of very fine particles and an abundance of intraclasts suggest that the environment is strongly influenced by bio- and physical erosion. Fast-growing algae have likely reached an abundance beyond the grazing capacity, which has drastically reduced the space for coral settlement and recruitment, and thus has compromised the patch-reef resilience in this part of the Bahamian Archipelago.
机译：Patch Reefs及其周围的骨骼 - 鹈鹕 - 腔内晶石相对于现代（亚）热带碳酸盐平台非常丰富。与屏障和流苏礁相比，影响组成，矿物学和稳定同位素记录的过程的过程较少的关注，尽管许多PhanoRo型碳酸盐平台在潜在的大量沉积物中潜在的大量沉积物。为了更好地了解补丁礁设置的进化和沉积记录，本研究调查了Patch-Reef Biota（Scuba潜水调查）和组合物（岩射线图），矿物学（X射线衍射）和稳定同位素记录（质谱）东北海滩的Peri-Reefal沉积物，圣萨尔瓦多岛的迎风边缘，巴哈马。评估了大主石占主导地位的生态学，并记录了多移到更具机会主义的耐受耐受耐受性物种的石珊瑚覆盖的二等地下降。这些浅水（3-5米）贴片礁上最常见的石珊瑚是外交杂志，Porites astroides和p. porites和Halimeda lacrimosa在绿藻中占主导地位。 Peri-Reefal Sediment是由大致相等的纯碳酸盐砂组成，大致相等的化石和高镁铌铁 - HMC铌铁砧（HMC），平均MgCO 3含量为15.2％。体积沉积物同位素记录显示出非常有限的变化（Delta C-13 + 2.3份/千分比每千份，+ 3.2份每千份，达到0.8份/ 0.6份千分之一），这是一致的具有类似的现代化环境。缺乏非常细腻的颗粒和丰富的内术表明环境受到生物和物理侵蚀的强烈影响。快速增长的藻类可能达到了超出了放牧能力的丰富，这急剧减少了珊瑚结算和招聘的空间，因此损害了巴哈马群岛这一部分的贴片礁弹性。

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