Effects of Holocene sea level changes on subtidal palaeoecosystems, southeastern Brazil.
Effects of Holocene sea level changes on subtidal palaeoecosystems, southeastern Brazil.
复制标题
全新世海平面变化对巴西东南部潮下古生态系统的影响。
DOI：
10.1016/j.margeo.2016.08.007
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发表时间：
2016
期刊：
影响因子：
2.9
通讯作者：
D.
中科院分区：
文献类型：
--
作者：
Spotorno-Oliveira;P.;Tamega;F. T. S.;Oliveira;C. A.;Castro;J. W. A.;Coutinho;R.;Iryu;Y. and Bassi;D.
巴西东南部的海洋海岸沉积物提供了一个很好的机会，调查环境变化，如海平面和营养变化在全新世时期。在这项研究中，我们提出了从Arraial做卡波湾，里约热内卢州的沉积物记录。为了提高对该湾潮下带上部古生态系统演化动力学的认识，我们提供了一个全新世碳酸盐和混合硅质碎屑-碳酸盐沉积物的微相分析，从潮上带到潮下带。年龄-深度模型基于14 C测年，揭示了距今约7000 cal. years的基底年龄。在六个微相中，生物组分以蠕虫和珊瑚藻为主。一些从属组件也存在，包括微相决定薄壳双壳类。化石蠕虫以单种的过度生长的Petaloconchus varians为代表。珊瑚红藻以Lithophyllumpustulatum、Spongites fruticulosus、Spongites yendoi、Mesophyllumengelharti和未鉴定的膝状珊瑚为代表。微相分析表明，该湾上亚潮带生态系统底质随相对海平面的变化而变化：（1）在快速海侵趋势期，底质为粗软底质;（2）冰后期最高海平面缓慢下降至现今海平面后，底质为细软底质。在约7000年前，粗糙的软质基底的特征是由灌木状珊瑚和石英颗粒组成的大陆径流输入。冰后期海平面最高值后，高水位沿着上升流系统形成，形成了以碳酸盐为主的沉积。蠕虫和珊瑚，沿着与薄壳双壳类，在低沉降率设置和高营养水平的环境中茁壮成长。
Southeastern Brazilian marine coastal deposits provide an excellent opportunity to investigate environmental changes such as sea level and trophic variability during the Holocene period. In this study, we present a sediment record from Arraial do Cabo Bay, Rio de Janeiro State. In order to improve the understanding of the upper subtidal palaeoecosystem evolutionary dynamics of this Bay, we provide a microfacies analysis of Holocene carbonate and mixed siliciclastic-carbonate deposits cropping out today from the supratidal to the subtidal zones. The age-depth model is based on14C dating and revealed a basal age of ~ 7000 cal. years BP. In the six distinguished microfacies, the biogenic components are dominated by vermetids and coralline algae. A number of subordinate components are also present, including the microfacies determining thin-shelled bivalves. Fossil vermetids are represented by monospecific clusters of overgrowingPetaloconchus varians.Coralline red algae are represented byLithophyllumpustulatum,Spongites fruticulosus,Spongites yendoi,Mesophyllumengelharti, and unidentified geniculate corallines. The microfacies analysis revealed that the substrate of the benthic community in the upper subtidal ecosystem of the Bay changed according to the relative sea level: (1) during the rapid sea transgressive trend it was coarse soft substrate, (2) after the postglacial sea level maximum succeeding a slow decline to present sea level it changed into fine soft substrate. At ~ 7000 years ago the coarse soft substrate was characterised by fruticose corallines and composed of quartz grains from continental run off input. After the postglacial sea level maximum the highstand elevation along with the established upwelling system brought about a predominantly carbonate deposition. Vermetids and corallines, along with thin-shelled bivalves, thrived in a low sedimentation rate setting and high nutrient level environment.