Chondrodonta is an opportunistic, oyster-like bivalve, common in shallow-water carbonates of the Cretaceous Tethyan Realm. Despite its high abundance and widespread geographic distribution, the precise relationship between the early Aptian proliferation and environmental perturbations resulting from the Oceanic Anoxic Event 1a (OAE1a), has not been investigated. Stratigraphic and geochemical analyses of the lower Aptian Chondrodonta bedsets within the inner platform limestones of the Apulia Carbonate Platform (Gargano Promontory, southern Italy) are conducted to assess the environmental controls on the Chondrodonta proliferation and its timing and causal relationship to OAE1a. Chondrodonta occurs with sparse to common individuals within requieniid rudist floatstone–rudstones, forms monospecific biostromes during the early phase of stressed environmental conditions and then rapidly disappears at the peak of OAE1a. It proliferates in dysoxic seawater with relatively increased trophic sources, which correlate to increasing nutrient levels in the nearby pelagic realm. Chondrodonta-rich beds are associated worldwide with the onset of OAE1a and occur in a transitional context between a stable and a strongly stressed environment, where the opportunistic behaviour of Chondrodonta is rather efficient. Increasing nutrient load and unstable environmental conditions right below the peak of OAE1a created an environmental ‘window’ favourable for Chondrodonta to proliferate, outplaying the less tolerant benthos (for example, rudists). The occurrence, duration and position of the environmental window were controlled by local palaeogeographic and hydrodynamic settings (i.e. low energy, decreased seawater oxygenation and circulation). Further increase in inhospitable conditions, leading to OAE1a, constituted an upper threshold for Chondrodonta and allowed mesotrophic taxa like Bacinella–Lithocodium and orbitolinids to dominate the benthic communities. The present study suggests that the proliferation of Chondrodonta in shallow-water platform carbonates can be used as proxy for the initial phase of ecological stress related to OAE1a.

中文翻译：

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作为 OAE1a 开始时环境不稳定性的代表的软骨齿龙的增殖：来自普利亚碳酸盐平台浅水石灰岩的见解

Chondrodonta是一种机会主义的牡蛎状双壳类动物，常见于白垩纪特提斯王国的浅水碳酸盐岩中。尽管其丰度高且地理分布广泛，但尚未研究早期 Aptian 增殖与海洋缺氧事件 1a (OAE1a) 引起的环境扰动之间的确切关系。下阿普第阶的地层和地球化学分析Chondrodonta阿普利亚碳酸盐平台的内平台灰岩（加尔加诺岬，意大利南部）内bedsets被进行评估对环境控制Chondrodonta扩散和OAE1a其定时和因果关系。软骨齿类在 requieniid rudist floatstone-rudstones 中以稀疏到普通个体发生，在压力环境条件的早期阶段形成单一的生物群落，然后在 OAE1a 的高峰期迅速消失。它在营养来源相对增加的缺氧海水中增殖，这与附近远洋领域的营养水平增加有关。Chondrodonta富床与OAE1a的发病相关的全球和发生在一个稳定的和强强调环境，其中的机会主义行为之间的过渡方面Chondrodonta是相当有效的。增加营养负荷和不稳定的环境条件正下方OAE1a高峰创造了一个环境“窗口”有利于Chondrodonta增殖，胜过容忍度较低的底栖生物（例如，粗野生物）。环境窗口的出现、持续时间和位置受当地古地理和水动力设置（即低能量、海水氧化和循环减少）控制。在恶劣的条件下进一步增加，导致OAE1a，构成了上阈值Chondrodonta和允许中营养类群像Bacinella-Lithocodium和orbitolinids主宰底栖生物群落。本研究表明，增殖Chondrodonta在浅水平台碳酸盐可以用作代理针对与OAE1a生态压力的初始阶段。