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13It has long been known that extreme changes in North African hydroclimate occurred 14 during the late Pleistocene yet many discrepancies exist between sites regarding the timing, 15 duration and abruptness of events such as Heinrich Stadial (HS) 1 and the African Humid 16Period (AHP). The hydroclimate history of the Nile River is of particular interest due to its 17 lengthy human occupation history yet there are presently few continuous archives from the 18 Nile River corridor, and pre-Holocene studies are rare. Here we present new organic and 19 inorganic geochemical records of Nile Basin hydroclimate from an eastern Mediterranean 20 (EM) Sea sediment core spanning the past 28 ka BP. Our multi-proxy records reflect the 21 fluctuating inputs of Blue Nile versus White Nile material to the EM Sea in response to 22 2 gradual changes in local insolation and also capture abrupt hydroclimate events driven by 23 remote climate forcings, such as HS1. We find strong evidence for extreme aridity within 24 the Nile Basin evolving in two distinct phases during HS1, from 17.5 to 16 ka BP and from 25 16-14.5 ka BP, whereas peak wet conditions during the AHP are observed from 9-7 ka BP. 26We find that zonal movements of the Congo Air Boundary (CAB), and associated shifts in 27 the dominant moisture source (Atlantic versus Indian Ocean moisture) to the Nile Basin, 28 likely contributed to abrupt hydroclimate variability in northern East Africa during HS1 29 and the AHP as well as to non-linear behavior of hydroclimate proxies. We note that 30 different proxies show variable gradual and abrupt responses to individual hydroclimate 31 events, and thus might have different inherent sensitivities, which may be a factor partially 32 contributing to the controversy surrounding the abruptness of past events such as the AHP. Introduction 40The paleoclimate history of the Nile River valley in East Africa is of interest due to its 41 rich history of human occupation (Vermeersch and Van Neer, 2015). Relationships 42 between climate and the distribution of settlements on the Nile River corridor have long 43 been recognized and it is hypothesized that extreme changes in African hydroclimate 44 helped shape the growth and led to the decline of numerous complex societies [Kuper and 45 3 Kröpelin, 2006]. One of the most dramatic changes in North African hydroclimate, the so-46 called African Humid Period (AHP) [deMenocal et al., 2000], occurred during the early 47Holocene when increased rainfall allowed vegetation, lakes and human populations to 48 occupy a "green Sahara", a region that today is a hyperarid desert [Kuper and Kröpelin, 49 2006]. Variability in Nile River flow also played an important role in shaping Egypt's 50 civilizations with the collapse of the Old Kingdom at 4,160 years before present, attributed 51 to a 30 year absence of annual Nile flooding [Stanley et al., 2003]. Although lacking direct 52 evidence, it is hypothesized that HS1, which is recognized as an extreme and widespread 53 drought in North Afri...

Concordant U–Pb ages of c. 530–510 Ma and c. 470–420 Ma on titanite from calcsilicate, orthogneiss and amphibolite rocks constrain the age of high‐T metamorphism in the Early Palaeozoic mobile belt at the western margin of Proterozoic Gondwana (Argentina, 26–29°S). The U–Pb ages document the time of titanite formation at high‐T conditions according to the stable mineral paragenesis and occurrence of titanite in the metamorphic fabric. The presence of migmatite at all sample sites indicates temperatures were > c. 650 °C. Titanite formed at similar metamorphic conditions at different times on the regional and on the outcrop scale. The titanite crystals preserved their U–Pb isotopic signatures and chemical composition under ongoing upper amphibolite to granulite facies temperatures. Different thermal peaks or deformations are only detected by the different U–Pb ages and not by changes in the mineral paragenesis or metamorphic fabric of the samples. The range of U–Pb ages, e.g. in the Ordovician and Silurian (c. 470, 460, 440, 430, 420 Ma), is interpreted as the effect polyphase deformation with deformation‐enhanced recrystallization of titanite and/or different thermal peaks during a long‐standing, geographically fixed, high‐T regime in the mid‐crust of a continental magmatic arc. A clear correlation of the different ages with distinct tectonic events, e.g. collision of terranes, is not possible based on the present knowledge of the region.

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