Dates of Holocene environmental changes in Lake Bafa: A hierarchical Bayesian analysis of change points

Year 2023, Issue: 82, 23 - 36, 30.06.2023

Zeki Bora Ön

https://doi.org/10.17211/tcd.1283443

Abstract

The timing of the separation of Lake Bafa from the Aegean Sea and its subsequent transition to a
lake remains a topic of debate, with considerable uncertainties associated with the proposed dates
for these transitions. This study introduces a novel approach, hierarchical Bayesian change point
analysis (HBCPA), to identify tipping points in paleoenvironmental time series. The objective is to
offer more precise and objectively selected results concerning the previously uncertain transition
dates of Lake Bafa’s geological evolution in the Holocene. The method presented in this study is
applied to analyze stable oxygen and carbon isotope data from foraminifer and ostracod shells,
as well as total organic carbon (TOC) data, obtained from the BAFA09P02 sediment core. Results
indicate that the transition from a marine to an isolated lagoon environment occurred around
2060 years BP, with an 89% uncertainty interval ranging from 2250 to 1870 years BP. Additionally,
the transition from an isolated lagoon to a brackish lake environment is estimated to have occurred
around 595 years BP, with an 89% uncertainty interval ranging from 780 to 425 years BP. The
results of this study illustrate that the suggested HBCPA approach holds the capability to identify
tipping points in environmental data while quantifying their intrinsic uncertainties.

Keywords

Büyük Menderes Valley, Gibbs sampling, Maiandros River, MCMC, Miletos

Holosen’de Bafa Gölü’ndeki ortamsal değişikliklerin tarihleri: Hiyerarşik Bayes değişim noktası analizi

Abstract

Bafa Gölü’nün Ege Denizi’nden ayrılmasının ve ardından tatlısu gölüne geçişinin zamanlaması
tartışmalıdır ve bu değişimler için önerilmiş olan tarihlerin belirsizlik aralıkları oldukça
geniştir. Bu çalışmada, paleoçevre verilerinin analizinde kullanılmak üzere yeni bir yaklaşım
olarak “hiyerarşik Bayes değişim noktası analizi” (HBCPA) önerilmektedir ve sonuç olarak
Bafa Gölü’nün Holosen’de ortamsal değişim tarihleri için önerilmiş geniş belirsizlik aralıklarını
daraltma amacını taşımaktadır. Önerilen yöntem, BAFA09P02 çökel karotu foraminifer ve
ostrakod kavkılarından elde edilen duraylı oksijen ve karbon izotop verileri ile toplam organik
karbon (TOC) verileri üzerinde uygulanmıştır. Sonuçlar, denizel ortamdan kapalı lagünel ortama
geçişin yaklaşık GÖ 2060 yıl civarında gerçekleştiğini ve %89 belirsizlik aralığının GÖ 2250 ila
1870 yılları aralığında olduğunu göstermektedir. Kapalı bir lagünden acısu göl ortamına geçişin
ise yaklaşık GÖ 595 yıl civarında gerçekleştiği ve %89 belirsizlik aralığının GÖ 780 ila 425 yıllarını
kapsadığı bulunmuştur. Bu çalışmanın sonuçları, önerilen HBCPA yönteminin jeolojik verilerde
çevresel değişim noktalarını, sahip oldukları belirsizlikleri ile ölçme potansiyeline sahip olduğunu
göstermektedir.

Keywords

Büyük Menderes Vadisi, Gibbs örneklemesi, Maiandros Nehri, Milet, MZMC

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